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May 31, 2023:
In collaboration with a few research institutes, our lab’s research finds that a CH4 sink is enhanced with increasing SOC content on regional and global scales. The finding suggests that the future global methane cycling will be intimately coupled with future global SOC dynamics. The study appeared in Nature -Communication on May 30, 2023: Jaehyun Lee, J., Y. Oh, S. T. Lee, Y. O. Seo, J. Yun, Y. Yang, J. Kim, Q. Zhuang & H. Kang, Soil organic carbon is a key determinant of CH4 sink in global forest soils. Nat Commun 14, 3110 (2023). https://doi.org/10.1038/s41467-023-38905-8.
May 2, 2023:
Xuan led a new study by invoking a Fourier transform and spectrum analysis method to evaluate the effects of precipitation and evapotranspiration on simulated and observed soil moisture variability at the global scale. One of the key findings is that soil moisture is mainly affected by precipitation at weekly to seasonal time scales and by evapotranspiration at seasonal to annual time scales.
The full citation: Xi, X., Zhuang, Q., Kim, S., & Gentine, P. (2023). Evaluating the effects of precipitation and evapotranspiration on soil moisture variability within CMIP5 using SMAP and ERA5 data. Water Resources Research, 59, e2022WR034225. https://doi.org/10.1029/2022WR034225
April 29, 2023:
Congratulations: Youmi and Bailu defended their dissertation in Spring of 2020 and 2023, respectively!
April 21, 2023: Xuan passed his PhD preliminary exam and advanced to his PhD Candidacy, congratulations!
April 20, 2023: Bailu passed her PhD dissertation defense, congratulations Dr. Zhao!
April 12, 2023:
Our lab is part of a FAA grant to analyze the impacts of aviation biofuel use on carbon cycling.
March 27, 2023:
A study led by Xiangyu was published today. Previous research suggests that there might be significant uncertainties coming from “double accounting” emissions from freshwater bodies and wetlands. This study quantifies the methane emissions from both land and freshwater bodies in the pan-Arctic with two process-based biogeochemistry models by minimizing the double accounting at the landscape scale.
Citation: Liu, X. and Zhuang, Q.: Methane emissions from Arctic landscapes during 2000–2015: an analysis with land and lake biogeochemistry models, Biogeosciences, 20, 1181–1193, https://doi.org/10.5194/bg-20-1181-2023, 2023.
March 24, 2023:
Our lab published a study that uses a mechanistically-based aquatic biogeochemistry model to quantify the global lake and reservoir methane emissions for the first and the last decades of the 21st century. We find that current emissions are 24.0 ± 8.4 Tg CH4 yr−1 from lakes larger than 0.1 km2, under the RCP8.5 scenario, a 58–86% growth in emissions from the global freshwater lakes and reservoirs is estimated.
Citation: Zhuang, Q., Guo, M., Melack, J. M., Lan, X., Tan, Z., Oh, Y., & Leung, L. R. (2023). Current and future global lake methane emissions: A process-based modeling analysis. Journal of Geophysical Research: Biogeosciences, 128, e2022JG007137. https://doi.org/10.1029/2022JG007137
March 17, 2023:
Yiming led a study that revised a sophisticated ecosystem model to improve simulations of soil temperature profile and their influences on vegetation, ecosystem carbon pools and fluxes. The study finds that, with warmer soil temperature in winter and cooler soil temperature in summer simulated with the revised model considering vegetation shift and snow effects, the region will release 1.54 Pg C/year to the atmosphere for present-day and 66.77–87.95 Pg C in 2022–2100. The canopy effects due to vegetation shift, however, will get more carbon sequestered into the ecosystem at 1.00 Pg C/year for present day and 36.09–44.32 Pg C/year in 2022–2100. This study highlights the importance to consider the interactions between snow, vegetation shift and soil thermal dynamics in simulating carbon dynamics in the region.
The full citation of the study is “Xu, Y. and Q. Zhuang (2023), The importance of interactions between snow, permafrost and vegetation dynamics in affecting terrestrial carbon balance in circumpolar regions, Environ. Res. Lett. 18 044007, DOI 10.1088/1748-9326/acc1f7"
December 19, 2022: Congratulations to Ye, Yiming and Xiangyu who have passed their PhD qualifying exams!
April 7, 2022: Bailu passed her preliminary exam and advanced to a PhD candidate, congratulations!
March 2, 2022: Mingyang passed her PhD defense, congratulations, Dr. Guo!
December 1, 2021: Congratulations to Xuan, who passed his PhD qualifying exams, a major milestone towards his PhD!
May 12, 2021: Bailu led a study to quantify fire severity impacts on carbon budget in northern North America, which has been published in Scientific Report and highlighted by Purdue science news below https://www.eaps.purdue.edu/news/articles/2021/0513_zhuang_wildfires.html
Lei led a study that investigating the fate of Arctic permafrost in the 21st century published in Environmental Research Letters. https://iopscience.iop.org/article/10.1088/1748-9326/abd6a8. The study was highlighted at https://www.eaps.purdue.edu/news/articles/2021/0115_zhaung_permafrost.html
12/4/2020: Congratulations, Mingyang passed her preliminary exam becoming a PhD candidate!
11/30/2020: Bailu passed her qualifying exams to continue her PhD program at EAPS, congratulations!
7/16/2020: Youmi passed her dissertation defense, congratulations, Dr. Oh!
7/7/2020: Mingyang led a study revealing increasing ice-free days drove Arctic lake methane emissions. See Purdue News Release: https://www.purdue.edu/newsroom/releases/2020/Q3/bubbling-methane-emissions-caused-by-ice-free-days-in-arctic-lakes.html See ScienceDaily: https://www.sciencedaily.com/releases/2020/03/200326124141.htm
Citation: Guo, M., Q. Zhuang, Z. Tan, N. Shurpali, S. Juutinen, P. Kortelainen and P. Martikainen, 2020, Rising methane emissions from boreal lakes due to increasing ice-free days, Environ. Res. Lett. 15 064008. https://doi.org/10.1088/1748-9326/ab8254.
April 20, 2020: Licheng passed his dissertation defense today, congratulations, Dr. Liu!
March 30, 2020
Our lab published an important study on Arctic methane emissions led by Youmi. See the News Release below: https://https://www.purdue.edu/newsroom/releases/2020/Q1/purdue-study-downgrades-arctic-methane-emissions-thanks-to-soil-microbes.html
Citation: Oh, Y., Zhuang, Q., Liu, L. et al. Reduced net methane emissions due to microbial methane oxidation in a warmer Arctic. Nat. Clim. Chang. (2020). https://doi.org/10.1038/s41558-020-0734-z
See Xin Hua News: https://xinhuanet.com/english/2020-04/14/c_138975713.html
November 6, 2019: Congratulations to Mingyang passing her Qualify Exams to continue her PhD program at EAPS!
July 10, 2019
Our NASA land-use and land-cover change project focusing on Northern Eurasia has drawn a significant conclusion on carbon and nitrogen interactions under changing climate and land use conditions. Our findings were just published in Nature-Communications today!
Abstract: Nitrogen (N) availability exerts strong control on carbon storage in the forests of Northern Eurasia. Here, using a process-based model, we explore how three factors that alter N availability—permafrost degradation, atmospheric N deposition, and the abandonment of agricultural land to forest regrowth (land-use legacy)—affect carbon storage in the region’s forest vegetation over the 21st century within the context of two IPCC global-change scenarios (RCPs 4.5 and 8.5). For RCP4.5, enhanced N availability results in increased tree carbon storage of 27.8 Pg C, with land-use legacy being the most important factor. For RCP8.5, enhanced N availability results in increased carbon storage in trees of 13.4 Pg C, with permafrost degradation being the most important factor. Our analysis reveals complex spatial and temporal patterns of regional carbon storage. This study underscores the importance of considering carbon-nitrogen interactions when assessing regional and sub-regional impacts of global change policies.
Full Citation: Kicklighter, D. W., J. M. Melillo, E. Monier, A. P. Sokolov, and Q. Zhuang (2019) Future nitrogen availability and its effect on carbon sequestration in Northern Eurasia. Nature Communications 10, 3024, doi: 10.1038/s41467-019-10944-0.
June 20, 2019
Junrong passed her PhD dissertation defense, entitled ” Modeling the Impacts of Changes in Soil Microbes and Mosses on Arctic Terrestrial Ecosystem Carbon Dynamics“, congratulations, Dr. Zha!
May 16, 2019
Peng led a study published in Global Change Biology. The study provides a valuable information for Midwest corn production and management under future changing climate conditions. The study was highlighted by EAPS Department news at Purdue:https://www.eaps.purdue.edu/news/articles/2019/maize.html
Full Citation: Zhu, P, Zhuang, Q, Archontoulis, SV, Bernacchi, C, Müller, C. Dissecting the nonlinear response of maize yield to high temperature stress with model‐data integration. Glob Change Biol. 2019; 00: 1– 15. https://doi.org/10.1111/gcb.14632
April 29, Youmi passed her preliminary exam and became a PhD candidate, congratulations!
April 26, Sirui passed his PhD dissertation defense, congratulations Dr. Wang!
November 21, 2018
A study on tropical peatland carbon dynamics led by Sirui was just published in PNAS – a great contribution to the field!
Full citation: Wang, S., Zhuang, Q., Lähteenoja, O., Draper, F., and Cadillo-Quiroz, H (2018), Potential shift from a carbon sink to a source in Amazonian peatlands under a changing climate, Proceedings of the National Academy of Sciences Nov 2018, 201801317; DOI: 10.1073/pnas.1801317115
Abstract: Amazonian peatlands store a large amount of soil organic carbon (SOC) and its fate under a future changing climate is unknown. Here we use a process-based peatland biogeochemistry model to quantify the carbon accumulation for peatland and non-peatland ecosystems in the Pastaza-Marañon foreland basin (PMFB) in the Peruvian Amazon from 12,000 years before present to 2100 AD. Model simulations indicate that warming accelerates peat SOC loss while increasing precipitation accelerates peat SOC accumulation at millennial time scales. The uncertain parameters and spatial variation of climate are significant sources of uncertainty to modeled peat carbon accumulation. Under warmer and presumably wetter conditions over the 21st century, SOC accumulation rate in the PMFB slows down to 7.9 (4.3~12.2) g C m%& yr%) from the current rate of 16.1 (9.1~23.7) g C m%& yr%) and the region may turn into a carbon source to the atmosphere at -53.3 (-66.8~-41.2) g C m%& yr%) (negative indicates source), depending on the level of warming. Peatland ecosystems show a higher vulnerability than non-peatland ecosystems as indicated by the ratio of their soil carbon density changes (ranging from 3.9 to 5.8). This is primarily due to larger peatlands carbon stocks and more dramatic responses of their aerobic and anaerobic decompositions in comparison with non-peatland ecosystems under future climate conditions. Peatland and non-peatland soils in the PMFB may lose up to 0.4 (0.32~0.52) Pg C by 2100 AD with the largest loss from palm swamp. The carbon-dense Amazonian peatland may switch from a current carbon sink into a source in the 21st century. Purdue News release: https://www.purdue.edu/newsroom/releases/2018/Q4/major-natural-carbon-sink-may-soon-become-a-carbon-source.html
September 20, 2018
Junrong published her Arctic carbon balance study in Biogeosciences. Congratulations!
Citation: Zha, J. and Zhuang, Q.: Microbial decomposition processes and vulnerable arctic soil organic carbon in the 21st century, Biogeosciences, 15, 5621-5634, https://doi.org/10.5194/bg-15-5621-2018, 2018.
August 1, 2018
In collaboration with multiple institutions, our lab published a study in Ecological Applications.
Abstract: We summarize the results of a recent interagency assessment of land carbon dynamics in Alaska, in which carbon dynamics were estimated for all major terrestrial and aquatic ecosystems for the historical period (1950–2009) and a projection period (2010–2099). Between 1950 and 2009, upland and wetland (i.e., terrestrial) ecosystems of the state gained 0.4 Tg C/yr (0.1% of net primary production, NPP), resulting in a cumulative greenhouse gas radiative forcing of 1.68 × 10−3 W/m2. The change in carbon storage is spatially variable with the region of the Northwest Boreal Landscape Conservation Cooperative (LCC) losing carbon because of fire disturbance. The combined carbon transport via various pathways through inland aquatic ecosystems of Alaska was estimated to be 41.3 Tg C/yr (17% of terrestrial NPP). During the projection period (2010–2099), carbon storage of terrestrial ecosystems of Alaska was projected to increase (22.5–70.0 Tg C/yr), primarily because of NPP increases of 10–30% associated with responses to rising atmospheric CO2, increased nitrogen cycling, and longer growing seasons. Although carbon emissions to the atmosphere from wildfire and wetland CH4 were projected to increase for all of the climate projections, the increases in NPP more than compensated for those losses at the statewide level. Carbon dynamics of terrestrial ecosystems continue to warm the climate for four of the six future projections and cool the climate for only one of the projections. The attribution analyses we conducted indicated that the response of NPP in terrestrial ecosystems to rising atmospheric CO2 (~5% per 100 ppmv CO2) saturates as CO2 increases (between approximately +150 and +450 ppmv among projections). This response, along with the expectation that permafrost thaw would be much greater and release large quantities of permafrost carbon after 2100, suggests that projected carbon gains in terrestrial ecosystems of Alaska may not be sustained. From a national perspective, inclusion of all of Alaska in greenhouse gas inventory reports would ensure better accounting of the overall greenhouse gas balance of the nation and provide a foundation for considering mitigation activities in areas that are accessible enough to support substantive deployment.
Citation: McGuire, A. D., Genet, H. , Lyu, Z. , Pastick, N. , Stackpoole, S. , Birdsey, R. , D'Amore, D. , He, Y. , Rupp, T. S., Striegl, R. , Wylie, B. K., Zhou, X. , Zhuang, Q. and Zhu, Z. (2018), Assessing historical and projected carbon balance of Alaska: A synthesis of results and policy/management implications. Ecol Appl. . doi:10.1002/eap.1768
August, 1, 2018
Congratulations!, Xiaoliang’s study has been highlighted in EOS!
July, 11, 2018
Peng’s study on crop modeling has also appeared in Global Change Biology!
Citation: Zhu, Peng, Zhenong Jin, Qianlai Zhuang, Philippe Ciais, Carl Bernacchi, Xuhui Wang, David Makowski, David Lobell, The important but weakening maize yield benefit of grain filling prolongation in the US Midwest. Glob Change Biol. 2018;00:1–13. https://doi.org/10.1111/gcb.14356
July, 11, 2018
Yang’s excellent work on accelerating spin-up process was published in Biogeosciences! Congratulations!
Citation: Qu, Yang, Shamil Maksyutov, and Qianlai Zhuang, Technical Note: An efficient method for accelerating the spin-up process for process-based biogeochemistry models, Biogeosciences, 15, 3967–3973, 2018 https://doi.org/10.5194/bg-15-3967-2018
July, 11, 2018
Zeli has extended his aquatic modeling to temperate lakes, resulting in an excellent paper in Water Resources Research!
Citation: Tan, Zeli., Yao, Huaxia, & Zhuang, Qianlai (2018). A small temperate lake in the 21st century: Dynamics of water temperature, ice phenology, dissolved oxygen, and chlorophyll a. Water Resources Research, 54. https://doi.org/10.1029/2017WR022334
June, 25, 2018
Zhou led a study on the role of wetland ecosystems in the carbon and greenhouse gas budgets in Alaska in Ecological Applications. A great contribution to the field, congratulations!
Citation: Lyu, Z. , Genet, H. , He, Y. , Zhuang, Q. , McGuire, A. D., Bennett, A. , Breen, A. , Clein, J. , Euskirchen, E. S., Johnson, K. , Kurkowski, T. , Pastick, N. J., Rupp, T. S., Wylie, B. K. and Zhu, Z. (2018), The role of environmental driving factors in historical and projected carbon dynamics of wetland ecosystems in Alaska. Ecol Appl. . doi:10.1002/eap.1755
June, 12, 2018
Zhou successfully defended her dissertation research, entitled “Quantifying Arctic Terrestrial Ecosystem Carbon Dynamics Using Mechanistically-Based Biogeochemistry Models and In Situ and Satellite Data. Congratulations, Dr. Lyu!
June, 6, 2018
Licheng published his study on global soil CO dynamics in ACP. A great contribution to the field.
Citation: Liu, L., Zhuang, Q., Zhu, Q., Liu, S., van Asperen, H., and Pihlatie, M.: Global soil consumption of atmospheric carbon monoxide: an analysis using a process-based biogeochemistry model, Atmos. Chem. Phys., 18, 7913-7931, https://doi.org/10.5194/acp-18-7913-2018, 2018.
June, 5, 2018
Xiaoliang led a study on quantifying the impacts of global sea-level rise on wetland methane emissions in JGR-Biogeosciences. This is among the first study in assessing the impacts using earth system modeling approach.
Citation: Lu, X., Zhou, Y., Zhuang, Q., Prigent, C., Liu, Y., & Teuling, A. (2018). Increasing methane emissions from natural land ecosystems due to sea-level rise. Journal of Geophysical Research: Biogeosciences, 123. https://doi.org/10.1029/2017JG004273
April, 12, 2018
Zhou Lyu led a study on the role of snow pack on carbon dynamics in the Arctic, published in JGR-Biogeoscience.
Lyu,Z.,&Zhuang,Q.(2018).Quantifying the effects of snowpack on soil thermal and carbon dynamics of the Arctic terrestrial ecosystems. Journal of Geophysical Research: Biogeosciences, 123. https://doi.org/10.1002/ 2017JG003864
Abstract: Snow insulation effects modify soil and carbon dynamics in northern middle to high latitudes (45°–90°N). This study incorporates these effects by introducing a snow model into an existing soil thermal model in a biogeochemistry modeling framework, the Terrestrial Ecosystem Model. The coupled model is used to quantify snow insulation effects on carbon and soil thermal dynamics in 45°–90°N region for the historical period (2003–2010) and the future period (2017–2099) under two climate scenarios. The revised modelcapturesthesnowinsulationeffectsandimprovestheestimatesofsoilthermaldynamicsandtheland freeze-thaw as well as terrestrial ecosystem carbon dynamics. Historical mean cold-season soil temperature at 5 cm depth driven with satellite-based snow data is 6.4°C warmer in comparison with the original model simulation. Frozen area in late spring is estimated to shrink mainly over eastern Siberia, in central to eastern Europe, and along southern Canada in November. During each nongrowing season in the historical period, 0.41 Pg more soil C is released due to warmer soil temperature estimated using the new model. During 2003–2010, the revised model estimates that the region accumulated 0.86 Pg less C due to weaker gross primary production, leading to a regional C loss at 0.19 PgC/year. The revised model projects that the region will lose 38–51% permafrost area by 2100 and continue to be a C source under the low-emission scenario(RepresentativeConcentrationPathway2.6)buttobegraduallytransitioningintoaweaksinkinthe latter half of the 21st century under the high-emission scenario (Representative Concentration Pathway 8.5).
April, 11, 2018
In collaboration with a number of institutions, our lab published a study on the role of permafrost degradation on carbon cycling in the Arctic in PNAS.
McGuire, A.D., D.M. Lawrence, C. Koven J.S. Clein, E. Burke, G. Chen, E. Jafarov, A.H. MacDougall, S. Marchenko, D. Nicolsky, S. Peng, A. Rinke, P. Ciais, I. Gouttevin, D.J. Hayes, D. Ji, G. Krinner, J.C. Moore, V.E. Romanovsky, C. Schädel, K. Schaefer, E.A.G. Schuur, and Q. Zhuang. 2018. The dependence of the evolution of carbon dynamics in the northern permafrost region on the trajectory of climate change. Proceedings of the National Academy of Sciences, 6 pages, doi:10.1073/pnas.1719903115
Abstract: We conducted a model-based assessment of changes in permafrost area and carbon storage for simulations driven by RCP4.5 and RCP8.5 projections between 2010 and 2299 for the northern permafrost region. All models simulating carbon represented soil with depth, a critical structural feature needed to represent the permafrost carbon–climate feedback, but that is not a universal feature of all climate models. Between 2010 and 2299, simulations indicated losses of permafrost between 3 and 5 million km2 for the RCP4.5 climate and between 6 and 16 million km2 for the RCP8.5 climate. For the RCP4.5 projection, cumulative change in soil carbon varied between 66-Pg C (1015-g carbon) loss to 70-Pg C gain. For the RCP8.5 projection, losses in soil carbon varied between 74 and 652 Pg C (mean loss, 341 Pg C). For the RCP4.5 projection, gains in vegetation carbon were largely responsible for the overall projected net gains in ecosystem carbon by 2299 (8- to 244-Pg C gains). In contrast, for the RCP8.5 projection, gains in vegetation carbon were not great enough to compensate for the losses of carbon projected by four of the five models; changes in ecosystem carbon ranged from a 641-Pg C loss to a 167-Pg C gain (mean, 208-Pg C loss). The models indicate that substantial net losses of ecosystem carbon would not occur until after 2100. This assessment suggests that effective mitigation efforts during the remainder of this century could attenuate the negative consequences of the permafrost carbon–climate feedback.
April, 6, 2018
Peng passed his PhD defense, congratulations Dr. Zhu!
April, 5, 2018
Tong passed her PhD final exam, congratulations Dr. Yu!
April, 4, 2018
Yang passed his PhD defense, congratulations Dr. Qu!
April, 3, 2018
Jurong passed her preliminary exam, become a PhD Candidate!
January, 10, 2018
Congratulations to Yang, having a LAI modeling study published at Ecosphere. Citation and Abstract are below: Qu, Y., and Q. Zhuang. 2018. Modeling leaf area index in North America using a process-based terrestrial ecosystem model. Ecosphere 9(1):e02046. 10.1002/ecs2.2046
Abstract. Leaf area index (LAI) is often used to quantify plant production and evapotranspiration with terrestrial ecosystem models (TEMs). This study evaluated the LAI simulation in North America using a data assimilation technique and a process-based TEM as well as in situ and satellite data. We first optimized the parameters related to LAI in the TEM using a Markov Chain Monte Carlo method, and AmeriFlux site-level and regional LAI data from advanced very high-resolution radiometer. The parameterized model was then verified with the observed monthly LAI of major ecosystem types at site level. Simulated LAI was compared well with the observed data at sites of Harvard Forest (R2 = 0.96), University of Michigan Biological Station (R2 = 0.87), Howland Forest (R2 = 0.96), Morgan Monroe State Forest (R2 = 0.85), Shidler Tallgrass Prairie (R2 = 0.82), and Donaldson (R2 = 0.75). The root-mean-square error (RMSE) between modeled and satellite-based monthly LAI in North America is 1.4 m2 /m2 for the period of 1985 2010. The simulated average monthly LAI in recent three decades increased by (3 0.5)% in the region, with 1.24, 1.46, and 2.21 m2 /m2 on average, in Alaska, Canada, and the conterminous United States, respectively, which is consistent with satellite data. The model performed well for wet tundra, boreal forest, temperate coniferous forests, temperate deciduous forests, grasslands, and xeric shrublands (RMSE 1.5 m2 /m2 ), but not for alpine tundra and xeric woodlands (RMSE 1.5 m2 /m2 ). Both the spring and fall LAI in the 2000s are higher than that in the 1980s in the region, suggesting that the leaf phenology has an earlier onset and later senescence in the 2000s. The average LAI increased in April and September by 0.03 and 0.24 m2 /m2 , respectively. This study provides a way to quantify LAI with ecosystem models, which will improve future carbon and water cycling studies.
December, 29, 2017
In collaboration with U. of Alaska Fairbanks and the USGS, our lab published a study on the role of Alaskan upland ecosystems in the regional carbon budget, thanks to Yujie and Zhou’s great contribution. The full citation is below:
Genet, H., He, Y., Lyu, Z., McGuire, A. D., Zhuang, Q., Clein, J., D'Amore, D., Bennett, A., Breen, A., Biles, F., Euskirchen, E. S., Johnson, K., Kurkowski, T., (Kushch) Schroder, S., Pastick, N., Rupp, T. S., Wylie, B., Zhang, Y., Zhou, X. and Zhu, Z. (2017), The role of driving factors in historical and projected carbon dynamics of upland ecosystems in Alaska. Ecol Appl. doi:10.1002/eap.1641
November, 13, 2017
Chang had an excellent publication in JGR-Earth Surface that used a three-dimensional, high spatial-temporal resolution modeling approach. Citation: Liao, C., & Zhuang, Q. (2017). Quantifying the role of snowmelt in stream discharge in an Alaskan watershed: An analysis using a spatially distributed surface hydrology model. Journal of Geophysical Research: Earth Surface, 122. https://doi.org/10.1002/2017JF004214
Abstract:This study uses a spatially distributed surface hydrology model to investigate the role of snowmelt in stream discharge for the Tanana Flats Basin in interior Alaska. The Parameter ESTimation code is used to calibrate the model with observed stream discharge data. The model was further evaluated using remote sensing-based snow cover product and in situ snowpack water equivalent (SWE) observations. A 36 year (1980–2015) U.S. Geological Survey Precipitation-Runoff Modeling System simulation shows (1) the monthly stream discharge from the Tanana Flats Basin in April decreased by 44%; (2) snow cover area at high altitudes (above 2000 m) decreased in summer, both SWE and snowmelt also decreased significantly, especially in spring; (3) the timings of snowmelt onset and ending shifted by 2 (earlier) and 5 (later) days per decade, respectively; and (4) snowmelt accounts for 40% of the annual stream discharge. This study provides a quantitative tool to investigating hydrological systems considering the impacts of snow dynamics in cold regions. This study also suggests that future warming will further decrease snow coverage, advance snow melting time, and hereafter change the stream discharge dynamics in the Arctic.
October, 27, 2017
Congratulations to Youmi, who passed her qualifying exams to continue her PhD program at EAPS!
September, 15, 2017
Zeli led developed a process-based aquatic biogeochemistry model that has been just published in Journal of Advances in Modeling Earth Systems! This is a significant contribution to the field.
Tan, Z., Zhuang, Q, Shurpali, N. J, Marushchak, M. E, Biasi, C, Eugster, W, and Anthony, K. W (2017), Modeling CO2 emissions from Arctic lakes: Model development and site-level study, J. Adv. Model. Earth Syst., 9, doi:10.1002/2017MS001028
September, 15, 2017
Youmi Oh, an EAPS graduate student studying environmental geosciences, has been awarded the NASA Earth and Space Science Fellowship (NESSF). The competitive NESSF Fellowship Award provides funding for student travel, research supplies, and a stipend. Oh’s primary research aims to understand how trees respond to drought and climate change. She has been working with Dr. Lisa Welp – her co-advisor and EAPS Assistant Professor – to explore seasonal changes in the Morgan Monroe State Forest in Indiana. “I have been very interested in modeling atmosphere and biosphere interactions,” she said. “Understanding how forest tree species respond to such environmental stress has important consequences for global carbon balance and climate change feedbacks.” For the NESSF Fellowship, Oh will be working with Dr. Qianlai Zhuang, her co-advisor and EAPS Distinguished Professor, to investigate the importance of a novel methane-oxidizing bacteria in the pan-Arctic methane budget. This was the subject of a paper she was lead author of in Geophysical Research Letters, and has been a subject of her interest for some time. “The NASA proposal I wrote with Dr. Qianlai Zhuang is based on the project I worked for my M.S. degree at Princeton,” she said. “This project is important because the methane-oxidizing bacteria may be a key to explain inter-annual variability of atmospheric methane concentrations, and the discrepancy between methane models and observations.” The NESSF Fellowship will provide funding for Oh’s research for up to three years.
See EAPS news release: https://www.eaps.purdue.edu/news/articles/2017/oh-nasa-fellowship.html
August, 16, 2017
Congratulations to Chang, who has started his Post-Doctoral Scientist position at the Pacific Northwest National Laboratory (PNNL)!
June, 8, 2017
Youmi won a prestigious 3-year NASA Fellowship. Congratulations! Her research proposal is entitled “High Affinity Methanotrophs are an Important Overlooked Methane Sink in the Pan–Arctic Methane Budget”
April, 14, 2017
Chang passed PhD final exam. Congratulations, Dr. Liao!
April, 14, 2017
Licheng Liu, Peng Zhu and Sirui Wang passed their preliminary exams and advanced to PhD candidates, big congratulations to them!
February, 27, 2017
Peng Zhu published a study on Geophysical Research Letters.Job well done!
Abstract: Increasing atmospheric CO2 affects photosynthesis involving directly increasing leaf carboxylation rates, stomatal closure, and climatic effects. The direct effects are generally thought to be positive leading to increased photosynthesis, while its climatic effects can be regionally positive or negative. These effects are usually considered to be independent from each other, but they are in fact coupled through interactions between land surface exchanges of gases and heat and the physical climate system. In particular, stomatal closure reduces evapotranspiration and increases sensible heat emissions from ecosystems, leading to decreased atmospheric moisture and precipitation and local warming. We use a coupled earth system model to attribute the influence of the increase in CO2 on gross primary productivity (GPP) during the period of 1930–2011. In our model, CO2 radiative effects cause climate change that has only a negligible effect on global GPP (a reduction of 0.9 ± 2% during the last 80 years) because of opposite responses between tropical and northern biomes. On the other hand, CO2 physiological effects on GPP are both positive, by increased carboxylation rates and water use efficiency (7.1 ± 0.48% increase), and negative, by vegetation-climate feedback reducing precipitation, as a consequence of decreased transpiration and increased sensible heat in areas without water limitation (2.7 ± 1.76% reduction).When considering the coupled atmosphere-vegetation system, negative climate feedback on photosynthesis and plant growth due to the current level of CO2 opposes 29–38% of the gains from direct fertilization effects.
Citation: Zhu, P., Q. Zhuang, P. Ciais, L. Welp,W. Li, and Q. Xin (2017), Elevatedatmospheric CO2negatively impactsphotosynthesis through radiativeforcing and physiology-mediatedclimate feedback, Geophys. Res. Lett.,44, doi:10.1002/2016GL071733.
February, 15, 2017
Chang has published an excellent study with a 3D modeling approach! Congratulations!
Abstract: This study uses a three-dimensional groundwater flow model to investigate groundwater dynamics and groundwater–surface water (GW-SW) interactions considering the effects of permafrost distribution for the Tanana Flats Basin in interior Alaska. The Parameter ESTimation (PEST) code is used to calibrate the model with observed stream discharge data. A 36-year MODLFOW-USG regional simulation shows the following. (1) Permafrost impedes groundwater movement in all directions and through taliks provides a major pathway to connect the groundwater and surface water systems. More than 80% of the vertical groundwater flow occurs within the permafrost-free zones. (2) Permafrost holds a significant amount of water that cannot be easily released through groundwater movements; however, water above the permafrost table has much higher renewal rates than deep groundwater. (3) Groundwater upwelling supports the base flow for the Tanana River and its tributaries throughout the year and feeds water to the wetland ecosystems at the Tanana Flats through unfrozen zones. Stream leakage is also highly correlated with stream discharge. Our study suggests that cold regional hydrological cycle studies should consider the effects of permafrost distribution under future warming conditions. This study provides a robust three-dimensional hydrological modeling tool that can be applied for the regions underlain with either continuous or discontinuous permafrost.
Citation: Chang Liao and Qianlai Zhuang (2017) Quantifying the Role of Permafrost Distribution in Groundwater and Surface Water Interactions Using a Three-Dimensional Hydrological Model. Arctic, Antarctic, and Alpine Research: February 2017, Vol. 49, No. 1, pp. 81-100.
February, 2, 2017
Zhenong published another excellent study as part of his dissertation in Global Change Biology this week!
Abstract: Heat and drought are two emerging climatic threats to the US maize and soybean production, yet their impacts on yields are collectively determined by the magnitude of climate change and rising atmospheric CO2 concentrations. This study quantifies the combined and separate impacts of high temperature, heat and drought stresses on the current and future US rainfed maize and soybean production and for the first time characterizes spatial shifts in the relative importance of individual stress. Crop yields are simulated using the Agricultural Production Systems Simulator (APSIM), driven by high-resolution (12 km) dynamically downscaled climate projections for 1995–2004 and 2085– 2094. Results show that maize and soybean yield losses are prominent in the US Midwest by the late 21st century under both Representative Concentration Pathway (RCP) 4.5 and RCP8.5 scenarios, and the magnitude of loss highly depends on the current vulnerability and changes in climate extremes. Elevated atmospheric CO2 partially but not completely offsets the yield gaps caused by climate extremes, and the effect is greater in soybean than in maize. Our simulations suggest that drought will continue to be the largest threat to US rainfed maize production under RCP4.5 and soybean production under both RCP scenarios, whereas high temperature and heat stress take over the dominant stress of drought on maize under RCP8.5. We also reveal that shifts in the geographic distributions of dominant stresses are characterized by the increase in concurrent stresses, especially for the US Midwest. These findings imply the importance of considering heat and drought stresses simultaneously for future agronomic adaptation and mitigation strategies, particularly for breeding programs and crop management. The modeling framework of partitioning the total effects of climate change into individual stress impacts can be applied to the study of other crops and agriculture systems.
Citation: Jin, Z., Zhuang, Q., Wang, J., Archontoulis, S. V., Zobel, Z. and Kotamarthi, V. R. (2017), The combined and separate impacts of climate extremes on the current and future US rainfed maize and soybean production under elevated CO2. Glob Change Biol. doi:10.1111/gcb.13617
January 18, 2017
Shaoqing accepted a post-doctoral offer from University of Minnesota to work on plant traits based modeling. Congratulations!
January 12, 2017
Lulu just published her dissertation chapter in Environmental Research Letters! You might be interested in reading.
Song, L. Q. Zhuang, Y. Yin, X. Zhu and S. Wu (2017), Spatio-temporal dynamics of evapotranspiration on the Tibetan Plateau from 2000 to 2010, Environ. Res. Lett. 12, (2017) 014011, doi:10.1088/1748-9326/aa527d
December 9, 2016
Zhenong’s excellent study on agriculture systems from his dissertation was just published in Precision Agriculture, congratulations!
Jin, Z., Prasad, R., Shriver, and Q. Zhuang (2016), Crop model- and satellite imagery-based recommendation tool for variable rate N fertilizer application for the US Corn system, Precision Agric., doi:10.1007/s11119-016-9488-z
November 26, 2016
Sirui published new study on Biogeosciences!
Abstract Northern high latitudes contain large amounts of soil organic carbon (SOC), of which Alaskan terrestrial ecosystems account for a substantial proportion. In this study, the SOC accumulation in Alaskan terrestrial ecosystems over the last 15 000 years was simulated using a process-based biogeochemistry model for both peatland and non-peatland ecosystems. Comparable with the previous estimates of 25–70 Pg C in peatland and 13–22 Pg C in non-peatland soils within 1 m depth in Alaska using peat-core data, our model estimated a total SOC of 36–63 Pg C at present, including 27–48 Pg C in peatland soils and 9–15 Pg C in non-peatland soils. Current vegetation stored 2.5–3.7 Pg C in Alaska, with 0.3–0.6 Pg C in peatlands and 2.2–3.1 Pg C in non-peatlands. The simulated average rate of peat C accumulation was 2.3 Tg C yr−1, with a peak value of 5.1 Tg C yr−1 during the Holocene Thermal Maximum (HTM) in the early Holocene, 4-fold higher than the average rate of 1.4 Tg C yr−1 over the rest of the Holocene. The SOC accumulation slowed down, or even ceased, during the neoglacial climate cooling after the mid-Holocene, but increased again in the 20th century. The model-estimated peat depths ranged from 1.1 to 2.7 m, similar to the field-based estimate of 2.29 m for the region. We found that the changes in vegetation and their distributions were the main factors in determining the spatial variations of SOC accumulation during different time periods. Warmer summer temperature and stronger radiation seasonality, along with higher precipitation in the HTM and the 20th century, might have resulted in the extensive peatland expansion and carbon accumulation.
Citation Wang, S., Zhuang, Q., and Yu, Z.: Quantifying soil carbon accumulation in Alaskan terrestrial ecosystems during the last 15 000 years, Biogeosciences, 13, 6305-6319, doi:10.5194/bg-13-6305-2016, 2016.
November 23, 2016
Junrong passed her qualifying exams to continue her PhD program at EAPS, congratulations!
Oct. 12, 2016
Zeli’s methane inverse modeling study was just published in ACP. This is a significant achievement, congratulations!
ABSTRACT: Understanding methane emissions from the Arctic, a fast-warming carbon reservoir, is important for projecting future changes in the global methane cycle. Here we optimized methane emissions from north of 60˚ N (pan-Arctic) regions using a nested-grid high-resolution inverse model that assimilates both high-precision surface measurements and column-average SCanning Imaging Absorption spectrometer for Atmospheric CHartogrphY (SCIAMACHY) satellite retrievals of methane mole fraction. For the first time, methane emissions from lakes were integrated into an atmospheric transport and inversion estimate, together with prior wetland emissions estimated with six biogeochemical models. In our estimates, in 2005, global methane emissions were in the range of 496.4–511.5 Tg yr¯1, and pan-Arctic methane emissions were in the range of 11.9–28.5 Tg yr¯1. Methane emissions from pan-Arctic wetlands and lakes were 5.5–14.2 and 2.4–14.2 Tg yr¯1, respectively. Methane emissions from Siberian wetlands and lakes are the largest and also have the largest uncertainty. Our results indicate that the uncertainty introduced by different wetland models could be much larger than the uncertainty of each inversion. We also show that assimilating satellite retrievals can reduce the uncertainty of the nested-grid inversions. The significance of lake emissions cannot be identified across the pan-Arctic by high-resolution inversions, but it is possible to identify high lake emissions from some specific regions. In contrast to global inversions, high-resolution nested-grid inversions perform better in estimating near-surface methane concentrations.
CITATION: Tan, Z., Q. Zhuang, D. K. Henze, C. Frankenberg, E. Dlugokencky, C. Sweeney, A. J. Turner, M. Sasakawa, and T. Machida (2016). Inverse modeling of pan-Arctic methane emissions at high spatial resolution: what can we learn from assimilating satellite retrievals and using different process-based wetland and lake biogeochemical models? Atmos. Chem. Phys., 16, 12649-12666.
Sept. 30, 2016
Shaoqing just passed his final exam. Congratulations Dr. Liu!
Sept. 4, 2016
EAPS alumna recognized for research
An EAPS alumna, Yaling Liu, has been honored with an award from the Ecological Society of America (ESA).
The Elizabeth Sulzman Award honors research conducted by a graduate student, and published within two years of his or her graduation. Liu, who received her Ph.D. from Purdue University in 2014, received the award for a journal article about drought in northern China, which was published by Scientific Reports in 2015. The award was officially presented at the ESA annual meeting on August 9.
Reflecting back on her time at Purdue, Dr. Liu said the Purdue environment was helpful in the development of her research.
“The vigorous research atmosphere and diverse research activities on campus greatly inspired and motivated me,” she said. “The most helpful part was constant coaching from my advisors, from technical skills to critical thinking to research philosophy, as well as inspiring discussions with fellow lab mates.”
In the article, Liu and her colleagues, including EAPS Professors Qianlai Zhuang and Dev Niyogi, analyze the conditions surrounding the region’s dropping water supply. The analysis included recent changes in the region’s climatology, but also considered agricultural practices in order to find a solution to the food security problem the region is facing.
“Alternative agriculture practices that could help meet food demand without compromising future water resources need to be pursued for sustainable agriculture,” the authors concluded.
Dr. Liu is now serving as a Post Doctorate researcher at the Pacific Northwest National Laboratory of the United States Department of Energy. Her research is focused on human and nature interactions related to water and energy resources.
The award-winning article can be read in its entirety at https://www.nature.com/articles/srep11261.
Sept. 4, 2016
Sirui’s studies on Alaskan carbon dynamics in peatlands were just published in JGR-Biogeoscience and BG-Discussion!
This study uses an integrated modeling framework that couples the dynamics of hydrology, soil thermal regime, and ecosystem carbon and nitrogen to quantify the long-term peat carbon accumulation in Alaska during the Holocene. Modeled hydrology, soil thermal regime, carbon pools and fluxes, and methane emissions are evaluated using observation data at several peatland sites in Minnesota, Alaska, and Canada. The model is then applied for a 10,000 year (15 ka to 5 ka; 1 ka = 1000 cal years before present) simulation at four peatland sites. We find that model simulations match the observed carbon accumulation rates at fen sites during the Holocene (R2 = 0.88, 0.87, 0.38, and −0.05 using comparisons in 500 year bins). The simulated (2.04 m) and observed peat depths (on average 1.98 m) were also compared well (R2 = 0.91). The early Holocene carbon accumulation rates, especially during the Holocene thermal maximum (HTM) (35.9 g C m− 2 yr− 1), are estimated up to 6 times higher than the rest of the Holocene (6.5 g C m− 2 yr− 1). Our analysis suggests that high summer temperature and the lengthened growing season resulted from the elevated insolation seasonality, along with wetter-than-before conditions might be major factors causing the rapid carbon accumulation in Alaska during the HTM. Our sensitivity tests indicate that, apart from climate, initial water table depth and vegetation canopy are major drivers to the estimated peat carbon accumulation. When the modeling framework is evaluated for various peatland types in the Arctic, it can quantify peatland carbon accumulation at regional scales.
, , , , and (2016), Quantifying peat carbon accumulation in Alaska using a process-based biogeochemistry model, J. Geophys. Res. Biogeosci., 121, doi:10.1002/2016JG003452.
Abstract (Biogeosciences Discussion):
Northern high latitudes contain large amounts of soil organic carbon (SOC), in which Alaskan terrestrial ecosystems account for a substantial proportion. In this study, the SOC accumulation in Alaskan terrestrial ecosystems over the last 15,000 years was simulated using a process-based biogeochemistry model for both peatland and non-peatland terrestrial ecosystems. Comparable with the previous estimates of 25–70 Pg C in peatland and 13–22 Pg C in non-peatland soils within 1 m depth in Alaska, our model estimated a total SOC of 36–63 Pg C at present, including 27–48 Pg C in peatland soils and 9–15 Pg C in non-peatland soils. Vegetation stored only 2.5–3.7 Pg C in Alaska currently with 0.3–0.6 Pg C in peatlands and 2.2–3.1 Pg C in non-peatlands. The simulated average rate of peat C sequestration was 2.3 Tg C yr−1 with a peak value of 5.1 Tg C yr−1 during the Holocene Thermal Maximum (HTM) in the early Holocene, four folds higher than the average rate of 1.4 Tg C yr−1 over the rest of the Holocene. The SOC accumulation slowed down, or even ceased, during the neoglacial climate cooling after the mid-Holocene, but accumulation increased again in the 20th century. The model-estimated peat depths ranged from 1.1 to 2.7 m, similar to the field-based estimate of 2.29 m for the region. We found that the changes in vegetation types and their distributions due to climate change were the main factors determining the spatial variations of SOC accumulation during different time periods. Warmer summer temperature and stronger radiation seasonality, along with higher precipitation in the HTM and the 20th century might have resulted in the extensive peatland expansion and carbon accumulation, implying that soil C accumulation would continue under future warming conditions.
Wang, S., Zhuang, Q., and Yu, Z.: Quantifying Soil Carbon Accumulation in Alaskan Terrestrial Ecosystems during the Last 15,000 Years, Biogeosciences Discuss., doi:10.5194/bg-2016-284, 2016.
July. 25, 2016
Shaoqing’s study on CO2 effects on global carbon dynamics was just published in Ecosphere!
Current terrestrial ecosystem models are usually driven with global average annual atmospheric carbon dioxide (CO2) concentration data at the global scale. However, high-precision CO2 measurement from eddy flux towers showed that seasonal, spatial surface atmospheric CO2 concentration differences were as large as 35 ppmv and the site-level tests indicated that the CO2 variation exhibited different effects on plant photosynthesis. Here we used a process-based ecosystem model driven with two spatially and temporally explicit CO2 data sets to analyze the atmospheric CO2 fertilization effects on the global carbon dynamics of terrestrial ecosystems from 2003 to 2010. Our results demonstrated that CO2 seasonal variation had a negative effect on plant carbon assimilation, while CO2 spatial variation exhibited a positive impact. When both CO2 seasonal and spatial effects were considered, global gross primary production and net ecosystem production were 1.7 Pg C·yr−1 and 0.08 Pg C·yr−1 higher than the simulation using uniformly distributed CO2 data set and the difference was significant in tropical and temperate evergreen broadleaf forest regions. This study suggests that the CO2 observation network should be expanded so that the realistic CO2 variation can be incorporated into the land surface models to adequately account for CO2 fertilization effects on global terrestrial ecosystem carbon dynamics.
Liu, S., Zhuang, Q., Chen, M., Gu, L., 2016. Quantifying spatially and temporally explicit CO2 fertilization effects on global terrestrial ecosystem carbon dynamics. Ecosphere 7(7). doi:10.1002/ecs2.1391
July. 20, 2016
Zhenong’s another study was just published online in Climatic Change!
Static thermal requirements (T req ) are widely used to model the timing of phenology, yet may significantly bias phenological projections under future warming conditions, since recent studies argue that climate warming will increase T req for triggering vegetation phenology. This study investigates the temporal trend and inter-annual variation of T req derived from satellite-based spring and autumn phenology for the alpine and temperate vegetation on the Tibetan Plateau from 1982 to 2011. While we detected persistent warming in both spring and autumn across this time period, we did not find a corresponding long-term increase in T req for most of the study area. Instead, we found a substantial interannual variability of T req that could be largely explained by interannual variations in other climatic factors. Specifically, the number of chilling days and fall temperature were robust variables for predicting the dynamics of T req for spring onset and autumn senescence, respectively. Phenology models incorporating a dynamic T req algorithm performed slightly better than those with static T req values in reproducing phenology derived from SPOT-VGT NDVI data. To assess the degree to which T req variation affects large-scale phenology and carbon cycling projections, we compared the output from versions of the Terrestrial Ecosystem Model that incorporated static and dynamic T req values in their phenology algorithms. Under two contrasting future climate scenarios, the dynamic T req setting reduced the projected growing season length by up to 1–3 weeks by the late twenty-first century, leading to a maximum reduction of 8.9 % in annual net primary production and ~15 % in cumulative net ecosystem production for this region. Our study reveals that temporal dynamics of T req meaningfully affect the carbon dynamics on the Tibetan Plateau, and should thus be considered in future ecosystem carbon modeling.
Jin, Z., Zhuang, Q., Dukes, J.S., He, J.-S., Sokolov, A.P., Chen, M., Zhang, T., Luo, T., 2016. Temporal variability in the thermal requirements for vegetation phenology on the Tibetan plateau and its implications for carbon dynamics. Clim. Change 1–16. doi:10.1007/s10584-016-1736-8.
July. 20, 2016
Zhenong led an important study on quantifying the impacts of extreme climate events on crop yield. Excellent job!
Stresses from heat and drought are expected to increasingly suppress crop yields, but the degree to which current models can represent these effects is uncertain. Here we evaluate the algorithms that determine impacts of heat and drought stress on maize in 16 major maize models by incorporating these algorithms into a standard model, the Agricultural Production Systems sIMulator (APSIM), and running an ensemble of simulations. Although both daily mean temperature and daylight temperature are common choice of forcing heat stress algorithms, current parameterizations in most models favor the use of daylight temperature even though the algorithm was designed for daily mean temperature. Different drought algorithms (i.e., a function of soil water content, of soil water supply to demand ratio, and of actual to potential transpiration ratio) simulated considerably different patterns of water shortage over the growing season, but nonetheless predicted similar decreases in annual yield. Using the selected combination of algorithms, our simulations show that maize yield reduction was more sensitive to drought stress than to heat stress for the US Midwest since the 1980s, and this pattern will continue under future scenarios; the influence of excessive heat will become increasingly prominent by the late 21st century. Our review of algorithms in 16 crop models suggests that the impacts of heat and drought stress on plant yield can be best described by crop models that: (i) incorporate event-based descriptions of heat and drought stress, (ii) consider the effects of nighttime warming, and (iii) coordinate the interactions among multiple stresses. Our study identifies the proficiency with which different model formulations capture the impacts of heat and drought stress on maize biomass and yield production. The framework presented here can be applied to other modeled processes and used to improve yield predictions of other crops with a wide variety of crop models.
Jin, Z., Zhuang, Q., Tan, Z., Dukes, J.S., Zheng, B., Melillo, J.M., 2016. Do maize models capture the impacts of heat and drought stresses on yield? Using algorithm ensembles to identify successful approaches. Glob. Chang. Biol. doi:10.1111/gcb.13376
July. 1, 2016
Zhenong led an important study on quantifying the impacts of extreme climate events on crop yield. Excellent job!
Current quantification of climate warming mitigation potential (CWMP) of biomass-derived energy has focused primarily on its biogeochemical effects. This study used site-level observations of carbon, water, and energy fluxes of biofuel crops to parameterize and evaluate the community land model (CLM) and estimate CO2 fluxes, surface energy balance, soil carbon dynamics of corn (Zea mays), switchgrass (Panicum virgatum), and miscanthus (Miscanthus × giganteus) ecosystems across the conterminous United States considering different agricultural management practices and land-use scenarios. We find that neglecting biophysical effects underestimates the CWMP of transitioning from croplands and marginal lands to energy crops. Biogeochemical effects alone result in changes in carbon storage of −1.9, 49.1, and 69.3 g C m−2 y−1 compared to 20.5, 78.5, and 96.2 g C m−2 y−1 when considering both biophysical and biogeochemical effects for corn, switchgrass, and miscanthus, respectively. The biophysical contribution to CWMP is dominated by changes in latent heat fluxes. Using the model to optimize growth conditions through fertilization and irrigation increases the CWMP further to 79.6, 98.3, and 118.8 g C m−2 y−1, respectively, representing the upper threshold for CWMP. Results also show that the CWMP over marginal lands is lower than that over croplands. This study highlights that neglecting the biophysical effects of altered surface energy and water balance underestimates the CWMP of transitioning to bioenergy crops at regional scales.
Zhu, P., Zhuang, Q., Eva, J., Bernacchi, C., 2016. Importance of biophysical effects on climate warming mitigation potential of biofuel crops over the conterminous United States. GCB Bioenergy. doi:10.1111/gcbb.12370.
June. 13, 2016
Xudong published his last dissertation chapter in JGR-Atmosphere, an excellent contribution to the field – congratulations!
Warming-induced changes in structures and functions of northern terrestrial ecosystems (NTEs), including their regulation on terrestrial biogeochemistry and surface energy balance, may exert positive or negative feedback to the climate system. However, the relative importance among these biogeochemical and biogeophysical feedback is not well understood. Here we use a terrestrial ecosystem model to quantify spatially explicit ecosystem-climate feedback over NTEs (north of 50°N) under four climate change scenarios from 2010 to 2100, including biogeochemical feedback from climate-induced changes in net CH4 exchanges (NME) and net CO2 exchanges (NCE) and biogeophysical feedback from changes in surface energy partitioning associated with snow cover and vegetation biomass dynamics. Our results indicate that (1) biogeochemical and biogeophysical feedback are attributed more to the changes in NME and snow cover dynamics, respectively; (2) net biogeophysical feedback is much larger than net biogeochemical feedback; (3) NTEs will cause a net positive radiative forcing of 0.04–0.26 W m−2 between 2010 and 2100. Our findings support the notion that NTEs will exert positive net climate feedback; however, our estimation of positive net biogeochemical feedback including NME- and NCE-induced effects is contrary to previous studies showing negative net biogeochemical feedback including NCE-induced effect only. This study highlights the importance of NME-induced biogeochemical effect in regulating ecosystem-climate feedback in NTEs and implies that previous studies without considering NME-induced effect might have underestimated the intensity of total terrestrial feedback to the climate system.
Zhu, X., Zhuang, Q., 2016. Relative importance between biogeochemical and biogeophysical effects in regulating terrestrial ecosystem-climate feedback in northern high latitudes. J. Geophys. Res. Atmos. 121, 5736–5748. doi:10.1002/2016JD024814
June. 13, 2016
Xiaoliang extended his dissertation research on the impacts of lateral water flow on global wetland methane emissions, which was just published in JGR-Biogeosciences, job well done!
The effect of surface water movement on methane emissions is not explicitly considered in most of the current methane models. In this study, a surface water routing was coupled into our previously developed large-scale methane model. The revised methane model was then used to simulate global methane emissions during 2006–2010. From our simulations, the global mean annual maximum inundation extent is 10.6 ± 1.9 km2 and the methane emission is 297 ± 11 Tg C/yr in the study period. In comparison to the currently used TOPMODEL-based approach, we found that the incorporation of surface water routing leads to 24.7% increase in the annual maximum inundation extent and 30.8% increase in the methane emissions at the global scale for the study period, respectively. The effect of surface water transport on methane emissions varies in different regions: (1) the largest difference occurs in flat and moist regions, such as Eastern China; (2) high-latitude regions, hot spots in methane emissions, show a small increase in both inundation extent and methane emissions with the consideration of surface water movement; and (3) in arid regions, the new model yields significantly larger maximum flooded areas and a relatively small increase in the methane emissions. Although surface water is a small component in the terrestrial water balance, it plays an important role in determining inundation extent and methane emissions, especially in flat regions. This study indicates that future quantification of methane emissions shall consider the effects of surface water transport.
Lu, X., Zhuang, Q., Liu, Y., Zhou, Y., Aghakouchak, A., 2016. A large-scale methane model by incorporating the surface water transport. J. Geophys. Res. Biogeosciences 121, 1657–1674. doi:10.1002/2016JG003321
May. 21, 2016
Yueyang just published a study in Global and Planetary Change!
In the circumpolar north (45–90°N), permafrost plays an important role in vegetation and carbon (C) dynamics. Permafrost thawing has been accelerated by the warming climate and exerts a positive feedback to climate through increasing soil C release to the atmosphere. To evaluate the influence of permafrost on C dynamics, changes in soil temperature profiles should be considered in global C models. This study incorporates a sophisticated soil thermal model (STM) into a dynamic global vegetation model (LPJ-DGVM) to improve simulations of changes in soil temperature profiles from the ground surface to 3 m depth, and its impacts on C pools and fluxes during the 20th and 21st centuries. With cooler simulated soil temperatures during the summer, LPJ-STM estimates ~ 0.4 Pg C yr− 1 lower present-day heterotrophic respiration but ~ 0.5 Pg C yr− 1 higher net primary production than the original LPJ model resulting in an additional 0.8 to 1.0 Pg C yr− 1 being sequestered in circumpolar ecosystems. Under a suite of projected warming scenarios, we show that the increasing active layer thickness results in the mobilization of permafrost C, which contributes to a more rapid increase in heterotrophic respiration in LPJ-STM compared to the stand-alone LPJ model. Except under the extreme warming conditions, increases in plant production due to warming and rising CO2, overwhelm the e enhanced ecosystem respiration so that both boreal forest and arctic tundra ecosystems remain a net C sink over the 21st century. This study highlights the importance of considering changes in the soil thermal regime when quantifying the C budget in the circumpolar north.
Jiang, Y., Zhuang, Q., Sitch, S., O’Donnell, J.A., Kicklighter, D., Sokolov, A., Melillo, J., 2016. Importance of soil thermal regime in terrestrial ecosystem carbon dynamics in the circumpolar north. Glob. Planet. Change 142, 28–40. doi:10.1016/j.gloplacha.2016.04.011
May. 3, 2016
Congratulations to Maria, who passed her qualifying exams to continue her PhD program!
May. 3, 2016
Prof. Zhang just published a study in Geoderma!
Understanding the impacts of climate change and agricultural management practices on soil organic carbon (SOC) dynamics is critical for implementing optimal farming practices and maintaining agricultural productivity. This study examines the influence of climatic variables and agricultural management on carbon sequestration potentials in Tai-Lake Paddy soils of China using the DeNitrification-DeComposition (DNDC, version 9.1) model, with a high-resolution soil database (1:50,000). Model simulations considered the effects of no-tillage, the application rates of manure, N fertilization, and crop residue, water management, and changes in temperature and precipitation. We found that the carbon sequestration potential in the top soils (0–30 cm) for the 2.32 Mha paddy soils of the Tai-Lake region varied from 4.71 to 44.31 Tg C under the feasible management practices during the period of 2001–2019. The sequestration potential significantly increased with increasing application of N-fertilizer, manure, conservation tillage, and crop residues, with an annual average SOC changes ranged from 107 to 121 kg C ha− 1 yr− 1, 159 to 326 kg C ha− 1 yr− 1, 78 to 128 kg C ha− 1 yr− 1, and 489 to 1005 kg C ha− 1 yr− 1, respectively. Toward mitigating greenhouse emissions and N losses, no-tillage and increase of crop residue return to soils as well as manure application are recommended for agricultural practice in this region. Our analysis of climate impacts on SOC sequestration suggests that the rice paddies in this region will continue to be a carbon sink under future warming conditions. Specifically, with rising air temperature of 2.0 °C and 4 °C, the average annual SOC changes were 52 and 21 kg C ha− 1 yr− 1, respectively.
Zhang, L., Zhuang, Q., He, Y., Liu, Y., Yu, D., Zhao, Q., Shi, X., Xing, S., Wang, G., 2016. Toward optimal soil organic carbon sequestration with effects of agricultural management practices and climate change in Tai-Lake paddy soils of China. Geoderma 275, 28–39. doi:https://dx.doi.org/10.1016/j.geoderma.2016.04.001.
May. 3, 2016
Congratulations to Zhou, who passed her preliminary exam and became a PhD candidate at Purdue!
Apr. 22, 2016
Zhenong successfully defended his dissertation research, congratulations Dr.Jin! Zhenong has taken a post-doctoral scientist offer from Standford University!
Apr. 22, 2016
Congratulations to Yang! He passed his preliminary exam and became a PhD candidate!
Apr. 22, 2016
Congratulations to Tong! She passed her preliminary exam and became a PhD candidate!
Feb. 15, 2016
Xibao just published his study in Scienceo of The Total Environment. Congratulations!
There are tremendous theoretical, methodological and policy challenges in evaluating the impact of land-use change on the degradation of ecosystem services (ES) at the regional scale. This study addresses these challenges by developing an interdisciplinary methodology based on the Procedure for Ecological Tiered Assessment of Risk (PETAR). This novel methodology integrates ecological models with a land-use change model. This study quantifies the multi-dimensional degradation risks of ES in the Taihu Lake Basin (TLB) of China from 1985 to 2020. Four key ES related to water purification, water quantity adjustment, carbon sequestration and grain production are selected. The study employs models of Denitrification-Decomposition (DNDC), Soil-Water-Atmosphere-Plant (SWAP), Biome-BGC and Agro-ecological Zoning (AEZ) for assimilations. Land-use changes by 2020 were projected using a geographically weighted multinomial logit-cellular automata (GWML-CA) model. The results show that rapid land-use change has posed a great degradation risk of ES in the region in 1985–2020. Slightly less than two-thirds of the basin experienced degradation of ES over the 1985–2010 period, and about 12% of the basin will continue to experience degradation until 2020. Hot spots with severe deterioration in 2010–2020 are projected to be centered around some small and less developed cities in the region. Regulating accelerated urban sprawl and population growth, reinforcing current environmental programs, and establishing monitoring systems for observing dynamics of regional ES are suggested as practical counter-measures.
Xu, X., Yang, G., Tan, Y., Zhuang, Q., Li, H., Wan, R., Su, W., Zhang, J. (2016), Ecological risk assessment of ecosystem services in the Taihu Lake Basin of China from 1985 to 2020. Sci. Total Environ. 554, 7–16. doi:10.1016/j.scitotenv.2016.02.120.
Feb. 15, 2016
Liming just published his study in Agriculture, Ecosystems and Environment.Congratulations!
Agro-ecosystem models have been widely used to quantify soil organic carbon (SOC) dynamics based on digital soil maps. However, most of the studies use soil data of single or limited choices of map scales, thus the influence of map scales on SOC dynamics has rarely been quantified. In this study, six digital paddy soils databases of the Tai-Lake region in China at scales of 1:50,000 (P005), 1:200,000 (P02), 1:500,000 (P05), 1:1,000,000 (P1), 1:4,000,000 (P4), and 1:14,000,000 (P14) were used to drive the DNDC (DeNitrification & DeComposition) model to quantify SOC dynamics for the period of 2001–2019. Model simulations show that the total SOC changes from 2001 to 2019 in the top layer (0–30 cm) of paddy soils using P005, P02, P05, P1, P4, and P14 soil maps would be 3.44, 3.71, 1.41, 2.01, 3.57 and 0.10 Tg C,respectively. The simulated SOC dynamics are significantly influenced by map scales. Taking the total SOC changes based on the most detailed soil map, P005, as a reference, the relative deviation of P02, P05, P1, P4, and P14 were 7.9%, 58.9%, 41.6%, 3.9%, and 97.0%, respectively. Such differences are primarily attributed to missing soil types and spatial variations in soil types in coarse-scale maps. Although the relative deviation of P4 soil map for the entire Tai-Lake region is the lowest, substantial differences (i.e., 22–1010%) exist at soil subgroups level. Overall, soil map scale of P02 provides best accuracy for quantifying SOC dynamics of paddy soils in the study region. Considering the soil data availability of entire China, P1 soil map is also recommended. This study suggested how to select an appropriate scale of input soil data for modeling the carbon cycle of agro-ecosystems.
Zhang, L., Zhuang, Q., Zhao, Q., He, Y., Yu, D., Shi, X., and Xing, S., (2016). Uncertainty of organic carbon dynamics in Tai-Lake paddy soils of China depends on the scale of soil maps. Agric. Ecosyst. Environ. 222, 13–22. doi:10.1016/j.agee.2016.01.049.
Feb. 2, 2016
Shaoqing and Min led a study addressing the direct radiative effects of tropospheric aerosols on changes of global surface soil moisture, published in Climatic Change today!
A coupled modeling framework including a terrestrial ecosystem model and an atmospheric radiative transfer model is used to evaluate the aerosols’ direct radiative effects on the surface soil moisture in global terrestrial ecosystems during 2003–2010.We conduct two sets of model runs with and without aerosols in a hindcast mode. Comparison analysis indicates that the simulated soil moisture is comparable with other existing products and satellite retrievals. Simulations with aerosol loadings show an increase in the surface soil moisture by 3.8 ± 0.4 % and 4.1 ± 0.5 % during growing seasons (June to September) in temperate and boreal Northern Hemisphere (>10 °N) and thewhole year in tropical regions (−10°S~10°N). This positive effect is as large as 30 % in dense-vegetated ecosystems, such as tropical forests and temperate broadleaf evergreen forests. The effect of aerosols on soil moisture varies with local leaf area index and climate, and exhibits seasonal variations. Surface soil moisture is persistently affected by high aerosols loadings in Amazonian tropical forests during drought seasons of 2005 and 2010. This study highlights the importance to consider the aerosols’ effects in impacting the soil moisture dynamics of the global terrestrial ecosystems.
Liu, S., Chen, M., and Zhuang, Q. (2016). Direct radiative effects of tropospheric aerosols on changes of global surface soil moisture. Climatic Change, 1–13. https://doi.org/10.1007/s10584-016-1611-7
Jan. 22, 2016
Shaoqing led a study addressing the atmospheric CO2 effects on gross primary productivity and net ecosystem carbon exchange, published in Agricultural and Forest Meteorology today!
Quantitative understanding of regional gross primary productivity (GPP) and net ecosystem exchanges (NEE) and their responses to environmental changes are critical to quantifying the feedbacks of ecosystems to the global climate system. Numerous studies have used the eddy flux data to upscale the eddy covariance derived carbon fluxes from stand scales to regional and global scales. However, few studies incorporated atmospheric carbon dioxide (CO2) concentrations into those extrapolations. Here, we consider the effect of atmospheric CO2 using an artificial neural network (ANN) approach to upscale the AmeriFlux tower of NEE and the derived GPP to the conterminous United States. Two ANN models incorporating remote sensing variables at an 8-day time step were developed. One included CO2 as an explanatory variable and the other did not. The models were first trained, validated using eddy flux data, and then extrapolated to the region at a 0.05o × 0.05o (latitude × longitude) resolution from 2001 to 2006. We found that both models performed well in simulating site-level carbon fluxes. The spatially-averaged annual GPP with and without considering the atmospheric CO2 were 789 and 788 g C m−2 yr−1, respectively (for NEE, the values were −112 and −109 g C m−2 yr−1, respectively). Model predictions were comparable with previous published results and MODIS GPP products. However, the difference in GPP between the two models exhibited a great spatial and seasonal variability, with an annual difference of 200 g C m−2 yr−1. Further analysis suggested that air temperature played an important role in determining the atmospheric CO2 effects on carbon fluxes. In addition, the simulation that did not consider atmospheric CO2 failed to detect ecosystem responses to droughts in part of the US in 2006. The study suggests that the spatially and temporally varied atmospheric CO2 concentrations should be factored into carbon quantification when scaling eddy flux data to a region.
Liu, S., Zhuang, Q., He, Y., Noormets, A., Chen, J., and Gu, L. (2016). Evaluating atmospheric CO2 effects on gross primary productivity and net ecosystem exchanges of terrestrial ecosystems in the conterminous United States using the AmeriFlux data and an artificial neural network approach. Agricultural and Forest Meteorology, 220, 38–49. https://doi.org/10.1016/j.agrformet.2016.01.007
Jan. 17, 2016
Liming just published his study in Soil and Tillage Research. Congratulations!
Using the DeNitrification-DeComposition (DNDC, version 9.5) model, we investigated the soil organic carbon (SOC) changes from 1980 to 2009 in Eastern China's upland-crop fields in northern Jiangsu Province. A currently most detailed high-resolution soil database, containing 17,024 polygons at a scale of 1:50,000, derived from 983 unique upland soil profiles, was used. A coarser county-level soil database was also used for a pair-wise simulation for comparison. We found that SOC changes modeled with the county-level soil database differ significantly from those with high-resolution soil data, with the deviation ranging from −64% to 8.0% in different counties. This implies that coarse soil data may lead to large biases in SOC simulation. With the high-resolution database, the model estimates a SOC increase of 37.89 Tg C in the top soils (0–50 cm) over the study area of 3.93 Mha for the past three decades, with an average rate of 322 kg C ha−1 year−1. The SOC accumulation in the study region accounts for 10.2% of annual national carbon sequestration of upland soils, compared with the fraction of 3.7% in the total upland area of China. This underscores its significance to national climate mitigation. The annual SOC change varied between 61 to 519 kg C ha−1 year−1, mainly driven by the variations in N-fertilizer and manure applications. This study highlights the significance of high-resolution soil databases in quantifying SOC changes. Our high-resolution estimates of SOC will support farming and carbon management in this region.
Zhang, L., Zhuang, Q., Li, X., Zhao, Q., Yu, D., Liu, Y., Shi, X., Xing, S., and Wang, G., (2016). Carbon sequestration in the uplands of Eastern China: an analysis with high-resolution model simulations. Soil and Tillage Research. 158: 165-176. https://dx.doi.org/10.1016/j.still.2016.01.001.
Jan. 9, 2016
Qing just published his study in Ecosphere. Congratulations!
Reliability of terrestrial ecosystem models highly depends on the quantity and quality of the data that have been used to calibrate the models. Nowadays, in situ observations of carbon fluxes are abundant. However, the knowledge of how much data (data length) and which subset of the time series data (data period) should be used to effectively calibrate the model is still lacking. This study uses the AmeriFlux carbon flux data to parameterize the Terrestrial Ecosystem Model (TEM) with an adjoint-based data assimilation technique for various ecosystem types. Parameterization experiments are thus conducted to explore the impact of both data length and data period on the uncertainty reduction of the posterior model parameters and the quantification of site and regional carbon dynamics. We find that: (1) the model is better constrained when it uses two-year data comparing to using one-year data. Further, two-year data is sufficient in calibrating TEM's carbon dynamics, since using three-year data could only marginally improve the model performance at our study sites; (2) the model is better constrained with the data that have a higher “climate variability” than that having a lower one. The climate variability is used to measure the overall possibility of the ecosystem to experience all climatic conditions including drought and extreme air temperatures and radiation; (3) the U.S. regional simulations indicate that the effect of calibration data length on carbon dynamics is amplified at regional and temporal scales, leading to large discrepancies among different parameterization experiments, especially in July and August. Our findings are conditioned on the specific model we used and the calibration sites we selected. The optimal calibration data length may not be suitable for other models. However, this study demonstrates that there may exist a threshold for calibration data length and simply using more data would not guarantee a better model parameterization and prediction. More importantly, climate variability might be an effective indicator of information within the data, which could help data selection for model parameterization. We believe our findings will benefit the ecosystem modeling community in using multiple-year data to improve model predictability.
Zhu, Q., and Zhuang, Q., (2015). Ecosystem biogeochemistry model parameterization: Do more flux data result in a better model in predicting carbon flux? Ecosphere 6(12):283. https://dx.doi.org/10.1890/ES15-00259.1.
Jan. 8, 2016
Jan. 3, 2016
Zeli just published his study in JGR-Biogeosciences. Congratulations!
The importance of methane emissions from pan-Arctic lakes in the global carbon cycle has been suggested by recent studies. These studies indicated that climate change influences this methane source mainly in two ways: the warming of lake sediments and the evolution of thermokarst lakes. Few studies have been conducted to quantify the two impacts together in a unified modeling framework. Here we adapt a region-specific lake evolution model to the pan-Arctic scale and couple it with a lake methane biogeochemical model to quantify the change of this freshwater methane source in the 21st century. Our simulations show that the extent of thaw lakes will increase throughout the 21st century in the northern lowlands of the pan-Arctic where the reworking of epigenetic ice in drained lake basins will continue. The projected methane emissions by 2100 are 28.3 ± 4.5 Tg CH4 yr−1 under a low warming scenario (Representative Concentration Pathways (RCPs) 2.6) and 32.7 ± 5.2 Tg CH4 yr−1 under a high warming scenario (RCP 8.5), which are about 2.5 and 2.9 times the simulated present-day emissions. Most of the emitted methane originates from nonpermafrost carbon stock. For permafrost carbon, the methanogenesis will mineralize a cumulative amount of 3.4 ± 0.8 Pg C under RCP 2.6 and 3.9 ± 0.9 Pg C under RCP 8.5 from 2006 to 2099. The projected emissions could increase atmospheric methane concentrations by 55.0–69.3 ppb. This study further indicates that the warming of lake sediments dominates the increase of methane emissions from pan-Arctic lakes in the future.
Tan, Z., and Zhuang, Q., (2015), Methane emissions from pan-Arctic lakes during the 21st century: An analysis with process-based models of lake evolution and biogeochemistry, J. Geophys. Res. Biogeosci., 120, doi:10.1002/2015JG003184.PDF
Dec. 29, 2015
Yujie just published her study in JGR-Biogeosciences. Congratulations!
Soil carbon dynamics of terrestrial ecosystems play a significant role in the global carbon cycle. Microbial-based decomposition models have seen much growth recently for quantifying this role, yet dormancy as a common strategy used by microorganisms has not usually been represented and tested in these models against field observations. Here we developed an explicit microbial-enzyme decomposition model and examined model performance with and without representation of microbial dormancy at six temperate forest sites of different forest types. We then extrapolated the model to global temperate forest ecosystems to investigate biogeochemical controls on soil heterotrophic respiration and microbial dormancy dynamics at different temporal-spatial scales. The dormancy model consistently produced better match with field-observed heterotrophic soil CO2 efflux (RH) than the no dormancy model. Our regional modeling results further indicated that models with dormancy were able to produce more realistic magnitude of microbial biomass (<2% of soil organic carbon) and soil RH (7.5 ± 2.4 Pg C yr−1). Spatial correlation analysis showed that soil organic carbon content was the dominating factor (correlation coefficient = 0.4–0.6) in the simulated spatial pattern of soil RH with both models. In contrast to strong temporal and local controls of soil temperature and moisture on microbial dormancy, our modeling results showed that soil carbon-to-nitrogen ratio (C:N) was a major regulating factor at regional scales (correlation coefficient = −0.43 to −0.58), indicating scale-dependent biogeochemical controls on microbial dynamics. Our findings suggest that incorporating microbial dormancy could improve the realism of microbial-based decomposition models and enhance the integration of soil experiments and mechanistically based modeling.
He, Y., Yang, J., Zhuang, Q., Harden, J. W., McGuire, A. D., Liu, Y., Wang, G., and Gu, L., (2015), Incorporating microbial dormancy dynamics into soil decomposition models to improve quantification of soil carbon dynamics of northern temperate forests, J. Geophys. Res. Biogeosci., 120, doi:10.1002/2015JG003130.D-14-0030.1 PDF.
Dec. 11, 2015
Congratulations to Sirui, who passed his qualifying exams to continue his PhD program!
Dec. 11, 2015
Congratulations to Zeli! He accepted a Post-Doctoral Scientist offer from the Pacific Northwest National Laboratory!
Dec. 10, 2015
Congratulations to Licheng Liu who passed his PhD qualifying exams!
Dec. 5, 2015
Chang led a study on quantifying the drought impact on global plant production, which was just published in Earth Interactions. Congratulations!
Droughts dramatically affect plant production of global terrestrial ecosystems. To date, quantification of this impact remains a challenge because of the complex plant physiological and biochemical processes associated with drought. Here, this study incorporates a drought index into an existing process-based terrestrial ecosystem model to estimate the drought impact on global plant production for the period 2001–10. Global Moderate Resolution Imaging Spectroradiometer (MODIS) gross primary production (GPP) data products are used to constrain model parameters and verify the model algorithms. The verified model is then applied to evaluate the drought impact. The study indicates that droughts will reduce GPP by 9.8 g C m-2month-1 during the study period. On average, drought reduces GPP by 10% globally. As a result, the global GPP decreased from 106.4 to 95.9 Pg C yr-1 while the global net primary production (NPP) decreased from 54.9 to 49.9 Pg C yr-1. This study revises the estimation of the global NPP and suggests that the future quantification of the global carbon budget of terrestrial ecosystems should take the drought impact into account.
Liao, C and Zhuang, Q., (2015), Reduction of Global Plant Production due to Droughts from 2001 to 2010: An Analysis with a Process-Based Global Terrestrial Ecosystem Model. Earth Interact., 19, 1–21. doi: https://dx.doi.org/10.1175/EI-
Nov. 20, 2015
November 20, 2015. Zhou successfully defended her MS thesis, Congratulations!
Nov. 10, 2015
November 10, 2015. Tong successfully defended her MS thesis, Congratulations!
Oct. 2, 2015
October 2, 2015. Zeli successfully defended his dissertation research, entitled “Quantifying Terrestrial And Aquatic Ecosystem Methane Emissions With Process-Based Biogeochemical And Atmospheric Transport And Chemistry Models”. Congratulations Dr. Tan!
Sep. 11, 2015
Sept. 14, 2015 - Congratulations to Guangcun led a study published in Climactic Change!
There is a pressing need to develop earth system models (ESMs), in which ecosystem processes are adequately represented, to quantify carbon-climate feedbacks. In particular, explicit representation of the effects of microbial activities on soil organic carbon decomposition has been slow in ESM development. Here we revised an existing Q10-based heterotrophic respiration (RH) algorithm of a large-scale biogeochemical model, the Terrestrial Ecosystem Model (TEM), by incorporating the algorithms of Dual Arrhenius and Michaelis-Menten kinetics and microbial-enzyme interactions. The microbial physiology enabled model (MIC-TEM) was then applied to quantify historical and future carbon dynamics of forest ecosystems in the conterminous United States. Simulations indicate that warming has a weaker positive effect on RH than that traditional Q10 model has. Our results demonstrate that MIC-TEM is superior to traditional TEM in reproducing historical carbon dynamics. More importantly, the future trend of soil carbon accumulation simulated with MIC-TEM is more reasonable than TEM did and is generally consistent with soil warming experimental studies. The revised model estimates that regional GPP is 2.48 Pg C year−1 (2.02 to 3.03 Pg C year−1) and NEP is 0.10 Pg C year−1 (−0.20 to 0.32 Pg C year−1) during 2000–2005. Both models predict that the conterminous United States forest ecosystems are carbon sinks under two future climate scenarios during the 21st century. This study suggests that terrestrial ecosystem models should explicitly consider the microbial ecophysiological effects on soil carbon decomposition to adequately quantify forest ecosystem carbon fluxes at regional scales.
Hao, G., Zhuang, Q., Zhu, Q., He, Y., Jin, Z., and Shen, W. (2015). Quantifying microbial ecophysiological effects on the carbon fluxes of forest ecosystems over the conterminous United States. Climatic Change, 1-14. doi: 10.1007/s10584-015-1490-3
In collaboration with several national and international institutions, our lab just published a study on the relation between methane emissions from northern wetlands and see ice decline in Geophysical Research Letters!
The Arctic is rapidly transitioning toward a seasonal sea ice-free state, perhaps one of the most apparent examples of climate change in the world. This dramatic change has numerous consequences, including a large increase in air temperatures, which in turn may affect terrestrial methane emissions. Nonetheless, terrestrial and marine environments are seldom jointly analyzed. By comparing satellite observations of Arctic sea ice concentrations to methane emissions simulated by three process-based biogeochemical models, this study shows that rising wetland methane emissions are associated with sea ice retreat. Our analyses indicate that simulated high-latitude emissions for 2005–2010 were, on average, 1.7 Tg CH4 yr−1 higher compared to 1981–1990 due to a sea ice-induced, autumn-focused, warming. Since these results suggest a continued rise in methane emissions with future sea ice decline, observation programs need to include measurements during the autumn to further investigate the impact of this spatial connection on terrestrial methane emissions.
Parmentier, F. J. W., Zhang, W., Mi, Y., Zhu, X., Huissteden, J., Hayes, D. J., Zhuang, Q., Christensen, T. R., and David McGuire, A. (2015). Rising methane emissions from northern wetlands associated with sea ice decline. Geophysical Research Letters. doi : 10.1002/2015GL065013.
Sep. 11, 2015
Our lab has just published a study on quantifying the dynamics of CO2 and CH4 of the terrestrial ecosystems in the Arctic in Environmental Research Letter.
Estimates of the seasonal and interannual exchanges of carbon dioxide (CO2) and methane (CH4) between land ecosystems north of 45 N and the atmosphere are poorly constrained, in part, because of uncertainty in the temporal variability of water-inundated land area. Here we apply a process-based biogeochemistry model to evaluate how interannual changes in wetland inundation extent might have influenced the overall carbon dynamics of the region during the time period 1993-2004. We find that consideration by our model of these interannual variations between 1993 and 2004, on average, results in regional estimates of net methane sources of 67.86.2 Tg CH4 yr-1, which is intermediate to model estimates that use two static inundation extent datasets (51.3±2.6 and 73.0±3.6 Tg CH4 yr-1). In contrast, consideration of interannual changes of wetland inundation extent result in regional estimates of the net CO2 sink of -1.28±0.03 Pg C yr-1 with a persistent wetland carbon sink from -0.38 to -0.41 Pg C yr-1 and a upland sink from -0.82 to -0.98 Pg C yr-1. Taken together, despite the large methane emissions from wetlands, the region is a consistent greenhouse gas sink per global warming potential (GWP) calculations irrespective of the type of wetland datasets being used. However, the use of satellite-detected wetland inundation extent estimates a smaller regional GWP sink than that estimated using static wetland datasets. Our sensitivity analysis indicates that if wetland inundation extent increases or decreases by 10% in each wetland grid cell, the regional source of methane increases 13% or decreases 12%, respectively. In contrast, the regional CO2 sink responds with only 7-9% changes to the changes in wetland inundation extent. Seasonally, the inundated area changes result in higher summer CH4 emissions, but lower summer CO2 sinks, leading to lower summer negative greenhouse gas forcing. Our analysis further indicates that wetlands play a disproportionally important role in affecting regional greenhouse gas budgets given that they only occupy approximately 10% of the total land area in the region.
Zhuang, Q., Zhu, X., He, Y., Prigent, C., Melillo, J. M., McGuire, A. D., Prinn, R. G., and Kicklighter, D. W. (2015), Influence of changes in wetland inundation extent on net fluxes of carbon dioxide and methane in northern high latitudes from 1993 to 2004, Environ. Res. Lett. 10 (2015) 095009.
Sep. 2, 2015
Our lab was just funded with a project entitled "Understanding mechanistic controls of heterotrophic CO2 and CH4 fluxes in a peatland with deep soil warming and atmospheric CO2 enrichment” by DOE in collaboration with Dr. Jason Keller and Dr. Scott Bridgham at Chapman University and University of Oregon. The overall objective of this renewal is to expand our mechanistic understanding of how deep warming of peat and CO2 enrichment in a bog affect C mineralization and CH4 dynamics and to incorporate that understanding into Earth system models.
Sep. 2, 2015
Welcome Junrong Zha to our lab for pursuing her PhD at Purdue! Junrong hasa BS degree of Atmospheric Sciences from the University of Science and Technology of China.
Aug. 28, 2015
Prof. Liming Zhang, a visiting professor at Purdue during the 2014-201 academic year, published a paper on Soil and Tillage Research. Congratulations!
Rising temperatures and elevated atmospheric CO2 are two factors that simultaneously affect the dynamics of soil organic carbon (SOC). This study separately examines the effects arise from these two factors in Tai-Lake Paddy soils using DeNitrification–DeComposition (DNDC) model, with the currently most detailed soil database for the paddy region of China. The soil database is at a scale of 1:50,000, containing 52,034 paddy soil polygons derived from 1107 unique paddy soil profiles. Our simulations indicate that, the SOC in the top soils (0-30 cm) increases 0.83,1.09,1.32, and 1.51 Tg C under conventional management (3.44 Tg C) in the 2.32 Mha paddy soils of the Tai-Lake region from 2001 to 2019, respectively, with the atmospheric CO2 concentration increases at 1.5, 2.0, 2.5, and 3.0 times the normal rate (1.9 ppm year-1). By contrast, with rising air temperature of 0.5, 1.0, 1.5, 2.0, 3.0, and 4.0, the SOC decreases 0.09, 0.54, 0.69, 1.13, 1.80, and 2.51 Tg C under conventional management, respectively. Thus, the effect of carbon sink induced from CO2 fertilization at the 2.0 times normal CO2 concentration increase rate could generally offset the effect of carbon source resulted from a 2.0 C air temperature increase. In addition, the paddy soils in this region tend to persistently be a sink of atmospheric CO2 under warming and elevated CO2 scenarios, even if when the air temperature has increased by 4 C. These results suggest that SOC storage in paddy soils of this region is prone to benefit from future global climate change and this carbon sequestration potential in the agro-ecosystems is likely to contribute to climate mitigation under current agricultural practices, despite any negative effects derived from warming. As a representative of paddy soils in eastern China, the insights gained from the Tai-Lake region may be potentially transferable to other paddy soils in eastern China where 95% of the total of China is located.
Wang, G., Zhang, L., Zhuang, Q., Yu, D., Shi, X., Xing, S., Xiong, D., Liu, Y. Quantification of the soil organic carbon balance in the Tai-Lake paddy soils of China, Soil and Tillage Research, Volume 155, January 2016, Pages 95-106, ISSN 0167-1987, https://dx.doi.org/10.1016/j.still.2015.08.003.
Aug. 10, 2015
Zhenong led a study published in Environmental Research Letters today! Congratulations!
Methane (CH4) is a potent greenhouse gas (GHG) that affects the global climate system. Knowledge about land–atmosphericCH4 exchanges on the Qinghai-Tibetan Plateau (QTP) is insufficient. Using a coupled biogeochemistry model, this study analyzes the net exchanges ofCH4 andCO2 over the QTP for the period of 1979–2100. Our simulations show that the region currently acts as a netCH4 source with 0.95 TgCH4 y−1 emissions and 0.19 TgCH4 y−1 soil uptake, and a photosynthesis Csink of 14.1 TgCy−1. By accounting for the netCH4 emission and the netCO2 sequestration since 1979, the region was found to be initially a warming source until the 2010s with a positive instantaneous radiative forcing peak in the 1990s. In response to future climate change projected by multiple global climate models (GCMs) under four representative concentration pathway (RCP) scenarios, the regional source ofCH4 to the atmosphere will increase by 15–77% at the end of this century. Net ecosystem production (NEP) will continually increase from the near neutral state to around 40 TgC y−1 under all RCPs except RCP8.5. Spatially,CH4 emission or uptake will be noticeably enhanced under all RCPs over most of the QTP, while statistically significant NEP changes over a large-scale will only appear under RCP4.5 and RCP4.6 scenarios. The cumulativeGHGfluxes since 1979 will exert a slight warming effect on the climate system until the 2030s, and will switch to a cooling effect thereafter. Overall, the total radiative forcing at the end of the 21st century is 0.25–0.35Wm−2, depending on the RCP scenario. Our study highlights the importance of accounting for bothCH4 and CO2 in quantifying the regionalGHGbudget.
Jin, Z., Zhuang, Q., He, J. S., Zhu, X. and Song, W. (2015). Net exchanges of methane and carbon dioxide on the Qinghai-Tibetan Plateau from 1979 to 2100.Environmental Research Letters, 10(8), 085007
Aug. 10, 2015
In collaboration with Peking University, our lab published a study focusing on Tibetan wetland methane emissions in JGR-Biogeoscience.
The vast wetlands on the Tibetan Plateau are expected to be an important natural source of methane (CH4) to the atmosphere. The magnitude, patterns and environmental controls of CH4 emissions on different timescales, especially during the nongrowing season, remain poorly understood, because of technical limitations and the harsh environments. We conducted the first study on year-round CH4 fluxes in an alpine wetland using the newly developed LI-COR LI-7700 open-path gas analyzer. We found that the total annual CH4 emissions were 26.4 and 33.8 g CH4 m−2in 2012 and 2013, respectively, and the nongrowing season CH4 emissions accounted for 43.2–46.1% of the annual emissions, highlighting an indispensable contribution that was often overlooked by previous studies. A two-peak seasonal variation in CH4fluxes was observed, with a small peak in the spring thawing period and a large one in the peak growing season. We detected a significant difference in the diurnal variation of CH4 fluxes between the two seasons, with two peaks in the growing season and one peak in the nongrowing season. We found that the CH4 fluxes during the growing season were well correlated with soil temperature, water table depth and gross primary production, whereas the CH4 fluxes during the nongrowing season were highly correlated with soil temperature. Our results suggested that the CH4emission during the nongrowing season cannot be ignored and the vast wetlands on the Tibetan plateau will have the potential to exert a positive feedback on climate considering the increasing warming, particularly in the nongrowing season in this region.
Song, W., Wang, H., Wang, G., Chen, L., Jin, Z., Zhuang, Q. and He, J. S. (2015). Methane emissions from an alpine wetland on the Tibetan Plateau: Neglected but vital contribution of non‐growing season. J. Geophys. Res. Biogeosci., 120, doi:10.1002/2015JG003043
July. 9, 2015
Yaling led a study published in Nature- Scientific report today! Congratulations!
Northern China is one of the most densely populated regions in the world. Agricultural activities have intensified since the 1980s to provide food security to the country. However, this intensification has likely contributed to an increasing scarcity in water resources, which may in turn be endangering food security. Based on in-situ measurements of soil moisture collected in agricultural plots during 1983–2012, we find that topsoil (0–50 cm) volumetric water content during the growing season has declined significantly (p < 0.01), with a trend of −0.011 to −0.015 m3 m−3 per decade. Observed discharge declines for the three large river basins are consistent with the effects of agricultural intensification, although other factors (e.g. dam constructions) likely have contributed to these trends. Practices like fertilizer application have favoured biomass growth and increased transpiration rates, thus reducing available soil water. In addition, the rapid proliferation of water-expensive crops (e.g., maize) and the expansion of the area dedicated to food production have also contributed to soil drying. Adoption of alternative agricultural practices that can meet the immediate food demand without compromising future water resources seem critical for the sustainability of the food production system.
Liu, Y., Pan, Z., Zhuang, Q., Miralles, D., Teuling, A., Zhang, T., An, P., Dong, Z., Zhang, J., He, D., Wang L., Pan, X., Bai, W and Niyogi (2015), D Agriculture intensifies soil moisture decline in Northern China. Sci. Rep. 5, 11261; doi: 10.1038/srep11261.
May. 19, 2015
Zeli led a study that was published in Environ. Res. Lett today, congratulations!
Methane is the second most powerful carbon-based greenhouse gas in the atmosphere and its production in the natural environment through methanogenesis is positively correlated with temperature. Recent field studies showed that methane emissions from Arctic thermokarst lakes are significant and could increase by two- to four-fold due to global warming. But the estimates of this source are still poorly constrained. By using a process-based climate-sensitive lake biogeochemical model, we estimated that the total amount of methane emissions from Arctic lakes is 11.86 Tg yr−1, which is in the range of recent estimates of 7.1–17.3 Tg yr−1 and is on the same order of methane emissions from northern high-latitude wetlands. The methane emission rate varies spatially over high latitudes from 110.8 mg CH4 m−2 day−1 in Alaska to 12.7 mg CH4 m−2 day−1 in northern Europe. Under Representative Concentration Pathways (RCP) 2.6 and 8.5 future climate scenarios, methane emissions from Arctic lakes will increase by 10.3 and 16.2 Tg CH4 yr−1, respectively, by the end of the 21st century.
April. 22, 2015
Congratulations to Zhenong receiving Bilsland Dissertation Fellowship for Spring 2016. This is a highly competitive and prestigious award. The Bilsland Dissertation Fellowship provides support to outstanding Ph.D. candidate in their final year of doctoral degree completion. Bilsland Fellows are expected to devote full-time efforts to the completion of all doctoral degree requirements and to receive the doctoral degree at the conclusion of the fellowship tenure
April. 12, 2015
Zeli led a study that was published in Journal of Advances in Modeling Earth Systems today, congratulations!
To date, methane emissions from lakes in the panarctic region are poorly quantified. In order to investigate the response of methane emissions from this region to global warming, a process-based climate-sensitive lake biogeochemical model was developed. The processes of methane production, oxidation, and transport were modeled within a one-dimensional sediment and water column. The sizes of 14C-enriched and 14C-depleted carbon pools were explicitly parameterized. The model was validated using observational data from five lakes located in Siberia and Alaska, representing a large variety of environmental conditions in the arctic. The model simulations agreed well with the measured water temperature and dissolved CH4 concentration (mean error less than 1C and 0.2 uM, respectively). The modeled CH4 fluxes were consistent with observations in these lakes. We found that bubbling-rate-controlling nitrogen (N2) stripping was the most important factor in determining CH4 fraction in bubbles. Lake depth and ice cover thickness in shallow waters were also controlling factors. This study demonstrated that the thawing of Pleistocene-aged organic-rich yedoma can fuel sediment methanogenesis by supplying a large quantity of labile organic carbon. Observations and modeling results both confirmed that methane emission rate at thermokarst margins of yedoma lakes was much larger (up to 538 mg CH4 m-2 d-1) than that at nonthermokarst zones in the same lakes and a nonyedoma, nonthermokarst lake (less than 42 mg CH4 m-2 d-1).The seasonal variability of methane emissions can be explained primarily by energy input and organic carbon availability.
Tan, Z., Zhuang, Q., & Walter Anthony, K. (2015). Modeling methane emissions from arctic lakes: Model development and site‐level study. Journal of Advances in Modeling Earth Systems, doi: 10.1002/2014MS000344
April. 6, 2015
Yaling led a study that was published in Journal of Geophysical Research – Atmosphere today, congratulations! Yaling completed her PhD dissertation research in December of 2014, now she is a Post-Doctoral Scientist at the Pacific Northwest National Laboratory.
The ecosystems in Northern Eurasia (NE) play an important role in the global water cycle and the climate system. While evapotranspiration (ET) is a critical variable to understand this role, ET over this region remains largely unstudied. Using an improved version of the Terrestrial Ecosystem Model with five widely used forcing data sets, we examine the impact that uncertainties in climate forcing data have on the magnitude, variability, and dominant climatic drivers of ET for the period 1979–2008. Estimates of regional average ET vary in the range of 241.4–335.7 mm yr−1 depending on the choice of forcing data. This range corresponds to as much as 32% of the mean ET. Meanwhile, the spatial patterns of long-term average ET across NE are generally consistent for all forcing data sets. Our ET estimates in NE are largely affected by uncertainties in precipitation (P), air temperature (T), incoming shortwave radiation (R), and vapor pressure deficit (VPD). During the growing season, the correlations between ET and each forcing variable indicate that T is the dominant factor in the north and P in the south. Unsurprisingly, the uncertainties in climate forcing data propagate as well to estimates of the volume of water available for runoff (here defined as P-ET). While the Climate Research Unit data set is overall the best choice of forcing data in NE according to our assessment, the quality of these forcing data sets remains a major challenge to accurately quantify the regional water balance in NE.
Liu, Y., Zhuang, Q., Miralles, D., Pan, Z., Kicklighter, D., Zhu, Q., He, Y., Chen, J., Tchebakova, N., Sirin, A., Niyogi, D., & Melillo, J. (2015). Evapotranspiration in Northern Eurasia: Impact of forcing uncertainties on terrestrial ecosystem model estimates. Journal of Geophysical Research: Atmospheres,
Congratulations to Shaoqing and Chang, both passed their Preliminary Exams and became PhD candidates!
Feb. 12, 2015
Congratulations to Guangcun! He accepted a Research Scientist offer from the Southern China Botanical Garden, Chinese Academy of Sciences, to continue his soil biogeochemical modeling research.
January 12, 2015
Welcome Maria joining our lab to pursue her doctoral degree at Purdue!
December 22, 2014
A study led by Zhangcai is highlighted by the journal of GCB Bioenergy!
Carbon and nitrogen dynamics in bioenergy ecosystems: 2. Potential greenhouse gas emissions and global warming intensity in the conterminous United States Biofuel made from conventional and cellulosic crops such as maize, switchgrass and Miscanthus is an alternative to fossil fuels. Biofuels are thought to mitigate greenhouse gas (GHG) emissions by removing carbon dioxide from the atmosphere during their growth. As interest in bioenergy develops, it is important to quantify the GHG mitigation potential of the crops. One method of estimating biofuel production and GHG mitigation is through a mechanistic model. A mechanistic model can produce results that resemble observations of a natural, observed phenomenon. Zhangcai Qin and his coauthors developed an agroecosystem model (AgTEM) that incorporates biogeochemical and ecosystem processes that include crop phenology, biomass allocation, nitrification and denitrification as well as agronomic management of irrigation and fertilization. AgTEM is based on the Terrestrial Ecosystem Model (TEM). It is one of the most commonly used ecosystem models for estimating carbon, nitrogen and water dynamics. TEM was modified by the authors for use on a bioenergy agroecosystem level in the United States, an area that is under-studied and not encompassed by TEM. AgTEM provides the ability to investigate crop yield, biomass, net carbon exchange, and nitrous oxide emissions. Using the model, the authors compared potential greenhouse gas (GHG) emissions from maize (Zea mays L.), switchgrass (Panicum virgatum L.) and Miscanthus (Miscanthus x giganteus) grown on current maize-producing areas in the United States. Among the three plants, they found that Miscanthus is the most productive biofuel and is responsible for the lowest GHG emissions. Miscanthus can even act as a source of GHG capture if no nitrogen is applied. Switchgrass still offers significant GHG savings but is not as productive as Miscanthus in terms of producing biofuel. More land would be required into order to find switchgrass more productive. If Miscanthus is substituted for maize to produce biofuel, then potential land savings and lower GHG emissions may be found. The authors suggest that maize grain for ethanol production could lower GHG emissions if a high-yield hybrid is bred and agriculture management improvements are made. Caution is suggested when using the model for multiple-year and large-scale simulations as the results may not be accurate and could be deleterious when advising farm management practices. The model used in this study is best suited for evaluating ecosystem services and environmental impacts.
Qin, Z., Zhuang, Q. and Zhu, X. (2013), Carbon and nitrogen dynamics in bioenergy ecosystems: 2. Potential greenhouse gas emissions and global warming intensity in the conterminous United States. GCB Bioenergy. doi: 10.1111/gcbb.12106
December 22, 2014
Zhou passed her qualifying exam for her PhD program, congratulations!
December 22, 2014
Tong passed her qualifying exam for her PhD program, congratulations!
November 25, 2014
Congratulations to Shaoqing and Min, who led an study published in Geophysical Research Letters!
Liu, S., M. Chen, and Q. Zhuang (2014), Aerosol effects on global land surface energy fluxes during 2003–2010, Geophys. Res. Lett., 41, doi:10.1002/2014GL061640
Abstract:Aerosols affect downward solar radiation, impacting the terrestrial carbon cycle and energy budget. Here we apply a coupled modeling framework of a terrestrial ecosystem model and an atmospheric radiative transfer model to evaluate aerosol direct radiative effects, and in turn, their effects on the surface heat fluxes of global terrestrial ecosystems during 2003-2010. We find that aerosols loadings decrease the mean latent heat flux by 2.4W m-2(or evapotranspiration by 28 mm) and sensible heat flux by 16.0W m-2. As a result, global mean soil moisture as well as the evaporative fraction has increased by 0.5% and 4.0%, respectively. Spatially, aerosol effects are significant in the tropical forest and temperate broadleaf evergreen forest. This study is among the first studies to quantify aerosols effects on the heat fluxes in the global terrestrial ecosystems. The study suggests that both direct and indirect aerosol radiative effects through aerosol-cloud interactions should be considered to quantify the global energy budget in future.
November 22, 2014
Yang passed his qualifying exam for his PhD program, congratulations!
November 25, 2014
Congratulations to Prof. Zhuang being selected as the University Faculty Scholar at Purdue! This award is a well-deserved recognition of his contributions to the research mission of Purdue.
October 27th, 2014
Yujie passed her PhD final exam today. Congratulations Dr. He! Yujie will start her Post-doc position at U. of California at Irvine in December, 2014.
October 18th, 2014
Zhangcai led a biofuel study has been just published and featured on the cover: https://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291757-1707/homepage/qin.htm
fossil fuels. Biofuels are thought to mitigate greenhouse gas (GHG) emissions by removing carbon dioxide from the atmosphere during their growth. As interest in bioenergy develops, it is important to quantify the GHG mitigation potential of the crops. One method of estimating biofuel production and GHG mitigation is through a mechanistic model. A mechanistic model can produce results that resemble observations of a natural, observed phenomenon.
Zhangcai Qin and his coauthors developed an agroecosystem model (AgTEM) that incorporates biogeochemical and ecosystem processes that include crop phenology, biomass allocation, nitrification and denitrification as well as agronomic management of irrigation and fertilization. AgTEM is based on the Terrestrial Ecosystem Model (TEM). It is one of the most commonly used ecosystem models for estimating carbon, nitrogen and water dynamics. TEM was modified by the authors for use on a bioenergy agroecosystem level in the United States, an area that is under-studied and not encompassed by TEM. AgTEM provides the ability to investigate crop yield, biomass, net carbon exchange, and nitrous oxide emissions.
AgTEM was validated by plotting simulations against observed data sets from 29 field experiment sites, including 82 site-treatment (i.e., N input level) observational sets. The sites include bioenergy ecosystems of maize, switchgrass, and Miscanthus. AgTEM simulations of crop net primary productivity, the rate at which plants incorporate atmospheric carbon through photosynthesis, was consistent with the observational data sets. N2O emissions were well-estimated in the model, with AgTEM providing satisfactory estimates under complex circumstances. Biomass was estimated from NPP values. Yield was determined using the previously mentioned biomass values in an existing model (Lobell, 2004 and Monfreda et al. 2008) that incorporates parameters necessary for accurately estimating anticipated yield.
The authors note that AgTEM requires fine-tuning because there are minor uncertainties when utilizing such a model. Other agricultural management techniques such as tillage and crop rotation were not considered and may affect biomass and N2O emissions. The observational data could be biased because of experimental uncertainty. More observational data is especially needed for Miscanthus and switchgrass in order to reduce uncertainties. AgTEM currently operates at a regional level. Local climate, soil and vegetation data are required for site-specific simulations.
Qin, Z., Zhuang, Q. and Zhu, X. (2013), Carbon and nitrogen dynamics in bioenergy ecosystems: 1. Model development, validation and sensitivity analysis. GCB Bioenergy. doi: 10.1111/gcbb.12107
Zhangcai obtained his PhD in 2013. Currently he is a Post-Dotoral Scientist at Argonne National Laboratory
October 2nd, 2014
Welcome our new PhD students: Licheng Liu from School of Physics of Peking University, Sirui Wang from the Department of Earth and Space Sciences of the University of Science and Technology of China (USTC), and Peng Zhu from the Institute of Remote Sensing and Application of the Chinese Academy of Sciences!
Congratulations to Yujie, who accepted a Post-Docoral Scientist offer from University of California – Irvine!
Congratulations to Yaling, who accepted a Post-Doctoral Scientist offer from Pacific Northwest National Laboratory!
Yaling passed her PhD dissertation defense, congratulations, Dr. Liu!
Congratulations to Yujie! She has a new study published today!
Citation: He, Y., J. Yang, Q. Zhuang, A. D. McGuire, Q. Zhu, Y. Liu, and R. O. Teskey (2014), Uncertainty in the fate of soil organic carbon: A comparison of three conceptually different decomposition models at a larch plantation, J. Geophys. Res. Biogeosci., 119, doi:10.1002/2014JG002701.
Conventional Q10 soil organic matter decomposition models and more complex microbial models are available for making projections of future soil carbon dynamics. However, it is unclear (1) how well the conceptually different approaches can simulate observed decomposition and (2) to what extent the trajectories of long-term simulations differ when using the different approaches. In this study, we compared three structurally different soil carbon (C) decomposition models (one Q10 and two microbial models of different complexity), each with a one- and two-horizon version. The models were calibrated and validated using 4 years of measurements of heterotrophic soil CO2 efflux from trenched plots in a Dahurian larch (Larix gmelinii Rupr.) plantation. All models reproduced the observed heterotrophic component of soil CO2 efflux, but the trajectories of soil carbon dynamics differed substantially in 100 year simulations with and without warming and increased litterfall input, with microbial models that produced better agreement with observed changes in soil organic C in long-term warming experiments. Our results also suggest that both constant and varying carbon use efficiency are plausible when modeling future decomposition dynamics and that the use of a short-term (e.g., a few years) period of measurement is insufficient to adequately constrain model parameters that represent long-term responses of microbial thermal adaption. These results highlight the need to reframe the representation of decomposition models and to constrain parameters with long-term observations and multiple data streams. We urge caution in interpreting future soil carbon responses derived from existing decomposition models because both conceptual and parameter uncertainties are substantial.
Congratulations to Yaling, who has an excellent study published in Climatic Change!
Citation: Liu, Y., Q. Zhuang, Z. Pan, D. Miralles, N. Tchebakova, D. Kicklighter, J. Chen, A. Sirin, Y. He and G. Zhou (2014). Response of evapotranspiration and water availability to the changing climate in Northern Eurasia. Climatic Change: 1-15.
Northern Eurasian ecosystems play an important role in the global climate system. Northern Eurasia (NE) has experienced dramatic climate changes during the last half of the 20th century and to present. To date, how evapotranspiration (ET) and water availability (PET, Northern Eurasian ecosystems play an important role in the global climate system. Northern Eurasia (NE) has experienced dramatic climate changes during the last half of the precipitation had changed in response to the climatic change in this region has not been well evaluated. This study uses an improved version of the Terrestrial Ecosystem Model (TEM) that explicitly considers ET from uplands, wetlands, water bodies and snow cover to examine temporal and spatial variations in ET, water availability and river discharge in NE for the period 1948–2009. The average ET over NE increased during the study period at a rate of 0.13 mm year−1 year−1. Over this time, water availability augmented in the western part of the region, but decreased in the eastern part. The consideration of snow sublimation substantially improved the ETestimates and highlighted the importance of snow in the hydrometeorology of NE. We also find that the modified TEM estimates of water availability in NE watersheds are in good agreement with corresponding measurements of historical river discharge before 1970. However, a systematic underestimation of river discharge occurs after 1970 indicates that other water sources or dynamics not considered by the model (e.g., melting glaciers, permafrost thawing and fires) may also be important for the hydrology of the region.