Modeling impacts of climate change on carbon dynamics in a steppe ecosystem in Inner Mongolia, China
- 457 Downloads
In this study, a process-oriented biogeochemistry model, denitrification–decomposition (DNDC), was employed and adapted to interpret and integrate the field observations that the tested ecosystem was a weak sink of atmospheric carbon dioxide (CO2) in 2004 but a strong source in 2005 during the growing seasons. Then we applied the model to predict long-term impacts of climate change on carbon (C) dynamics in the semiarid grassland.
Materials and methods
To adapt DNDC for the targeted grassland, we modified the default values of several grass parameters such as maximum biomass production, biomass partitions, plant tissue C/N ratio, and accumulative thermal degree days based on local observations. Daily weather data for 2004 and 2005 in conjunction with soil properties and management practices for the location were utilized as inputs to simulate the grass growth and soil C dynamics. The modeled C fluxes were compared with the eddy tower data. Sensitivity tests were conducted with a baseline and twelve alternative climate scenarios of 100 years for the target grassland.
Results and discussion
The observed and modeled CO2 fluxes data were well in agreement (P < 0.0001), both showing that the grassland shifted from a sink to a source of atmospheric CO2 from a wet year (2004) to a dry year (2005) over growing season. Simulations of 100 years found that, under the fenced conditions, (1) the tested ecosystem would gain C with the baseline climate conditions at a rate of 200 kg C/ha/year; (2) the warmer and drier climate scenario made the worst case having the lowest grass production with 72 kg C/ha/year lost from the soil carbon pool; and (3) the cooler and wetter climate scenario made the best case having the highest biomass production with 790 kg C/ha/year sequestered in the soil during the simulated 100 years.
DNDC model could be used for the prediction of C dynamics in this semiarid grassland ecosystem. Since the ecosystem production is precipitation-limited, a cooler or wetter future climate would substantially elevate the C sequestration capacity of the grassland. However, the C sequestration potential could significantly decrease and even become negative to turn the ecosystem to a source of atmospheric CO2 if the climate turned to be warmer and/or drier in the coming 100 years.
KeywordsClimate change Carbon flux DNDC Eddy covariance Grassland
The study reported in this paper was supported by the major research plan organized by the National Natural Science Foundation of China (90711001). The participation of Changsheng Li in the study was supported by NSF Biocomplexity in the Environment/Coupled Natural-Human Cycles Program (0508028) and NASA Terrestrial Ecology project “Modeling carbon dynamics in high latitude wetlands” (NNX09AQ36G). We thank the two anonymous reviewers for their valuable comments and suggestions on the earlier versions of the manuscript. The authors also would like to thank Ri Xu, Zaixing Zhou, and Ligang Wang for their help.
- Baldocchi D, Falge E, Gu LH, Olson R, Hollinger D, Running S, Anthoni P, Bernhofer C, Davis K, Evans R, Fuentes J, Goldstein A, Katul G, Law B, Lee XH, Malhi Y, Meyers T, Munger W, Oechel W, KTP U, Pilegaard K, Schmid HP, Valentini R, Verma S, Vesala T, Wilson K, Wofsy S (2001) FLUXNET: a new tool to study the temporal and spatial variability of ecosystem-scale carbon dioxide, water vapor, and energy flux densities. Bull Am Meteorol Soc 82:2415–2434CrossRefGoogle Scholar
- Chen ZZ, Wang SP (2000) Chinese typical grassland ecosystem. Science Press, BeijingGoogle Scholar
- Falge E, Baldocchi D, Olson R, Anthoni P, Aubinet M, Bernhofer C, Burba G, Ceulemans R, Clement R, Dolman H, Granier A, Gross P, Grunwald T, Hollinger D, Jensen NO, Katul G, Keronen P, Kowalski A, Lai CT, Law BE, Meyers T, Moncrieff H, Moors E, Munger JW, Pilegaard K, Rannik U, Rebmann C, Suyker A, Tenhunen J, Tu K, Verma S, Vesala T, Wilson K, Wofsy S (2001) Gap filling strategies for defensible annual sums of net ecosystem exchange. Agric For Meteorol 107:43–69CrossRefGoogle Scholar
- Falge E, Baldocchi D, Tenhunen J, Aubinet M, Bakwin P, Berbigier P, Bernhofer C, Burba G, Clement R, Davis KJ, Elbers JA, Goldstein AH, Grelle A, Granier A, Guomundsson J, Hollinger D, Kowalski AS, Katul G, Law BE, Malhi Y, Meyers T, Monson RK, Munger JW, Oechel W, Paw KT, Pilegaard K, Rannik U, Rebmann C, Suyker A, Valentini R, Wilson K, Wofsy S (2002) Seasonality of ecosystem respiration and gross primary production as derived from FLUXNET measurements. Agric For Meteorol 113:53–74CrossRefGoogle Scholar
- IPCC (2007) Climate change 2007: the physical science basis. Contribution of Working Group I to the fourth assessment report of the intergovernmental panel on climate change. Cambridge University Press, CambridgeGoogle Scholar
- Jiang S (1985) An introduction on the inner mongolia grassland ecosystem research station. Academia Sinica. Inner mongolia grassland ecosystem research station. Res Grassland Ecosyst 1:1–10Google Scholar
- Kesik M, Bruggemann N, Forkel R, Kiese R, Knoche R, Li CS, Seufert G, Simpson D, Butterbach-Bahl K (2006) Future scenarios of N2O and NO emissions from European forest soils. J Geophys Res 111Google Scholar
- Law BE, Falge E, Gu L, Baldocchi DD, Bakwin P, Berbigier P, Davis K, Dolman AJ, Falk M, Fuentes JD, Goldstein A, Granier A, Grelle A, Hollinger D, Janssens IA, Jarvis P, Jensen NO, Katul G, Mahli Y, Matteucci G, Meyers T, Monson R, Munger W, Oechel W, Olson R, Pilegaard K, Paw KT, Thorgeirsson H, Valentini R, Verma S, Vesala T, Wilson K, Wofsy S (2002) Environmental controls over carbon dioxide and water vapor exchange of terrestrial vegetation. Agric For Meteorol 113:97–120CrossRefGoogle Scholar
- Li CS, Frolking S, Frolking TA (1992a) A model of nitrous-oxide evolution from soil driven by rainfall events: 1. Model structure and sensitivity. J Geophys Res 97:9759–9776Google Scholar
- Li CS, Frolking S, Frolking TA (1992b) A model of nitrous-oxide evolution from soil driven by rainfall events: 2. Model applications. J Geophys Res 97:9777–9783Google Scholar
- Sundquist ET (1993) The global carbon-dioxide budget. Science 259:934–941Google Scholar
- Wang JW, Cai C (1988) Studies on genesis, types and characteristics of the soils of the Xilin River Basin. In: Inner Mongolia Grassland Ecosystem Research Station (ed.). Res Grassland Ecosyst 3:23–83Google Scholar
- Yuan F, Han XG, Ge JP, Wu JG (2008) Net primary productivity of Leymus chinensis steppe in Xilin River Basin of Inner Mongolia and its responses to global climate change. Chin J Appl Ecol 19:2168–2176Google Scholar