Dynamics of carbon storage and GHG balance in response to multiple global changes in wetlands in the Sanjiang Plain, Northeast China during 1949-2008

Background/Question/Methods

Natural wetlands, one of the largest carbon pools on the earth, hold much higher carbon density than other ecosystems and potentially exert a tremendous effect upon the global carbon cycle. Therefore, a great deal of increasing concerns have been raised on how and to what extent the spatio-temporal patterns of carbon storage and greenhouse gases (GHGs) balance in wetland ecosystems are influenced by a wide variety of environmental changes. The Sanjiang Plain, a floodplain in Northeast China that encompasses large area of natural freshwater wetlands, has been experiencing extensive natural and anthropogenic disturbances such as climate warming, land conversion, enhanced nitrogen fertilizer inputs etc. However, the magnitude, spatial and temporal patterns of carbon dynamics in this area remain far from certain. Here we used a process-based ecosystem model, Dynamic Land Ecosystem Model (DLEM) together with field experiments and observations to estimate and attribute the variations of carbon storages and GHGs emissions in response to multiple environmental changes in climate, atmospheric components (CO₂, nitrogen deposition, tropospheric ozone), land use and land management in the Sanjiang Plain during 1949-2008.

Results/Conclusions

Our study finds that the carbon storage declined in the Sanjiang Plain over the past 6 decades and land use change contributed the largest to the total decrease. N-induced CO₂ uptake has been largely offset by the concurrent emissions of CH₄ and N₂O due to N enrichment, especially in the recent decades. However, both atmospheric N deposition and land conversion from wetlands to croplands were found to mitigate climate warming in terms of global warming potential (GWP) of the three major GHGs (CO₂, CH₄ and N₂O). The modeling results in our study are consistent with field observations. The historical estimation and attribution of GHG balance over the Sanjiang Plain can provide insightful points for understanding the underlying mechanisms of GHGs exchange between wetland ecosystem and the atmosphere and improving land use policy and management strategies in the future.