Scientific update
Applying the EPIC model to explain historical changes in soil organic carbon (SOC) stocks in the Roige wetland, China
Introduction
Wetlands cover 6% of the world’s land surface and account for 12% of the global carbon (C) pool. Estimation of the C pool is a prerequisite for management and protection of wetland resources and implementation of C sink enhancement plans. The international important Roige wetland is a typical marsh located in the northeast of the Qinghai-Tibet Plateau and soil organic carbon (SOC) storage is one of its most important ecosystem services. Since the 1970s management practices such as drainage, peat exploitation, and grazing in the Roige wetland may have affected its SOC stock. To estimate the extent to which SOC stocks have altered since that period, we use the EPIC model to estimate the change in SOC over time and also the driving factors of this change. The outcome of this study could be useful for the forthcoming management and restoration of the area.
Methodology
This study consisted of two steps: i) defining the parameters and input variables for EPIC (30 years), for example, soil, climate, land cover, and land management data, and ii) defining land cover and land management scenarios. The scenarios were as follows: i) wetland: wetland without drainage and no grazing (WET+NOTDR+NOGRAZ), wetland drained and no grazing (DR+NOGRAZ), wetland drained and lower grazing intensity (DR+LOWGRAZ), wetland drained and higher grazing intensity (DR+HIGHGRZA); ii) grassland: no grazing (NOGRAZ), lower grazing intensity (LOWGRAZ), higher grazing intensity (HIGHGRAZ). We subsequently evaluated the main drivers of the changes in SOC stock.
Results and Conclusion
SOC stocks in wetland (Figure 1a) are consistently higher than in grassland (Figure 1b) as wetland soils are subjected to lower aeration and C mineralization. In the long term, therefore, there is C accumulation in wetland soils that have not been drained (WET+NOTDR+NOGRAZ, Figure 1a). Nevertheless, C stock buildup is reversed following wetland drainage. In both land cover types, more intense grazing promotes the increase in nutrient input from animal waste, therefore promoting soil fertility and, finally, an increase in SOC stock.
Figures 1a and 1b. SOC stock change in different scenarios (click on the image to enlarge).
Drainage is one of the main driving factors for C loss in Roige wetland. Grazing could be beneficial to C accumulation. However, more research is needed focusing on the boundary of grazing intensity. The outcomes of this study highlight the need for wise land use management to protect wetland, especially the capacity of C accumulation.
Note
Kun Ma of the School of Nature Conservation, Beijing Forestry University, Beijing, China, is a Chinese citizen. He was funded by IIASA’s Chinese National Member Organization and worked in the Ecosystems Services and Management (ESM) Program during the YSSP.
Supervisors
Juraj Balkovic and Rastislav Skalsky, Ecosystems Services and Management, IIASA
Please note these Proceedings have received limited or no review from supervisors and IIASA program directors, and the views and results expressed therein do not necessarily represent IIASA, its National Member Organizations, or other organizations supporting the work.