The Evaluation Of Carbon In Farmland In Yanhe River Catchment In Loess Hilly And Gully Region

Scientific evaluation of the carbon sequestration potential of farmland ecosystem is of great importance to the understanding of land use change and the relations between SOM(soil organic matter) and climate change as well as to the land use planning for the mitigation of climatic change through carbon sequestration by ecosystem.This study chooses Yanhe River catchment as a case study to quantitatively evaluate the carbon sequestration potential of farmland systems and its spatial change. Firstly, the catchment was divided into 17 environmental units according to the ingredient of rainfall and temperature to make sure of the representativeness of sampling units which were selected using environmental stratification sampling techniques. Then generalized additive model (GAM) is used to explore the relationships between the SOM density in natural ecosystem as well as in farmland ecosystem and environmental variables such as precipitation, temperature and topography using S-Plus platform.The results show that the SOM density in natural ecosystem is mainly affected by annual mean rainfall seasonality, annual mean temperature and slope grade while the SOM density in farmland ecosystem by annual average evaporation, annual average temperature in July and slope position. Using the established models for SOM density in natural ecosystem and farmland ecosystem, predictive distribution maps of the SOM density in natural ecosystem and farmland ecosystem are produced under GIS environment (ARCGIS 9.3). Then the predictive distribution map of the SOM density in natural ecosystem minus that of the SOM density in farmland ecosystem to evaluate the carbon sequestration potential of farmland ecosystem in Yanhe River catchment. The results indicate that the SOM density in Yanhe river catchment gradually increases from northwest to southeast and the total carbon sequestration potential is about 206.48×104t.This indicates that the carbon sequestration potential of farmland system in Yanhe River catchment is huge, and this conclusion has great implication for the strategy making of regional carbon sequestration and evaluation of ecological benefit of land use.