Simulation of Net Primary Productivity in Mongolia Using CASA Model, During 2000-2004

Abstract

Vegetation net primary productivity (NPP) is always used as an indicator of carbon cycling in terrestrial ecosystems at landscape and regional scales. Based on the CASA model, we analyzed the spatiotemporal pattern of growing season NPP from 2000 to 2004 using MODIS/NDVI and its relationship with precipitation. The result shows that the annual NPP in Mongolia has a tendency to slightly decrease from 61.13 in 2000 to 60 gC/m2 /yr in 2004, with an annual mean decrement of -0.259 gC/ m2 /yr. However, annual and inter-annual NPP trends showed spatial and temporal heterogeneity. NPP in forest and grassland has decreased with an average annual decrement of -1.03 (r2=0.262) and -0.49 (r2=0.324), meanwhile NPP in desert steppe and desert has increased with the annual average increment of 0.4327 (r2=0.322) and 0.2401 (r2=0.283), respectively. The correlation coeffi cient showed that mean growing season NPP in grassland and desert steppe were closely correlated with precipitation than forest and desert.

Keywords

• Net Primary Productivity
• CASA model
• spatial-temporal pattern