SIMULATION FOR NPP OF GRASSLAND ECOSYSTEM IN QINGHAI-TIBETAN PLATEAU BASED ON THE PROCESS MODEL

Qinghai-Tibetan Plateau plays an important role in estimating net primary productivity of grassland ecosystem for global carbon cycling research. In this paper, boreal ecosystem productivity simulator (BEPS) model was modified according to the characteristics of grassland canopy. A hypothesis of horizontal homogeneity and vertical layer was put forward for grassland canopy and BEPS was modified to GEPS (grassland ecosystem productivity simulator) to simulate the NPP of grassland ecosystem. With MODIS products (MOD15A2 and MOD12Q1) and routine meteorological data, net primary productivity of grassland ecosystem was simulated in Qinghai-Tibetan Plateau in 2006 based on GEPS. The result shows that NPP of grassland ecosystem in Qinghai-Tibetan Plateau is between 20 and 500 gC/m(2).a, which is close to the other studies. The spatial distribution of NPP of grassland ecosystem in Qinghai-Tibetan Plateau has the trend of decreasing from east to west. Finally the seasonal change of NPP was investigated based on monthly NPP, which has good coherence with the seasonal changes of temperature. This study suggests that the process model GEPS - is suitable to simulate NPP of grassland ecosystem in Qinghai-Tibetan Plateau.