Model of the Net Primary Productivity of Terres-trial Ecosystems in China and its Response to Cli-mate Change

The present study proposed to distinguish agricultural vegetation from natural vegetation when modelling net primary productivity (NPP), and developed a NPP model specifically for agricultural vegetation in China. The new model and the ZHOU & ZHANG model 1996 were then used to simulate NPP for agricultural land and natural ecosystems in China, respectively. The results showed that the overall accuracy improved when simulating the present NPP. As a general trend, NPP declined from southeast to northwest, with the lowest NPP in the Xinjiang Autonomous region. Except in extremely arid or extremely humid areas, agricultural NPP was usually lower than natural NPP, especially in northeastern China and the North China plain. The two models were also used to simulate NPP in China under three climatic change scenarios. The results demonstrated that if air temperature increased by 2°C and rainfall decreased by 20 %, both low NPP and high NPP area would decrease, resulting in an increase of medium NPP area. The other two scenarios, characterized by a temperature increase of 2°C, combined with precipitation increase of 20 % and with precipitation unchanged, showed a decrease in low NPP area and a increase in medium and high NPP area, however, the former resulted in a greater medium NPP increase. In conclusion, our approach supplied better predictions than those based on only a natural NPP model.