Estimation Of Net Primary Productivity In Qinghai Province With LUE Model

Terrestrial ecosystem carbon cycle is one of the key content of global change research, while terrestrial ecosystem productivity is the core problem of global change research. Net Primary Productivity (NPP) plays an important role in global biogeochemical cycle, and is one of the most important component in the process of carbon cycle. NPP directly indicates the amount of CO2 fixed by terrestrial vegetation, thus influences other processes in carbon cycle and global climate change.Based on Light Use Efficiency (LUE) conceptual model, we summary the advantages and disadvantages of estimating NPP via LUE models and analyze potential problems lying in the estimation of NPP via LUE models. We discussed the key variables and parameters involved in these potential problems in detail. And then we build a LUE model (NPP-EMSC) to estimate the terrestrial ecosystem net primary productivity in Qinghai.The results show that, in 2009, Qinghai's total terrestrial NPP was 58.23 Tg C and the average NPP was 92 g C·m-2·a-1. The main spatial pattern of NPP is:NPP gradually decreased from southeast of Qinghai to northwest of Qinghai the maximum value is 700 g C·m-2·a-1. The value of NPP are the greatest in forest ecosystem of east and southeast of Qinghai, which fluctuating in the range of 100～300 g C·m-2·a-1. In most parts of middle region of Qinghai, the NPP value is below 100 g C·m-2·a-1. The NPP value in Qaidam basin is almost 0 g C·m-2·a-1. as the vegetation in this place is sparse. In the temporal scale, NPP shows obvious seasonal variation characteristics and significant spatial heterogeneity.We analyze the relationship between NPP and precipitation and accumulated temperature, the results show that NPP has a better correlation with accumulated temperature than precipitation. In the region of annual precipitation below 450mm, precipitation has a higher contribution over accumulated temperature, while at other ranges, accumulated temperature plays a more important role. NPP decreases with the increase of elevation, and the flat region and south slope is below other regions in Qinghai.