Estimation of NPP in Western China using remote sensing and the C-Fix model

Net primary productivity (NPP) is a key component of the terrestrial carbon cycle. The accurate estimation of NPP on regional and global scale is crucial for the studies of global change. In this paper, the Monteith type parametric model-C-Fix, the 1 km SPOT4/VEGETATION data as well as the global meteorological data provided by Meteo France were used to estimate NPP of the terrestrial ecosystems in Western China (73°-112°E, 26°-50°N) for the year of 2002. The total yearly NPP of Western China was estimated at 0.96 P (=10¹⁵)g C in 2002, but the total mean NPP was only equal to 168 g C/m²/year over the study area of 4.5 million km². The spatial pattern of the annual accumulated NPP as well as the monthly dynamics of NPP in Western China were illustrated and descript in detail. In addition, the NPP-values in the annual accumulated level and the mean level for the different ecosystems were evaluated by using the newest 1:1M land-use map of Western China. The results showed that the spatial and temporal patterns of NPP in Western China are attributable to the complex interaction between natural environment, various climates and human activities. Although Western China has a large area of land, the total mean NPP level is very low due to the hard natural conditions. Among them, the restricted water resource is the main element to control the NPP of Western China.