Estimation of net primary productivity of green coniferous forest in complex terrain

摘要

In the terrestrial carbon cycle, gross primary production (GPP), net primary production (NPP), and heterotrophic respiration and their corresponding geographical and seasonal variations are the key components. NPP, the difference between GPP and autotrophic respiration, is an important ecosystem process. Estimating NPP is essential for evaluating the carbon balance and understanding the effects of climate change on vegetation. In mountain areas, irregular terrain significantly affects spatial variations of climatic variables and the reflectance of pixels in remote sensing imagery. Consequently, the variations perhaps affect the estimation of net primary productivity (NPP). A Photosynthetic curve model based on a new vegetation index derived from universal pattern decomposition(VIUPD), is used to analyze topographic influences on NPP by evaluating topographic effects on primary input data to the model, including both VIUPD and climatic data. VIUPD is the vegetation index derived from universal pattern decomposition method, which is independent of sensor band-spectral characters. A typical green coniferous forest in Yoshino Mountain, Japan, was employed as the study area. The results show that the average NPP is significantly increased after removing topographic influences on VIUPD; the average NPP has a relatively minimal change when only topographic effects on climatic data are considered. When both topographic effects on VIUPD and climatic data are considered, the average NPP is 1.80kgm-2yr-1, which is very similar to the ground measurement result of 1.74 kgm-2yr-1.