Evaluation On Vegetation Net Primary Productionbased On CASA Model In The Shaanxi Province

Net primary productivity(NPP)refers to the amount of dry organic matter produced by plants per unit time and per unit area.NPP is an important index of ecosystem function and a key element in the carbon cycle,reflecting the integrated effects of climate change and human activities on terrestrial vegetation.The results of many of these studies indicate a generally positive trend in NPP,likely due to a warming climate,increased nitrogen deposition and CO2 fertilization and the amount of carbon dioxide fixed by photosynthesis increases accompany with the decrease of the amount in the atmosphere,which correspondingly weaken the effect of greenhouse.SoNPP is an important factor to determine the ecosystem carbon source and adjust the ecological processes,also NPP plays an important role in global changes and carbon balance.This study based on the theory of CASA model with the utilization of MODIS-NDVI,temperature,precipitation,solar radiation and vegetation types data of Shaanxi Province as parameters to estimate the NPP in Shaanxi Province from 2000 to 2014 and analyze the spatial and temporal distribution and interannual or intermonthly variation.The research contents are as follows:(1)Due to the differences of light energy utilization in different vegetations,thisstudy improves the CASA model and establishesa light energy utilization model ofShaanxi Province for the sake of improving precision and adaptation.(2)This study estimates the NPP of Shaanxi Province from 2000 to 2014 and theSpatio-temporal data set.It also analyzes the spatial and temporal distribution andinterannual or intermonthly variation.(3)Based on the estimated results,research is mainly focused on the incidencerelation between climate,atmosphere,land cover and NPP.The possibility on theevaluation of biological carbon emissions and the quality of Shaanxi Provinceterrestrial ecosystem with NPP.