NPP Retrieval Based On CASA Model And Their Correlation With Climatic Factors In Shaanxi Province

NPP (Net Primary Production, NPP) is not only a direct reflection of the production capacity of vegetation communities under natural conditions, characterization quality status of terrestrial ecosystems, but also an important factor determine ecosystem carbon source/sink and regulate ecological processes, and plays an important role in global change and the carbon balance.The paper based on CASA model, use of remote sensing and GIS tools, combining MODIS/NDVI data, meteorological data and land use data, estimate Shaanxi Province NPP from 2000 to 2013 year, and then analysis spatial and temporal of Shaanxi Province based on NPP. The results showed that:(1) The spatial distribution, which is characterized by generally expressed as latitude distribution, decreasing from Southern to Northern Shaanxi, and spatial variation of characteristics and vegetation type has a better consistency; The time distribution characteristics are as obvious seasonal variation, showed a single peak curve. From 14 years of NPP overall distribution point of view:in 2000-2013 the average annual total NPP was 1.30×108 gC·a-1, the annual average of NPP was 633.15 gC·m-2·a-1, along with the overall presentation NPP trend of increasing latitude decreases, in which Shannan> Guanzhong> Shanbei;(2) The interannual variability shows an overall growth trend from 2000 to 2013 year, the annual NPP value range of each year at 550.03 gC·m-2·a-1 to 671.95 gC· m-2·a-1, the total range between 1.13 × 108 gC·a-1 to 1.38 ×108 gC·a-1, in which the maximum in 2012, the minimum in 2001, the interannual variability in Shannan Region shows more intense volatility than Guanzhong and Shanbei Region;(3) From the point of view changes during the year:average monthly NPP trend curve showing a single peak, the range between 10.21 gC·m-2·mon-1 to 109.94 gC· m-2·mon-1, the largest values appear in July, the minimum in January, Monthly changes NPP range between 6.53 gC·m-2·mon-1 to 85.18 gC·m-2·mon-1 in Shanbei Region, the maximum in August and the minimum in January,, monthly changes NPP range between 11.85 gC·m-2·mon-1 to 113.23 gC·m-2·mon-1 in Guanzhong Region, the maximum in July and the minimum occurs in January, monthly changes NPP range between 13.17 gC·m-2·mon-1 to 144.67 gC·m-2·mon-1 in Shannan Region, the maximum in July and the minimum in January, another year in the 2000-2013 inter-annual variation in NPP case is different;(4) From the analysis of different vegetation types:mixed forests> deciduous broadleaf forest> savanna> croplands> shrublands> grasslands.NPP by the combined effects of spatial and temporal distribution of a variety of different reasons, including changes in land cover caused by human factors, urban development, and meteorological factors, Shaanxi Province from south to north span large, climate differences, across three climatic zones, generally north subtropical climate, Guanzhong and most Shanbei Region belong to the warm temperate climate, the northern part of Shanbei Region along the Great Wall belongs to the middle temperate climate, so the annual change in the value of the NPP influenced by weather conditions, this paper analyzes annual temperature, precipitation when these two meteorological factors and found that there was a significant correlation with the NPP value.