| Vegetation is the main body of terrestrial ecosystem. The Vegetation Net Primary Productivity is an important part of the carbon cycle and plays an significant role in global climate change and carbon cycle.This study was carried out in Kailu County, Tongliao City, based on improved remote sensing inversion CASA model, supported by the software ArcGIS and ENVI, to acquire the land use classification data through TM data supervising classification; to get the vegetation coverage classified data and Simple Ratio Index and other required parameters by extracting NDVI and using dimidiate pixel model, and meanwhile, to estimate NPP of different years with aid of climate data to research on the extraction of small scale and high resolution NPP remote sensing inversion. Based on these data, NPP distribution characteristics, influential factors and etc. of Kailu County were analyzed.The results of this study are as following:(1) The types of land use and NDVI were processed and obtained by using TM remote sensing image data; with the help of meteorological data, parameters of CASA model were calculated to get the distributed data of Fractional Photosynthetic Active Radiation, Absorbed Photosynthetic Active Radiation and other factors; finally, according to the CASA model, the estimation of NPP of Kailu County was acquired.(2) Kailu County, located in the alluvial plain, is flat, with relatively more arable land, and had a relatively higher NPP, however, the north and northwest areas, had more sandy and grassland, and had a relatively lower NPP. For the overall area of Kailu County, the NPP of September 2002 was 0～73gC·m-2·month-1, the distribution of the higher value was less, and the distribution of the NPP less than 15 gC·m-2·month-1 is relatively wider. The general NPP was relatively low due to the fact that the land with 0.1～0.3 vegetation coverage accounted for 44.05% of the total area. In September 2006, the range of NPP was 0～85gC·m-2·month-1, the distribution of NPP less than 45gC·m-2·month-1 was wider, the land with 0.1～0.5 vegetation coverage accounted for 52.83%, and the general NPP was relatively higher compared with that of September 2002; in September 2010, the range of NPP was 94 gC·m-2·month-1, the corresponding high coverage area increased, causing the increase in the high value area with NPP of 60～94gC·m-2·month-1 in 2010, and the general NPP was relatively higher.(3) Through the overall analysis of meteorological factors of the September of 2002, 2006 and 2010, it was found that the trend of the solar radiation and the monthly average temperature was not obvious, the trend of NDVI and rainfall was generally increasing, and the NPP was affected by rainfall when other factors being equal. So, the change of NPP was the result of the collaborated operation of all the factors. In 2002, the monthly average rainfall was relatively less, the water deficiency of vegetation would affect the vegetation photosynthesis, and lower the NPP. In general, the influence of different parameters on NPP is different.(4) The falling gradient of Kailu County concentrated in the range of 0.1～8.4°. from the perspective of slope, the NPP average of the area with the slope of 0～0.5° is the highest and the NPP average of the area with the slope of 0～0.5° is the lowest. From the perspective of timing, the NPP averages of different slopes were raising from 2010 to 2012. After analyzing the NPP distribution of different slope direction, it is found that NPP is generally free from the influence of slope direction, due to the small undulating terrain of the study area.(5) In the study on NPP of different vegetation types, the general NPP distribution in Kailu County is arable land> forest land> pasture land. By analyzing the present situation of Kailu County, it is found that Kailu County is located in the alluvial plain, so farmland is the main type of land use, and forest land is relatively less, there are only a part of forest and a few plantations along the road. The difference between cover areas led to the significant difference between NPP totals. |
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