Estimation Of Gross Primary Productivity Of Forest Ecosystems Based On RS And GIS

Forest ecosystem is the principal part of terrestrial ecosystem.Quantifying gross primary productivity(GPP)of forest ecosystem and analyzing the spatio-temporal variations would help for understanding the dynamic development of terrestrial carbon and the response of climate change,and to promote the sustainable development of forestry in China.At this stage,the application potential of remote sensing(RS)and geographic information science(GIS)in forest ecosystem GPP research needs to be further explored,which was an important data acquisition and spatio-temporal analysis technology.Based on RS and GIS,this study estimated and analysed the GPP of forest ecosystem at different scales.The main research contents and results are as follows.(1)Based on MODIS remote sensing data,quantitative remote sensing technology was used to retrieve the enhanced vegetation index and land surface water index.Spatial interpolation algorithm was used to obtain raster data of temperature and photosynthetic active radiation.Spatial and temporal variations of environmental factors were analyzed by using GIS spatial analysis technology as spatial driving data of the model.(2)Based on the non-linear least squares fitting function,the parameters of maximum light use efficiency in the vegetation photosynthesis model were optimized.Finally,the correlation between GPP simulated by the model and the measured values of the site was as high as 0.76(P<0.05),and the simulation results of the model were significantly improved.(3)Based on the optimized VPM model of the platform of Matlab platform,the spatio-temporal changes of the National Forest GPP with a resolution of 1 km and its correlation with environmental factors were simulated and analyzed from 2000 to 2015.The annual average of forest GPP in China was 1294.62 g C/m2/year,which increased significantly at the rate of 6.57 g C/m2/year2(P<0.05).Forest GPP was significantly positively correlated with photosynthetic positively correlated with photosynthetic effective radiation and temperature,and negatively correlated with precipitation by the SPSS statistical software.In the spatial scale,light and temperature are the main influencing factors of GPP in forest ecosystem by using GIS statistical technology.(4)Based on the CEVSA2 model,the forest GPP of Shennongjia Forestry District with a resolution of 250 meters was simulated from 1981 to 2015,The average annual GPP of forest area was 1256.54 g C/m2/year,and increased significantly at the rate of 5.15 g C/m/year.The spatio-temporal characteristics were analyzed by using ArcGIS.The forest GPP is negatively correlated with precipitation,and positively correlated with temperature and total radiation.In the spatial scale,the interannual change of GPP in about 67.83%of forest ecosystem is controlled by temperature.