Analysis On Spatiotemporal Change Of NET Primary Productivity And Its Driving Factors In Hunshandake Sandland From 2000 To 2013

In the study,it uses solar energy utilization rate of the CASA model as the foundation,and uses 2000-2013 MODIS NDVI data during the month scale,temperature,precipitation,solar radiation data and different sandland types,the combination of remote sensing and geographic information system technology,which estimates Hunshandake sandland vegetation net primary productivity of growing season in 14 years(4-10 month).Also,it discuss relation between vegetation net primary productivity and climate.These aims,distinguishing the relative role of human activities from climatic changes in terms of their impact on sandland,are accomplished by examining a relative impact contribution index(RICI).So,it gets the following conclusion:1.During 2000-2013 years,net primary productivity of growing season NPP showed an increasing trend in Hunshandake sandland,which increased from 193.20 gC/m2/yr to 299.96 gC/m2/yr,the increase rate of 2.51/a.The area of high NPP increased while that of low NPP gC·(m2·a)-1)decreased.In recent 14 years,it shows that the effectiveness of ecological restoration in Hunshandake sandland and shows that to a certain extent the ecological restoration project such as returning farmland to forest(grass)has been revealed.2.Distribution from the spatial pattern of NPP in study area,the area with increasing trend is accounted for 81.39% of the total area,and the area with significant increase is 11.98%,mainly located in northern,central and southern fringe regions of the study area.The paper show a significant decreasing trend(area is 0.49%)in the eastern region of study area.By analysising on the fluctuation of vegetation NPP value,the standard deviation and coefficient of variation of net primary productivity in the southern and western region of the study area are larger than other regions,significantly affected by external interference,while vegetation cover is weaker responses to external factors in the central and eastern region.3.Because Hunshandake sandland sand is located in a typical arid and semi-arid climate zone,so the NPP by the impact of climate change is quite obvious.The area of between NPP and precipitation is a positive correlation,accounting for 98.85% of study area,and by P<0.05 significance test.Precipitation is the most direct and important factor in the change of NPP.On the contrary,temperature has a significant inhibition on NPP in the study area.The area of between NPP and temperature is a positive correlation,accounting for 0.01% of study area,and by P<0.05 significance test.But both precipitation and temperature have a positive effect on NPP in the Central and southern regions of the study area,precipitation is just more significant.While precipitation have a negative effect on NPP in eastern fringe regions of the study area.The analysis shows that climate is not the only factor that affects the NPP.4.By means of statistical investigation of Zhenglan Banner,from the population,the number of livestock,change of all kinds of soil area,farmer income,GDP and the primary industry and the first industry accounted for the social economy and the percentage changes in 6 aspects of human activity are analyzed.The human activities on regional ecosystem restoration is essential.It is suggested that the macro policy control and ecological construction should be continued to strengthen.5.The PNPP and ANPP estimated from the Thornthwaite and the CASA were used to develop the RICI to quantitatively assess the climate and human activities impacts on NPP in Hunshandake sandland from 2000 to 2013.The annual dynamics of RICI were revealed.The results reveal that human activities caused a loss of 189.56 gC·(m2·a)-1 in NPP in Hunshandake sandland.Although human activities to sandland were somehow mitigated by conservation,human activities still played positive roles in the study area.In the five dune types,obvious spatiotemporal differences were found for human activities and the fixed sand dunes had the lowest level of human activities with minimum RICI(36.73%)and maximum change slope value.Saline-alkali land has experienced the greatest impact of human activities,whose RICI value is 60.08%.The values of RICI in all dune types were negative,indicating that the effects of human activities on various types of sandy land decreased gradually with the gradual restoration of vegetation,mainly due to climate and vegetation conditions.