Effects Of Climate And Land Use Change On The Changes Of Vegetation Coverage In The Farming-Pastoral Ecotone Of Northern China

Since the beginning of the 21 st century,the global climate issue has become a hot spot for scientists.In the face of rising temperatures,global warming leads to unbalanced precipitation,and humans use irrational use of natural resources to cause damage to vegetation in varying degrees,intensified the contradiction between man and nature,making the environmental situation more and more complex,and the problems of vegetation change and land use urgently need to be solved.The IPCC's four assessment reports in the world academic field indicate that global temperature has increased by 0.46?to 0.75? over the last 100 years,and its change trend is approximately 0.32-0.94?/100 a.Scientists have made predictions that by the year 2100,the global temperature will rise about 1.5-5.9?.Based on this,it can be seen that there will be a historic and major change in the global climate.Climate change is the main controlling factor in determining the vegetation type and geographical distribution.Vegetation is the comprehensive response and indicator of regional climate change characteristics.There is an inseparable link between the two.Therefore,the study of regional climate change response to regional vegetation cover has become one of the important directions of global change research.In recent years,many experts and scholars in related fields have carried out a variety of LUCC(Land-Use and Land-Cover Change)researches on agricultural and pastoral ecotones,and obtained a lot of research results,and related researches are mainly distributed in The northern agro-pastoral ecotone has revealed in detail the spatial shifts in land use in the study area and the drivers of these changes.This has important and significant implications for the active implementation of the regional sustainable development strategy,as well as changes in regional vegetation cover.It also has a positive promotion effect.This study mainly used the vegetation NDVI data,meteorological data,and two periods of land use data in the 14 years(2000-2013)of the farming-pastoral ecotone in northern China,and analyzed the temporal and spatial characteristics of vegetation cover in the study area in detail.Its interannual response characteristics and correlation spatial distribution of precipitation and temperature over the same period,and according to the rules of land-use interpretation,stratified extraction of target land types,accurate interpretation accuracy,and finally drawn into two phases of land use Vector maps were then superimposed on the NDVI raster map of vegetation.Through statistics of land use changes and NDVI changes,the effects of land use change on the vegetation cover changes in the farming-pastoral ecotone of northern China were studied.And obtained the following in conclusion:According to the law of time,the average NDVI in the growing season of the study area and the NDVI in the spring,summer and autumn as a whole show a slowly increasing trend from the perspective of the law of time;from the perspective of the spatial variation trend,the spatial distribution of NDVI in the study area as a whole shows an increasing trend from southwest to northeast.From the analysis of the correlation between vegetation NDVI and climatic factors,there are phenomena of uneven temporal and spatial distribution of temperature and precipitation in each region of the farming-pastoral ecotone of northern China.Through the statistics of the relationship between climatic factors and vegetation NDVI in the farming-pastoral ecotone of northern China in different seasons,it is found that the proportion of the pixels whose vegetation NDVI is positively correlated with precipitation is much larger than the proportion of the pixels that are positively correlated with the temperature.This shows that in addition to human activities and ecological restoration projects,the change in precipitation is one of the important factors for the increase and decrease of vegetation in the study area.From the angle of land utilization/land coverage in the northern farming-pastoral ecotone from 2000 to 2013,the land use types in the study area from 2000 to 2013 have been converted frequently.In general,there is a significant increase in grassland and water area,and land use patterns in which cultivated land and unused land are generally increasing.The factors affecting land use change are complex,but they are basically related to the warming and drying of the climate in the north,the adjustment of regional industrial structure,and the implementation of a series of ecological protection projects by the state.If the current land use policy is to continue to be implemented in the future,the pattern of land use in the northern agricultural-pastoral ecotone will become more reasonable in the future and will eventually stabilize.