Response Of Landuse/Cover Change To Climate Change In The Agro-Pastoral Ecotone Of Northwest China In The Past 30 Years

There is a complex relationship between Land Use/Cover Change(LUCC)and climate change,understanding the interaction mechanism between the two has important significance for the sustainable development of regional land and social economy,and the coordinated development of people and nature.The northwest agro-pastoral ecotone is drought and its windy erosion is strong.The ecological environment is extremely fragile.It is extremely sensitive to climate change disturbances.Therefore,studying how LUCC responds to climate change in this region has important reference value for local future land planning,socio-economic sustainable development and ecological environment construction.This paper uses the statistics of the seven phases of land use data from 1986 to 2015,the annual temperature and precipitation provided by weather station,NDVI data,Digital Elevation Model(DEM)data,etc.,mathematical statistics and Spatial analysis and other methods were used to analyze the temporal and spatial characteristics of LUCC and climate change in the past 30 years in the agro-pastoral ecotone of Northwest China.Based on the characteristics of the two,the response of LUCC to climate change in the region over the past 30 years was analyzed from the aspects of spatial distribution and contribution degree.The main conclusions be obtained as follows:(1)Between 1986 and 2015,the land use in the northwest agro-pastoral ecotone was dominated by cultivated land,grassland and unused land,and the remaining types accounted for less.The rate of change and the area of transfer of each land use/cover type are quite different,and the variation range is wider.From the perspective of land use structure,the land use structure change was the most significant between 2000 and 2010,and the types with large changes in area were sandy land and medium and low coverage grassland.From the perspective of rate of change,the fastest rate of change is for other construction sites,followed by urban construction land and other forest land,and the other types of change rate are smaller.From the perspective of the transfer area,the land areas with large transfer areas in the northwest agro-pastoral ecotone in the past 30 years are grassland,sandy land and cultivated land.Grassland is the most violent land use type in the study area,and grassland and other types have undergone significant conversion.The part transferred from sandy land is mainly medium and low coverage grassland,and the transferred part mainly becomes dryland,medium and low coverage grassland and so on.The part of the cultivated land transferred mainly comes from the middle and low coverage grassland and the sandy land,and the transferred part is mainly changed into forest land and grassland.From the perspective of the spatial extent of change,the distribution of cultivated land,grassland,and unused land is larger,and the remaining types of change are smaller.The change of cultivated land is mainly distributed in south of the Great Wall.The change of unused land is mainly distributed in north of the Great Wall.The change of grassland is distributed in almost the entire study area.(2)In the past 30 years,the annual average temperature in the northwestern farming-pastoral ecotone has generally shown an upward trend,with an average temperature increase rate of 0.034 °C/a.The performance,spatially,is higher in the north and the east,lower in the north and the west.The average precipitation showes an insignificant increase,with an average increase rate of 0.37 mm/a.In space,it shows the characteristics of less east and west,and gradually decreases from east to west.The annual average rate of change of the two has significant differences in space.The northwestern part of Etuoke Banner has a faster heating rate,while the Etuokeqian Banner has a negative annual average temperature.The precipitation in Shenmu County and other areas increased rapidly,while the annual precipitation in Lingwu County and the northwest of Etuoke Banner showed a decreasing trend.(3)In the past 30 years,the land use/cover types of the northwest agro-pastoral ecotone have different responses to climate change,and the impact of climate factors on LUCC has greater spatial heterogeneity.The forest land,low-coverage grassland and unused land in the whole study area are greatly affected by the annual average temperature and annual average precipitation.The high-coverage grassland in the southeastern part of the study area is affected by the annual temperature and the annual average precipitation.The water is greatly affected by the annual average temperature and less affected by the annual average precipitation,and the remaining types are less affected by climate change.From the perspective of its spatial distribution,the frequency of land use/cover change is basically increased with the increase of heating rate,and decreases with the increase of precipitation rate.From the severity of the change,the most violent type in the cooling region is the water area,and the most responsive type in the warming area is the forest land.The most responsive type in the region where the precipitation rate is greater than 1 mm/a is the unused land.The most violent type of regional response is woodland.(4)Based on the calculation results of residual trend method,it is preliminarily believed that the contribution of climate change to LUCC in agro-pastoral zone of Northwest China during the study period is 21.92%,and the contribution of human activities to LUCC is 78.08%.The contribution of climate change to LUCC in the southeastern and eastern parts of the study area is between 10% and 50%,and the contribution to LUCC in other regions is less than 10%(1998-2015).