| Central Asia is located in the inland and has a dry climate,which is one of the most fragile regions in the global ecosystem.With changing of climate,Central Asia regional ecological environment problems have seriously restricted the central Asian countries in economic and social development,and induced extensive concern from the international community.However,the research on relationship between vegetation and climate in Central Asia is relatively weak,and the response mechanism of vegetation dynamics to climate change are still unclear.Research on the response of vegetation to climate change such as precipitation,temperature,and evapotranspiration in Central Asia has of great significance for understanding the relationship between vegetation and climate,improving the regional ecological environment,and promoting the construction of the “Belt and Road”economic belt.In this study,we used the trend analysis method,dual-variable spatial autocorrelation model and correlation analysis model to explore the response and lag of vegetation to climate factors under different land types in Central Asia,which is in order to provide theoretical reference and data support for ecological environment protection and restoration.The results showed that:(1)There are six land types includeing cultivated land,grassland,forest land,construction land,water region area,and unused land in study area.The area of Cultivated land and water region showed a decreasing trend during 1990-2010.The area of forest land,construction land and unused land increased significantly,while it was stable for total grassland area.The landscape structure of Central Asia maintians good diversity,and each type of patch evenly distributed in the landscape.The landscape fragmentation dregree of each type of patch was reduced.The shape of each type kept significantly complex,however,it had a regularization trend and the polymerization degree of each type of pacth had been significantly increased.The advantage of forest land,grassland,construction land and unused land was gradually weakened.(2)The NDVI changes of cultivated land,forest land and grassland experienced a downward trend in the annual scale,but the change of unused land annual NDVI showed an upward trend.-0.001747 / 10 a,-0.0001513 / 10 a,and-0.00125 / 10 a respectively.During the growing season and spring scale,the NDVI changes of cultivated land,forest land,grassland and unused land exhibited an increasing trend;0.000525 / 10 a,0.005701 /10 a,0.002371 / 10 a,-0.0003254 / 10 a respectively.In summer,the NDVI trend ofcultivated land,grassland,and unused land increased,and the trend of NDVI of forest land showed a downward trend.-0.003409 / 10 a,-0.004113 / 10 a,-0.0003148 / 10 a,0.001963 /10 a respectively.The NDVI of cultivated land,grassland and unused land decreased in autumn,however,the NDVI of forest land exhibited an increased trend.The changes in NDVI of cultivated land and unused land in winter experienced decreasing trend,and the NDVI of grassland and forest land showed rapidly increasing trend,-0.009841 / 10 a,0.001321 / 10 a,0.02148 / 10 a,0.03968 / 10 a respectively.(3)The NDVI of annual,growing season and summer scales was positively correlation with precipitation in cultivated land,grassland and the regional overall,however,negatively correlated with evapotranspiration.The NDVI in growing season and summer scales was positively correlated with precipitation in unused land.The NDVI of forest land was a positive correlation with precipitation in Summer.There were positively correlated with temperature and evapotranspiration in cultivated land,forest land,grassland,unused land and the regional overall during spring.In autumn,the NDVI of regional overall,cultivated land,forest land and grassland was negatively correlated with precipitation instead of NDVI of unused land was positively correlated with evapotranspiration.the regional overall NDVI was negatively correlated with precipitation,the forest NDVI was positively correlated with temperature,however,the grassland NDVI was positively correlated with temperature and evapotranspiration during winter.(4)During Growing season scale(from May to September),a one-month or two-month time lag was found in the response of NDVI to precipitation,temperature and evapotranspiration in Central Asia. |
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