Abstract:

The ecology of the Tarim River Basin,Xinjiang,China is relatively fragile.During the past few decades,unreasonable development and utilization have resulted in serious damage to the vegetation coverage.Due to the implementation of the ecological comprehensive management project in the Tarim River Basin and by recent climate change,the temporal and spatial distribution of vegetation in the basin has undergone certain changes.Clarifying the relationship between vegetation coverage change and climate change of the basin,as well as human activities,can provide a scientific reference for ecological maintenance and management in the Tarim River Basin.Hence,based on MODIS-NDVI and using the Sen+Mann-Kendall trend analysis,coefficient of variation method,Hurst index,partial correlation analysis,and residual analysis,this study analyzed the temporal and spatial change characteristics and sustainability of vegetation coverage in the Tarim River Basin from 2000 to 2018 and investigated and distinguished the range and extent of the impacts of temperature and precipitation climatic factors as well as human activities on vegetation coverage changes.The results are summarized as follows:(1) The level of vegetation coverage in the Tarim River Basin has increased significantly with clear stage changes.The vegetation changes varied from an increasing trend to a decline before 2008 and then increased rapidly.The vegetation increase is mainly concentrated in Korla,Yanqi,Aksu,Kuqa,Kashi,and the region of the central Tianshan Mountains.The vegetation variation near the Kuluktag Mountains is relatively small.(2) More strongly affected by regional geomorphologic patterns,the vegetation coverage of the Tarim River Basin in the north is greater than that in the south,and the vegetation coverage in the west is greater than in the east.The area of relatively high vegetation coverage is distributed in the mountainous areas,oasis areas,and the oasisdesert interlaced zone.In addition,the basin vegetation is distributed along the river,shaped as a strip.(3) The vegetation coverage trend in the Tarim River Basin is mostly unchanged (50.80%) and the improved trend area (37.97%) is mainly concentrated in the oasis with abundant water resources in the basin.The stability of vegetation coverage in the Tarim Basin is in a state that “the outer side of the basin is higher than the inner side and high and low fluctuations coexist and the moderate fluctuation is mostly”.The response of vegetation activity is significant in areas covered with high vegetation amounts such as mountainous areas.Most regions in the study area will maintain the existing stable trend.The area of unsustainable vegetation coverage change (30.83%) is mainly distributed in mountainous areas and water systems and the sustainable area (69.17%) is mostly concentrated in oasis,oasisdesert interlaced zone,and desert area.(4) The NDVI in the Tarim River Basin has a significant negative correlation with temperature in most areas (72.92%).The NDVI is positively correlated with precipitation in most areas (82.48%).The combined effects of temperature and precipitation on the NDVI gradually increase from northeast to southwest and the impact of precipitation on the NDVI is more significant.The areas where human activities have positive effects on vegetation change are mainly distributed in the oasis,oasisdesert transition zone,and the lower reaches of the Tarim River.In areas with relatively low human activity such as deserts and mountainous areas,the NDVI residuals are also affected by other linear factors of continuous change.

Key words: vegetation coverage, spatial-temporal variations, climatic factor, human activity, the Tarim River Basin