Spatio-temporal Distribution Characteristics Of Vegetation Water Use Efficiency And Its Relationship With Impacting Factors In Tianshan Mountains,China

Water use efficiency(water use efficiency WUE)is an important index to measure the coupling degree of carbon and water cycle in ecosystem.To estimate the vegetation wue in the China segment of Tianshan Mountain and the main oases in the north and south,and to analyze the temporal and spatial variation of vegetation,and to explore the influencing factors.It is of great significance to the protection of ecosystem and the rational utilization and development of agricultural water resources in this region.In this paper,based on MOD16A2 ET and MD17A2H GPP product data,RS,GIS is used to analyze the temporal and spatial variation of ET,GPP in the China segment of Tianshan Mountain.At the same time,the data of these two products are used to estimate the vegetation water use efficiency in this area.The temporal and spatial variation characteristics of vegetation wue and their correlation with topography,LUCC variation,temperature and precipitation in this area are discussed.(1)In the last 19 years,the interannual variation of ET in the China segment of Tianshan Mountain showed an obvious increasing trend,and the interannual variation rate was 3.2666 mm;The annual variation of ET in the four seasons showed a significant increasing trend,and the average et change rate in summer was the largest,which was 1.2874 mm;In space,87.79%of the areas showed an increasing trend.(2)The interannual variation of GPP in the China part of Tianshan Mountain showed a fluctuating trend,with a variation rate of 0.747719 gC/m²,but a significant change,while the interannual variation of GPP in the four seasons showed a decreasing trend except in summer,but it was not significant in the other three seasons.In space,the trend range of interannual variation of GPP was-44.10?74.00 gC/m²,and the increasing trend range was 61.27%,of which 24.16% increased significantly(p<0.01).The area with slight increase(p<0.05)accounted for 4.31,and the range of decreasing death accounted for 38.73 of the whole area,of which the significant decrease accounted for 23.466,the area basically unchanged accounted for 34.60%.(3)the interannual variation of WUE in the China part of Tianshan Mountain showed a fluctuating decreasing trend,with a variation rate of-0.0117 gC mm^-1m^-2,a range of WUE variation of 0.990.34 gC mm^-1m^-2 for 19 years,and an annual average wue of 0.099 gC mm^-1m^-2;The annual average WUE value of 13 different basins in the China part of Tianshan Mountain is the largest in the Tarim River main stream area,which is obviously higher than that of the other 12 watersheds,and has a significant regional character in space.The annual average WUE worth range of Yili River Valley and Eimin River Basin is basically similar.The elevation of Tianshan mountain peak is more than 6000 m,and with the elevation increasing,WUE is lower and lower.The trend range of interannual variation was-0.095?0.087 gC mm^-1m^-2,and the range of increasing trend was 16.68%in the whole region,among which the area with significant increase(p<0.01)accounted for 2.56%.The area with slight increase(p<0.05)accounted for 14.12,and the range of decreasing death accounted for 29.13%of the whole area,of which the significant decrease was 1.25%,the slight decrease was 27.88%,and the area basically unchanged accounted for 54.18%.(4)The characteristics of vegetation WUE changes at different altitudes.In the regions above 1000 m,the WUE value of vegetation at higher altitude is lower than that of year,and the WUE value of area below 1000 m is irregular.The characteristics of WUE change in the same land use types,and the different study periods,The distribution of WUE value of different land use types was as follows:paddy field>other forest land>open forest land>shrub>dry land>low coverage grassland>woodland>China coverage grassland>high coverage grassland.(5)In the analysis of the driving forces of vegetation WUE and climate factors in China Tianshan,33.23%of the China Tianshan region is influenced by the strong temperature,and 8.57%of the area is influenced by the strong driving force of precipitation.5.63%of the regions were strongly driven by air temperature and precipitation,13.13%were influenced by weak drive of temperature and precipitation,and 39.44% were affected by non-climatic factors.