张家口清水河上游流域植被指数时空变化特征

摘要

为研究清水河上游流域植被指数的时空变化特征及其驱动因子,基于1999-2015年张家口清水河上游流域的气象数据、SPOT Vegetation NDVI数据,结合NDVI与RUE研究该时段研究区植被指数的时空变化,并分析多年来气候和人类活动对植被覆盖度变化的影响.结果表明:1)清水河上游流域植被指数从东向西逐渐减小;2)1999-2015年研究区植被指数不断波动,并呈现上升趋势,85％的区域为植被改善区;其中,8.5％为明显改善区,71.6％为中度改善区;3)1999-2015年,研究区植被变化的主要驱动因子为人类活动,且该区人类活动主要表现为正向干扰;4)年降水量影响年NDVI的波动,同时也是研究区植被空间分布的决定性因子.该研究为地区植被恢复、生态系统稳定和景观功能完善,提供科学依据和决策服务.%[Background] Vegetation as the natural link between soil,atmosphere and water,plays an essential role in soil erosion control,water resource regulation,water quality improvement,regional microclimate improvement and soil and water conservation function.Qingshui River Basin is located in Chongli County,which is one of the host cities of 2022 Winter Olympics.But the region has a special geologic structure with a lot of gravels,and faces other problems like soil erosion and water shortage,which cause a low afforestation survival rate.Therefore,it is of great significance to study the change of vegetation coverage and its driving factors for local vegetation recovery and water and soil conservation.[Methods] Based on the meteorological data and SPOT vegetation NDVI data of 1999-2015 in the upstream basin of Qingshui River,Zhangjiakou,we studied the temporal and spatial variation of vegetation coverage of the study area in 1999-2015.Using the methods of trend analysis and partial correlation analysis,we analyzed the driving factors of NDVI changes combining NDVI and RUE with the precipitation data,temperature data and land use map in the study area.[Results] 1) The NDVI in the upper reaches of Qingshui River Basin is between 0.3 and 0.9 during 1999 to 2015.The NDVI values between different land uses from large to small are successively open forest land,forest,shrub land,grass land,dryland,towns and rural areas,and bottomland.And the vegetation coverage in the study area has a strong spatial distribution and decreased gradually from east to west.2) The NDVI of the study area fluctuated continuously and had an upward trend during 1999 to 2015.The study showed 85％ of the study area was vegetation-improved area,8.5％ of which was obviously improved area and 71.6％ was moderately improved area.3) The results of partial correlation analysis between the annual precipitation,annual average temperature and NDVI of each pixel in 1999-2015 showed that the area in which the annual precipitation and NDVI were significantly related accounted for 1.36％ and the annual average temperature and NDVI were not significantly related.4) Annual precipitation affects the fluctuation of annual NDVI and was also the decisive factor of vegetation spatial distribution in the study area.5) Combining NDVI and RUE,the results showed that 69％ of the study area was moderately positive interference area,and 16％ was strongly positive interference area,and 14％ was no obvious interference area.[Conclusions] In the Qingshui River Basin,both climate change and human activity influenced the change of vegetation coverage.The main driving factor of vegetation change in the study area in 1999 -2015 was human activity,which was mainly positive to vegetation improvement.The climate factors greatly influenced the fluctuation of vegetation and limited to the change range of vegetation improvement,which made the spatial distribution of vegetation changed hardly,while the vegetation changed yearly was driven by human activity.