生态修复前后祁连山地区植被覆盖变化

祁连山是我国重要的生态屏障,定量评估气候变化和人类活动对植被变化的影响对祁连山生态保护和修复具有重要意义。以祁连山地区为研究区,分析1986—2020年植被覆盖时空动态变化,计算气候变化及人类活动对植被覆盖变化的贡献率,进而评估生态修复工程对于植被覆盖变化的影响程度。结果表明：(1)1986—2020年间祁连山地区植被覆盖度呈现显著增加趋势,变化趋势为0.022/10a;中高覆盖度主要分布在东南地区,西北地区仍然是以低覆盖度为主,且1999年的退耕还林还草工程施行后,中低覆盖度向中高覆盖度方向转化。(2)祁连山地区植被覆盖变化是气候因素和人类活动共同作用的结果。气候因素对植被覆盖的贡献率为93.40%,人类活动贡献率为6.60%,气候因素是祁连山区植被变化的主导因素,但人类活动在植被变化中的影响程度逐年增加。祁连山地区植被覆盖呈转好趋势,这主要是因为退耕还林还草等生态工程极大地改善了祁连山地区的植被覆盖状况,为后续植被的恢复和生态系统的稳定奠定了良好的基础。

Vegetation coverage variation in the Qilian Mountains before and after ecological restoration

Qilian Mountains is an important ecological barrier in China. Quantitative assessment of the effects of climate change and human activities on vegetation variation is of great significance to the ecological protection and restoration of the Qilian Mountains. The temporal and spatial dynamics of vegetation coverage in the Qilian Mountains from 1986 to 2020 were analyzed. The contribution rates of climate change and human activities to vegetation coverage variation were calculated. Furthermore, the influences of ecological restoration project on the change of vegetation coverage were evaluated. In this paper, using the Google Earth Engine platform of Landsat NDVI, Qilian Mountains ecological restoration through JavaScript programming code research before and after the change of vegetation coverage. At the same time, in order to quantitative evaluate the contribution of climate change and human activities, by adopting the method of multiple regression residuals in Qilian Mountains before and after the ecological restoration of vegetation coverage change were analyzed. And then explore the role of ecological restoration engineering in Qilian Mountains, and which will provide a scientific basis for later of Qilian mountains ecological restoration plan and the development direction. The results showed that:(1) the vegetation coverage in the Qilian Mountains showed a significant increase trend with the increase rate of 0.022/10a from 1986 to 2020. There was a transition from the middle-low coverage to the middle-high coverage after the project of returning farmland to forest and grassland in 1999. (2) Vegetation variation in the Qilian Mountains is the result of climate factors and human activities. The contribution rate of climate factors to vegetation coverage is 93.40%, and that of human activities is 6.60%. Qilian Mountains region of vegetation coverage change and the precipitation, air temperature, drought index expression is significantly positively related, and the relative humidity is negative correlation. During the study period, drought index, the temperature had the greatest influence on vegetation growth, in other words, vegetation coverage affected by the local drought degree is the largest, the average temperature on the influence degree of the vegetation coverage shows the trend to increase, and drought index, the precipitation is characterized by weakening trend. Climate is the dominant factor of vegetation variation in Qilian Mountains, but the influence of human activities is increasing year by year. Ecological projects are the main driving force of vegetation coverage improvement in the Qilian Mountains such as returning farmland to forests and grassland, which also laid a good foundation for the follow-up vegetation restoration and ecosystem stabilization.