1.Beijing forest univercity;2.College of Soil and Water Conservation,Beijing Forestry University
Second Tibetan Plateau Scientific Expedition and Research Program (STEP)(2019QZKK0608)，Innovation and Entrepreneurship Training Program for College Students at Beijing Forestry University (Renqing Nowu: X202210022049)
在全球气候暖湿化背景下,对位于半干旱地区的青海省河湟谷地植被NDVI变化状况进行监测与归因分析,对青海省生态环境建设具有指导意义。研究利用2000—2020年MODIS NDVI年与相关气象等数据,采用Theil-Sen median趋势检验法、偏相关性分析等方法,研究河湟谷地NDVI时空变化特征,利用地理探测器进行驱动因素分析。研究结果表明：(1)近二十年河湟谷地地区的植被NDVI呈波动增长趋势,显著增长区域面积为2.2×104 km2(P<0.05),占河湟谷地总面积的53.39%；植被NDVI显著下降区域面积有7.0×102 km2(P<0.05),主要分布在湟水谷地中部,占总面积的1.69%；(2)驱动因素上,NDVI与气温、降水均有较强的相关性,呈正相关区域分别占总面积的50.3%、80.1%。通过对自然因子进行偏相关分析,可以发现植被显著上升的区域主要分布在海拔2800~3100m、坡度15°、坡向为北向的区域,在高程小于3200m范围内,植被NDVI变化趋势随着高程的增加而呈现上升趋势,其中显著上升的面积为54.37%。(3)综合偏相关性分析与地理探测器对植被NDVI变化归因分析可知,不同土壤类型上的植被变化差异明显,年降雨量以及人类活动是河湟谷地植被NDVI变化主要影响因素,且多因子对NDVI的影响存在交互作用,呈现相互增强和非线性增强关系。有效明晰复杂的植被变化驱动因素,对未来青海省河湟谷地生态建设规划以及生态工程实施提供理论支撑。
Under the background of global climate warming and humidification, monitoring and attribution analysis of NDVI changes in vegetation in the Hehuang Valley of Qinghai Province, located in semi-arid areas, has guiding significance for the construction of ecological environment in Qinghai Province. The study utilized MODISNDVI data from 2000 to 2020 and related meteorological data, using Theil Sensedian trend test, partial correlation analysis, and other methods to study the spatiotemporal variation characteristics of NDVI in the Hehuang Valley, and used geographic detectors for driving factor analysis. The research results indicate that: (1) The vegetation NDVI in the Hehuang Valley region has shown a fluctuating growth trend in the past twenty years, with a significant increase in the area of 2.2 × 104km2 (P<0.05), accounting for 53.39% of the total area of the Hehuang Valley; The area with a significant decrease in vegetation NDVI is 7.0 × 102km2 (P<0.05), mainly distributed in the central part of the Huangshui Valley, accounting for 1.69% of the total area; (2) In terms of driving factors, NDVI has a strong correlation with temperature and precipitation, with positively correlated regions accounting for 50.3% and 80.1% of the total area, respectively. Through partial correlation analysis of natural factors, it can be found that the areas with significant vegetation increase are mainly distributed in areas with an altitude of 2800~3100 meters, a slope of 15 °, and a slope direction of north. Within the range of elevation less than 3200 meters, the NDVI change trend of vegetation shows an upward trend with the increase of elevation, with a significant increase area of 54.37%. (3) Based on the partial correlation analysis and the attribution analysis of geographical detectors on NDVI changes of vegetation, it can be seen that vegetation changes in different soil types are significantly different. Annual rainfall and human activities are the main influencing factors for NDVI changes of vegetation in Hehuang Valley, and the impact of multiple factors on NDVI is interactive, showing mutual enhancement and nonlinear enhancement relationships. Effectively clarify the complex driving factors of vegetation change, and provide theoretical support for the future ecological construction planning of Hehuang Valley in Qinghai Province and the implementation of ecological engineering.