Quantitative Analysis of Climate Variability and Human Activities on Vegetation Variations in the Qilian Mountain National Nature Reserve from 1986 to 2021

Abstract

Rapid climate variability and intense human activities generate obvious impacts on the Qilian Mountains ecosystem. The time series of fractional vegetation coverage (FVC) from 1986 to 2021 were used to quantify the impact of climate variability and human activities on vegetation variations in the Qilian Mountain National Nature Reserve (QMNNR), using 3147 land satellite images based on the Google Earth Engine cloud platform. The contributions of climate variability and human activities to FVC were quantified using multiple regression residual analysis. Partial correlation and correlation methods were used to quantify the impact of temperature, precipitation, and human activity footprints on FVC. The results showed that from 1986 to 2021, the increase rate of FVC was 1.7 × 10−3 y−1, and the high vegetation coverage of the FVC was mainly distributed in the southeastern part of the reserve. In contrast, the low vegetation coverage was mainly distributed in the northwest part of the reserve. The Mann–Kendall mutation test found that the year of 2009 was the year of the mutation. The growth rate of FVC from 2010 to 2021 was greater than that from 1986 to 2009. In addition, climate variability and human activities exhibited a remarkable spatial heterogeneity in FVC changes. Climate variability and human activities contributed 49% and 51% to the increase in FVC in the reserve, respectively, and the contribution of human activities was greater than that of climate variability. The warming and humidification phenomena in the reserve were obvious. However, precipitation was the dominant factor affecting the dynamic changes in FVC. This study improves our understanding of the response of vegetation dynamics to the climate and human activities in the QMNNR.

Spatiotemporal Variations of Vegetation and Its Response to Climate Change and Human Activities in Arid Areas—A Case Study of the Shule River Basin, Northwestern China*

“…The NDVI is commonly used to derive the FVC [50]. The FVC can better measure surface vegetation conditions and ecological environment changes [35]. The FVC was calculated using the Band Math calculation module of ENVI 5.0 after projection conversion and mosaicking with Equation (3):…”

“…where NDVIsoil and NDVIveg represent the values of bare soil and full vegetation cover (with a 95% confidence limit), respectively [35,51]…”

“…It is commonly assumed that FVC is affected by the combined impact of two factors: human activities and climate variability [26,27,29,35,58,[60][61][62][63]. The response of vegetation conditions to temperature and precipitation is often nonlinear [41].…”

“…Techniques such as Geographic Information Systems (GIS) and remote sensing (RS) have been employed to study the dynamic evolution of vegetation [26]. For instance, a fractional vegetation coverage (FVC) time series analysis from 1986 to 2021 in the Qilian Mountain National Nature Reserve revealed that climate variability and human activities contributed significantly to vegetation variations [35]. Similarly, the Qinghai-Tibet Plateau's vegetation changes have been attributed to human activities and climate variability [34,36,37].…”

“…The ecological fragility of the basin, exacerbated by climate variability and human activities, poses significant challenges. Extreme events such as precipitation, drought, and human activities like farming, industrial, and construction further destabilize vegetation coverage [35,41,42]. Monitoring vegetation growth and change is essential for promoting ecological protection and sustainable economic development in the region.…”