Dynamics and climatic drivers of evergreen vegetation in the Qinling-Daba Mountains of China

Abstract

The Qinling-Daba Mountains (QBM), which are a major feature of China's north–south transitional zone, play important roles in the geographical and ecological patterns of China. The spatiotemporal changes in winter evergreen vegetation in the QBM are closely related to the protection of vegetation in China and have profound impacts on the sustainable development of vegetation in North and South China. This study aimed to introduce geographical distribution measurement methods into vegetation cover research by geographically characterizing evergreen vegetation, temperature, and precipitation. We used gravity centre analysis and standard deviation ellipse (SDE) methods to statistically analyse the concentration tendency, principal orientation, dispersion trend, and distribution differences of the winter normalized difference vegetation index (WNDVI), average temperature in winter (WAT), and accumulated precipitation in winter (WAP) in 1986–1990, 1991–1995, 1996–2000, 2001–2005, 2006–2010, and 2011–2015. The results show that (1) the gravity centres of the WNDVI and WAT in the QBM moved northwards, indicating that winter temperature is the main factor driving the northwards movement of evergreen vegetation in the QBM. (2) The angle between the development orientations of the WNDVI and the WAT remained basically stable, at close to horizontal, indicating that the development orientation of evergreen vegetation is mainly affected by winter temperature in the QBM. (3) The spatial differentiation coefficient between the WNDVI and the WAP decreased from 0.21 to 0.07; thus, the spatial distribution difference between evergreen vegetation and winter precipitation decreased gradually. These results confirm that in the QBM, winter temperature is the main factor affecting the overall evolution and development orientation of winter evergreen vegetation and that winter precipitation is the main factor affecting the internal distribution pattern of winter evergreen vegetation. The results of this study have reference value for evaluating the spatial distribution of evergreen vegetation development and resource management in the QBM.