Spatio-Temporal Changes of Vegetation Cover and Its Influencing Factors in Northeast China from 2000 to 2021

Abstract

The foundation of study on regional environmental carrying capacity is the detection of vegetation changes. A case of Northeast China, we, with the support of normalized difference vegetation index (NDVI) of MOD13A3 (MOD13A3-NDVI), use a three-dimensional vegetation cover model (3DFVC) to acquire vegetation cover from 2000 to 2021. Vegetation trends are then monitored by the spatio-temporal analysis models including the empirical orthogonal function (EOF), the Sen’s slope (Sen), the Mann-Kendall test (MK) and the Hurst index (Hurst). Additionally, we, through the multi-scale geographically weighted regression model (MGWR), explore the spatial heterogeneity of vegetation response to its influencing factors. On the basis of this, it is by introducing the structural equation model (SEM) that we figure out the mechanisms of vegetation response to climate and human activity. The main results are as follows: (1) Compared with the dimidiate pixel model (FVC), 3DFVC, to some extent, weaken the influence of terrain on vegetation cover extraction with a good applicability. (2) From 2000 to 2021, the average annual vegetation cover has a fluctuating upward trend (0.03·22a−1, p < 0.05), and spatially vegetation cover is lower in the west and higher in the east with a strong climatic zoning feature. In general, vegetation cover is relatively stable, only 7.08% of the vegetation area with a trend of significant change. (3) In terms of EOF (EOF1+EOF2), EOF1 has a strong spatial heterogeneity but EOF2 has a strong temporal heterogeneity. As for the Hurst index, its mean value, with an anti-persistence feature, is 0.451, illustrating that vegetation is at some risk of degradation in future. (4) MGWR is slightly better than GWR. Vegetation growth is more influenced by the climate (precipitation and temperature) or human activity and less by the terrain or soil. Besides, precipitation plays a leading role on vegetation growth, while temperature plays a moderating role on vegetation growth. What is more, precipitation, on different temperature conditions, shows a different effect on vegetation growth.