Abstract
Based on long term NDVI (1982–2015), climate, topographic factors, and land use type data information in Shaanxi Province, multiple methods (linear regression, partial and multiple correlation analysis, redundancy analysis and boosted regression trees method) were conducted to evaluate the spatial-temporal change footprints and driving mechanisms in the pixel scale. The results demonstrated that (1) the overall annual average and seasonal NDVI in this region showed a fluctuating upward trend, especially in spring. The difference between the end of season (eos) and start of season (sos) gradually increased, indicating the occurrence of temporal “greening” across most Shaanxi Province. (2) The overall spatial distribution of annual mean NDVI in Shaanxi Province was prominent in the south and low in the north, and 98.83% of the areas had a stable and increasing trend. Pixel scale analysis reflected the spatial continuity and heterogeneity of NDVI evolution. (3) Trend and breakpoint evaluation results showed that evolutionary trends were not homogeneous. There were obvious breakpoints in the latitude direction of NDVI evolution in Shaanxi Province, especially between 32–33 °N and in the north of 37 °N. (4) Compared with precipitation, the annual average temperature was significantly correlated with the vegetation indices (annual NDVI, max NDVI, time integrated NDVI) and phenology metrics (sos, eos). (5) Considering the interaction between environmental variables, the NDVI evolution was dominated by the combined influence of climate and geographic location factors in most areas.
Highlights
The plant community composed of various vegetation is the producer in the ecosystem, which plays a stabilizing and integrating role in the overall natural environment of the land
The size of the boxplot was relatively large in some years, which indicated that there was a large difference between the NDVI values of each pixel in Shaanxi Province in that year
Redundancy analysis (RDA) Results was dominated by crop land
Summary
The plant community composed of various vegetation is the producer in the ecosystem, which plays a stabilizing and integrating role in the overall natural environment of the land. Global Inventory Monitoring and Modeling System (GIMMS NDVI3g , NDVI for short in this paper) is the longest time series of global vegetation data available at present; it is both reliable and accurate and is universally applicable for tracing vegetation change [9]. According to this dataset, Ye et al [10] analyzed the change characteristics of vegetation in the global large-scale region, and the global NDVI had a distinct seasonal trend. Jiao et al [11] studied the impact of climate change on vegetation cover in China from 1982 to 2013
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