Spatio-temporal variation characteristics of NDVI and its response to climate on the Loess Plateau from 1985 to 2015

摘要

The response between NDVI and climate has been a hot topic in recent research. Based on the data of GIMMS NDVI 3g and five climatic factors (precipitation, humidity, atmospheric pressure, air temperature, and sunshine hours), we evaluate spatial-temporal variation characteristics of the Normalized Difference Vegetation Index (NDVI) on the Loess Plateau and its response to climate by Sen+Mann-Kendall, redundancy analysis (RDA) variance decomposition and correlation analysis methods. The results showed that: (1) At the annual scale, the change of vegetation manifested an overall upward trend. However, there was severe degradation (2.49%) in the region, which was mainly distributed in Hohhot City, eastern Yan'an City, eastern Qinghai Province, and along Baoji-Xianyang and Xi'an-Weinan linear district. (2) The correlation between NDVI and atmosphere pressure was negative, while the correlation between NDVI and other four climatic factors was positive. (3) The independent impact and the combined impact of climatic elements, topographical elements and geographical elements were different under different land uses. The uneven spatial distribution of NDVI under different land uses was driven by climatic elements groups. (4) The bi-direction lag effects between NDVI and climatic factors showed the characteristics of short (1-3 months) or long (3-6 months) term under different land uses. Except for atmospheric pressure, the effects were positive in the short-term and negative in the long-term, while atmospheric pressure exhibited the opposite. This study can be conducive to forecast and evaluate the vegetation dynamics under the background of global climate change and provide a theoretical basis for the protection of the regional ecological environment.