Abstract
The hilly area of central Sichuan is one of the ecologically fragile regions in the upper reaches of the Yangtze River, and it is also the main part of ecological engineering construction. The ecological environment in the study area is related to the ecological security in the middle and lower reaches of the Yangtze River. Recent years have witnessed a great change in vegetation cover in this area as a result of climate change. Therefore, it is necessary to identify the changing patterns of vegetation cover and the impacts of climate change on the vegetation cover change in the study area. In this paper, the characteristics of vegetation cover change over the past 15 years were analyzed, based on the dataset of MODIS NDVI from 2001 to 2015 as well as the climate data from 55 meteorological stations, with methods such as maximum value composite (MVC), linear regression and correlation coefficient. The results showed that the annual maximum average NDVI in the hilly areas of central Sichuan has increased at a rate of 5.84/10a (P<0.01), while the summer average NDVI has increased at a rate of 1.6/10a (P>0.1). The spatial distribution of annual NDVI significantly increased (31.58%) was greater than the significantly decreasing trend (2.90%). Besides, areas with significantly positive correlation and significantly negative correlation between NDVI and precipitation in summer accounted for 16.91% and 2.5% of the total area, respectively. And, the correlation between NDVI and precipitation in summer was different in different regions.
Highlights
Climate change and human activities are major driving factors of changes in global terrestrial ecosystems and regional terrestrial ecosystems[1,2]
2.2 Data Source 2.2.1 Acquisition of MODIS data The MODIS13Q1 normalized different vegetation index (NDVI)(250 m,16-day) dataset used in this study were obtained from the Geographical Information Monitoring Cloud Platform for the period from 2001 to 2015, and the annual maximum NDVI is calculated by Maximum Value Composite (MVC)[20], efficiently removed the "noise" in all time series from cloud, atmosphere and Solar altitude angle
Where θslope is the slope of regression; n is the number of years, and NDVIi represents the annual maximum NDVI value or summer NDVI
Summary
Climate change and human activities are major driving factors of changes in global terrestrial ecosystems and regional terrestrial ecosystems[1,2]. There are studies showing that different ecological types of vegetations have different responses to climate change and human activities[13,14,15]. Liu[17] and Wang[18] et al used the GIMMS/NDVI to quantify the dynamic changes of vegetation in the Jialing river basin. They considered that the tendency of vegetation changes is different in different research phases. Yang[19] et al aimed to analyze the characteristics of landscape pattern changes in the hilly area of central Sichuan, and concluded that high vegetation cover types gradually loses its advantage. We can establish a scientific evidence for regional vegetation protection and soil erosion management as well as ecological project
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