Abstract
Observing vegetation normalized difference vegetation index (NDVI) changes, climate change characteristics, and their response relationship have a great significance to the ecosystem's regulation and improvement the human settlements. Based on GIMMS AVHRR NDVI and MODIS NDVI datasets as well as temperature, precipitation, and sunshine duration data, this study used unitary linear trend analysis, correlation analysis, RS, and GIS data to analyze the spatiotemporal variation characteristics of vegetation NDVI in the middle and upper reaches of the Yellow River between 1989 and 2018. It also analyzed the spatiotemporal response between vegetation NDVI and climate factors (temperature, precipitation, and sunshine duration). The results showed that the vegetation NDVI in the study area had an increasing trend over the past 30 years, growing by 31.28%, and the NDVI change in 81.83% of the pixels was positive, the highest being 0.025. The temperature in the middle and upper reaches of the Yellow River showed an obvious upward trend, showing an overall distribution pattern of low temperature in the southwest and high temperature in the southeast. The precipitation showed a gentle upward trend and a spatial distribution pattern of a gradual decrease from southeast to northwest. The sunshine duration showed an obvious decreasing trend and a spatial distribution pattern of gradually increasing from southeast to northwest. In the past 30 years, the annual mean NDVI in the study area had a positive correlation with temperature and precipitation and a negative correlation with sunshine duration.
Highlights
AS one of the most important components of the Earth's terrestrial ecosystem, vegetation has the function of connecting ecological elements, such as the atmosphere, soil, and water, thereby playing an extremely important role in regional climate regulation, human settlements maintenance, carbon sequestration, oxygen release, biodiversity protection, and other ecological service functions, and it can provide a strong guarantee for the natural ecosystem and human life [1]– [5]
Vegetation dynamics are affected by natural factors and human activities, and climate is the main factor that determines the distribution of vegetation types
This study aimed to provide a theoretical basis for the ecological protection and high-quality development of the Yellow River basin, especially around the upper and middle reaches of the Yellow River
Summary
AS one of the most important components of the Earth's terrestrial ecosystem, vegetation has the function of connecting ecological elements, such as the atmosphere, soil, and water, thereby playing an extremely important role in regional climate regulation, human settlements maintenance, carbon sequestration, oxygen release, biodiversity protection, and other ecological service functions, and it can provide a strong guarantee for the natural ecosystem and human life [1]– [5]. The normalized difference vegetation index (NDVI) is an effective indicator of large-scale vegetation cover changes [9]– [14], can represent the surface vegetation cover and vegetation growth, and can be used to monitor vegetation changes and explain the impact of weather/climate events on the human settlements [15]– [17]. The use of different NDVI products may cause certain differences in the results, but they still have obvious advantages in the studies on large-scale vegetation cover changes and their causes as well as in land cover identification [21]. Vegetation activities have exhibited an increasing trend [22], and the vegetation cover of the Eurasian continent [23], China [24], and the eastern region of China [25] has shown certain changes. The most significant climatic factors are temperature, precipitation, and sunshine duration [26]
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