NDVI Indicates Long-Term Dynamics of Vegetation and Its Driving Forces from Climatic and Anthropogenic Factors in Mongolian Plateau

Abstract

In recent years, global warming and intense human activity have been responsible for significantly altering vegetation dynamics on the Mongolian Plateau. Understanding the long-term vegetation dynamics in this region is important to assess the impact of these changes on the local ecosystem. Long-term (1982–2015), satellite-derived normalized difference vegetation index (NDVI) datasets were used to analyse the spatio-temporal patterns of vegetation activities using linear regression and the breaks for additive season and trend methods. The links between these patterns and changes in temperature, precipitation (PRE), soil moisture (SM), and anthropogenic activity were determined using partial correlation analysis, the residual trends method, and a stepwise multiple regression model. The most significant results indicated that air temperature and potential evapotranspiration increased significantly, while the SM and PRE had markedly decreased over the past 34 years. The NDVI dataset included 71.16% of pixels showing an increase in temperature and evaporation during the growing season, particularly in eastern Mongolia and the southern border of the Inner Mongolia Autonomous region, China. The proportion indicating the breakpoint of vegetation dynamics was 71.34% of pixels, and the trend breakpoints mainly occurred in 1993, 2003, and 2010. The cumulative effects of PRE and SM in the middle period, coupled with the short-term effects of temperature and potential evapotranspiration, have had positive effects on vegetation greening. Anthropogenic factors appear to have positively impacted vegetation dynamics, as shown in 81.21% of pixels. We consider rapid economic growth, PRE, and SM to be the main driving factors in Inner Mongolia. PRE was the main climatic factor, and combined human and livestock populations were the primary anthropogenic factors influencing vegetation dynamics in Mongolia. This study is important in promoting the continued use of green projects to address environmental change in the Mongolian Plateau.

Monitoring Vegetation Change and Its Potential Drivers in Inner Mongolia from 2000 to 2019

“…Areas with low NDVI fluctuations accounted for 61.7% of the total area, mainly distributed in Hulunbuir, the Xing'an League, Tongliao, and Chifeng, with the vegetation types of forest, typical steppe, and meadow steppe. Fluctuation of NDVI in the Xilingol League, where typical steppes are distributed, was also low, which may be related to the good ecological environmental conditions of its forest and grassland areas; these are not easily influenced by external forces [1]. Additionally, the amplitude of fluctuations in grassland areas was greater than that in forest areas, which may be attributed to the grassland areas being under high pressure from population and livestock, and more strongly disturbed by human activities than forest areas.…”

“…Vegetation is an important component of ecosystems and plays a key role in the carbon cycle [1][2][3]. Distinctive interannual and seasonal variations have been observed while studying vegetation trends [2,4,5].…”

“…Numerous studies have shown that the normalized difference vegetation index (NDVI) correlates well with the biomass and leaf area indices, allowing a good representation of the surface vegetation coverage. This can be used to effectively characterize vegetation activity and productivity and is suitable for representing changes in surface vegetation cover [1,[8][9][10]. With recent advancements in remote sensing technology, moderate resolution imaging spectroradiometer (MODIS) NDVI has become the primary data source for large-scale vegetation cover research because of its advantageous characteristics, such as high quality, wide areal coverage, high temporal resolution, and accessibility [11][12][13].…”

“…Overall, the objectives of this study were: (1) To study the interannual variations of the NDVI characteristics during 2000-2019 for each vegetation type in Inner Mongolia using time series analyses and Mann-Kendall tests; (2) to assess the NDVI stability over the last 20 years in Inner Mongolia by calculating the coefficient of variation; (3) to detect breakpoints in the NDVI at the pixel scale using the STM method and to conduct a trend analysis at each stage; (4) to predict future trends in vegetation dynamics in Inner Mongolia using the Hurst exponent and R/S analysis; and (5) to quantify the mechanisms of single and compound influences of natural and anthropogenic factors on the NDVI using Geodetector. The results of this study can provide a basis for understanding vegetation trends and ecosystem evolution and for predicting the future direction of vegetation growth in Inner Mongolia.…”

Time-Lagged Correlation between Soil Moisture and Intra-Annual Dynamics of Vegetation on the Mongolian Plateau

“…ERA5 has been available since 1979, The ecosystem is mainly composed of grassland (70%) [37], with relatively small areas of forests in the north and northeast, shrubs in the south and southeast, farmland and sparse vegetation in the Gobi desert, and sandy areas in the southwest, which form an important and unique geographical landscape of Eurasia [30]. Therefore, we divided the vegetation into three primary types namely, I: forest, II: grassland, and III: desert vegetation, and further classified them into secondary types namely I-1, coniferous forest; I-2, broad-leaved forest; II-1, forest steppe; II-2, typical steppe; II-3, desert steppe [38]. The MP serves as an important and ideal region for research on the response of arid and semi-arid ecosystems to global climate change [39].…”