关键词: 内蒙古高原, 归一化植被指数, 水热条件, 地理探测器, 人类活动

Abstract: Based on MODIS−NDVI remote sensing data, meteorological data and vegetation type data, combining trend analysis, coefficient of variation and geographic detector, the variation characteristics of NDVI in five vegetation types of desert grassland, deciduous oak forest, meadow grassland, typical grassland and shrubs-grasses semi-desert in the Inner Mongolia Plateau from 2000 to 2020 and its relationship with meteorological factors were analyzed, while the human activities effects on NDVI of different vegetation types were separated using residual analysis. The results show that from 2000 to 2020, the regional average NDVI of Inner Mongolia Plateau showed an increasing trend, with an average growth rate of 0.013·10y⁻¹, with a spatially graded band distribution from west to east. The NDVI of deciduous oak forests increased the fastest（0.032·10y⁻¹）, while that of shrubs-grassy semi-deserts increased the slowest（0.009·10y⁻¹）. The proportion of improved vegetation in the study area to total area of the study area was 91.59%, and the proportion of low and medium-low fluctuation area to the total area of study area was 89.75%. But the meadow grassland was more seriously degraded, and the proportion of degraded area to the total area of this vegetation type was 13.63%, while the proportion of improved vegetation in the other four vegetation types to the total area of their respective vegetation types was over 90%. Both NDVI of different vegetation types and the whole plateau were most strongly correlated with precipitation, and the two-factor enhancement or non-linear enhancement interaction between meteorological factors was obvious, with the combined effect of water and heat being the dominant factor influencing the whole plateau NDVI. The impact of human activities in the study area over the past 21 years had been increasing and contributed to NDVI of the plateau vegetation, with the proportion of the enhanced area of human activities in each of the five vegetation types reaching over 70% of the total area of the respective vegetation types.

Key words: Inner Mongolia Plateau, NDVI, Hydrothermal conditions, Geographic detector, Human activities