Spatiotemporal changes and drivers of fractional vegetation cover in Inner Mongolia grassland of China

Abstract: Grassland has been one of the most widely distributed vegetation types on earth. There is also a huge carbon stock with the strong carbon sink function in the global carbon cycle. Fractional vegetation cover (FVC) can be used to monitor and quantify the vegetation growth over a long time series. The specific definition can be the vertical projection of above-ground parts of vegetation (including leaves, stems and branches) per unit area on the ground as a percentage of the total area of the statistical areas. There is also an important FVC impact on the ecosystem functions, such as soil and water conservation, as well as the sand-fixing. This study aims to accurately characterize the evolution and attribution of vegetation growth in the Inner Mongolia grassland of northwest China from 2001 to 2020. A dimidiate pixel model was used to produce the year-by-year FVC dataset using MOD13Q1 product. Meanwhile, a Sen + Mann-Kendall trend analysis was implemented to determine the spatial and temporal variation of FVC. The correlation and geodetector analysis were also made for the relationships between the FVC and climatic/socio-economic factors. The results show that there was a regional and spatial distribution with the high FVC values in the east, whereas, the low FVC values in the west, with a multi-year mean FVC value of 0.44. There were the significant differences in the FVC between the various grassland types. Specifically, the FVC values with the mean values were ranked in the descending order of the meadow (0.70), the meadow steppe (0.64), the typical steppe (0.41), and the desert steppe (0.13). More importantly, the better and greener grassland vegetation was achieved over the past 20 years. Moreover, 77.96% of the grassland area showed an increasing trend in the FVC, while the 15.21% of the grassland in the region was improved significantly, particularly with the most typical MuUs and Horqin Sands in the study area. Five indicators were also chosen (MAP, MAT, population density, per capital GDP, and Livestock density) to explore the influence of FVC. The correlation and geodetector analysis demonstrated that the climatic factors were posed the much more significant influence on the FVC, the most of which was the precipitation, compared with the socio-economic factors. Consequently, the spatial and temporal patterns of FVC were varied significantly in the different grassland types. A strong support can be given from the responses to the climatic and socioe-conomic factors, in order to assess the ecological and environmental conditions for the less degradation and desertification of grassland in Inner Mongolia. The finding can also provide a scientific basis for the decision-making on the ecological restoration and sustainable grassland.