# Monitoring Vegetation Change and Its Potential Drivers in Inner Mongolia from 2000 to 2019
## 4 Discussion  
The NDVI values in Inner Mongolia indicated a generally decreasing trend before 2009, and then increasing, which is consistent with the results of existing studies [78]. Additionally, the sudden change in NDVI in the central part of Genhe city in Hulunbeier between 2002 and 2005 may be attributed to the frequent grassland fire events in the forest areas of Inner Mongolia during this period [79]. Most of the remaining areas north of central Inner Mongolia mutated between 2008 and 2014, and vegetation showed an increased trend after the mutations. This may be attributed to the positive effect of the \"Fifth Phase of the Three-Northern Shelter Forest Program\" [80]. The breakpoints in the northern parts of Baotou and Wulanchabu occurred between 2014 and 2017. This may be attributed to the government of Baotou that began artificial restoration and the development of heavily polluted mining areas in 2011, for which physical separation and remediation methods were used to remove heavy metals in the soil to comply with the National Environmental Quality Standards for Soil in China [81; 82]. Additionally, vegetation in the Sizizwang Banner area increased because of the combined effect of increased precipitation and reduced anthropogenic grazing [44]. In the northwestern regions of Ordos, Bayannur, and the Alxa League, the vegetation deteriorated to varying degrees owing to a combination of natural and human factors, such as reduced precipitation, overgrazing, and human reclamation of land. Vegetation around water bodies showed a small improvement. For example, Moon Lake and the surrounding areas of the Alxa League transitioned from a significant decrease to an increase in NDVI before, and after the mutation, respectively [83]. The average temperature in Inner Mongolia increased and precipitation decreased from 2000 to 2009, leading to increased drought in Inner Mongolia and inhibiting vegetation growth [49]. The influence of precipitation on vegetation in Inner Mongolia mainly occurred in areas where agricultural vegetation and grasslands are distributed. Conversely, the effect of precipitation is less than that of temperature in forests, probably because agricultural  
Figure 12: Ecological detector results for each factor of the NDVI in Inner Mongolia from 2000 to 2019. Note: positions marked with Y in the figure indicate significant differences in the influence of each factor on the spatial distribution of vegetation NDVI, with different influence mechanisms; positions marked with N indicate the lack of significant differences in the influence mechanisms of the two factors on the spatial distribution of NDVI. vegetation and grasslands are more sensitive to changes in precipitation. The influence of natural factors is also reflected in the vegetation breakpoint years and the changes in their trends before and after the breakpoints. The cumulative effect of precipitation and soil moisture on desert steppe and desert areas in the northwest is more pronounced and lasts longer than that in other areas because of their fragile ecological environment. This makes them less adaptable to changes in external natural conditions. Additionally, the increased frequency and intensity of extreme climatic events, such as droughts and high-temperature heat waves, can lead to significant changes in vegetation cover [77; 84]. Soil types in Inner Mongolia are distributed from northeast to southwest in the order of black soil, dark brown loam, black calcium soil, chestnut calcium soil, brown loam, black kiln soil, gray calcium soil, wind-sand soil, and gray-brown desert soil, and the stability of vegetation growth varies greatly among different soil types. Black and blackish-chestnut soils in the central and northeastern parts of the country have high contents of organic matter, strong water retention properties, and good natural conditions, which are conducive to the growth of vegetation. The stability of vegetation in this area is correspondingly high, with the occurrence of fewer breakpoints.