Response of spatiotemporal variability in soil pH and associated influencing factors to land use change in a red soil hilly region in southern China

Abnormal changes in soil acidity and alkalinity impact regional food security and sustainable development of terrestrial ecosystems, especially under land use change. The regulation of soil acidity and alkalinity requires a clear understanding of soil pH variability and its influencing factors under regional land use change. This study explored the patterns of soil pH variability under land use change between 1984 and 2018 in a red soil hilly region (Xunwu County, Jiangxi Province) in southern China. We identified the key factors influencing regional spatiotemporal variability in soil pH and analyzed the response of soil pH variability to land use change. The results showed that the mean pH values of surface soil samples in 1984 (n = 595) and 2018 (n = 580) were 5.35 and 5.05, respectively. The soil pH change between the two periods ranged from -0.91 to 0.32, with a mean value of -0.30. In total, 91.72% of the study area showed an acidification trend from 1984 to 2018. The spatiotemporal variability in soil pH was influenced by elevation, slope, distance to rivers, changes in distance to roads, and changes in the nitrogen fertilizer application rate. The main land use conversion modes were cropland and forest transferred to garden and other land. The soil pH decreased in 15 of 16 conversion modes of cropland land, garden, forest, and other land, whereas a pH increase of 0.32 occurred under conversion from cropland to garden. Changes in distance to roads, changes in the nitrogen fertilizer application rate, and slope played a dominant role in soil pH variability under land use change. This study provides fundamental data for the formulation of soil acidity and alkalinity control measures, which in turn contributes to regional improvement of agricultural production stability and sustainable development.