Key Soil Physicochemical Properties Regulating Microbial Community Structure under Vegetation Restoration in a Karst Region of China

Background: Vegetation restoration influences soil properties considerably, which in turn interact with microbial community structure and regulate ecosystem stability. However, the influence of soil physical properties on soil microbial community structure has been poorly characterized. Methods: We investigated changes in soil physicochemical properties and bacterial and fungal diversity and composition after natural restoration (grasslands (GL)) and afforestation (artificial forests (AF)) for more than 40 years in a karst faulted basin in China. Results: Compared with that in undamaged natural forests (NF), AF enhanced soil organic carbon and nutrient contents markedly, whereas GL improved soil water stable aggregate, bulk density, and pH. Alpha diversity analyses suggested that vegetation restoration had no significant effect on Chao 1 index and Shannon index of bacterial and fungal communities. However, according to the nonmetric multidimensional scaling analysis results, the dissimilarities in bacterial and fungal community composition between GL and NF were more distinct than those between AF and NF. Such diverse responses of bacterial community structure to vegetation restoration were largely explained by soil pH. Additionally, soil pH, porosity, bulk density, and field capacity were significantly correlated with fungal community structure (P < 0.05). Conclusion: Vegetation restoration in ecologically fragile areas should focus on understanding interactions between microbial community structure and soil chemical properties as well as physical properties.