Soil microbial communities undergo changes in various succession stages following a wildfire in an alpine forest

Wildfires are the typical ecological disturbances to forests globally, vegetation regeneration and successional routes may be altered, changing coniferous forests into broad-leaved forests, shrublands, or grasslands. As soil microbes mediate soil function and different biogeochemical cycles, taking into account the effects of disturbance on soil microbes is essential. However, little is known about the response of the soil microbial community to this succession, especially in alpine forest ecosystems. Here, we studied the differences between soil bacterial communities of three different vegetation succession in an alpine forest ecosystem after wildfire and compared them to a control unburned soil. The results showed that there were significant differences in soil properties of vegetation successional after wildfire. Compared to coniferous forests and broad-leaved forest soil plots, shrubland soil plots had higher pH (4.02±0.02); SOC and TN had no significant differences, but broad-leaved forest soil plots had higher TP (1.36±0.08). Compared to burned soil plots, the unburned soil plots had higher SOC (101.32±7.70), TN (6.02±0.29), and N:P (6.66±0.54). Vegetation successional after wildfire significantly changed the Shannon, chao1, pielou, and Simpson diversity index of soil bacterial community. Compared to unburned soil plots, the relative abundance of Acidobacteria decreased by 16.53%, 5.57%, and 5.13% in shrublands, coniferous forests, and broad-leaved forests, respectively. While the relative abundances of Actinobacteria increased by 4.53% in coniferous forest soil plots, the relative abundances of Chloroflexi increased by 10.93% and 6.87% in shrublands soil plots and broad-leaved forest soil plots, respectively. Principal coordinates analysis (PCoA) analysis indicated that the similarity of soil bacterial communities was higher in different succession after wildfire. We found soil bacterial communities significantly influenced by elevation (r2=0.86, p=0.0005), pH (r2=0.46, p=0.0005), and C: N (r2=0.45, p=0.0015). This study provides a better understanding of the correlation between soil microbial communities and the function of alpine forest ecosystems after wildfires.