Higher temperatures decreased the abundance of arbuscular mycorrhizal fungi and the complexity of their networks by reducing tree diversity

Temperature plays a crucial role in regulating the community of arbuscular mycorrhizal fungi (AMF) by influencing plant diversity and soil nutrient. Here, we compared the characteristics of AMF between bulk soil and rhizosphere soil at two temperature levels in the karst forest. The AMF community composition, abundance, and diversity significantly differed between the cool region with a mean annual temperature (MAT) of 12.9 degrees C and the warm region with a MAT of 21.7 degrees C. Higher tree diversity was observed in the cool region compared to the warm region. In contrast to the warm region, the cool region showed greater AMF abundance in both bulk soil and rhizosphere soil, along with higher AMF richness and Shannon index in the bulk soil. However, AMF diversity was lower in the cool region than in the warm region in the rhizosphere soil, attributed to intense rhizosphere activity in the high-temperature area. The complexity of the co-occurrence network increased more significantly in the cool region by strengthening the associations among AMF taxa, particularly within the rhizosphere soil, compared to the warm region. The MAT exhibited a negative correlation with AMF abundance and diversity in the bulk soil, as well as AMF abundance in the rhizosphere soil. Tree diversity (e.g., richness) and the ratio of carbon to nitrogen were positively correlated with AMF abundance and diversity in the bulk soil as well as AMF abundance in the rhizosphere soil. These results suggest that lower temperatures promote tree diversity and increase soil nutrient availability, ultimately resulting in a greater abundance of AMF and a more complex network of AMF taxa. Therefore, it is essential to consider climatic factors when predicting the impact of plant-mycorrhizal symbiosis dynamics on vegetation restoration in the fragile karst ecosystem.