Hydrothermal patterns manipulate the growth adaptability of an endangered cypress by mediating microbial community...

Hydrothermal conditions alter soil fungal diversity, nutrient availability, and enzyme activity, thereby critically influencing the growth adaptability of Calocedrus macrolepis to climate change. The response of plants to climate change is governed by the dynamic balance of temperature and water. However, it remains unclear how hydrothermal patterns modulate plant adaptability by affecting the underground soil microbial community. Here we test the hypothesis that the different hydrothermal conditions change the diversity and abundance of soil fungi and bacteria, which in turn regulate soil nutrients, and ultimately change the growth adaptability of Calocedrus macrolepis, a Quaternary glacial relict plant in China. We selected three distinct climate zones in Yunnan Province, China, to simulate altered hydrothermal conditions. In each zone, we comprehensively analyzed soil characteristics, microbial community, and seedling growth phenotypes. We found that bacterial diversity showed no significant change, but fungal diversity differed markedly among zones. With increasing temperature, the richness of Actinobacteriota and Ascomycota increased, while Acidobacteriota decreased. Increasing rainfall led to a decrease in Chloroflexi and Basidiomycota richness. Significant variations were also observed in soil characteristics such as organic matter, nutrients, and enzyme activities. Rainfall was associated with increased available potassium, total phosphorus, and total potassium, while higher temperatures were linked to reduced organic matter, alkaline hydrolysable nitrogen, available phosphorus, total nitrogen, and total potassium. The phenotypic traits showed significant variation across climate zones, with enhanced growth under increased rainfall but inhibited growth under elevated temperatures. Our results indicate that hydrothermal conditions modulated soil pH, nutrient status, and enzyme activity. These changes, in turn, were linked to shifts in fungal diversity, ultimately affecting the growth adaptability of Calocedrus macrolepis.