Abstract

The interaction between plants and soil biogeochemical processes plays a key role in shaping microbial communities, especially under extreme conditions like those in the dry Andes. Polylepis tarapacana, one of the few trees able to survive in these conditions, influences soil development in significant ways. This study examines how P. tarapacana impacts soil microbial communities across varying tree cover. The presence of the tree was found to increase soil organic matter and pH, associated with changes in microbial composition and abundance. Bacterial phyla such as Verrucomicrobiota, Gemmatimonadota, and Nitrospirota increased significantly to the high cover site, while Chloroflexota and Armatimonadota decreased significantly to the absent cover site. Saprotrophic fungi and pathogens thrived with less plant cover, while ericoid mycorrhizal fungi were more prevalent in high and absent cover areas. Sulfur respiration rose in high cover sites, while ammonification decreased in medium cover areas. Enzymatic activities related to phosphorus, nitrogen, and carbon capture also increased with tree cover, along with heterotrophic respiration. These findings suggest that improved soil conditions in areas with higher tree cover enhance microbial communities and soil functions.