Alkaline phosphatase activity mediates soil organic phosphorus mineralization in a subalpine forest ecosystem

Abstract Microorganisms play a crucial role in soil organic P mineralization. However, how microbial and environmental traits mediate this process in subalpine forests remains largely unknown. This study comprehensively investigated the effects of alkaline (ALP) and acid phosphatase activities on soil P availability, and explored microbial and environmental drivers of the two phosphatase activities, in a dark coniferous forest along an altitude gradient of Mount Gongga in the Tibetan Plateau. Our results revealed that alkaline rather than acid phosphatase activity consistently explained the altitudinal and seasonal dynamics of soil available P content, which suggests an important role of ALP in regulating soil P availability in the subalpine forest. Multiple linear regression and partial least squares path modeling analyses identified soil total N, followed by total C as the dominant predictors of the two phosphatase activities. Moreover, alkaline phosphatase activity was modulated by soil N:P ratio as well, which could be because the transcriptions of ALP-encoding genes are under the control of P starvation response regulation. Unexpectedly, alkaline phosphatase activity was found to be closely related with comparatively less abundant phoD-harboring genera, such as N2-fixers Chrysosporum and Anabaenam, but not with the abundance and diversity of phoD gene. We concluded that alkaline phosphatase activity primarily modulated by soil total N and the N:P ratio mediates organic P mineralization in subalpine forest soils. This study provided a novel insight into the ecological regulation of P cycling in mountain forest ecosystems.