Elevation, soil pH and calcium availability shape regional and local scale spatial patterns of PhoD gene abundance in tropical and subtropical forests

Abstract Organic phosphorus mineralization is a critical process in the phosphorus cycle, governing phosphorus bioavailability for plants. The PhoD gene, which encodes the key enzyme alkaline phosphatase, serves as a valuable biomarker for this process. Soil microbes harbouring the PhoD gene mediate this process by secreting extracellular alkaline phosphatases. This gene is widespread across diverse bacterial phyla, and its significance has been extensively reported in agroecosystems, particularly in response to fertilizer inputs. However, the spatial distribution of the PhoD gene in natural ecosystems along environmental gradients and its consequent effects on phosphorus dynamics remain unclear. We investigated the spatial distribution of the PhoD gene abundance across 20‐ha study areas in tropical (Nabanhe, Bubeng) and subtropical (Ailaoshan) forests spanning broad elevation gradients but narrow latitudinal ranges. Our objectives were to (a) characterize its spatial patterns, (b) identify the key drivers of its variation across local and regional scales and (c) determine the influence of soil chemical properties. PhoD gene abundance and detectability differed sharply among forests. Abundance was highest and most ubiquitous in mid‐elevation Nabanhe (1015.86–1235.64 m), intermediate in low‐elevation Bubeng (712.05–860.05 m) and lowest in high‐elevation Ailaoshan (2443.78–2586.13 m), where the gene was frequently undetectable. A distinct difference among sites was the higher frequency of non‐detection in Ailaoshan compared to the other sites. The results identified elevation, soil pH and calcium as the top three predictors of PhoD gene abundance and distribution at the regional scale. Soil pH was a consistent driver at both regional and local scales. Regionally, the effect of elevation was mediated by changes in soil pH and macronutrients (total carbon, total nitrogen, total phosphorus). However, at local scales, the spatial pattern was associated with variations in soil parent material, which influenced both soil pH and calcium. In summary, PhoD gene abundance varied significantly across the forest ecosystems. Our investigation demonstrates how elevation‐driven environmental changes shape the genetic potential for phosphorus mineralization, underscoring the need for broader scale studies to project the responses of this key microbial process to global change. Read the free Plain Language Summary for this article on the Journal blog.