Ambient climate and experimental drought strongly shape the richness and abundance of soil microbial communities in a tropical montane cloud forest.

Tropical montane forests are undergoing rapid climate change, with declining cloudiness and warming in higher elevations. While impacts on vegetation are increasingly documented, effects on belowground microbial communities and ecosystem processes remain poorly studied. We investigated how experimental drought and warming influence soil microbial communities and decomposition across a 900-m elevation gradient in the tropical montane forests of the Dominican Republic. Precipitation exclusion shelters simulated drought at high (2250 m a.s.l.) and low elevation (1350 m a.s.l.) and high elevation soils were translocated to the lower elevation to simulate warming. Fungal and bacterial communities were measured by DNA sequencing over 11 months, in addition to soil properties and litter decomposition. Fungal richness increased under drought but was unchanged following translocation, whereas bacterial richness and abundance were largely unaffected by either treatment. Decomposition was consistently faster at the lower (warmer) site but slowed under intense drought at both elevations. Soil carbon was higher at high elevation, consistent with slower decomposition. Overall, these results indicate cooler and wetter conditions promote structurally and functionally complex fungal communities. As temperature and precipitation patterns change, fungal communities are more likely to shift in response, altering decomposition and nutrient cycling, with implications for carbon storage in tropical montane ecosystems, especially at high elevations.