Unveiling unique microclimate regimes across tropical montane forests in East Africa

The spatiotemporal characteristics of microclimate temperatures are critical for understanding biodiversity patterns and ecosystem processes. However, the temperature patterns in highly biodiverse tropical montane forests remain largely understudied, despite the vulnerability of these ecosystems to changing climates and deforestation. Here, we combined one year of in-situ microclimate temperature measurements from 37 locations across tropical montane forests in East Africa with satellite-derived environmental variables (including canopy height, leaf area index, elevation, latitude and slope aspects) and reanalysis macroclimate data to generate high-resolution understory temperature maps based on a linear mixed-effects model. Using these maps, we derived nine microclimate temperature metrics, classified microclimate regimes, identified their driving factors, and analyzed microclimatic diversity (i.e., number of different microclimate regimes occurred in a specific region) along latitudinal and elevational gradients. Our results show that two environmental variables - latitude and elevation - strongly regulate microclimate regime distribution, shaping their clustering through absolute temperature and variability metrics. Dominant microclimate regimes shifted with elevation, but this pattern was not consistent across absolute latitudes. Warmer regimes exhibited greater seasonality, while colder regimes had higher isothermality, and both of them possessed greater annual temperature ranges compared with moderate regimes. These patterns highlighted how microclimate regimes were structured through both absolute temperatures and variability, representing local thermal environments and influencing ecological conditions. Moreover, microclimatic diversity displayed a prominent peak around 1900 m above sea level (asl) along the elevational gradient from 800 m to 3500 m asl and exhibited several hotspots across mountains in East Africa, which can serve as a large-scale indicator of forest heterogeneity. Our results shed new light on how microclimate temperatures may interact with tropical mountain environments and provide a more nuanced understanding between microclimatic diversity and biodiversity, with crucial implications for the modelling of biodiversity patterns.