Microhabitat and seasonal dynamics of soil fauna communities in upper Andean successional forests

Abstract

Soil fauna play a crucial role in supporting soil functions and their communities change along forest successional gradients. However, our understanding of their temporal dynamics is limited, particularly in tropical mountain ecosystems with pronounced seasonal precipitation patterns. Additionally, the impact of forest successional stage on the regulation of seasonal changes in soil fauna communities remains poorly understood. In this study, we examined the changes of soil fauna communities across climatic seasons and microhabitats in mature and secondary forests of upper Andean tropical forests (UATF). We collected 168 soil samples (30x30x5 cm) across four climatic seasons (two wet and two dry) from 14 permanent plots in four UATF sites during La Niña event. Microclimatic data (air, surface, and soil temperatures, and soil moisture) were recorded every 15 minutes for a year using TOMST dataloggers. Our findings reveal that soil fauna richness and abundance significantly increase during wet seasons, although species composition remained unchanged. This increase is mainly due to higher soil moisture levels, which control soil fauna attributes. We also observed an interaction between climatic season and microhabitat: during wet seasons, when soils are water-saturated, more species migrate to the litter layer, whereas during dry seasons, when water availability is reduced, species tend to aggregate in the soil. However, no interactions were detected between these factors and successional stages. Soil moisture directly influenced soil fauna richness and abundance in both mature and secondary forests. Overall, our study highlights that soil fauna in UATF exhibit clear climatic seasonality, shaping microhabitat variability independent of forest successional stage.