Depth-dependent dynamics of microarthropods in forest floors along temperature and soil phosphorus gradients

Abstract

Forest floors buffer harsh environmental conditions and insulate soil, thereby mitigating the effect of climate extremes on soil fauna. Conversely, the soil fauna is key for shaping the structure of forest floors. We investigated the distribution patterns of two major decomposer microarthropod groups (Collembola and Oribatida) across the different layers of the forest floor (Ol, Of/Oh) and the upper mineral soil (Ah) of 12 forest sites representing temperature and phosphorus gradients. A total of 58 Collembola and 144 Oribatida species were recorded. Phosphorus as main factor neither significantly affected the abundance of Collembola nor that of Oribatida. Oribatida richness significantly increased with increasing temperature but decreased with increasing phosphorus level. The abundance, richness and biomass of both microarthropod groups were at a maximum in the Of/Oh layer followed by the Ah and Ol layer. Collembola and Oribatida community structure also varied with temperature and phosphorus levels but this depended on layer. We identified soil and litter carbon-to-nitrogen ratio, pH, Gram-positive bacterial phospholipid fatty acids (PLFAs) and thickness of Ol and Of/Oh layers as important drivers for Collembola and Oribatida communities. These findings highlight the critical influence of temperature, phosphorus and forest floor stratification on soil microarthropod communities, alongside additional other soil properties. The differential responses of Collembola and Oribatida to temperature and phosphorus gradients underscore functional and ecological differences between these groups, with Oribatida being more sensitive to climatic and nutrient changes. Overall, the results emphasize the importance of maintaining the structural integrity of forest floors to support diverse and resilient soil fauna communities.