Effects of soil fauna on early-stage litter decomposition across diverse tropical ecosystems in east Malaysia

Litterbag studies from temperate zones have shown a significant effect of soil fauna on litter decomposition. However, understanding the decomposition dynamics in tropical regions remains limited compared to temperate regions. Here we investigated the impact of soil meso- and macrofauna on litter decomposition rates at three contrasting locations in tropical area of the Eastern part of Peninsular Malaysia (tropical forest near Tasik Kenyir, permaculture in Pahang and urban soils in Universiti Malaysia Terengganu campus). We conducted litterbag experiments with different mesh sizes and soil faunal sampling to investigate the effect of soil meso- and macrofauna on litter decomposition (Fig. 1). As decomposition is fast in the tropics, we expose litterbags for three months and collect them every month. Litter mass loss increased over time, with higher decomposition rates observed in tropical forests and permaculture compared to urban soils. Tropical forest soils host significantly more diverse communities of soil fauna than the other two sites. The principal component analyses (PCA) revealed divergence in the community structure of taxonomic and functional groups among different locations, with urban soils primarily comprising Araneae, Protura, and Diplura, while permaculture and tropical forests mainly consisted of Acari and Collembola. Size analyses revealed that soil macrofauna enhanced decomposition rates in permaculture, while mesofauna affected decomposition in urban soils. The C:N ratio of litter in litterbags increased after three months of incubation in permaculture and tropical forest without any significant differences among mesh sizes. Random forest analyses highlighted the importance of soil moisture and texture (content of sand, silt and clay) influencing soil biota associated with decomposition processes.