Scale-dependent soil macronutrient heterogeneity reveals effects of litterfall in a tropical rainforest

Aims: Soil spatial heterogeneity is an important factor partitioning environmental niches and facilitating species coexistence, especially in tropical rainforests. However, fine-scale spatial variability of soil macronutrients and its causative factors are not well understood. We investigate this fine-scale variability and how it relates to environmental factors. Methods: We conducted intensive soil sampling (361 samples) in a 1 ha plot in a tropical rainforest in Southwest China to investigate patterns of spatial heterogeneity in soil acidity and macronutrients and explored how the soil properties were influenced by topography and litterfall using a scale-wise wavelet analysis. Results: Topography showed great variability at larger scales (>25 m) compared to litterfall properties, which peaked at about 25 m. Soil pH showed variation at large scales and was significantly correlated with topography, whereas soil total nitrogen, ammonium nitrogen, available phosphorus, and potassium showed variation at finer scales and were significantly correlated with litterfall chemical fluxes. A dominant species of canopy tree was non-randomly distributed in high litterfall input sites. Conclusions: This study shows that fine-scale spatial variability of soil macronutrients is strongly influenced by litterfall chemical fluxes, highlighting the importance of biotic factors for understanding fine-scale patterns of soil heterogeneity in tropical rainforests.