Effect of topography and litterfall input on fine-scale patch consistency of soil chemical properties in a tropical rainforest

Aims: Spatial aggregation of soil chemical properties, or nutrient patches, may be generated by topography and plants and can seasonally fluctuate because of climate. Whether nutrient patches maintain consistency (no change in ranking through sequential sampling), through temporal scales, and whether topography and litterfall contribute to the persistence of such ranking is rarely tested. Methods: In a 1-ha tropical rainforest plot in Southwest China, we measured soil pH, total N, NH₄–N, NO₃–N, and available P and K for four times and assessed the patch structure (patterns of patch distribution) and their temporal consistency. We then tested how structure and consistency of chemical soil properties were affected by topography and chemical inputs from litterfall. Results: All soil chemical properties showed significant seasonal fluctuations, but patch consistency was higher for soil pH, total N, and available P and K compared to NH₄–N or NO₃–N. Topography influenced pH patch consistency while annual litterfall input was important for maintaining patch consistency in total N and available P and K. Conclusions: Fine-scale consistency of patches in soil pH, total N, and available P and K suggest they may exert stable selection pressures on species for niche differentiation, while consistency of soil NH₄–N and NO₃–N require further study.