Local-scale determinants of elemental stoichiometry of soil in an old-growth temperate forest

Aims: Elemental stoichiometry of soil is a useful indicator of nutrient constraints. The aim of this study is to assess the relative contributions of local-scale determinants to the soil carbon/nitrogen ratio (C:N) and nitrogen/phosphorus ratio (N:P) in a 25 ha temperate forest plot. Methods: Leaf litter biomass at 967 soil sampling points was predicted using mapped tree distribution and leaf litter data (150 traps) for seven tree species. Boosted regression trees (BRT) were used to examine the relative contribution of local-scale variables to key elemental stoichiometry of soil. These variables included leaf litter input, neighbor species composition, soil pH and moisture, and topography. Results: Both biotic and abiotic variables influenced soil C:N and N:P ratios, but abiotic factors had a greater influence. Soil pH was the most important predictor of soil C:N and N:P with a strong positive correlation. Topography and soil moisture explained more of the local-scale variability of soil C:N and N:P ratios than tree composition and leaf litter inputs. Conclusions: Our results suggest soil pH was a better predictor of local-scale spatial variability of soil elemental stoichiometry than tree composition and leaf litter inputs in temperate forests. These results improve our understanding of the mechanisms underlying the heterogeneity of soil nutrients.