The influence of bigleaf maple on forest floor and mineral soil properties in a coniferous forest in coastal British Columbia

Bigleaf maple (Acer macrophyllum Pursh) is a common tree species in coastal forests of the Pacific Northwest. We studied the influence of bigleaf maple on forest floor and mineral soil properties in a forest dominated by Douglas-fir [Pseudotsuga menziessi (Mirb.) Franco] and western hemlock [Tsuga heterophylla (Raf.) Sarg.]. Twelve plots containing bigleaf maple were compared to paired plots without the influence of bigleaf maple. Compared to conifer plots, forest floors at bigleaf maple plots were significantly thinner, but the total contents of C in both forest floor and surface mineral soils did not differ between bigleaf maple and conifer plots. This suggests that the bigleaf maple litter may not be fully decomposing; rather a portion of the decomposing litter may be transforming into recalcitrant soil organic matter. Bigleaf maple plots had significantly higher pH, NO3-N concentrations and contents and mineralizable N contents in the forest floor as well as significantly higher cation exchange capacity and concentrations of N (total, mineralizable and NO3-N) and exchangeable K, Ca and Mg in the mineral soil. The changes in soil chemical properties suggest that the presence of bigleaf maple in conifer forests may cause a modest improvement in soil fertility.