A multivariate analysis of tree species influence on forest floor fertility /

The objective of this study was to assess tree species influence on forest floor fertility in a mixed forest stand using Redundancy Analysis (RDA). Eighty microsites were located in a beech-hemlock-red maple forest. Forest floor was analyzed for thirteen variables; total N, P, K, Ca and Mg, extractable Ca, Mg and K, mineralizable N (NH$ sb{4+}$), basal microbial respiration (CO$ sb2$), pH, thickness and bulk density. The influence of seven tree species was calculated as a function of tree diameter and distance from each microsite. Spatial patterns were detected by using correlograms and incorporated in a variation-partitioning model with trend surface analysis. Tree species, microtopography, and spatial structure explained 53% of the total variation in forest floor data. The fraction explained by tree species alone (16%) was studied with a RDA ordination biplot. The main source of variation in the soil data was related mainly to the opposite effects of American beech and eastern hemlock on calcium while most of the other species had a beneficial effect on soil fertility. This study showed the potential of RDA as a tool for studying the role of tree species in mixed forests