CANOPY TREE - SOIL INTERACTIONS WITHIN TEMPERATE FORESTS - EFFECTS OFSOIL ELEMENTAL COMPOSITION AND TEXTURE ON SPECIES DISTRIBUTIONS

We compared the distribution of adult trees and relatively stable soil properties as part of a study of feedbacks between canopy tree specie s and soils. In southern New England, soils under Fraxinus americana L . (FRAM) and Acer rubrum L. (ACRU) had high contents of total CaO and MgO. Under Quercus rubra L. (GURU) and Fagus grandifolia Ehrh. (FAGR), contents of CaO and MgO were low. Sites with Acer saccharum Marsh. (A CSA) and Tsuga canadensis (L.) Carr. (TSCA) varied across a wide range of total CaO and MgO. However, below 0.8% CaO, ACSA was absent and FA GR, GURU, and TSCA were dominant. From 0.8 to 1.5% CaO, ACSA and FRAM increased with increasing CaO content, while the frequency of other sp ecies declined. Above 1.5% CaO, there was no relationship between CaO content and ACSA and FRAM abundance, but FAGR and QURU were largely ab sent. Canopy tree species also varied significantly with texture, whic h we attribute to the higher Ca and Mg contents of the more sandy soil s, rather than to soil physical effects. Correlations between Ca avail ability and forest composition are well known for calcareous versus no ncalcareous soils. Apparently, much subtler variations in supply of mi neral nutrients also alter competitive interactions and impose pattern ing on the distribution of canopy trees within stands.