Canopy tree-soil interactions within temperate forests: effects of soil 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 species and soils. In southern New England, soils under Fraxinus americanaL. (FRAM) and Acer rubrum L. (ACRU) had high contents of total CaO and MgO. Under Quercus rubra L. (QURU) and Fagus grandifoliaEhrh. (FAGR), contents of CaO and MgO were low. Sites with Acer saccharumMarsh. (ACSA) 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 FAGR, QURU, and TSCA were dominant. From 0.8 to 1.5% CaO, ACSA and FRAM increased with increasing CaO content, while the frequency of other species declined. Above 1.5% CaO, there was no relationship between CaO content and ACSA and FRAM abundance, but FAGR and QURU were largely absent. Canopy tree species also varied significantly with texture, which we attribute to the higher Ca and Mg contents of the more sandy soils, rather than to soil physical effects. Correlations between Ca availability and forest composition are well known for calcareous versus noncalcareous soils. Apparently, much subtler variations in supply of mineral nutrients also alter competitive interactions and impose patterning on the distribution of canopy trees within stands. Resume : La distribution d'arbres adultes et les proprietes relativement stables du sol on ete comparees au cours d'une etude des reactions reciproques entre les especes d'arbres de la voute et les sols. Dans le Sud de la Nouvelle-Angleterre, les sols sous Fraxinus americanaL. (FRAM) et Acer rubrum L. (ACRU) contenaient un fort taux de CaO et de MgO total. Sous Quercus rubra L. (QURU) et Fagus grandifolia Ehrh. (FAGR), le contenu en CaO et en MgO etait par contre bas. Les sites avec Acer saccharumMarsh. (ACSA) et Tsuga canadensis(L.) Carr. (TSCA) presentaient une grande variation du CaO et