CHEMICAL CHARACTERISTICS OF SOILS UNDER SPRUCE-FIR FORESTS IN EASTERN MAINE

Abstract

Soils supporting even-aged spruce-fir stands in eastern Maine are highly acid with soil pH often found to be a useful indicator of potential tree growth. This investigation examined the chemical characteristics of these soils at 22 spruce-fir sites and the relationship between soil chemical properties and site productivity. Each major soil horizon exhibited a distinctly different chemical environment. Spruce-fir site productivity was found to be significantly correlated with B horizon organic-P, O horizon pH, and the total organic matter content of the mineral soil horizons. Soil pH increased with depth in the profile ranging from a mean value of 3.13 in the O horizon (i.e. F + H) to 4.91 in the C horizon. Significant correlations were exhibited between pH and exchangeable Ca, exchangeable Al, and extractable Al throughout the profile. Fractionation of P in the B horizons demonstrated that occluded-P was the most concentrated of the fractions measured, with the order of relative abundance for the P fractions being occluded-P > Al-P > organic-P > Fe-P > Ca-P > extractable-P. Sampling of soils for evaluating the potential for forest growth in this region must be carried out by horizons, as these differ remarkably with respect to those variables that have been shown to have an influence on tree growth. Key words: pH, site quality, organic matter, phosphorus, aluminum, spruce-fir