Some Effects of Stem Flow from Forest Canopy Trees on Chemical Properties of Soils

The most abundant elements contained in stem flow from American beech (Fagus grandifolia), red oak (Quercus rubra), and sugar maple (Acer saccharum) were C >>> K = Ca > Na = Mg = P. Variations in leaching potential and in concentration of chemical constituents around the base of beech trees, due to non-uniform stem flow, produced considerable variation in chemical properties of soil around the stems. The presence or absence of organic litter in surface soil samples caused only slight differences in chemical properties of the samples. Systematic variations in chemical properties of Bennington and Dekalb soils were developed with radial symmetry with respect to the stems of several tree species. Generally, the greater the difference in chemical properties of these soils with respect to distance from the tree stem, the greater the quantity of stem flow from the tree. In soil under those trees with relatively large quantities of stem flow, organic C, exchangeable K, and ⁽ 137)Cs increased, while pH decreased progressively inward toward the stems, particularly in the upper 10-20 cm of soil. The magnitude of variations was greater in Bennington soil than in the more acidic and coarser textured Dekalb soil, and greater under beech trees and red oak than under sugar maple, pignut hickory (Carya glabra), and white oak (Quercus alba). The variations under beech and red oak were attributed mainly to effects of stem-flow water, whereas those under the other species were attributed mainly to effects of organic litter or to a combination of the two effects. The content of the fallout radioisotope ⁽ 137)Cs in soil under the trees was used as substantiating evidence of the quantity of stem flow the trees.