FACTORS DETERMINING DIFFERENCES IN SOIL-PH IN ADJACENT CONIFER AND ALDER-CONIFER STANDS

Tree species may differ in their influence on biogeochemical cycles, leading to differing rates of soil acidification. Three characteristics of the soil exchange complex which regulate soil pH were observed: the quantity of acids present, which can be represented as the total cation-exchange capacity (CEC); the degree of dissociation of the acids, commonly called base saturation; and the affinity of the acids for H+, or acid strength. The difference in pH resulted primarily from greater acid strength of soil organic matter under alder, and secondarily from lower base saturation of the exchange complex. -from Authors