Loblolly pine plant community structure and soil solution aluminum, organic acids, calcium, magnesium, and pH

Vegetative cover may influence soil chemical properties by producing organic acids that can modify the toxicity are responsible for high levels of nontoxic soil solution aluminum (Al). This study was conducted to determine the effect of loblolly pine (Pinus taeda L.) plant community structure, i.e., differing vegetative covers, on exchangeable cation distribution, and soil solution concentration of aluminum (Al) and organic acids. Soil was sampled were taken from 8-year-old forest plots with differing plant community structure (herbaceous-hardwood-pine, herbaceous-pine, hardwood-pine, and pine only), and measured for exchangeable cations. Soil solution extracts were analyzed for Al, organic acids, and the major cations and anions. There were significant differences in exchangeable Al, and calcium (Ca) among communities. Soil pH was highest in the herbaceous-pine community, while other communities did not differ in soil pH. Oxalic, citric, malic, and succinic acids were detected in soil solution for all communities, but did not differ significantly among communities. Calculated Al activity was less than those determined by the 8-hydroxy quinoline (15 sec) method. For these conditions, calculated Al activities did not change by accounting for the Ca- and magnesium (Mg)-organic acid complex. The Al activities found were similar to previous reported levels that were considered nontoxic.