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

Vegetative cover may influence soil chemical properties by producing organi c acids that can modify the toxicity are responsible for high levels of non toxic soil solution aluminum (Al). This study was conducted to determine th e 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 sample d were taken from 8-year-old forest plots with differing plant community st ructure (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 wer e significant differences in exchangeable Al, and calcium (Ca) among commun ities. Soil pH was highest in the herbaceous-pine community, while other co mmunities did not differ in soil pH. Oxalic, citric, malic, and succinic ac ids 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 condition s, calculated Al activities did not change by accounting for the Ca- and ma gnesium (Mg)-organic acid complex. The Al activities found were similar to previous reported levels that were considered nontoxic.