Effects of Pinus densiflora on soil chemical and microbial properties in Pb-contaminated forest soil

We investigated the effect of Pb uptake by Pinus densiflora and the Pb fraction in forest soil. We also investigated thechange in soil physicochemical characteristics, microbial activity, and root exudates of Pinus densiflora in Pb-contaminatedsoils. Three-year-old pine seedlings were exposed to 500 mg/kg Pb for 12 months. The metal fractions were measuredusing sequential extraction procedures. Additionally, factors that affect solubility (three soil enzyme activities andamino acids of root exudate compounds) were also determined. The results showed that Pb contamination significantlydecreased enzyme activities due to soil characteristics. In addition, organic matter, nitrate content, and Pb concentrationwere time dependent. The results indicate that changes in the Pb fraction affected Pb uptake by pine trees due to anincrease in the exchangeable Pb fraction. The concentrations of organic acids were higher in Pb-spiked soil than those incontrol soil. Higher rhizosphere concentrations of oxalic acid resulted in increased Pb uptake from the soil. These resultssuggest that pine trees can change soil properties using root exudates due to differences in the metal fraction.