Characterization of soil low-molecular-weight organic acids in the Karst rocky desertification region of Guizhou Province, China

摘要

Soil low-molecular-weight （LMW） organic acids play important roles in the soil-forming process and the cycling of nutrients in Karst regions. In this study, we quantified the contents of LMW organic acids （including lactate, acetate, formate, malate, and oxalate） in soil solution over the Karst region of Guizhou Province, China using ion chromatography. The concentration of total LMW organic acids in topsoil solution ranged from 0.358 to 1.823pmol＇g-1, with an average of 0.912p.mol.gL The mean concentrations of lactate, acetate, formate, malate, and oxalate were 0.2124-0.089, 0.3024-0.228, 0.301-4-0.214, 0.014zk0.018 and 0.086＋0.118 pmol.g-% respectively. There were also significant difference in the contents of these acids among four phases of rocky desertification, and their concentrations decreased with the aggravation of rocky desertification. The concentrations of the LMW organic acids were significantly positive correlated each other. Significant positive correlations were also observed among individual LMW organic acids in soil solution, and between them and soil available P, available K, exchange- able Ca, respectively. Furthermore, the concentrations of LMW organic acids were significantly positively corre- lated with inorganic anions （chlorides, nitrates, and sulfates） in Karst topsoil solution. Therefore, the concen- trations of soil LMW organic acids might be one of driving force in the Karst rock desertification process in Guizhou Province.