Jipeng Wang;Yanhong Wu;Jun Zhou;Haijian Bing;Hongyang Sun;Jing Luo;Shengyan P

State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu 610059 (China; State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu 610059 (China);Key Laboratory of Mountain Surface Processes and Ecological Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041 (China)

hedley;drying;air;in forest;soils;p pool

Hedley labile phosphorus (P) pools in soil tend to be several times larger than annual forest requirements, even in highly weathered soils characterized by P limitation. The discrepancy between plant and soil P status could be partly attributable to the frequently adopted air-drying pretreatment that tends to increase soil P solubility. In this study, the effects of air-drying on the distribution of Hedley P fractions were examined using soils collected under 4 forest types at Gongga Mountain, southwestern China. The results showed that the microbial biomass P (P mic) in the organic horizon decreased markedly after air-drying. The concentrations of Hedley labile P in the air-dried samples were 31%-73% more than those in the field-moist samples. Consequently, the air-drying-induced increments of Hedley labile P pools in the surface soil horizons were 0.8-3.8 times the annual plant P requirements. The organic horizon was more susceptible to the air-drying-induced increases in Hedley labile P than the mineral horizon, probably because of the stronger release of P mic and disruption of soil organic matter. The quality of P, indexed by the ratio of Hedley labile P to slowly cycling P, shifted in favor of the Hedley labile fractions after air-drying, further revealing that air-drying changed the distribution of Hedley P pools in forest soils. These indicated that the effects of air-drying could not be ignored when interpreting the discrepancy between the P status of plants and the Hedley labile P pools in forest soils. To more efficiently evaluate the P status in forest soils via the Hedley fractionation procedure, the use of field-moist soils is recommended.