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Air-drying changes the distribution of Hedley phosphorus pools in forest soils
- WANG, Jipeng, WU, Yanhong, ZHOU, Jun, BING, Haijian, SUN, Hongyang, LUO, Ji, PU, Shengyan
- Pedosphere 2017
- air drying, annuals, forest types, fractionation, microbial biomass, organic horizons, phosphorus, soil organic matter, solubility, China
- Hedley-labile phosphorus (P) pools of soils tend to be several times larger than annual forest requirements, even in highly weathered soils featured by P limitation. We assume that the discrepancy between plant and soil P status is 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 (Pmic) in the organic horizon decreased markedly after air-drying. The concentrations of Hedley-labile P in the air-dried samples increased by 31-73% compared with 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. Probably due to the stronger release of the Pmic and disruption of soil organic matter, the organic horizon was more susceptible to the air-drying induced increases in Hedley-labile P than the mineral horizon. 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. The data from this study indicated that the air-drying effects could not be ignored to interpret the discrepancy between the P status of plants and the Hedley-labile P pools in forest soils. To better evaluate the P status in forest soils by the Hedley fractionation procedure, the use of field-moist soils is recommended.