Abstract
The loss of phosphorus (P) during the early pedogenesis stage is important at the ecosystem level, and it also plays an important role in the global P cycle. The seasonal variation of total P (Pt) and its fractions along a young soil chronosequence (Hailuogou chronosequence) on the eastern slope of Gongga Mountain, SW China, was investigated based on the modified Hedley fractionation technique to understand P loss during the early pedogenesis stage. The results showed that the mineral P (mainly apatite) was the dominant fraction of Pt in the C horizon of the soil, and the seasonal difference in Pt and its fractions was insignificant. In the A horizon, Pt concentrations decreased markedly compared with those in the C horizon, and as the age of the soil increased, the inorganic P (Pi) significantly decreased and the organic P (Po) prominently increased. Seasonally, the P fractions exhibited various distributions in the A horizon. The variation of Pt and its fractions revealed that the P loss was rapid along the 120-year soil chronosequence. The P stocks in soils (0–30 cm) started to decrease at the 52 year site. And the P stock depletion reached almost 17.6% at the 120-year site. The loss of P from the soil of the Hailuogou chronosequence was mainly attributed to weathering, plant uptake, and transport by runoff. About 36% P loss was transported into plant biomass P at the 120 year site. The data obtained indicated that the glacier retreat chronosequence could be used to elucidate the fast rate of P loss during the early pedogenic stage.
Highlights
Phosphorus (P) is one of the limiting nutrients in diverse natural habitats, including freshwater, marine, and terrestrial biomes (Huang et al, 2013; Elser, 2012), especially as nitrogen (N) deposition increases (Elser et al, 2007; Craine & Jackson, 2010; Cramer, 2010)
One is by P occlusion over time by biological and geochemical processes in which P is transformed into stable organic forms (Turner et al, 2007), which are difficult to mineralize (Walker & Syers, 1976). Another is the direct loss of bio-available P as well as other P fractions by plant uptake, soil erosion, runoff transport, etc
Was P lost during the 120 years of pedogenesis? The ratios of the Pt concentrations in the A horizon to that in the C horizon partly revealed the continuous loss of P with soil age
Summary
Phosphorus (P) is one of the limiting nutrients in diverse natural habitats, including freshwater, marine, and terrestrial biomes (Huang et al, 2013; Elser, 2012), especially as nitrogen (N) deposition increases (Elser et al, 2007; Craine & Jackson, 2010; Cramer, 2010). Due to the unique global P cycle (Newman, 1995; Fillippelli, 2008), the content of bio-available P in the soil decreases continuously during pedogenesis (Walker & Syers, 1976), resulting in P becoming the limiting nutrient and ecosystem regression in extreme situations (Walder, Walker & Bardgett, 2004; Vitousek et al, 2010). One is by P occlusion over time by biological and geochemical processes in which P is transformed into stable organic forms (Turner et al, 2007), which are difficult to mineralize (Walker & Syers, 1976) Another is the direct loss of bio-available P as well as other P fractions by plant uptake, soil erosion, runoff transport, etc. Compared with occluding immobilization, the direct loss of P in mountain regions was almost completely neglected in former studies, and the loss rate and pathway were far from clear
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