|Brucker, E; Spohn, M: Formation of soil phosphorus fractions along a climate and vegetation gradient in the Coastal Cordillera of Chile, Catena, 180, 203-211 (2019), doi:10.1016/j.catena.2019.04.022|
Despite the importance of hosphorus (P) for ecosystems, the effect of climate and vegetation on the formation of P fractions is not well understood. Therefore, we explored the formation of soil P fractions along a climosequence covering an arid, semi-arid, Mediterranean and humid site in the Coastal Cordillera of Chile. We determined Hedley P fractions (water extractable P, labile P, secondary mineral P, apatite P and residual P) as well as total organic P (TOP) in two soils on each of the four study sites. We calculated apatite dissolution rates based on the soil production rate and the soil P fractions, which has never been done before, according to our knowledge. Apatite P was the dominant P fraction in the soils at the arid and the semiarid site, and it decreased from the arid to the humid site by 96%. Residual P and secondary mineral P dominated at the humid site. The increase in plant available P along the climosequence went along with an increase in TOP. Apatite was strongly positively correlated with soil pH across all soils. The apatite dissolution rate increased with mean annual precipitation from 0 to 34mgPm−2 yr−1, leading to an increase in plant available P (sum of water extractable P and labile P) along the climosequence from the arid to the humid site. In conclusion, our study shows that the extent to which apatite in soil is dissolved, and the apatite dissolution rate strongly increase with precipitation, leading to an increase in the concentrations of secondary soil P fractions (secondary mineral P, labile P and TOP) along the climosequence.