The Biogeochemistry of Phosphorus Cycling and Phosphorus Availability Along a Desert Soil Chronosequence

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Abstract
The biochemistry of the weathering, landscape movements, and chemical transformations of phosphorus and its availability of plants were examined in a chronosequence of soils developed from quartz monzonite alluvium in southern New Mexico. Total P in the soil profile decreased with increasing soil age and was removed from the ecosystem as readily as the most leachable base cations. Although Ca—bound forms of P decreased with increasing soil age, Ca—P remained the singlee largest fraction of total P in all soils. In contrast, Fe— and Al—bound P was a very small percent of total P in all soils. There was little evidence for the stabilization of P by soil organic matter within this ecosystem; both soil organic P and microbial P represented very small pools of total soil P. Phosphorus availability, measured by in situ resin bags, was not well correlated with soil age or total soil P, and P concentrations in shrub tissues did not reflect changes in forms or total amounts of soil P. The biogeochemical cycle of P in this system differs sharply from that in a more mesic, forested system, where fixation by iron and aluminium oxides and biologic activity play more dominant roles in the conservation of P within the ecosystem.