Phosphorus fractions in grassland and shrubland soils at the Sevilleta NWR

This study examined the concentration of organic and inorganic phosphorus in surface soils of a Bouteloua gracilis-Bouteloua eriopoda grassland, and a Larrea tridentata shrubland, in the northern Chihuahuan Desert, New Mexico, USA. In this desert where the grassland vegetation has a uniform spatial distribution and individual shrubs have a patchy spatial distribution across the landscape, vegetation strongly influences the distribution of soil nutrients. Most studies of soil phosphorus fractions in desert soils have focused primarily on inorganic P fractions and have demonstrated the importance of geochemical controls on soil P cycling. This study addressed the question of whether organic phosphorus, determined by the presence of different vegetation types, also contributes to soil P cycling. Within soils of similar age, topography, parent material, and climatic regime, samples were collected under and between vegetation and analyzed for P fractions following a modified sequential fractionation scheme.