| The role of vegetation in regulating the spatial distribution of soil nutrients, with particular attention to soil phosphorus, was examined in a semiarid ecosystem in south-central New Mexico. In the grassland, where vegetation forms a relatively uniform cover over the landscape, soil nutrients followed a homogeneous spatial pattern. In the shrubland, where vegetation forms a relatively patchy cover over the landscape, soil nutrients followed a heterogeneous spatial distribution. In particular, N, P, and K, showed greatest concentrations under the shrub canopy; whereas, Na, showed greatest concentrations in the intershrub space. These results demonstrate the importance of biological processes to ecosystem structure and function in semiarid regions.; The distribution of phosphorus in Chihuahuan desert soils varies depending on the specific fraction of soil phosphorus. Using a sequential laboratory method for phosphorus fractionation, the total phosphorus pool may be separated into labile, non-occluded and occluded fractions of phosphorus. In the grassland, all fractions of soil phosphorus follow a uniform distribution reflecting the uniformity of plant cover. In the shrubland, the distribution of labile, non-occluded, and occluded phosphorus reflects the heterogeneity of plant cover. A small, but essential, pool of organic phosphorus and the labile phosphorus fractions are concentrated under the shrub canopy, but those fractions under geochemical control are equally concentrated under and between shrubs.; A literature survey of soil phosphorus data from studies that exclusively followed the sequential phosphorus fractionation method of Hedley et al. (1982) shows that the organic phosphorus content in the labile fractions may provide an index of biological and geochemical influences on soil phosphorus cycling in different soils. |
