Vegetation and Soil Patterns on a Chihuahuan Desert Bajada

Abstract
Vegetation and soils were sampled along a 1100-m transect on a bajada in southern New Mexico [USA] to determine if present vegetation patterns can be interpreted from soil patterns. Species cover was measured in 66 plots, each 50.3 m2. Of these, 22 were randomly chosen as sites for soil pits, which were described and analyses conducted on the top (A1) horizon. The plots were clustered into 4 communities: Erioneuron pulchellum desert grassland transition, Larrea tridentata desert shrub, Bouteloua curtipendula semidesert grassland and B. eriopoda desert grassland. Soils of these communities differ significantly in pH, Mg, organic C and total N. These soil chemistry differences could be due to relatively recent changes from Bouteloua grassland to Larrea shrubland, as indicated by the dead shrub data and as documented for many bajadas in southern New Mexico. Soil series and geomorphic surface patterns, which are not readily affected by recent vegetation changes, suggest that Larrea may always have been an important shrub on shallow calcareous soils (of erosional surfaces) in southern New Mexico. Its importance as a mosaic type in the once extensive desert grasslands has probably been underestimated.

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