Modified topsoil islands within patchy Mediterranean vegetation in SE Spain

The spatial distribution of some chemical and physical soil properties was determined in the microenvironment of individual plants of three matorral s pecies (Rosmarinus officinalis L., Sipa tenncissima L., Anthyllis cytisoide s L.) in an area of patchy vegetation in south-east Spain. The influence of isolated plants on the chemical and physical status of the topsoil decreas ed significantly from the plant axis to the bare inter-plant area, giving r ise to "islands" of improved topsoil properties beneath each plant (i.e., i ncreased organic matter content and aggregate stability, and decreased bulk density, penetration resistance, shear strength and rock fragment content and cover). The degree and lateral extent of topsoil modification was signi ficantly more pronounced under Rosmarinus and Stipa plants than under Anthy llis shrubs, mainly because of the differential influences of species morph ology (i.e., above ground structure) and components (i.e., canopy and litte r covers) on soil properties and erosion/sedimentation processes. (C) 1999 Elsevier Science B.V. All rights reserved.