Humus Forms in Mediterranean Scrublands with Aleppo Pine

Abstract

Commonly reported effects of pine on topsoil include acidification, a decrease in biological activity, and an accumulation of surface organic matter. Such effects have not been documented for Mediterranean woodland and scrubland areas. This research evaluated humus profiles beneath pine and adjacent vegetation on the basis of previous knowledge on soil animal communities and vegetation. Two Mediterranean sites with aleppo pine (Pinus halepensis P. Mill.) and scrubland vegetation were compared, one in Spain (Navarre), the other in Italy (Sicily). Humus profiles were sampled under main vegetation types, comprising aleppo pine, rosemary (Rosmarinus officinalis L.), and bare ground in both sites, along transects with increasing pine influence. Quantitative morphological methods were used to analyze and compare humus profiles, and data were analyzed using correspondence analysis. In both sites the influence of aleppo pine on humus forms was well‐defined but minor, increasing the appearance of an Oe horizon characterized by intense activity of litter‐dwelling fauna and fungi. Under all vegetation types, and in both sites, the organo‐mineral A horizon was of the mull type, although the composition of the soil‐building fauna varied between Navarre and Sicily. There was more heterogeneity among vegetation types in Navarre, where aleppo pine was planted on derelict land, than in Sicily where aleppo pine was a component of natural vegetation (maquis). A decreasing influence of pine was perceptible in the inner edge of the pine plantation in Navarre, or under the crown of individual trees in Sicily.