The structure and dynamics of an Abies pinsapo forest in southern Spain

Abstract

The forest composition and age-diameter relationships of Abies pinsapo were studied in a natural forest in the Nature Reserve of the Sierra de Grazalema (southern Spain). The composition and structure of the forest was very different with respect to gaps and closed forest. Altitudinal differences in forest composition were also found. Abies pinsapo was the dominant species, Quercus rotundifolia and Quercus faginea were the other important overstorey species. The diameter distributions of A. pinsapo were skewed toward the larger size classes, with a large seedling proportion of about 70%. Abies pinsapo establishment rates were higher in the gaps. Seedlings of Abies pinsapo established under the closed canopy forest had suppressed growth, as indicated by their relatively advanced ages. Seedlings and saplings with suppressed growth can survive for a mean of 40 years, constituting a pool from which canopy trees may be recruited. Results show that the pinsapo forest of the Sierra de Grazalema is in equilibrium and that its dynamics are conditioned by a small-sapling bank and canopy gap formation.