FRAGMENTS SIZE IN THE PINE-OAK FOREST, SIERRA DE QUILA, JALISCO STATE

Abstract

Species richness, composition and abundance of tree species were assessed in relation to the size of fragments in the pine-oak forest of the protected natural area of Sierra de Quila. Two kinds of fragments were selected (10-50 hectares and >50 hectares) in open (canopy cover >40%) and closed canopy (<40%). forest. Tree inventory (DBH ≥ 7 cm) in 76 concentric sampling plots (0.05 ha) was made in a systematic sampling net. In the open forest were recorded from 1 to 17 species and in the closed forest from 16 to 24 species. Even though the difference of species richness was not significant (p>0.06) between types of cover and fragment size, there is more evenness in abundance in the open forest. Six outstanding species, Alnus acuminata, Clethra hartwegii, Pinus herrerae, Quercus candicans, Quercus excelsa and Tilia mexicana were not found in any condition <50 hectares. By ordination techniques it was found that in both fragment sizes, altitude, soil type and broad-leaf abundance significantly correlated with tree species associations. Hill side and pine abundance were relevant in open forest, while average diameter and tree density correlated with closed forest. Distribution patterns are crucial elements for integral landscape conservation and of the different conditions in which forest covers develop.