Tree species richness complementarity, disturbance and fragmentation in a Mexican tropical montane cloud forest

Tropical montane cloud forest exhibits great heterogeneity in species composition and structure over short geographic distances. In central Veracruz, Mexico, the conservation priority of seven cloud forest fragments was assessed by considering differences in woody plant species richness and complementarity of species among sites, forest structure, tree mortality, and timber and firewood extraction as indicators of anthropogenic disturbance. Densities of trees greater than or equal to5 cm dbh (360-1700 trees/ha) were different among the sites, but basal area (35.3-89.3 m/ha) did not differ among fragments. The number of dead trees ranged from 10-30 to 170-200 trees/ha. The fragments' species composition was different but complementary. The Morisita-Horn index indicated low similarity between fragments. A non-parametric estimator of species richness indicated that more sampling effort would be necessary to complete the inventory (15 additional trees and two understory shrub species). Unfortunately, most of the fragments are threatened with deforestation. The number of cut trees was similar among sites (0-15 cut trees/0.1 ha). Sites with immediate need for conservation were close to settlements, with high numbers of cut trees and no legal protection. The selected sites represent the variety of situations that exist in the region. Given the high complementarity observed between fragments, a regional conservation approach will be required to preserve the last repositories of part of the tremendous biodiversity of the once continuous forest in this region.