Sinecological analysis of the montane rain forrest of Omiltemi, Guerrero
The floristic composition, structure, and texture of 1 ha of mesophytic mountain forest in Omiltemi, Guerrero, is described. With 138 species of vascular plants in the plot, this forest is very rich, with epiphytes, trees and herbs comprising the most diverse growth forms. The geographic affinities of this forest are diverse; many elements are shared with the andean-mesoamerican regions, and others are present in the deciduous forests of eastern United States. The Omiltemi forest is similar to other communities from western Mexico, and many of the endemic elements of this region occur in Omiltemi. This forest is structurally dense, approximately 24 m high, without a well-defined stratification. The canopy is made up mainly by Carpinus caroliniana and Quercus uxoris; Pinus ayacahuite is an emergent tree. The understory is rich in small-statured tree species. The horizontal distributions of the trees were analyzed, and only two understory species had a clumped pattern. Density is 2,096 trees/ha, total basal area is 49.82 m2/ha and cover is 263.8% The most important! species in the forest structure are those reaching the canopy. Two trends in the diametric structures of tree species populations were found: 1) with classes of small sizes having high frequencies, and gradually decreasing towards classes of larger sizes, and 2) with classes of intermediate sizes having lower frequencies than classes of smaller and larger sizes. The internal spatial variation of the forest structure was analyzed using multivariate methods. Tropical species were usually found in more humid places, while species of temperate affinities occurred in more exposed sites. Five floristic groups were recognized, and their associated structural features are described. This forest bears leaves throughout the year, although some of the most abundant species of the canopy are deciduous. The textural characteristics of pollination, dispersal and tree architecture are described. In addition, the mixed character of the mesophytic mountain forest of Omiltemi is discussed and related to its marginal geographic location.