VARIATION IN THE ABUNDANCE OF TIMBER TREES BY EDGE EFFECT IN A TROPICAL SUBDECIDUOUS FOREST

Abstract

Background: The edge effect differentially affects the species in their life stages. We analyzed the environmental conditions associated with the abundance by life stage of four species of timber trees on the edge of a subdeciduous tropical forest. Hypothesis: The edges have higher light incidence and temperature, favorable conditions for the seedlings, so it is expected that the edge will have more abundance of seedlings with respect to the forest interior. Species under study: Bursera simaruba (L.) Sarg., Cedrela odorata L., Guazuma ulmifolia Lam., Lysiloma divaricatum (Jacq.) J.F. Macbr. Study site and dates: Reserva de la Biosfera ``El Cielo{''} (Tamaulipas), Mexico. January-December 2016. Methods: The abundance by life stages and environmental conditions were quantified within the gradient. These variables were correlated, in addition the requirements between stages were contrasted and they were associated with the identified environments. Results: Guazuma ulmifolia showed a negative response to the edge effect, while Cedrela odorata responded positively. The environmental requirements differed between the first life stages and adults. The abundance of the seedlings was associated to conditions of higher light incidence. Conclusions: Environmental requirements differentially affect each life stage. The abundance of seedlings increases in conditions of higher light incidence, but not in the rest of the stages, except in C. odorata. The loss of cover and the consequent formation of borders can lead to a reduction in the abundance of these species, with economic implications.