Edge type effect on germination of oak tree species in the Highlands of Chiapas, Mexico

Abstract

The purpose of this study was to examine the effect of habitat edges on the probability of acorn germination of three oak species ( Quercus crassifolia Humb. and Bonpl., Quercus rugosa Née and Quercus laurina Humb. and Bonpl.). The effects of edge type (hard and soft), habitat type (grassland, edges and forest) and leaf litter cover (covered or uncovered acorns) on acorn germination was evaluated by the experimental establishment of acorns along transects crossing habitat edges. More acorns developed into seedlings in grasslands (38%) than in the forest edge (18%) or the forest interior (15%). In sites with soft edges, a higher number of seedlings emerged from acorns covered by litter compared with acorns sowed in the adjacent forest edge and forest interior ( P < 0.05). In sites with hard edges, fewer seedlings emerged in the edge (14%) compared with the adjacent grassland (38%), and the adjacent forest (20%) presented intermediate values. However, in sites with soft edges significant differences in seedling emergence were recorded between the grassland (38%) and the forest (10%), whereas the edge presented intermediate values (23%). The effect of leaf litter cover on acorn germination was only significant in grasslands in sites with soft edges ( P < 0.05). Acorns in grasslands received relatively little insect damage (10%) compared with the edge (19%) and the forest (30%, P < 0.05), emphasising the importance of acorn dispersal for successful oak establishment. The implications for regeneration of these oak species and the dynamics of montane oak forests in Mexico are discussed.