Tree regeneration in felling and natural treefall disturbances in a semideciduous tropical forest in Mexico

Abstract

Tree regeneration was compared among closed-canopy sites and 4–11-year old natural and felling gaps in a selectively logged semideciduous tropical forest in southeastern Mexico. Closed-canopy sites and gaps were selected stratified randomly. In addition, all large natural and felling gaps encountered were sampled. All stems ≤5 cm dbh were sampled in sets of 10 m 2 plots in closed-canopy sites and gaps. The origins of the 10 tallest stems in each gap were also determined. Rubber-tired skidder disturbance in felling gaps resulted in a fourfold increase in the relative abundances of a set of shade-intolerant species. The logging process also promoted root sprouting, primarily among shade-intolerant species, but also in several shade-tolerant species. Advance growth accounted for a higher proportion of tall stems in natural than felling gaps and most of these stems were of shade-tolerant species. The proportion of tall stems that originated from seeds or small seedlings at the time of gap formation was higher in felling than natural gaps and increased with canopy openness only in felling gaps. These stems were primarily from shade-intolerant species. A lack of response to canopy openness in natural gaps was likely a result of relatively low levels of understory and substrate disturbance coupled with the absence of large natural gaps with high canopy openness. The maintenance of shade-intolerant and tolerant timber species in this forest would appear to require, at minimum, the creation of large gaps with understory and substrate disturbance within a matrix of forest logged by single-tree selection methods in which understory damage was minimized.