Shrub Cover Influence on Seedling Growth and Survival Following Logging of a Tropical Forest

Logging in tropical forests may create large canopy openings. These gaps provide suitable conditions for some opportunistic shrubs and herbs to take advantage of the surge in resources and rapidly colonize disturbed sites. This dense plant cover may limit forest regeneration by interfering with tree seedling establishment, growth, and survival by altering the light and nutrients available to seedlings, modifying herbivore behavior, or a number of other factors. In Kibale National Park (Uganda), old logging sites are mainly covered by dense stands of Acanthus pubescens Engl., which appear to inhibit tree regeneration. We wanted to identify the ecological processes underlying this regeneration collapse. To do so, we designed a factorial experiment to evaluate the influences of herbivory and vegetation cover on the growth and survival of tree seedlings. We compared the survival and growth of transplanted tree seedlings in A. pubescens stands and logged forests, in the presence or absence of the understory vegetation layer (logged forest) or vegetation cover (A. pubescens), and with or without herbivory. We found no evidence to support the hypothesis that herbivory is significantly higher under dense A. pubescens cover. Seedling survival was not influenced by the environment. Seedling growth, however, was positively influenced by the removal of A. pubescens, suggesting that changes in resource availability associated with the presence of A. pubescens, may be important for regeneration. Our results suggest that sustained cutting of A. pubescens cover could foster the growth of established seedlings and could lead to tree regeneration and habitat restoration. Abstract in French is available in the online version of this article.in French is available in the online version of this article.