The effects of herbivory, land-use and climate change on seedling establishment in southern Africa

Abstract

In intact ecosystems, factors such as herbivory and light and water availability affect seedling establishment. Land-use change and climate change are now affecting forests globally, influencing seedling establishment directly via changes in light availability and precipitation and indirectly by affecting herbivory. The present study evaluated the ecological complexity of seedling establishment in response to interactions between these factors. The growth and survival of a pioneer species and two later successional species were measured in a factorial experiment testing the effects of land-use change, water availability, and herbivory. The study was conducted on Mt. Gorongosa in central Mozambique, a protected area that is experiencing high levels of land-use change and is in need of forest restoration. The pioneer species, Erythrina lysistemon, gained the most height in undisturbed, shaded environments where it invested resources in accessing light. Erythrina lysistemon grew the most in diameter in open areas. Khaya anthotheca, a later successional species, gained more biomass in disturbed, high light areas. The growth of Millettia stuhlmannii, another later successional species, was not affected by light. Drought conditions reduced survival of the later successional species, while flooding limited the survival of the pioneer species. Herbivory increased in disturbed areas and was negatively correlated with E. lysistemon root biomass. In summary, this study indicates land-use change and climate change may alter seedling establishment and community composition. Restoration efforts should focus on increasing seedling survival because although survival is limited in disturbed sites, seedlings that do survive grow successfully.