Theory and application of medium-term successional dynamics in secondary tropical forest

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There is a growing need to restore extensive areas of degraded habitat in tropical areas to forest in order to conserve biodiversity, mitigate the impacts of climate change (through carbon sequestration), reduce erosion and loss of topsoil, and provide for human livelihoods, yet little is known about how well tropical forest restoration strategies work beyond the first few years of establishment. This long-term experiment aims to address two key questions about tropical forest recovery. First, the research compares natural forest recovery to two different forest restoration approaches (a low and high intensity approach) to assess how the degree of human intervention affects the rate of tropical forest recovery. Second, the study evaluates the importance of the proximity of restored sites to remnant forest patches, which can serve as a source for colonizing plants and animals. Results of this study will provide critical guidance to land managers and policy makers on how to most effectively invest limited resources to improve the outcomes of the millions of hectares of tropical forest restoration being undertaken globally. The study will provide training for graduate and undergraduate students, and new inquiry-based learning program will actively engage high school students in the research. Over a decade ago, 13 experimental sites were established over a 100 square kilometer area in southern Costa Rica, each site with a range of surrounding forest cover. Each site has three experimental treatments: 1. no tree planting and natural recovery; 2. planting tree islands of three sizes (low intensity); and 3. planting the entire plot with trees (high intensity). Researchers will collect data on metrics to assess the next phase of forest succession, including measuring soil nutrients, local microclimate, seed dispersal, tree growth, and the establishment and survival of forest seedlings. In addition, plots will be used by collaborating scientists to study other facets of forest recovery such as insect community dynamics, and bird and bat behavior. The data will be used to address several questions about mid-stage forest recovery and how the pattern of recovery can change over time including: the effect of restoration interventions on within- and across-site biodiversity; the degree to which manipulations of initial conditions result in convergent or divergent successional trajectories from reference forest; and the relative importance of local- versus landscape-scale processes on forest recovery.