The role of remnant forest patches for habitat restoration in degraded areas of Palau

Abstract

To be successful, prescriptions for tropical forest restoration should facilitate natural recovery while also being easy to implement and inexpensive. In the Lake Ngardok Nature Reserve, Palau, we monitored native forest patches (4–275 m2) over 3 years to assess the influence of several low‐cost restoration methods on patch expansion, growth of naturally established tree saplings, density of naturally establishing tree seedlings, growth of planted tree seedlings, flower and fruit production, and bird and flying fox visitations. Treatments included fertilization, trimming of surrounding herbaceous vegetation, mulching of patch perimeters, and planting native tree seedlings. Fertilized patches expanded faster and were associated with higher growth rates of perimeter saplings, higher fruit and flower production and growth of adjacent planted Acacia auriculiformis trees. Trimming perimeter vegetation led to higher tree seedling densities and species diversity, but both trimming and fertilizer effects on patch perimeter measures decreased over time. Pterocarpus indicus, a high value native legume, was the fastest growing planted tree species. The most common visitors were small, omnivorous, predominately endemic bird species. Visitations to fertilized patches were more frequent than to non‐fertilized patches. The strongest predictors of visitation frequency were patch area, mean number of total fruits, and mean height of nearest neighboring trees. We conclude that forest succession can be accelerated by applying small amounts of fertilizer (approximately 22.5 g/m2 per application) to enhance tree growth and increase visitation rates of native pollinators and dispersers.