Restoring tropical forest–grassland mosaics invaded by woody exotics

摘要

Although important for biological conservation and provisioning of several ecosystem services, tropical forest-grassland mosaics face several threats, one of which is woody invasion in grasslands of these mosaics-an issue proving to be challenging to solve. We present a framework to guide grassland restoration in these mosaics that takes into account their unique ecology, outlines a general chronological sequence of restoration activities, and helps identify research priorities to guide restoration efforts. Specifically, we outline approaches to (1) increase the cost-effectiveness of restoration programs (e.g. selecting restoration targets and priority sites); (2) restore edaphic processes impacted by woody invasion; (3) maximize the establishment of native grass and forb species, and (4) maintain restored communities in the long-term by minimizing re-invasions. We apply this framework to montane southern Indian forest-grassland mosaics (locally called shola-grassland mosaics) invaded by nitrogen-fixing woody exotics to identify research priorities that can act as "game-changers" in the restoration of these ecosystems. These include (1) identifying invaded areas where passive restoration can be effective, (2) understanding the role of endogenous disturbances, particularly fire, in the spread and management of invasive species and the prevention of re-invasion, and (3) assessing the role of large-scale seed farming and emerging seed technologies for the use of seeds to effectively re-introduce native grassland species. Restoration frameworks that take into account unique ecologies are needed to make the most of the UN Decade on Ecosystem Restoration, and we present such a framework for forest-grassland mosaics-an important ecosystem that is generally neglected.