The perpetual forest: using undesirable species to bridge restoration.
Abstract
Conversion of established forests of undesirable species composition or structure to a multi-age, native forest community is a common restoration goal. However, for some ecosystems, the complexity of multiple disturbances and biotic factors requires unique approaches to advance community development. We use the longleaf pine (Pinus palustris Miller) ecosystem as a model of such a restoration paradigm with an approach that utilizes the undesirable species as a functional or structural bridge to foster ecological processes. In the conversion of adult slash pine (Pinus elliottii Engelm.) plantations to the biologically diverse longleaf pine forests that once dominated the south-eastern US Coastal Plain, we examine techniques for restoring and maintaining critical structural and functional components. Through partial and variable retention of the undesirable slash pine canopy, establishment of longleaf pine seedlings is facilitated, while maintaining fuels essential for prescribed fire, a necessary management practice for longleaf pine. Furthermore, we project that with subsequent fires, fine fuels and species richness will be encouraged in the ground cover, and with future slash canopy harvest, established longleaf pine seedlings will be released. In this study, we present a statistical approach that examines the compositional movement of vegetation in restoration sites over time relative to the reference conditions that are also changing through time. Synthesis and applications. Restoration efforts that remove undesirable species initially may actually hinder rather than facilitate restoration. Restoration of fire-maintained ecosystems in which the production of adequate fuels is an important consideration may require the retention of a portion of the existing canopy to provide fuels during the restoration process, even if the canopy is comprised of less preferred species. Individual species often provide similar structural features and influences on function within an ecosystem; thus, systems other than longleaf pine may also benefit from retention of the undesirable species through the restoration process. We conclude that a gradual approach to restoration may be advantageous when legacies of past management have altered complex ecological dynamics and promoted development along a successional pathway strongly differing from that of the reference conditions.