Nature and role of biological legacies

The complex interactions between disturbances and ecosystems are important current topics in ecological science. Disturbances of various types, intensities, frequencies, and sizes have very different consequences in terms of intermediate impacts and recovery processes. One of the important variables among disturbances is the biological legacies--types and quantities of organisms and organically-derived structures and patterns--that are left behind. As described by James MacMahon, disturbances can be viewed as processes that edit out different components of existing ecosystems leaving behind the unedited-the biological legacies. Important biological legacies include living organisms, organically-derived structures, and organically-generated spatial patterns. Organisms may persist as intact organisms , seed banks, spores, and parts with a capacity to regenerate the whole organism. Structural legacies include dead trees, logs, coral, and animal carcasses. Spatial patterns include chemical, physical, and microbial imprints on soils from specific species or communities. Strong spatial patterns also exist in disturbance intensity and, therefore, type and level of biological legacies at the level of the landscape as well as the patch. Unfortunately the scale and importance of biological legacies are not well understood or appreciated in ecological science nor is the diversity of impacts-the "editing" process. Emphasis in text presentations on disturbance and succession almost always emphasize recolonization from outside of the disturbed area rather than surviving organisms. Structural legacies are almost never considered in classical presentations on succession. The early focus on old fields in studies of secondary succession may be one reason for the lack of attention to legacies as well as the emphasis on development of general theoretical models that often fail to consider the idiosyncratic nature of each ecosystem, disturbance type, and specific event. Studies of recent large-scale disturbance events have increased the interest in biological legacies, however, beginning with research on ecosystem recovery following the Mount St. Helens eruption of May 1980. Other events, such as the Yellowstone Fires of 1988 and Hurricane Andrew in 1992, contributed significantly to the continuing development of the concept. In 1996 the U.S. LTER Program convened a small workshop at Wind River, Washington to discuss how the concept of biological legacies applies across a range of ecosystem types from forests to lakes. Nine scientists participated in this workshop. An outline, some text, and several tables were prepared for a definitive article on the concept of biological legacies but, unfortunately, has not been completed. More recently, the U.S. LTER Program identified biological legacies as the topic for one of the sessions at the LTER 2000 meeting that is to be held on August 2-4, 2000 at Snowbird, Utah. This new forum provides an impetus and opportunity to complete the initial report and critique and expand the concept of biological legacies. However, careful preparation is needed to fully realize the potential of this opportunity. I am requesting assistance from the National Center for Ecological Analysis and Synthesis in developing a fuller understanding of the concept of biological legacies, the application of the concept to various types of disturbances and ecosystems, and the diversity of ecological roles that such legacies can play. Specifically, I am requesting: (1) the opportunity to utilize facilities at NCEAS during April and May 2000 in completing the report of the initial workshop; and (2) support for bringing together at NCEAS a small (7-10 members) working group on biological legacies to critique and expand the earlier concepts and to assist in planning the session for the LTER 2000 meeting. The working group would be a mix of individuals from the original workshop and other scientists representing ecosystem types (e.g., near-shore marine) and topical areas not previously represented. Outcomes of this effort will include both a synthetic article on biological legacies for the peer-reviewed literature (e.g., BioScience) and a book based upon presentations and discussions at the LTER 2000 session.