This research project will further the development of long-term ecological research including, but not confined to, work at the LTER (Long-Term Ecological Research) sites currently supported by NSF. Objectives include: stimulating and facilitating collaborative research, especially joint experiments and comparative analyses, and syntheses of ecological concepts within and among biomes; development of standardized sampling programs, experimental designs, and data management procedures; and creation of a communication network for sites engaged in long-term research. Substantial progress was made in these activities during the last 4 years and the LTER Coordinating Committee (LTER/CC) recognizes the potential of and its responsibilities for development of a functional multi-site network. These activities will reflect an expanded commitment to realizing the potential for intersite activities. The largest body of work will be a series of comparative and synthetic studies led by senior scientists on: (1) productivity and its controls, utilizing major environmental gradients represented in the LTER systems; (2) disturbance and ecosystem dynamics, including processes in secondary succession, prediction of vegetation dynamics, and the role of various types of disturbances; (3) temporal variability across biome types and patterns of response to global changes; and (4) landscape and regional analyses. The data management working group will recruit a facilitator for the extensive planned data exchanges, continue development of standardized procedures, and implement electronic networking. The meteorological group will conduct two comparative environmental analyses of the sites, revise existing standards, and expand an earlier comparison of climates. Initiation of comparative stable isotope studies will assist in propagating this technology throughout the network. An intersite group will address major conceptual issues in ecosystem modeling. Finally, the LTER/CC will continue major communication activities, such as publication of newsletters, guidebooks, reports, and articles and presentation of symposia. Emphasis is on specific tasks and topics with a senior LTER scientist responsible for a productive conclusion to each activity. Furthermore, higher level syntheses which will contribute to the conceptual basis of ecology have been given priority. As before, individual LTER programs will make major contributions of funds and personnel and include non-LTER sites in all activities.