GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 31-13
Presentation Time: 4:55 PM


KOVARIK, Johanna L., United States Forest Service, Minerals and Geology Management, 740 Simms St, Golden, CO 80215 and BAICHTAL, James F., U.S. Forest Service, Tongass National Forest, Thorne Bay Ranger District, P.O. Box 19001, Thorne Bay, AK 99919,

The Tongass National Forest is the largest forest in the National Forest System in the United States, encompassing some 6.9 million hectares covering the islands of the Alexander Archipelago and the narrow band of mainland from Dixon Entrance to Yakutat Bay. The Tongass contains 78 percent of the total known karst in southeast Alaska, approximately 174,432 hectares primarily on Chichagof, Prince of Wales, and surrounding smaller Islands. Management focus is chiefly on areas where timber harvest is permitted, however the Tongass also contains designated karst geologic special and conservation areas, and caves which are managed for visitation. Research on the forest in relation to caves and karst systems began over 25 years ago and has covered a broad variety of topics from dye tracing and flow path delineation to LiDAR and remote sensing use for karst feature location. Forest geologists together with karst researchers developed a system of karst vulnerability mapping and classification, used in over 25 land management projects over the past 25 years including the Lab Bay, Logjam, Heceta Sawfly, Iyoutug, Tuxekan, Kosciusko, and Big Thorne timber sales. With the improvements in high-resolution data logging detailed characterization of karst aquifers and study of dissolution rates have occurred, with long-term monitoring and land use land change studies in progress. Studies on soils in karst areas and rare microbial communities in caves serve to further enchance understanding of forest-groundwater-dependent ecosystem dynamics. The forest and partners have worked to map caves since the early 1990s, and in the past ten years sea cave maps have been incorporated into a larger paleo shoreline predictive model, allowing archaeologists to locate heritage sites with greater accuracy and precision. Finally, past and ongoing paleoclimate, paleontology, and cave sediment studies will allow the Forest to understand the past climate dynamics within the area to better adapt management to the changing future. Areas where revitalized or new projects are needed include further work with cave climate studies, bat population and habitat surveys and monitoring, and subterranean biological inventory, surveys, and classification.