Abstracts Biological Sciences

Impacts of social trails around old-growth redwood trees in Redwood National and State Parks

by Claudia Voigt

Old-growth coastal redwood stands and the habitat they provide are the conservation target of Redwood National and State Parks (RNSP) in northern California. In recent years there has been greater access to location information about record-sized trees, and visitors have created networks of social trails in redwood groves, including one grove that has no formal access. Coupled with increasing visitor numbers, this has caused an alarming increase in recreational impacts in redwood groves. By providing visitors access to groves, managers accept that there will be ecosystem impacts, but data is needed to evaluate the degree of impact on trees, soil and understory vegetation. I assessed impacts of social trails around old-growth redwood trees in three alluvial flat groves with different use intensities in RNSP. In 2015 I mapped old-growth redwood trees and social trail networks around these trees. I randomly sampled 20 to 30 trees per site and collected baseline data on the spatial extent of disturbance and selected vegetation and soil indicators. Tree size (measured as diameter) proved to be significantly positively related with trampling disturbance around trees in two of the sites, while in the highest-use site, distance from the formal trail was most strongly related with disturbed area. The findings of this study will serve as initial baseline conditions for recreational impacts in these stands. RNSP can use the study design developed for this thesis to monitor changes in trail-related visitor impacts in old-growth redwood stands of management concern. Advisors/Committee Members: Martin, Steven.