A Trailside Study of a Coast Redwood Forest Understory Specis, Trillium ovatum, in the Santa Cruz Mountains

Mary Yan, San Jose State University

Abstract

To fully understand one of the world’s greatest terrestrial carbon sinks, the coast redwood forest, a co-occurring species may be the key to unique and accessible opportunities to collectively monitor the health of this important habitat. I investigated the relationship between hiking trails and Trillium ovatum within the redwood forests of three California State Parks. Utilizing quadrats across 115 one-meter plots and 58 10-meter transects, T. ovatum occurrence and abundance were recorded and analyzed with factors including proximity to trails, distance from streams, elevation, slope, canopy cover, duff depth, co-occurring understory species, and tree species dominance. Results indicated a higher abundance of T. ovatum near trails. Significant correlations were also detected between the occurrence of T. ovatum and S. sempervirens canopy cover, distance from stream, slope, and elevation; whereas no significant correlation was found with duff depth and total canopy cover. Occurrence of T. ovatum was not significantly correlated with the canopy dominance of individual tree species, although the count of T. ovatum was. Oxalis oregana was found to be positively correlated with T. ovatum and S. sempervirens canopy cover. These findings underscored the nuanced relationships between T. ovatum and different levels of anthropogenic disturbance, which is favorable for citizen science monitoring and suggests the utility of T. ovatum as an ecological indicator in the southern range of redwood forests.