TRAILSIDE ABUNDANCE OF TRILLIUM OVATUM IN THE COAST REDWOOD FORESTS OF THE SANTA CRUZ MOUNTAINS, CALIFORNIA

Human disturbance is often associated with a decline in the abundance of native understory species such as Trillium ovatum Pursh (Melanthiaceae); a species that has been used as an indicator of forest health and recovery following timber harvest. The relationship between this species and the moderate levels of disturbance created by recreational trail use, however, is not clearly understood. This perennial herb was studied in three California State Parks utilizing fifty-eight 10 m randomly-located transects, placed perpendicular to hiking trails and divided into ten sequential 1-m sample plots. Occurrence and abundance of T. ovatum were analyzed with regard to proximity of trails and a suite of abiotic and biotic variables. Results indicated a higher abundance of T. ovatum near hiking trails, with a negative correlation to the distance from those trails. Other abiotic variables associated with T. ovatum included a positive correlation with slope and negative correlations with elevation and distance to the nearest stream. Positive associations were also detected between T. ovatum and canopy cover, the canopy dominance of Sequoia sempervirens (D.Don) Endl., and the abundance of several other native understory species. These findings underscored the nuanced relationships between T. ovatum and different levels of anthropogenic disturbance.