Native component grasslands of the Marin Headlands

Steers, Robert; Spaulding, Heather

Grassland vegetation in the Marin Headlands, Golden Gate National Recreation Area, was sampled in 2011. Stands previously mapped approximately a decade prior by the National Park Service as containing a significant native species component were targeted. The methods utilized were based on those outlined in the San Francisco Bay Area Network, Inventory and Monitoring program’s draft plant community monitoring protocol. The purpose of this sampling effort was fourfold: 1) to field-test the methods outlined in the draft protocol, 2) to refine the classification of these grasslands from the base vegetation map that was used to select the stands sampled, 3) to better understand these grasslands in a regional context, and 4) to examine relationships between vegetative and environmental parameters at the sampling unit scale. Nine grassland stands were randomly chosen from the 71 previously mapped stands in the Marin Headlands study area. Species richness in the nine grassland stands was high and found to be similar to other California coastal prairies. The sample design, specifically the number of sample units per stand and the number of stands sampled, appeared to capture the majority of grassland species in the study area based on species accumulation curves. Using the data collected, all stands were classified as coastal prairie with two stands fitting within the Festuca idahoensis alliance and six fitting the Stipa pulchra alliance. All stands contained significant cover of native perennial grasses and forbs, including F. idahoensis and S. pulchra. However, exotic grasses were the most abundant group of plants in every stand surveyed. Correlations of vegetation and environmental parameters revealed that litter depth was negatively correlated with native annual species richness. Also, the density of fossorial mammal disturbances was positively correlated with total herbaceous species richness and also to the abundance of two common exotic plant species. At the landscape scale, the grasslands sampled in the Marin Headlands form a consistent and repeatable vegetation type that appears to be closely associated with soil derived from Franciscan complex chert, which is relatively uncommon elsewhere in the San Francisco Bay Area.

Native component grasslands of the Marin Headlands

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