Dune Scrub Communities and Their Correlation with Environmental Factors at Point Reyes National Seashore, California

Abstract

Dune scrub vegetation characterized by three soft-leaved shrubs, Haplopappus ericoides, Lupinus arboreus and Lupinus chamissonis, was sampled at Point Reyes National Seashore (PRNS), Marin County, California, using the Braun-Blanquet releve method. Eighty-one releves were made over a 1 year period and soil samples at 10 and 40 cm were analysed for particle diameter, per cent organic matter, per cent nitrogen, field capacity, and pH. Releves and species were organized into an association table using a computer program. Four plant community types were recognized from the association table: a type dominated by Lupinus arboreus, a type co-dominated by the latter with Haplo- pappus ericoides and Baccharis pilularis, a type dominated by L. chamissonis, and a type characterized by Eriophyllum staechadifolium with Lupinus arboreus. The releves were ordinated along three axes. Their grouping along two axes showed good agreement with the community types derived from the association table. One of the axes was correlated with organic matter, nitrogen, and particle diameter (per cent < 0.25 mm) which were all highly correlated with each other. Distance inland, which field measurements indicate affects the amount of salt spray deposition, is ordered along the second axis.