Ecology of the Elfin Forest

The Elfin Forest supports diverse natural plant and animal communities because of its very special combination of geologic, soil, and climatic environments. Most of the habitats in the Natural Area pose both severe survival problems for plants and animals and also rare opportunities for species that are adapted to these environments.

A little over a quarter of the Elfin Forest lies in tidal lands of Morro Bay estuary. Plant species living in the marsh area are specially adapted to tolerate repeated flooding, drying, and varying degrees of salinity. Soil salinity rather than flood water salinity is the major determinant of what plants thrive in different parts of the marsh. Salinity is modified by fresh water coming down Los Osos and Chorro Creeks and springs at the base of the sand dunes. Where soil salinity is high the Coastal Salt Marsh Community is found – predominately Pickleweed and Saltgrass. Lower salinity yields the Brackish Water Marsh Community – dominated by rushes and sedges. The demarcation between salt and brackish water marsh is not clear cut. Contrary to what you might expect, the brackish marsh species are mostly seen in areas that flood twice daily (adjacent to the base of the dunes and the springs) and the saltwater species are seen on higher marsh lands that floods less often (which concentrates the salt in the soil). Bordering the marshes, and above the high tide line, is the Riparian Woodland Community, where trees such as Sycamore and willows are able to survive because of fresh water coming to the surface.

Higher still are the old sand dunes, now stabilized by vegetation growing on them. The sand constituting these dunes is quite low in soil nutrients. It is also very coarsely textured, which causes rainwater to sink rapidly downward, soon lost to plants with shallow surface roots. The coastal surfaces of the sand dunes are also directly exposed to winds off the ocean and estuary, which carry fine salt-laden mist onto the land. The salt-laden breezes, combined with nutrient-poor and dry soils, limit vegetation on the dunes closest to the estuary to the Coastal Dune Scrub Community. Plants of this community, such as the California sagebrush and black sage, not only tolerate these conditions but thrive in the absence of the competition they would face in areas more favorable to a wider variety of species. Stunted by those salt-laden breezes and poor soils, the oaks of the Coastal Live Oak Woodland survive in the valleys sheltered behind the shoreline dunes and grow no taller than the crests of the dunes behind which they shelter. Farther inland and above the oak woodlands, on dry dune crests exposed to the sun and sea breezes is the Maritime Chaparral Community. This community is dominated by drought-tolerant and fire-prone shrubs such as Chamise and Buckbrush.