Rock Outcrop Community

Rock outcrops provide specialized habitats for both plants and animals.  Some species are restricted to the rock crevices or to the bare, dry rock surfaces.  Rock outcrops are mostly sparsely vegetated by extremely drought tolerant species on their surfaces and by moister requiring species in their crevices. In addition, plants that grow on rock outcrops are successionally pioneer species that are able to establish and survive on very shallow nutrient poor soil that forms on the rocks through physical and chemical weatering.  Plants that grow in these rock outcrop communities are often highly adapted to these conditions and are often endemic to these special conditions. For example, Selaginella bigelovii  (spike-moss or resurrection plant) is able to dry up almost completely and go dormant during the hot, dry summers.  However, when the rains come, this species rapidly springs to life, turns green and starts to undergo photosynthesis and grow.  It is able to "resurrect" itself.  As one explores these amazing rock outcrop communities, many microclimates will become apparent. Cracks, seeps, small caves, and overhangs may produce very lush mesic microhabitats with a diversity of ferns and herbs.

In the case of the Poly Canyon, many of the rock outcrops are serpentinite.  Serpentinite is a metamorphic, magnesium silicate rock, often green in color and slippery to the touch. (It is the California State rock!).  Serpentine and the soils derived from it have a number of traits inimical to plant growth.  It is low in some essential nutrients, especially calcium, and high in magnesium.  In addition, it is often high in toxic elements such as nickel and chromium.  As a result of these unusual conditions serpentine rock and soil support unusual, endemic floras including a large number of rare and endangered species.

Wildlife species around rock outcrops would include those listed for the grassland and coastal scrub communities.

Plants that occur on rock outcrops in Poly Canyon include:
Adiantum jordanii  (maidenhair fern)
Artemisia californica  (California sagebrush)
Dudleya spp.  (dudleya)
Eriogonum fasciculatum  (California buckwheat)
Eriophyllum confertifolium (golden yarrow)
Galium spp.  (bedstraw)
Pellaea andromedifolia  (coffee fern)
Pentagramma triangularis(goldback fern)
Phacelia spp.  (phacelia)
Polypodium californicum  (polypody fern)
Selaginella bigelovii  (club moss)
Yucca whipplei  (yucca)