Riparian communities are found bordering streams, lakes, and springs throughout California. The riparian community in Poly Canyon is found along Brizziolari creek, running through the canyon. These communities are usually composed of species of dedciduous trees such as willows, sycamores, and cottomwoods, along with shrubs and herbs. Many of these species are restricted to riparian communities.  Today riparian communites occupy less than one percent of California, however, in pre-colonial times a much larger area was occupied by these communities.  These communities are dependent on a permanent water supply and less effected by climatic or edaphic conditions as much other terrestrial communities, however these factors are important in determining community composition and structure.  Riparian communites are extremely diverse and species composition varies from site to site.  As these streams with riparian communites pass through different plant communities, various species from the surrounding communities joing the typical riparian species along the banks of the streams.  For example, in Poly Canyon coast live oak and California bay-laurel from the oak woodlands join the willows, cottonwoods, and sycamores to form the riparian woodland along Brizziolari Creek.

Microenvironments of a riparian community are variable.  Typically most of the dominant trees are deciduous, therefore, there is a seasonal fluctuation of light available to understory species.  When the trees have full canopies in spring and summer months, a dense shade is cast underneath.  This results in moderation of temperature fluctuation with lower day time and higher night time temperatures.  In addition, wind velocity is usually decreased and relative humidity in increased under the tree cover.  In general, the micrclimate within a riparian woodland or forest is usually much more mesic than in adjacent areas. This allows for the presence of some species to persist as riparian plants in areas that would otherwise be outside of  there range of tolerance.  For example, Sequoia sempervirens (coast redwood) becomes restricted to riparian habitats in the southern parts of its range (southern end of Big Sur near the San Luis Obispo-Monterey County line.

The soils of  riparian areas are generally composed of interbedded layers of coarse and fine sediments ranging from large boulders to gravel, sand, silt, and clay.  The finer particles tend to collect in areas where water movement is slow or stagnant and the coarse materials and boulders tend to accumulate where the water flow, at least seasonally, is very fast.  The soils along stream channels are generally coarse, and the upper horizons are well-aerated if exposed during low water flow periods.

These are dynamic changing environments with fluctuating water levels and carrying sediments from place to place and shifting channels.  During periods of flood, stream channels can be swept clean of vegetation, or the abrassive action of rapid moving sediment loads can scour trees and shrubs, or possibly uproot plants along the eroded banks. In areas of slow moving water, sediments are deposited forming sand or mud bars creating new areas for plant colonization.  A floodplain borders a stream on either side and over time, the stream will meander from side to side.  During the dry period when stream flow is greatly reduced, many plants may colonize the dried up stream beds, annual and perennial herbs as well as woody species.  However, they will usually be washed away with the onset of the winter rains.  In addition, stream flow is not uniform from year to year.  Areas closest to the stream are often in a perpetual pioneer stage where as those further from the stream may develop into more mature successional stages.  Lakes and resevoirs are also changing environments with fluctuating water levels and often subject to wave action.

Most of dominant woody plant species are adapted to periodic flooding.  Some have deep root systems that anchor the plant in place such as cottonwoods and some have flexible stems such as willows that allow the plant to bend with the current and recover once the water level has receded.

Riparian communities occur along waterways in a diversity of environmental conditions ranging from high elevation mountains to dry deserts.  As a result, like many plant communities, riparian communites in California are quite variable and change in species composition from place to place.

Please refer to California Vegetation by V.L Holland and David J. Keil. for more information on riparian communities or other plant communities of California.

Poly Canyon Riparian Community Dominants:
Plantanus racemosa (sycamore)
Populus balsamifera (black cottonwood)
Quercus agrifolia (coast live oak)
Salix lasiolepis (arroyo willow)
Umbellularia californica (California bay-laurel)

Poly Canyon Riparian Community Associates:
Artemisia douglasiana (mugwort)
Equisetum telmatiea (giant horsetail)
Juncus spp. (rush)
Mimulus guttatus (common monkeyflower)
Rubus ursinus (blackberry)
Rumex crispus (curly dock)
Sambucus mexicana (elderberry)
Toxicodendron diversilobum (poison oak)
Typha latifolia (cattail)