Upland Plant Communities of San Mateo and Santa Cruz Counties

"A traveler should be a botanist, for in all views, plants form the chief embellishment." —Charles Darwin

Upland plant communities have a profound effect on watershed processes and function. Vegetation influences the physical processes of water movement, nutrient mobilization, and soil deposition, and is also the foundation for various ecological interactions including the formation of terrestrial and aquatic food webs and habitat (FISRWG 1998). Disturbances within plant communities may result in alterations to the flow patterns of surface and belowground water, soil composition, and nutrient deposition, which in turn lead to changes in water quantity and quality, stream structure, sedimentation rate, and nutrient balance.

Plant Communities

A plant community is "an assemblage of plants with similar or complementary ranges of tolerances to various environmental factors" (Thomas 1961). Ecologists define plant communities based on a wide range of criteria, including physical traits such as climate and soil type, and biological attributes such as species composition, richness, abundance, plant density, structure, and spatial and temporal dynamics. Plant community ecologists study the interactions between biological features in plant communities (for example, competition among organisms, plant-herbivore relationships) as well as the influence of various abiotic features on individuals and groups of plants.

San Mateo and Santa Cruz Counties are home to a rich tapestry of plant communities, ranging from salt marsh to chaparral to redwood forest. Riparian plant communities occupy a relatively small percentage of the watershed (less than 5 percent) (RHJV 2000), yet play a profound role in supporting biological diversity in both the aquatic and terrestrial environment. Land cover mapping and associated vegetation community identification is often completed at scales which do not identify site-specific attributes of plant communities – such as density, population size, and so forth. These mapping efforts are useful for larger scale planning, but should be coupled with detailed mapping for watershed management and planning.

Photo of Scott Creek and surrounding estuary

Marsh habitat associated with the estuary at Scott Creek.

Beginning in the higher elevations of the Santa Cruz Mountains, a typical stream might pass through chaparral, grassland, oak woodland or redwood forest communities before reaching tidal marshes and its eventual confluence with the Pacific Ocean or the San Francisco Bay. Specific plant community types develop in response to physical and environmental conditions. Geology, soil characteristics, topography, and climatic conditions shape plant community development (Thomas 1961). However, once established, plant communities affect soil condition and microclimate. Communities differ in their capacity to hold soils and reduce erosional processes (FISWRG 1998). While some communities are strong stabilizing forces, others may be easily disturbed by human activity, such as the sand hills of Santa Cruz. Highly disturbed habitat loses its ability to provide beneficial ecosystem functions such as erosion control. Water availability is also influenced by community type, with communities differing in water uptake as well as control of water movement (see the Hydrology section for more information) (FISWRG 1998). Upland plant communities affect aquatic and riparian systems, and should be considered when developing watershed management plans.

Plant Community Classification

Numerous plant community classifications have been proposed for California, but no single system is widely accepted. One of the most current and detailed systems is described in A Manual of California Vegetation (Sawyer and Keeler-Wolf 1995). This system of classifying vegetation was developed by the California Native Plant Society (CNPS) and is gradually being adopted as the standard by many federal, state, and private entities. At this time, however, vegetation maps and spatial data that use the CNPS system are not available for San Mateo and Santa Cruz Counties. Over the years, geographic information system (GIS) mapping has incorporated a number of land cover / land use classification systems that include coverage of the area. A few of these include CalVeg2000, California Department of Forestry and Fire Protection; 1998 GAP Analysis, UC Santa Barbara; Coastal Change and Analysis Program (C-CAP), NOAA; and Farmland Mapping and Monitoring Program, State of California Department of Conservation. To access some of these GIS data sets for San Mateo and Santa Cruz Counties, visit the SRP GIS Data Inventory / Data Download.

map of landcover data from the CA Department of Forestry and Fire Protection

This map reflects 2002 multisource land cover data from the California Department of Forestry and Fire Protection.

Working in concert under a collaborative Cooperative Vegetation and Habitat Mapping and Classification memorandum of understanding (MOU), comprehensive vegetation and habitat mapping efforts are currently under development. These efforts will refine existing classification systems and provide more detailed information about the Central Coast plant communities. Visit the following Web sites for more information:

References

Federal Interagency Stream Restoration Working Group (FISRWG). 1998. "Stream Corridor Restoration: Principles, Processes, and Practices." Federal Interagency Stream Restoration Working Group (FISRWG). GPO Item No. 0120-A; SuDocs No. A 57.6/2:EN 3/PT.653. ISBN-0-934213-59-3. View on-line document.

Riparian Habitat Joint Venture (RHJV). 2000. "Version 1.0. The Riparian Bird Conservation Plan: a strategy for reversing the decline of riparian associated birds in California." California Partners in Flight. View on-line document.

Sawyer, J.O., and T. Keeler-Wolf. 1995. A Manual of California Vegetation. Sacramento, CA: California Native Plant Society.

Thomas, J.H. 1961. Flora of the Santa Cruz Mountains of California. A Manual of the Vascular Plants. Stanford, CA: Stanford University Press.