California Serpentine Foothill Streamside and Seep

This ecological system is found mostly in the central and inner northern Coast Ranges of California and Sierra Nevada foothills. It includes springs, seeps, and perennial and intermittent streams in serpentine substrates (true serpentinite but also other related substrates). Characteristic species include Salix breweri, Hesperocyparis sargentii, Frangula californica ssp. tomentella, Umbellularia californica, Cirsium fontinale, Stachys albens, Solidago spp., Packera clevelandii, Mimulus glaucescens, Mimulus guttatus, Aquilegia eximia, and Carex serratodens. Riparian portions of this system are disturbance-driven and require limited flooding, scour and deposition for germination and maintenance.

Characteristic species include Salix breweri, Hesperocyparis sargentii (= Cupressus sargentii), Frangula californica ssp. tomentella (= Rhamnus tomentella), Umbellularia californica, Cirsium fontinale, Stachys albens, Solidago spp., Packera clevelandii (= Senecio clevelandii), Mimulus glaucescens, Mimulus guttatus, Aquilegia eximia, and Carex serratodens. Riparian portions of this system are disturbance-driven and require limited flooding, scour and deposition for germination and maintenance.

This system is found in creek bottoms and stream terraces with serpentine-derived alluvium. Elevations range from 300-3000 m. Soils are saturated to moist throughout the growing season (Sawyer et al. 2009).

Steady groundwater flow and fire primarily disturb stands of this ecosystem. Plants resprout after flooding disturbance. Most serpentine riparian areas have moderate rather than large flooding events, and most serpentine riparian has low perennial flows not subject to vacillating events as non-serpentine areas. Serpentine riparian are less likely to be susceptible to drought and drying since the serpentine geology tends to release water slowly over time (T. Keeler-Wolf pers. comm. 2013). Frangula californica resprouts vigorously after fire (Sawyer et al. 2009). However, it is not known how often fires historically occurred in Frangula californica-dominated systems. Fire is less of a disturbance issue in willow-dominated systems, but fire does occur, and Salix generally resprouts after fires (Stromberg and Rychener 2010). Fires probably occur relatively frequently even though serpentine chaparral surrounding the riparian has lower fuels than typical non-serpentine chaparral (T. Keeler-Wolf pers. comm. 2013).

Conversion of this type has commonly come from direct impacts of mine development and road building. Conversion to agriculture is not a factor as the soil types are not conducive to agricultural use. Surrounding watershed dewatering due to climate change and water diversion for agriculture in the North Coast Ranges is a real threat. Mining and agriculture (legal and illegal) have altered stream hydrology in several parts of the range (Sawyer et al. 2009).

Riparian areas and their aquatic communities are directly affected by concentrated grazing, cutting of woody vegetation for timber and firewood, residential development, river channelization, regulation or diversion of flows, wildfire suppression, trapping (principally beaver), exotic species (both terrestrial and aquatic plants and animals), unregulated recreation (both motorized and nonmotorized), road building, mining, pollution, farming, channel dredging, bank armoring, and construction of dams and levees. These same communities are indirectly affected by human activities across their surrounding watersheds that alter watershed runoff and groundwater recharge and discharge via altered ground cover and water diversions and withdrawals, or cause pollution, including from atmospheric deposition. Although some serpentine areas are not as heavily used as they once were, including the Clear Creek area of San Benito County (CNPS and CDFG 2006). Currently threats to serpentine riparian areas may be reduced as mineral use is down, ORV use is down, and water levels in streams are low but relatively constant (T. Keeler-Wolf pers. comm. 2013). Invasive plant species that are often treats to riparian areas may be less of threat in serpentine ecosystems; however, some invasives are finding their way into serpentine soils (Batten et al. 2006).

The projected impacts of climate change on thermal conditions in northwestern California will be warmer winter temperatures, earlier warming in the spring, and increased summer temperatures. Currently, there is greater uncertainty about the precipitation projections than for temperature in northwestern California, but with some evidence for a slightly drier future climate relative to current conditions (PRBO Conservation Science 2011). Potential climate change effects could include: perennial streams may become intermittent; phreatophytic species under greater stress and death; drop in groundwater table; increased fire frequency due to warmer temperatures resulting in drier fuels; increased invasive species due to lack of competition from native species whose vigor is reduced by drought stress, and increased fire intervals favor certain invasive species (Brooks and Minnich 2006, Coffman 2007); and increased competition for water from all users, stresses the already overtaxed water allocation of California agricultural system (PRBO Conservation Science RBO 2011).

This system occurs in the central and inner northern Coast Ranges of California and Oregon and Sierra Nevada foothills.