Question

Be able to draw and label the habitats in a cross section of the Central Valley (California)?

Answer 1

Habitat design for special-status species requires careful consideration of site specific environmental conditions to create features that will develop into optimal habitat. In 2010, the East Bay Municipal Utility District constructed six wetlands, interconnected swales, and bioengineered grade control structures and installed native plants to enhance three drainages within the 42-acre Pavon Creeks watershed located in east Contra Costa County, California. Restoration of Pavon Creeks was implemented to mitigate for wetland and special-status species impacts associated with the seismic upgrade of San Pablo Dam. Two of the wetlands at Pavon Creeks were designed to provide breeding habitat for the California red-legged frog (Rana aurora draytonii). In addition to creating California red-legged frog breeding and dispersal habitat, restoration goals at Pavon Creeks included improving water quality, and reducing sediment loads to the larger Pinole Creek watershed. The sediment laden Pavon Creeks watershed presented unique design challenges. Restoration designs had to incorporate an increase in water storage, reduction in erosion, and retention of sediment while providing self-sustaining habitat for California red-legged frog. Despite a well thought-out design, adaptive management measures were required after the first wet season of monitoring to prevent sediment influx to the California red-legged frog ponds. This presentation reviews the design criteria for California red-legged frog habitat, design considerations in a sediment laden system, and adaptive management measures required to remediate effects of sediment on habitat.

Despite fairly extensive studies of bird populations along the Sacramento and Cosumnes Rivers in the Central Valley, studies of bird populations and their responses to habitat and landscape attributes at interior Sacramento-San Joaquin Delta restoration sites (Grizzly Slough, Decker, Sherman, and Twitchell Islands) are limited. We conducted point count and vegetation surveys at 12 restoration sites (n = 50) located within the west and north Delta during May and June, 2011. Sites included various habitat types including shrub scrub, riparian, and freshwater marsh. We evaluated bird species composition and richness, and also tested regression models that related these variables to 1) fine-scale habitat attributes (tree and shrub species richness, tree and shrub percent cover, herb cover and non-native species richness), 2) landscape attributes (area, area to perimeter ratio, and age), and 3) adjacent land cover (grassland, crop, riparian, wetland and water). Our results indicate low species richness when compared to Sacramento and Cosumnes sites, but a fairly high percentage of native species. Though songbird communities were prevalent, cowbird populations were a particular concern. Bird species abundance and richness were also significantly lower at sites we sampled that were linear versus nonlinear, smaller versus larger, younger versus older, and at sites with non-native versus native species. We found fine-scale habitat and landscape attributes to be useful in predicting species abundance and richness, however, adjacent land cover had little effect. These findings are used to provide guidance for restoration design (of interior island and setback levees) to enhance bird populations/ communities and also to suggest further research.

Evidence of long-term, sustainable natural plant communities is necessary to confirm ecological function in created vernal pools. We classified plant communities in created and natural vernal pools at three Central Valley project sites, and compared them to all known natural vernal pool communities in the region. Data were collected over two successive years when created pools were at least twelve years old, using protocols developed by Barbour and others (2003). Communities were classified using the key developed by these researchers. At the site within the Livermore Vernal Pool Region, one community keyed to a natural vernal pool association; other communities keyed to non-vernal pool communities. Dominance of exotic species in these pools may be due to dry conditions, loss of hydrologic function, and cessation of cattle grazing. Lack of grazing and changes to hydrology appear to have contributed to invasion by exotics also at the Southeastern Sacramento Valley Region site. Pools at the Northeastern Sacramento Valley Region site were less invaded, reflecting higher annual precipitation, lack of land use change, and moderate grazing. Communities of created and natural pools at Sacramento Valley sites keyed to natural associations with similar floristic composition and species constancies to regional vernal pool communities. Created pool associations were generally those of deeper, longer-inundated vernal pool habitats compared to natural vernal pool associations at the same site.