The best laid plans often go awry. When a buffer was established around the portion of Corral Hollow Creek that flows through Carnegie State Vehicular Recreation Area (SVRA) 7 years ago, the intent was to let the area recover through passive restoration. Unfortunately, restoration and recovery were impacted by the drought. This led to an opportunity for park staff to involve the community and implement a more active restoration approach to help improve the area’s vegetation density.
In late February 2017, Superintendent Randy Caldera reached out and let the ridership at Carnegie SVRA know of the park’s dilemma. What followed was a tremendous outpouring of support from the community and partners, allowing for the creek’s buffer to be restored with native riparian species.
The original project entailed removing active disturbance within the buffer area and allowing plants to recolonize bare areas through natural propagation. An increase in vegetation density in areas proximate to the creek would increase overall storm water quality in this waterway. While many native shrubs and forbs have been the initial successors to this area, the end goal of restoring riparian habitat has been proceeding at slower rates. Fremont cottonwood tree saplings could be observed throughout the creek, but not many other young tree species. This slow rate of recovery was very likely exasperated by the statewide drought.
In February 2016, native plant materials (seeds and pole cuttings) were collected from within the park for contract propagation off-site. The species included in this effort included three riparian tree species and one riparian shrub species: Fremont cottonwood (Populus fremontii), California sycamore (Platanus racemosa), red willow (Salix laevigata), and mule fat (Baccharis salicifolia). The rooted plants were ready for delivery in December 2016, but park staff was having difficulty allotting the time and personnel needed to get everything in the ground during the wet season.
Several riding groups responded to this call for help by establishing a volunteer date in early March and exhaustively circulating the details amongst the park visitors and local OHV communities. District 36 let the public know they would be providing a barbeque lunch for all volunteers. The day of the event, members of Carnegie Forever and the Carnegie Advisory Team approached visitors entering the park and informed them where and when the tree planting would take place. As a result, approximately 140 volunteers donated their time to restore the creek’s buffer with native riparian species.
Other groups in attendance included: CORVA, Blue Ribbon Coalition, Wandering Wheelers, Redneck Roosters, City Bike, Elevated Action Sports, Bay Area Riders Forum, Hayward Motorcycle Club, Dirt Diggers, Diablo 4×4, and California Conservation Corps (volunteers).
Two areas of the park’s floodplain were targeted for planting: the creek buffer between Carrol crossing and the ATV track (south of the campground), and the creek buffer north of the MX track and 4×4 play area. The first area was planted with 108 sycamores, 62 cottonwoods, 60 willows, and 73 mule fat shrubs (303 plants total). The second site was planted with 121 sycamores, 54 cottonwoods, 2 willows, and 128 mule fat shrubs (305 plants total). At the end of the day, the park volunteers planted a grand total of 608 native plants in four hours, stopping only because they ran out of trees to plant. Additionally, the weather contributed to success by raining ~0.5 inches several hours after the event.
The event surpassed the goal of planting 50 trees by a longshot. Riders brought their own tools and came ready to sweat and get the job done. It was an amazingly successful community event and Carnegie SVRA staff is immeasurably grateful for all the hard work park visitors put in to help out.
While the main purpose of restoring native riparian habitat to Corral Hollow Creek for this event was to improve storm water quality, other benefits must be acknowledged:
Beautification. The creek buffer, while closed to most forms of disturbance, is open to pedestrian traffic. This planting effort will enhance the perceived aesthetics of these areas, by providing groves of trees, rather than bare ground, to view. It will also provide shaded areas for visitors to explore and learn about the natural resources of their local park’s riparian zone.
Habitat. Many local wildlife species live and/or breed in trees and shrubs located within the creek’s buffer area. Amongst these are barn owls, great-horned owls, several bats, red-tailed hawks, and many smaller birds. By increasing the number of available trees for roosting, an increase in the amount of wildlife able to use the buffer area can be expected (although limited by natural boundaries: food availability, home range/territories, etc.).
Climate Resiliency. Lastly, park visitors were dismayed to find the entire park closed for a week after a flood in February 2017 damaged the park’s facilities on the valley floor. While the creek channel braided and damaged resources throughout the canyon, areas with mature trees were often relatively unscathed. Many of these stands of older, deep-rooted trees withstood the force of the flood waters and, in certain cases, prevented the creek from meandering too far from its original channel and acted as a natural form of protection for facilities. At the opposite end of the spectrum, during periods of intense drought, thickets of taller vegetation provide havens for wildlife as well as smaller statured, shallow-rooted plants. The trees planted by park visitors during this event will increase the overall resiliency of the park’s floodplain for local flora and fauna during extreme periods of climate conditions.