Vegetation in the Big Chico Creek Ecological Reserve is extremely varied, changing subtly as aspects of the microhabitat (slope, exposure, elevation, soil moisture, soil depth) change. Plant assemblages grade slowly into one another. In a particular transect, blue oaks in a savanna may gradually get denser until at some arbitrary point the habitat would be classified as a woodland, then a few interior live oaks will be mixed in, then more live oaks and a few canyon oaks. View the full list of Vascular Plant Species at the BCCER.
Gradually the canyon oaks will come to dominate, and other species (ponderosa pine, big-leaf maple, black oak, incense cedar) will be mixed in and the vegetation will be dense enough to be classified as forest. Because of these ubiquitous spatial gradients, a fine-scale vegetation map is impractical for making reserve-wide decisions. To provide a more practical tool, vegetation types have been grouped into broad-spectrum categories each representing a segment of the total vegetation gradient. These categories are: grassland, wet meadow, riparian, valley oak woodland, blue oak savanna/woodland, mixed woodland/forest, chaparral, and chaparral/savanna.
Grasslands (10 acres; 0.4% of the reserve) are open meadows, devoid of woody vegetation and dominated by grasses and forbs. Non-native plants such as wild oats, rip-gut brome, yellow-star thistle, and rose clover are usually abundant. A few native grasses and a diversity of mostly spring-blooming native forbs is present.
Wet Meadows (2 acres; 0.1% of the reserve) are uncommon and small, less than an acre in size. Soils are water-saturated close to the water source and grade to barely damp at the margins. Vegetation consists of native sedges, rushes, and forbs with the non-native Dallas grass often dominating near the margins. Clumps of native deer grass and rush are also common near the margins.
Riparian zones (20 acres: 0.8% of the reserve) are found in the floodplain of Big Chico Creek as well as some permanent tributaries. They contain a wide diversity of both woody and herbaceous plants including alders, willows, sycamores, spicebush, button-willow, California grape, deer grass, sedges and forbs such as umbrella plant and creek orchid. The invasive Scotch broom, edible fig, and Himalayan blackberry are common in some parts.
In the Blue oak savanna/woodland (262 acres; 10% of the reserve) the blue oak trees grade from scattered to dense enough to form a closed canopy. Some areas include a few gray (foothill) pines. The groundcover is mostly herbaceous, containing the same species as the grasslands, but usually including more native perennial grasses, particularly purple needle grass, blue wild rye, and California brome. Some scattered shrubs are present, particularly red berry, manzanita, and skunkbrush.
Valley oak woodland (6 acres; 0.2% of the reserve) is rare in the reserve and generally found next to open meadows in the bottom of the canyon. The under story is similar to that of blue oak woodland, but is usually brushier, containing poison oak, coffeeberry and skunkbrush.
The mixed woodland/forest category (299 acres; 11.5% of the reserve) is the most diverse assemblage. In the densest parts it includes over story species of interior live oak, canyon oak, black oak, gray pine, ponderosa pine, incense cedar, and Douglas fir. An under story layer may be formed of juveniles of canyon oak, live oak or incense cedar as well as big leaf maple and any of the typical chaparral shrubs. It grades to a closed-canopy woodland of interior live oaks mixed with blue oaks. Ground cover is also varied but usually includes a number of forbs and the native grasses, California and Torrey's melic, woodland brome, and blue wild rye. The main problem with subdividing this diverse assemblage is that the entire gradient can often be encountered within a few tens of meters.
Extensive stands of chaparral (603 acres; 23% of the reserve) are found in a few places, particularly toward the northern part of the reserve. These are almost impenetrable thickets of many species of shrubs including scrub oaks, buck brush, mountain mahogany, poison oak, California bay, Manzanita, honeysuckle and others. Gray pines are common in less dense areas. Ground cover is relatively limited when the shrubs are mature, but many forbs and grasses show up after a fire.
Chaparral/savanna: (1401 acres; 54% of the reserve) Large areas in the western part of the reserve are vegetated by varying width bands of chaparral interspersed with bands of savanna or grassland. (This banding is imposed by the underlying layers of substrate in the Tuscan Formation.) The chaparral bands contain the usual chaparral assemblage of shrubs and the savanna bands are similar to blue oak savanna except that gray pine is as common as blue oak and small patches of chaparral brush are scattered throughout.
Goals of vegetation management
1. Reduce wildfire threat. (Wildfires starting on the reserve or propagating across the reserve could damage vegetation, animal habitat, and research projects as well as threatening neighboring properties.)
2. Optimize browse and cover for wildlife.
3. Maximize diversity of native species.
4. Maintain natural plant communities.
5. Reduce populations of exotic species and prevent their spread.
6. Research the impacts of management strategies (e.g. fire or grazing) on target and non-target species.
7. Increase forage for livestock grazing if such a program is adopted in parts of the reserve.
Create shaded fuel breaks along reserve roads by removing shrubs, surface and ladder fuels, selectively leaving trees that will eventually be large enough to suppress shrub growth. Obviously fuel breaks will require maintenance, but the amount should decrease as the trees grow.
Fuel breaks don't stop a fire but they create an area of reduced fire intensity, providing a starting line for firefighters or reducing the heat that sweeps into an adjacent habitat. Drainage divides are natural places for a fuelbreak since fire burns rapidly uphill but slowly downhill and vegetation is generally sparse on ridge tops. (Most ridge tops in the reserve from the Musty Buck Ridge west have roads with existing firebreaks. All need maintenance and widening in spots.) See Coexisting with Fire in the BCCER.
In collaboration with CDF, use controlled burns to rejuvenate chaparral and savanna areas, keeping burn areas small (<40 acres) and adjacent areas in different parts of the rotation cycle. Before initiating a controlled burn, any dense brush around large trees should be manually removed to prevent tree damage. (Large trees are critical habitat components, providing nest and perch sites as well as seeds for reproduction and animal food.)
Controlled burns could also be used in woodland or even forest areas under conditions where the fire would burn slowly. Some fraction of seedlings as well as large trees should be protected by pre-fire removal of adjacent fuel. In forest areas, periodic manual removal of under-story fuel may be necessary to prevent destructive fires.
Control invasive woody species (broom, fig, and Himalayan blackberry) by pulling up roots or cutting at the base and immediately daubing the stump with herbicide. Experiment with burning, mowing, hand pulling, and herbicide treatment to determine the most effective, species-specific techniques for reducing or eliminating invasive herbaceous weeds such as yellow-star thistle and medusa-head grass.
Select in favor of perennial native grasses by gathering local seeds and dispersing them in favorable spots such as burned or disturbed areas to expand stands or start new stands. Use spring burns to reduce seed set of exotic annual grasses or forbs.
Protect selected oak seedlings
Monitor seedling survival of blue and valley oaks.In savanna areas where recruitment is inadequate, place "tree guards" or wire mesh rings around selected seedlings to enhance survival to the sapling stage.
Limit cattle grazing
Grazing has been a historical use of the reserve and may be re-instituted in future as a source of revenue, a teaching tool, or a means of reducing vegetation cover in selected localities. However, the historic pattern of grazing cattle through the wet season has obviously contributed to the current dominance of annual Mediterranean grasses. if cattle are to be on the reserve, they should be there as part of the overall management strategy, not just as strays from neighboring ranches as has occurred in the past. Forage on the reserve is limited and only available seasonally, so alternative pastures and a transportation system must be part of the plan. The BCCER can provide a place to evaluate grazing as a tool in a total vegetation management strategy, thereby providing a unique opportunity for students to observe a cooperative rather than a combative approach to range/wildland issues.
1. Grazing should not be put out "to bid"- this can encourage poor management and over-grazing.
2. Grazing should be managed by the University, potentially using University cattle.
3. Grazing should be part of specific research studies.
4. A monitoring program needs to be developed to appropriately time grazing. Stubble height in key areas is a commonly used indicator of when and if cattle need to be moved. However, cattle have other effects than just reduction of vegetative biomass, so impacts such as soil compaction, shifts in species dominance, and reproductive success of species such as native grasses and blue oaks should also be considered.