More info for the terms: cover, density, fire exclusion, fire frequency, fire regime, fire tolerant, frequency, mesic, nonnative species, root crown, shrub, shrubs, succession, tree, tussock
Fire adaptations: Coyote bush is moderately fire tolerant [63]. In areas of high shrub density, heat at coyote bush root crowns is often too low to cause mortality, and coyote bush is able to resprout from the root crown and roots [30,42]. Fires in such communities reduce crown cover but are not likely to reduce shrub density [42]. Fires that occur in areas with low shrub density and high herbaceous biomass create enough heat at the root crown to girdle and kill plants [30,42]. In oak woodlands and chaparral, most postfire recovery of coyote bush and other dominants is by sprouting. In coastal sage scrub, fire creates canopy gaps with exposed mineral soil that allow coyote bush and other coastal sage scrub species (most of which also have small, light seeds) to establish from seed and outcompete herbaceous vegetation [36]. Postfire sprouting of is also an important method of regeneration in coastal sage scrub dominates such as coyote bush and California sagebrush [35,66,67].
FIRE REGIMES: Fire frequency largely determines the extent of grasslands, coastal sage scrub, chaparral, and oak woodlands and whether coyote bush is present in each of these types. In grasslands, low fire frequency permits establishment of coyote bush and the gradual exclusion of herbaceous species [27,64]. In coastal sage scrub, chaparral, and oak woodland, decreasing fire frequency allows coyote bush to be replaced by more shade-tolerant species [64]. In mixed evergreen forests, closed-cone pine stands, and coast Douglas-fir stands, coyote bush is only important in early seral vegetation after fire or logging [27]. Transition from coyote bush scrub to mixed evergreen forest can occur in 50 years without fire. In some cases, however, tree recruitment is limited by crown closure, and fire exclusion does not result in type conversion but rather maintenance of a dynamic mosaic wherein reversion and succession allow both vegetation types to persist [8].
One study of vegetation dynamics in coastal sage scrub, grassland, and oak woodland near Santa Barbara found without fire or livestock grazing, coastal sage scrub was replaced by oak woodland at a rate of 0.3% annually. Grassland to coastal sage scrub transition occurred at a rate of 0.69% per year, and oak woodland reverted to grassland at a rate of 0.08% per year. On burned areas without livestock grazing or on unburned sites with livestock grazing, rates of transition of grassland to coastal scrub and coastal scrub to oak woodland were lower. On areas burned without grazing or grazed without burning the rate of oak woodland reversion to grassland was higher than on areas with neither burning nor grazing [8].
Coastal sage and coastal scrub: These community types are fire-dependent, with prominent shrubs establishing by seed and sprouting [35,36,66,67]. It is a flammable vegetation type that may burn 1 to 2 years after fire if dry conditions exist. With fire in less than 5-year intervals, or with overgrazing, coastal scrub generally reverts to annual nonnative grassland [34,59]. Fire exclusion in coastal sage scrub and mesic chaparral communities allows coast live oak, California bay, and other shade tolerant species to increase in density and reduce understory diversity and abundance [44,64]. In the absence of fire, coast live oak recruitment in chaparral and grassland is commensurate with their aerial extents; in coastal sage scrub, however, coast live oak recruitment exceeds that expected by chance alone. This is primarily because coyote bush is a nurse shrub for shade-tolerant tree seedlings, particularly coast live oak and California bay. With tree development, coyote bush is reduced or excluded [8].
Chaparral: Coyote bush is generally absent from mature chaparral, but after fire it occurs with other relatively short-lived shrubs and sub-shrubs including California sagebrush, rabbitbrush (Chrysothamnus spp.), California brittlebrush, yerba santa (Eriodictyon spp.), eastern Mojave buckwheat, golden-yarrow, monkeyflower (Mimulus spp.), and others [26]. Shade created by abundant sprouting of chaparral shrubs limits coyote bush seedling establishment; seedlings are most abundant in gaps where nonsprouting shrubs are eliminated and mineral soil is exposed [34,69]. As in coast scrub associations, high fire frequency can create annual grasslands of native and nonnative species [34].
Coastal prairie: Fire exclusion in coastal prairie allows coyote bush establishment, with best establishment in wet years [39,68]. Complete conversion of purple needlegrass (Nassella pulchra) tussock grassland to coyote bush/ripgut brome (Bromus diandrus) stands has been observed with 24 years of fire exclusion [39]. Coyote bush forms a closed canopy in about 2 to 3 years after invasion [30]. Keeley [34] maintains that California prairies that have been invaded by shrubs were, in most cases, disclimaxes maintained by fires set by Native Americans.
Greenlee and Langenheim [23] described FIRE REGIMES of potential coyote bush habitats in the Monterey Bay area; their results are summarized below. In all habitats there was a large decrease of fire frequency in the recent era, beginning in 1929 with restrictions against burning. "Probable mean fire interval" refers to estimates of fire intervals that are derived from historical or very limited physical evidence.
Fire regime Vegetation where burning concentrated Vegetation where burning incidental Recorded or calculated mean fire intervals (years) Probable mean fire intervals (years) Lightning Prairies 1-15 Coastal sage 1-15 Chaparral 10-30 Oak woodland 10-30 Mixed evergreen 15-30 Redwood forest 135 Aboriginal (until approximately 1792) Prairies 1-2 Coastal sage 1-2 Chaparral 18-21 Oak woodland 1-2 Mixed evergreen 50-75 Redwood forest 17-82 Spanish (1792 to 1848) Prairies 1-15 Coastal sage 1-15 Chaparral 19-21 Oak woodland 2-30 Mixed evergreen 50-75 Redwood forest 82 European-American (1847 to 1929) Prairies 20-30 Coastal sage 20-30 Chaparral 10-27 Oak woodland 50-75 Mixed evergreen 7-29 Redwood forest 20-50 Recent (1929 to present) Prairies 20-30 Coastal sage 155 Chaparral 155 Oak woodland 225 Mixed evergreen 215 Redwood forest 130
FIRE REGIMES for plant communities and ecosystems in which coyote bush occurs are presented below. More information regarding FIRE REGIMES and fire ecology of these communities can be found in the 'Fire Ecology and Adaptations' section of the FEIS species summary for the plant community or ecosystem dominants below.
Community or Ecosystem Dominant Species Fire Return Interval Range (years) California steppe Festuca-Danthonia spp. 51] Pacific ponderosa pine* Pinus ponderosa var. ponderosa 1-47 [1] coastal Douglas-fir* Pseudotsuga menziesii var. menziesii 40-240 [1,46,55] California mixed evergreen Pseudotsuga menziesii var. m.-Lithocarpus densiflorus-Arbutus menziesii California oakwoods Quercus spp. 1] coast live oak Quercus agrifolia 2 to 75 [23] canyon live oak Quercus chrysolepis blue oak-foothills pine Quercus douglasii-Pinus sabiniana Oregon white oak Quercus garryana 1] California black oak Quercus kelloggii 5-30 [51] redwood Sequoia sempervirens 5-200 [1,17,61] *fire return interval varies widely; trends in variation are noted in the species summary
