State 1
Historic State

State 1 represents the historic range of variability for this ecological site. This state no longer exists due to the ubiquitous naturalization of non-native species in the Mojave Desert. Periodic drought was the natural disturbance influencing this ecological site.

Data for this State does not exist, but dynamics and composition would have been similar to State 2, except with only native species present. See State 2 narrative for more detailed information.

Community 1.1
Historic Reference Community

This community phase no longer exists due to the naturalization of non-native species in the Mojave Desert. The historic reference community composition would have been similar to community phase 2.1, but without non-native species.

State 2
Reference State

State 2 represents the current range of variability for this site. Non-native annuals, including Mediterranean grass, red brome and red-stem stork’s bill (Erodium cicutarium) are naturalized in this plant community. Their abundance varies with precipitation, but they are at least sparsely present (as current years growth or present in the soil seedbank).

Community 2.1
Reference Plant Community

Figure 6. Community Phase 2.1

Figure 7. Community Phase 2.1

The reference plant community has an open two-tiered canopy less than 2 meters tall with creosote bush in the upper tier over big galleta and burrobush. Secondary shrubs may include white ratany (Krameria grayi), peach thorn (Lycium cooperi), California ephedra (Ephedra californica), button brittlebush (Encelia frutescens), Mojave yucca (Yucca schidigera), branched pencil cholla (Cylindropuntia ramosissima), and Wiggin's cholla (Cylindropuntia echinocarpa). At the southern limit of the range of this ecological site, Hall's shrubby spurge (Tetracoccus hallii) and lotebush (Ziziphus obtusifolia) may occur as trace species. Vegetative composition is approximately 60% shrubs, 25% grasses and 15% forbs. Perennial forbs and subshrubs may include California croton (Croton californicus), wishbone bush (Mirabilis laevis var. villosa), desert globemallow (Sphaeralcea ambigua), and brownplumed wirelettuce (Stephanomaria pauciflora). Annuals are seasonally present and may include bristly fiddleneck (Amsinckia tessellata), western Mojave buckwheat (Eriogonum mohavense), and birdcage evening primrose (Oenothera deltoides), among others. Approximate ground cover (basal and crown) is 5 to 15 percent. This site is stable in this condition.

Forest overstory.Allow no more than 5% of each species of this group, and no more than 15% in aggregate

Forest understory. Allow no more than 3% of each species of the grasses group, and no more than 5% in aggregate<br /> <br /> Allow no more than 2% of each species of the forbs group, and no more than 8% in aggregate

Community 2.2
Drought Response

This community phase is characterized by strong dominance by creosote bush due mortality of big galleta and burrobush, and an overall decline in cover and production due to branch-pruning and lack of recruitment of longer-lived species including creosote bush, and lack of emergence of annual forbs and grasses.

Big galleta may suffer very high rates of drought-induced mortality (Webb et al. 2003; Hereford et al. 2006); however, big galleta can respond very quickly to brief, intermittent rain during rare summer monsoonal events, which may sometimes buffer big galleta populations in the absence of more predictable winter rains. Burrobush may also suffer high rates of drought-induced mortality, with up to 68 percent mortality following one year of severe drought (Miriti et al. 2007).

Creosote bush is an evergreen species capable of utilizing moisture at any time of the year. This ability buffers populations from the effects of drought that occur as the absence of the winter rains (the primary source of moisture for this ecological site). Further, creosote bush germinates in response to moisture during the warm season, so may still recruit if warm season rains occur during winter drought (Hereford et al. 2006). Creosote bush exhibits branch-pruning during severe drought, but mortality during drought in the Mojave Desert is very low (Webb et al. 2003, Hereford et al. 2006).

Community 2.3
Fire regeneration community

This community phase is characterized by severe declines in creosote bush, and an increase in big galleta (10 to 50 percent increase in cover).

Initially, the post-burn community is dominated by big galleta, non-native grasses native annuals and native subshrubs. Subshrubs that often become dominant after fire include desert globemallow, brownplume wirelettuce, and desert marigold (Baileya multiradiata). With time, shrub cover increases with the recovery of species capable of resprouting (including Mojave yucca, white ratany, California jointfir, and peach thorn), and colonization by short-lived shrubs from off-site seed dispersal (including burrobush, rayless goldenhead [Acamptopappus sphaerocephalus], and Cooper's goldenbush [Ericameria cooperi]). As shrub cover increases, safe sites for creosote bush recruitment increases. With a long period of time without fire, creosote bush begins to regain dominance as shorter-lived species die out (Vasek 1983, Abella 2009, Vamstad 2009).

This community is an at-risk phase, as the increased cover and biomass of big galleta and non-native annual grasses increases the likelihood of repeat burning (D'Antonio and Vitousek 1992, Brooks et al. 2004, Brooks and Matchett 2006). If the fire return interval is less than 20 years, this community is very likely to transition to State 3.

Pathway 2.1a
Community 2.1 to 2.2

This pathway occurs with prolonged or severe drought.

Pathway 2.1b
Community 2.1 to 2.3

This pathway occurs with moderate to severe fire.

Pathway 2.2a
Community 2.2 to 2.1

This pathway occurs with time and a return to average or above average precipitation conditions.

Pathway 2.2b
Community 2.2 to 2.3

This pathway occurs with moderate to severe fire.

Pathway 2.3a
Community 2.3 to 2.1

This community phase occurs with time and the absence of additional disturbance.

State 3
Repeated fire State

This state develops when the fire return interval is less than 20 years. This state has been significantly altered from the natural range of variability found in States 1 and 2. Creosote bush is lost, and big galleta, non-native annual grasses, native sub-shrubs, and short-lived shrubs dominate the community. Annual grasses and forbs are abundant immediately post-fire, with dominance by big galleta, subshrubs and short-lived perennials several years post-fire.

Community 3.1
Big galleta/short-lived shrubs

This community phase develops with time without fire (5-20 years), and is dominated by big galleta, subshrubs (desert globemallow, desert trumpet, brownplume wirelettuce and desert marigold) and short-lived shrubs (burrobush, rayless goldenhead). Longer-lived shrubs that have resprouted may be patchily present. There is high cover of non-native and native annuals during wet years.

This community is at high risk of repeat burning due to high cover of fine fuels.

Community 3.2
Annual grass/Forbs

This community phase typically occurs one to five years post-fire. The community is dominated by non-native annual species including red brome, Mediterranean grass and red-stem stork’s bill, and native forbs, including bristly fiddleneck, western Mojave buckwheat and miniature woollystar (Eriastrum diffusum (many other native forbs could also be present). Native subshrubs including globemallow, desert trumpet, brownplume wirelettuce and desert marigold may be abundant. Big galleta cover is high, and there may be very sparse cover of resprouting shrubs including Mojave yucca, peach thorn, and California ephedra. Seedlings of short-lived shrubs may be present, and may include burrobush, rayless goldenhead, and Cooper’s goldenbush).

This community is at high-risk of repeat burning due to high fine fuel cover. This community is also susceptible to wind and water erosion, due to the loss of stabilizing shrub cover (Bull 1997). This can lead to arroyo development near ephemeral drainage channels. Furthermore, the loss of vegetation structure present in the historic and reference state decreases the suitability of this habitat for wildlife (Brooks et al. 2007, Vamstad 2009).

Pathway 3.1a
Community 3.1 to 3.2

This pathway occurs with fire.

Pathway 3.2a
Community 3.2 to 3.1

This pathway occurs with time without fire (> 5 years).

Transition T1
State 1 to 2

This transition occurred with the naturalization of non-native species in this ecological site. Non-native species were introduced with settlement of the Southwest Desert region in the 1860s.

Transition 2
State 2 to 3

This transition occurs when the fire return interval is less than 20 years.

Restoration pathway 1
State 3 to 2

Restoration of communities severely altered by repeat fire at the landscape scale is difficult. Methods may include aerial seeding of early native colonizers such as desert globemallow, desert trumpet, brownplume wirelettuce, desert marigold, and big galleta. Increased native cover may help to reduce non-native plant invasion, helps to stabilize soils, provides a source of food and cover for wildlife, including desert tortoise (Gopherus agassizii), and provides microsites that facilitate creosote bush establishment. However, the amount of seed required for success is often prohibitive. Large-scale planting of both early colonizers and community dominants tends to be more successful in terms of plant survival, especially if outplants receive supplemental watering during the first two years. Creosote bush can be successfully propagated from seed for outplanting. Pre-emergent herbicides (Plateau) have been used in the year immediately post-fire to attempt to inhibit or reduce brome invasion. How successful this is on a landscape scale, and the non-target effects have not yet been determined.