sign in sign up
<<
Home , Bull Valley Mountains, Fire regime, Lycium andersonii, Mojave Desert, Prunus fasciculata, Tule Desert (Arizona)

Chapter 6

Creosotebush, Blackbrush, and Interior Shrublands Matthew L. Brooks, Todd C. Esque, and Tim Duck

Introduction Creosotebush Scrub The vegetation, fire regime, and Fire Regime Condi- Introduction tion Class descriptions in this paper apply broadly to the Mojave , , and southern Great Low cover (5 to 30 percent) of woody of Basin of . More detail on these ­various heights (0.5 to 1.5 m [1.6 to 4.9 ft] character- topics, including estimated percentages within each con- izes Creosotebush scrub (Vasek and Barbour 1995). dition class, is provided for the Mojave-Colorado Plateau It occurs across the warm desert of western ecotone spanning southern , the Strip North America and is the most common assem- northwest of the , and southwestern , blage in the (fig. 1) (MacMahon 2000). including the area within the boundaries of the Southern Creosotebush scrub is typically found below 1,500 m Utah Fuel Management Demonstration Project (Hood (4,920 ft) on well-drained alluvial flats and slopes below and others, this volume; www.firelab.org/fep/research/ the blackbrush zone and above the saltbush zone that sufm/home.htm). Fire Regime Condition Classes (FRCC) often occur within valley basins (Vasek and Barbour are an interagency, standardized tool for describing the 1995). It phases into -steppe in regions with high natural range of variation in vegetation, fuels, and fire proportions of summer rainfall, typically encountered regime characteristics for a particular biogeographic in the eastern Mojave Desert and . or vegetation type. They summarize how past Creosotebush scrub is dominated by the type-­species land use and land management actions (or inactions) creosotebush (), which has the high- may have caused the FRCC to change. est cover and is the most wide-ranging plant species The three shrubland vegetation types that we review in the Mojave Desert (Rowlands and others 1982). are creosotebush scrub, blackbrush, and interior chap- It is most frequently associated with white bur-sage arral, which are typically situated along an increasing (), but a wide range of other elevation gradient where they co-occur. The interior can co-occur with creosotebush, including goldenhead chaparral vegetation type is sometimes considered to (Acamptopappus spp.), sa ltbush (Atriplex spp.), Mormon include both Arizona chaparral, which occurs mostly in tea (Ephedra spp.), goldenbush (Ericameria spp.), wild Arizona and , but also in southern Utah and buck wheat (Eriogonum fasciculatum), rat a ny (Krameria Nevad a, a nd mou nt a i n br ush (or Pet ra n chapa r ra l), wh ich spp.), winterfat (), boxthorn occurs primarily farther north in Utah and Colorado. ( spp.), indigo bush (Psorothamnus spp.), desert We focus on Arizona chaparral. Two vegetation types needleg rasses a nd I ndia n r iceg rass (Achnatherum spp.), dominated by big sagebrush (Artemisia tridentata) and galleta grass (Pleuraphis spp.), cholla, beavertail, and pinyon- (Pinus edulis, , and ot her cact i (Opuntia spp.), and Joshua , Mojave , Juniperus spp.) often intergrade between blackbrush and and others (Yucca spp.). Dominant non-native species interior chaparral in the alluvial soils of broad valleys include red brome (Bromus rubens), Mediterranean and foothill toe-slopes. Kitchen and McArthur (this split-grass (Schismus spp.), and red-stemmed filaree volume) reviewed big sagebrush and Tausch and Hood (Erodium cicutarium). (this volume) reviewed pinyon-juniper.

USDA Forest Service Gen. Tech. Rep. RMRS-GTR-202. 2007 97 Chapter 6—Creosotebush, Blackbrush, and Interior Chaparral Shrublands

Figure 1—Creosotebush (Larrea tridentata) scrub in the Mojave Desert.

Within the Mojave-Colorado plateau ecotone, creo- (Gopherus agassizii) and a variety of rodents incorpo- sotebush scrub reaches its northeast limit in south- rate the root structure into their burrows. Shrubs also western Utah near the entrance to provide concealment and escape cover from predators and follows the Valley to and shade from the sun. in Nevada. It occurs in most of this river drainage Many Mojave Desert shrubs are not fire-tolerant below 1,250 m (4,100 ft) elevation. Its distribution ­because their drought-adaptive features (thin bark, broadens below the Hurricane Fault in Utah, spreading shallow root system, small ) and high dead-to-live northward as far as Browse along and woody material ratio make them vulnerable to fire. Some then following the base of the red cliffs throughout species, including creosotebush, can resprout after burn- the Valley north of Washington, St. George, ing (fig. 2); however, survival rates decline significantly and Gunlock, Utah. There is a large stand south of if more than 10 percent of their aboveground biomass is St. George in the Blake Lambing Grounds and other consumed by fire (Brooks and Minnich 2006). ­Native stands are located throughout the . plants are generally slow to re-establish after fire Below the Gorge, the distribution spreads from the foot and recurrent fire may prevent their re-establishment of the and around Utah Hill, (Brooks and Minnich 2006; Brown and Minnich 1986; up the northward to Jackson Wash O’Leary and Minnich 1981). The loss of native plants almost meeting with the creosotebush scrub commu- can be followed by increased dominance of non-native nity west of the town of Gunlock. From Littlefield, annual grasses. The post-fire vegetation has typically Arizona, there is continuous creosotebush scrub all lower species diversity and plant structural diversity the way to Lake Mead and , Nevada, with than the native community, which can negatively ­affect only minor interruptions in very rocky areas. the (Brooks and Esque 2002; Esque and Creosotebush and associated plants provide much of others 2003) and other desert wildlife. Repeated burning the microhabitat diversity and vertical habitat structure in in creosotebush scrub can lead to significant decreases the Mojave Desert. Branches provide perches and nest- in plant species richness with each subsequent fire ing opportunities for songbirds, while desert tortoises (M. Brooks, unpublished data).

98 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-202. 2007 Chapter 6—Creosotebush, Blackbrush, and Interior Chaparral Shrublands

Figure 2—Creosotebush (Larrea tridentata) resprouting 1 year after a low intensity fire.

Historical Conditions create a long-lived fuelbed (Brooks 1999a). As a result, the historical annual plant fuelbed, prior to the invasion We do not know the pre-settlement fire conditions in by non-nat ive sp e cies, wa s probably t ra nsient, on ly last i ng warm desert plant communities such as creosotebush for one summer fire season after winters of exceptional scrub because the typical analytical methods, such as high rainfall. Perennial grasses may have been more and evaluating charcoal deposits in prevalent in creosotebush scrub before the introduction lakes, are not possible where the requisite and of livestock grazing, providing another source of fine lakes are not present (Brooks and Minnich 2006; Esque fuels that could additionally have helped carry fire in and Schwalbe 2002). It is generally thought that fires the past (Brooks and Minnich 2006). However, stands of in creosotebush scrub were an infrequent event in pre- perennial bunchgrasses were probably patchy, reflecting settlement desert habitats because fine fuels from winter localized soil conditions, and the discrete clumps of fine annual plants were probably sparse, only occurring in fuels created by individual bunchgrasses did not likely large amounts after exceptionally wet winters (Brooks create a continuous fuelbed. and Esque 2002; Brooks and Minnich 2006; Brown and Since settlement in the 1860s, creosotebush scrub has Minnich 1986; Esque and Schwalbe 2002; Humphrey been used for livestock operations along the ­Mojave 1974; O’Leary and Minnich 1981; Salo 2003). Fires Desert-Colorado plateau ecotone and elsewhere were probably more frequent in adjacent shrub-steppe throughout its range. Over the past two centuries, areas where perennial grasses provided additional fuel there has been widespread cattle and sheep use of continuity to carry fire. It appears that was this habitat. Widespread livestock grazing probably not historically a dominating influence in creosotebush promoted the invasion of the annual grasses red brome, scrub landscapes, except possibly where it intergraded cheatgrass, and Mediterranean split-grass (Brooks with shrub-steppe. and Pyke 2001), which create more continuous fine Creosotebush scrub fuels are comprised primarily of fuelbeds that can persist for years (Brooks 1999a). woody shrubs, but it is the fine fuels from annuals and Although these non-­native annual grasses have prob- perennial grasses that facilitate the ignition and spread ably been present for over 100 years (Brooks 2000a, of fires. Native annual plants usually break down rapidly b; Esque and Schwalbe 2002; Salo 2003), wildfire in during the summer after they are produced and do not creosotebush scrub has only been prevalent in this

USDA Forest Service Gen. Tech. Rep. RMRS-GTR-202. 2007 99 Chapter 6—Creosotebush, Blackbrush, and Interior Chaparral Shrublands region since the 1970s (Jerry Empey – BLM Color During the 1980s and early 1990s, fire frequency Country South Zone dispatch, personal communi- ­increased substantially within the Mojave Desert (Brooks cation). The recent increase in fire frequency was and Esque 2002; Brooks and Matchett 2006), and coincident with the end of the mid-century drought many of these fires occurred in creosotebush scrub. In (Hereford and others 2006) and the beginning of a the Opal Mountain and Stoddard Mountain regions of 2 0 ‑ye a r p e r io d of h ig h r a i n fa l l i n t he lat e 19 70 s ( Br o ok s , non-native annual grasses fueled recurrent and Esque 2002; Brooks and Minnich 2006). fires, and some areas burned as many as three times in 10 years (M. Brooks, unpublished data). This increase in fire frequency is attributed to high rainfall in 1983 Current Conditions and 1992, which produced prodigious amounts of fine fuels, especially of red brome. Rainfall was positively Fine fuels from non-native annual grasses currently correlated with fire size between 1980 and 2004 in the represent the most important fuelbed component in low-elevation ecological zone dominated by creosote- ­creosotebush scrub (fig. 3) (Brooks and Minnich 2006). bush scrub (Brooks and Matchett 2006). It appears Non-native annual grasses typically comprise >50 that fine fuels produced during years of high rainfall percent of the total annual plant biomass in creosote- are largely required for the development of large fires bush scrub (Brooks 1999b; Brooks and 2006). in this zone (Brooks and Matchett 2006; Brooks and Annual plants were monitored as livestock/wildlife Minnich 2006). forage in ­unburned areas near St. George, Utah, from During the middle 1990s through 2004, the number of 1980 through 1995 and ranged from 0 to 700 kg/ha (624 fires declined in lower and middle elevation zones where lbs/acre) (BLM and T. Esque, unpublished data). In un- creosotebush predominates (Brooks and Matchett 2006). burned areas near Littlefield, Arizona, the aboveground However, the amount of area burned at the ­upper eleva- production of ­annual plants was over 1,000 kg/ha (892 tion creosotebush ecotones increased slightly, reflecting lbs/acre) in 1993, and was comprised mostly of non- a trend toward increasingly larger fires. This trend was native annual grasses and forbs (Esque 1994). Above punctuated during the summer of 2005 when hundreds ground production of annual plants in a recurrently of thousands of acres burned in areas dominated by burned area of the ­Pakoon Basin of the creosotebush. The current fire return interval in this was measured at >2,000 kg/ha (1,784 lbs/ac) in 2001, region is still unknown, but it seems to be decreasing and was mostly comprised of Bromus spp. (T. Esque, due to the abundance of non-native invasive grasses unpublished data). after particularly wet years.

Figure 3—Highly flammable understory of red brome (Bromus rubens) in creosotebush (Larrea tridentata) scrub.

100 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-202. 2007 Chapter 6—Creosotebush, Blackbrush, and Interior Chaparral Shrublands

Fire Regime Condition Classes desert tortoise, is high. are frequent and wide- spread. Examples of FRCC 3 areas exist in the Pakoon Fire Regime Condition Class 1 (FRCC 1) Basin of , the of , and the Opal Mountain and Stoddard Valley FRCC 1 is characterized by vegetation and fire ­regime areas of California. Return intervals in this condition attributes within the natural range of variation. The risk class may be as short as 5 years. Fuel loads for areas in of losing key components, such as habitat FRCC 3 may exceed 2,000 kg/ha (1,784 lbs/acre) during diversity and cover sites for the desert tortoise, is low. peak years (T. Esque, unpublished data). The invasive This is the natural condition where invasive annual plant/fire regime cycle characterized by this condition grasses are largely absent, thus precluding the fine fuel class creates a feedback loop of decreasing habitat qual- buildup usually required to carry fire at lower and middle ity for wildlife and livestock. Native seedbanks may elevations in the Mojave Desert (Brooks and Matchett be depleted, lengthening the recovery times for native 2006; Brooks and Minnich 2006). Fire return intervals plants. Approximately 20 percent of the creosotebush are extremely long, except for areas near the base of scrub at the Mojave Desert-Colorado plateau ecotone mountains that experience locally higher rainfall and is in this condition class. fine fuel buildup from native annuals, or where creo- sotebush scrub intergrades with shrub-steppe. There is currently zero percent of the creosotebush scrub in FRCC 1 at the Mojave Desert-Colorado plateau ecotone Recommended Treatments in southern Utah, southern Nevada, and northwestern Arizona, because invasive, non-native annual grasses It is unlikely that areas can ever be restored to FRCC 1 have infested the entire area. However, many of the more due to the widespread distribution of non-native annual arid regions of the Mojave Desert further to the southwest grasses, but the size of their impact may be mitigated in California may classify as Condition Class 1. through appropriate land management policies. We recommend suppression of all wildfires (because most Fire Regime Condition Class 2 (FRCC 2) native vegetation in this community vegetation type responds poorly to fires) and minimization of surface FRCC 2 is characterized by vegetation and fire re- disturbances that promote the dominance of non-native gime attributes that have been moderately altered from annual grasses. Prescribed fires should not be conducted their natural range. The risk of losing key ecosystem except for small research burns designed to evaluate fire components, such as habitat diversity and cover sites behavior, fire effects, and fire management techniques for the desert tortoise, is moderate. Patchy fires of lim- and treatments. We also recommend a program of early ited extent are possible in more mesic regions during detection, evaluation, and eradication for new invasive any year. Risk of larger, more continuous fires is high plants before they become established. Many new plant during 10 to 20 percent of all years when rainfall is species are in the process of invasion, and some pose particularly high. Fire risk can be exceptionally high potential fire threats due to their ability to produce when successive years of above average rainfall promote large amounts of continuous fine fuels. New invaders the accumulation of non-native annual grass fuels (in of particular concern are mustards (for example, Bras- other words, production values in excess of 300 kg/ha sica tournefortii and Hirschfeldia incana) and peren- (268 lb/acre) in 2 or more successive years. An example nial grasses (for example, Pennisetum setaceum and of this dynamic occurred in the north of Cenchrus ciliaris) (Brooks and Esque 2002). St. George, Utah, and on the Beaver Dam Slope north In FRCC 2 areas suppress all wildfires and avoid of Littlefield, Arizona (T. Esque, unpublished data). conducting prescribed fires except for small research Approximately 80 percent of the creosotebush scrub at burns. Livestock grazing may reduce fine fuel loads the Mojave Desert-Colorado Plateau ecotone is in this temporarily and may be effective for managing fuels in condition class. small defined areas, such as at the wildland urban inter- Fire Regime Condition Class 3 (FRCC 3) face. However, regular grazing is required to maintain these managed fuel zones, except during years of very FRCC 3 is characterized by vegetation and fire regime low rainfall. Regular grazing may reduce dominance attributes that have been significantly altered from their of late seral native plants and increase the dominance natural range. The risk of losing key ecosystem compo- of non-native and early seral plants that are often more nents, such as habitat diversity and cover sites for the flammable.

USDA Forest Service Gen. Tech. Rep. RMRS-GTR-202. 2007 101 Chapter 6—Creosotebush, Blackbrush, and Interior Chaparral Shrublands

We recommend studies designed for the restora- ecotone, blackbrush is found on dry slopes and benches tion of FRCC 3 sites, which can include research on above the river canyons of southern Utah and northern adapted plant materials, propagation techniques, and Arizona (Turner 1994). It is also found mid-slope on planting techniques. Suppress all wildfires and avoid mountain ranges throughout this ecotone. conducting prescribed fires except for small research Blackbrush is dominated by the type-species, black- burns. Livestock grazing to reduce fuel loads may be brush ( ramosissima), which can comprise counterproductive in the long run if it also hinders the 90 to 95 percent of the total plant cover (Shreve 1942). re-establishment of late seral native plants. Cover of blackbrush is highest in late seral stands on shallow, sandy soils with strong petrocalcic (caliche) horizons where it is the primary dominant plant species. Blackbrush Cover of blackbrush is lowest in deeper, silty soils, or at its upper or lower ecotones, where it is co-dominant Introduction with other native species such as creosotebush, juniper, deser t a l mond ( fasciculata), A nderson wol f b er r y The blackbrush vegetation type is characterized by (), Joshua tree (), blad- relatively high cover (50 percent) of low statured (50cm der sage (Salazaria mexicana), desert needle grasses, [20 inches] tall), woody evergreen shrubs (fig. 4). It oc- Indian ricegrass, and galleta grass. Dominant non-native curs at the bioregional transition between the Mojave and species include the annuals red brome, cheatgrass, and , from California through Nevada, red-stemmed filaree. Arizona, and Utah (Bowns 1973). Blackbrush is typi- Blackbr ush is use d as wi nt er forage by de er a nd big hor n cally found in the elevational zone from 1,220 to 1,520 sheep (Bowns and West 1976), and provides cover for m (4,000 to 4,985 ft) above the creosotebush zone and nongame birds and small mammals (Brown and Smith below the interior chaparral or big sagebrush/pinyon- 2000). It also protects soil from water and wind erosion juniper zones (Beatley 1976; Bradley and Deacon 1967; and promotes soil fertility (Bowns 1973). Randall 1972). Within the Mojave-Colorado plateau

Figure 4—Blackbrush (Coleogyne ramosissima) dominated site with thread snakeweed (Gutierrezia microcephala), desert peach (), and Joshua tree (Yucca brevifolia).

102 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-202. 2007 Chapter 6—Creosotebush, Blackbrush, and Interior Chaparral Shrublands

Blackbrush shrublands are one of the more flammable were relatively uncommon (Croft 1950). The long-term vegetation types in the desert bioregion due to the high effects of these mid-century range burns are currently proportion of fine fuels and optimal fuel bulk density. being evaluated using repeat photography of histori- Blackbrush fires are usually stand-replacing, burning cal photos originally taken 5 to 10 years post-fire and plants to the ground and killing most of them. Individual analyses of field reports, memos, and vegetation plot fires can kill upwards of 80 percent of the of all data collected during the late 1940s through the early species in the soil seedbank (Brooks and Draper 2006). 1960s by range conservationists and foresters from the It is commonly thought that blackbrush stands take cen- BLM and the Forest Service, Intermountain Forest and turies to recover (Bowns 1973; Webb and others 1987). Range Experiment Station (M. Brooks, unpublished However, when only a portion of a blackbrush plant is data). consumed, it may survive and resprout from the root Prior to European contact (pre-settlement), late seral crown (Bates 1984; M. Brooks, personal observation). blackbrush stands were probably more extensive than Analyses of historical photographs from Joshua Tree they are today. The vast expanses of blackbrush range- National Park and southern Nevada also indicate that land that were burned to improve livestock production blackbrush stands can recover after as little as 50 to 75 during the mid-1900s are still dominated by early seral years (Minnich 2003; M. Brooks, unpublished data). It species and have been re-colonized only sporadically by seems probable that the ability of blackbrush to resprout blackbrush (M. Brooks, unpublished data). Blackbrush after burning varies across its wide geographic range, wit h i n t he D eser t Wi ld l i fe Ra nge a nd Nevad a Test Sit e i n which extends from the Colorado Plateau and southern southern Nevada that has not been managed for livestock Great Basin on through the Mojave Desert. In general, production since the 1930s, and likely was not burned the frequency of blackbrush resprouting after partial for rangeland improvement, does not currently contain consumption by fire seems to be highest in more mesic evidence of widespread historical burning (M. Brooks areas at the edges of its geographic range (M. Brooks, and T. Esque, personal observations). It therefore appears personal observation). that extensive burning to remove blackbrush probably created many of the vegetation stands where blackbrush is either absent or a sub-dominant species today. Historical Conditions The historical fuel complex in late seral blackbrush stands was probably similar to that observed in relatively undisturbed sites today, except for the current prevalence Blackbrush is considered a poor livestock forage spe- of Bromus spp. and Erodium cicutarium in many stands cies and ranchers noted that during the late 1930s and (Brooks and Matchett 2003). Vegetation characteristics of early 1940s, wildfires increased production of livestock these stands were characteristic of blackbrush in FRCC forage in blackbrush rangeland of southern Nevada and 1 described below. Shrub cover was likely comprised northwestern Arizona (Anonymous 1945). In an attempt primarily of blackbrush at 30 to 50 percent total cover, to further increase forage production, ranchers and the and interspaces were probably mostly bare, even dur- Bureau of Land Management (BLM) began a program ing years of high rainfall, due to root competition from of prescribed burning in the 1940s, during which time blackbrush. Other species, such as perennial grasses approximately 20 percent of the 161,875 ha (400,000 and early seral shrubs, probably occurred sporadically, acres) of blackbrush were burned by prescribed fire or as they do today, along wash stringers and on steep wildfire in southern Nevada (BLM, Las Vegas, Nevada, hillslopes where cover of blackbrush is typically low. grazing district 5) (Croft 1950). Many blackbrush fires Low amounts of fine fuels in interspaces probably also occurred in northwestern Arizona during this time limited fire spread to only extreme fire condi- (BLM, Arizona Strip, Arizona, grazing district 2). Ad- tions during which high winds, low relative humidity, ditional blackbrush burning likely occurred at least and low fuel moisture led to high intensity stand-replac- through the 1960s because a policy review during that ing crown fires. Natural fire return intervals appear to time by the Range and Forestry Officer of the Bureau have been on the order of centuries (Webb and others of Land Management in Nevada recommended that 1987). The long intervals without fire allowed late seral blackbrush burning be continued to increase livestock blackbrush stands to re-establish. forage (Dimock 1960). Before 1940, fires in these regions

USDA Forest Service Gen. Tech. Rep. RMRS-GTR-202. 2007 103 Chapter 6—Creosotebush, Blackbrush, and Interior Chaparral Shrublands

Current Conditions Matchett 2006). This is in contrast to the conclusions of Minnich (2003) who states that fine fuels that re- Blackbrush is considered to be one of the most flam- spond to short pulses of rainfall have less of an effect mable native plant assemblages in the Mojave Desert. on fire regimes in blackbrush than woody fuels that Many large fires have occurred in this vegetation type ­accumulate slowly over time. Both conclusions probably since the 1980s in the and Mormon have some validity, with fine-fuels taking precedence Mountains in Nevada, the Beaver Dam Mountains in at lower elevations of the blackbrush zone and woody Utah, the Black Mountains and in fuels taking precedence at higher elevations. At lower Arizona, and at Joshua Tree National Park in California elevations, spacing between blackbrush plants is often (Brooks and Esque 2002). Although fire is generally relatively high (~1m [3.3 ft]). This requires fine fuels to no longer advocated as a tool for range improvement, carry fire under most circumstances, whereas at higher ignitions from lightning and accidental ignitions along elevations spacing between blackbrush plants is often roads have been sufficient to burn significant acreage relatively small (<50cm [20 inches] (M. Brooks, personal of blackbrush during the past few decades. observation). At Joshua Tree National Park in California, blackbrush Reports from the mid-1900s also acknowledge the role was burned during the early 1990s to reduce woody fuel that non-native annual grasses, especially red brome, loads at the wildland-urban interface between Joshua can play in facilitating the spread of fire in blackbrush Tree and the town of Yucca Valley. During the first few (Dimock 1960; Holmgren 1960; Jenson and others post-fire years, the landscape was dominated by native 1960), although there was disagreement as to whether annual wildflowers, but by the fourth post-fire year, the the burned landscapes were more or less susceptible non-native annual grasses red brome and cheatgrass to reburning than unburned landscapes. Jenson and became the dominant annual plants and remained ­others (1960) thought the chances of reburning were as such into the 2000s (Brooks and Matchett 2003; low because they observed low fine fuel levels in post- M. Brooks, personal observations). The appearance fire landscapes. However, their observations were made of this new flashy fuelbed resulted in a change in fire during the mid-century drought (Hereford and others management at Joshua Tree. It put a stop to the use of 2006) when fine fuel loads were on the low end of their fire as a management tool until prescriptions could be possible range. In contrast, Holmgren (1960), who ac- identified that would not create continuous fuelbeds of companied Jenson and others on the same field visits, non-native annual grasses. At the current rate of burning thought that the danger of accidental fire in blackbrush during 1980s and 1990s, managers estimate that all the would be higher in areas that previously burned than blackbrush at Joshua Tree National Park will burn by in unburned areas if high winter rainfall had produced 2015 to 2020 (Hank McCutchen, Chief of Resources, more red brome biomass and other fine fuels. Prior to personal communication). This is a significant concern the invasion of red brome and cheatgrass during the because the blackbrush stands located there are disjunct late 1800s to early 1900s (Brooks 2000a; Young 2000), from the rest of the blackbrush range, and if all the stands fine fuel loads were likely not as great in either burned were to burn, it is very likely that blackbrush would not or unburned blackbrush stands. This resulted in fewer be able to re-establish. fires, possibly smaller fires, and fewer reburns. The fuel complex in blackbrush appears to be more conducive to burning now than in the past. Non-na- tive annual grasses currently occur in most blackbrush Fire Regime Condition Classes stands (M. Brooks, personal observations), although their dominance can vary significantly among sites Fire Regime Condition Class 1 (FRCC 1) (Brooks and Matchett 2003). Post-fire landscapes are even more dominated by these non-native grasses, which FRCC 1 is characterized by vegetation and fire ­regime raises concerns that they will promote recurrent fire and attributes within the natural range of variation. The prevent the re-establishment of Coleogyne ramosissima. risk of losing key ecosystem components, such as high This link between fine fuels and fire size is supported blackbrush cover and associated protection from soil by recent analyses that demonstrate that years of high erosion, is low. Mature blackbrush stands fall into this rainfall, which lead to high production of fine fuels, condition class. These stands are typically late seral are correlated with larger fires in the elevations where with occasional early seral patches created by infrequent blackbrush occurs in the Mojave Desert (Brooks and stand-replacing fires.

104 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-202. 2007 Chapter 6—Creosotebush, Blackbrush, and Interior Chaparral Shrublands

The fire regime for FRCC 1 is active crown fire Fire Regime Condition Class 3 (FRCC 3) carried primarily by blackbrush and perennial grasses Condition Class 3 is characterized by vegetation ­( Achnatherum spp. and Pleuraphis spp.) on deep silty and fire regime attributes that have been significantly soils. Burns are complete and stand-replacing, fire in- altered from their natural range. The risk of losing key tensity is high, and fire return intervals are >100 years. ecosystem components, such as high blackbrush cover Long fire return intervals allow for the typically slow and its associated protection from soil erosion, is high. process of blackbrush re-establishment. Approximately Blackbrush stands that burned during the 1900s, and 20 percent of the blackbrush at the Mojave Desert- have reburned at least once, fall into this condition class. Colorado Plateau ecotone in southern Utah, southern These stands are typically dominated by non-native Nevada, and northwestern Arizona is currently in this annuals and early seral perennials. Recurrently burned condition class. stands without livestock over-grazing can also have a Fire Regime Condition Class 2 (FRCC 2) large perennial grass component (Achnatherum spp. and Pleuraphis spp.). FRCC 2 is characterized by vegetation and fire regime The fire regime for this condition class is typically attributes that have been moderately altered from their surface fire carried primarily by non-native annual natural range. The risk of losing key ecosystem com- plants. Burns are patchy, fire intensity is low, and fire ponents, such as high blackbrush cover and associated return intervals are <50 years. Re-establishment by protection from soil erosion, is moderate. Blackbrush blackbrush is highly unlikely under this fire regime. stands with an intermix of late seral unburned patches ­Approximately 10 percent of the blackbrush at the and early seral burned patches are in this condition ­Mojave Desert-­Colorado plateau ecotone is in this condi- class. Blackbrush stands with patches that have been tion class, but this percentage could increase if ignition degraded by overgrazing, prescribed burning in the rates increase with burgeoning human populations and mid-1900s, or other forms of surface also if fine fuel continuity increases due to increased domi- fall into this condition class. These disturbances re- nance of non-native annual grasses that could occur if duce cover of blackbrush and increase cover of early atmospheric CO2 and rainfall levels increase (Brooks seral shrubs such as rabbitbrush (Chrysothamnus spp.), and Pyke 2001). sna kewe e d (Gutierrezia spp.), and wild buckwheat, early seral herbaceous perennials such as desert globemallow () and milkvetch (Astragalus spp.), Recommended Treatments and non-native annual plants such as red brome, cheat- grass, and red-stemmed filaree. Burned stands without In FRCC 1 areas suppress human-caused fires, but livestock over-grazing that are situated on deep, silty consider allowing lightning-caused wildfires to burn soils can also have a large perennial grass component unless significant populations of red brome or cheatgrass (Achnatherum spp. and Pleuraphis spp.). are present, or there are other reasons for suppression. Fires in late seral patches are active crown fires car- Prescribed fires should not be conducted except for small ried by blackbrush, perennial grasses (Achnatherum research burns designed to evaluate fire behavior, fire spp. and Pleuraphis spp.), and non-native annual grasses effects, and fire management techniques and treatments. (Bromus spp.). Burns are complete and fire intensity is Only apply fuels management treatments at the wildland high. Fires within early seral patches are passive crown urban interface to reduce fire hazard, or in wildland ar- fires or surface fires carried by perennial grasses and eas where fuel breaks are deemed necessary to achieve non-native annual grasses between the sparse cover of management goals. Realize that regular maintenance early seral shrubs. Burns are patchy and fire intensity may be required to maintain these managed fuel zones is low to moderate. because fuel treatments that involve replacement of late Fire return intervals in FRCC 2 stands are approximate- seral woody fuels with early seral fine fuels will reduce ly 50 to 100 years. This shorter fire return interval, and fire intensity, but may increase susceptibility to ignition over-grazing pressure from livestock, helps to maintain and rates of fire spread. dominance by early seral species and may prevent re- In FRCC 2 areas suppress all wildfires. Prescribed establishment by blackbrush. Approximately 70 percent fires should not be conducted except for small research of the blackbrush at the Mojave Desert-Colorado plateau burns. Minimize livestock grazing and other surface ecotone is in this condition class. disturbances on early seral stands, or where early seral

USDA Forest Service Gen. Tech. Rep. RMRS-GTR-202. 2007 105 Chapter 6—Creosotebush, Blackbrush, and Interior Chaparral Shrublands and late seral stands are intermixed. Do not apply fuels Interior Chaparral management treatments on late seral stands, except pos- sibly at the wildland urban interface to reduce fire haz- Introduction ards or in wildland areas where fuel breaks are deemed necessary to achieve management goals. Realize that Interior chaparral (Arizona chaparral) is characterized regular maintenance may be required to maintain these by moderate cover, ranging from 40 percent at dry sites managed fuel zones because fuel treatments that involve to 80 percent at wetter sites, of moderately tall statured (1 replacement of late seral woody fuels with early seral to 2.5 m [3.3 to 8.2 ft] tall), woody evergreen shrubs with fine fuels will reduce fire intensity, but may increase dense crowns (fig. 5) (Carmichael and others 1978). It is susceptibility to ignition, fire spread rates, and fire best represented in the foothills and mountain slopes and frequency. Fuels treatments on early seral stands domi- canyons in the sub-Mogollan region of central Arizona nated by non-native annual plants may include the use of (Pase and Brown 1994). Disjunct stands also occur in grass-specific herbicides. Carefully managed livestock the mountains of southwestern Utah, southern Nevada, grazing may reduce fine fuel loads temporarily, but may northwestern and southeastern Arizona, southern New hinder the re-establishment of blackbrush and other late Mexico, southwest Texas, and . It gener- seral species and thus, may be counterproductive in the ally occurs between 1,000 to 2,000 m (3,280 to 6,560 long-term. ft) in elevation above the desert grassland/shrub-steppe In FRCC 3 areas suppress all wildfires. Prescribed zone a nd b elow t he pi nyon-ju n ip er/p onderosa pi ne (Pinus fires should not be conducted except for small research ponderosa) zone (Keeley 2000). burns. Extreme measures may be required in these Within the Mojave-Colorado Plateau ecotone, in- stands. Revegetation with blackbrush and other late terior chaparral is best represented in the Pine Valley seral shrubs and perennial grasses, and exclusion of Mountains, Bull Valley Mountains, and Zion National livestock grazing and other surface disturbances, may Park in Washington County (Utah), the Virgin Mountains be necessary. Control of non-native annual grasses using of Mojave County (Arizona), and the Spring Mountains herbicides or early season prescribed fire implemented and Gold Butte regions of Clark County and various immediately before revegetation treatments may improve other mountain ranges in Lincoln County (Nevada). initial establishment rates of revegetated plants. In this region, it is characterized by turbinella live oak

Figure 5—Interior chaparral dominated by turbinella live oak (Quercus turbinella).

106 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-202. 2007 Chapter 6—Creosotebush, Blackbrush, and Interior Chaparral Shrublands

(Quercus turbinella), buckbrush (), and fire suppression further decreased the frequency of pointleaf manzanita (Arctostaphylos pungens), Wright wildfire, interior chaparral very likely did encroach into silktassel (Garrya wrightii), and narrowleaf yerba- lower elevation grasslands. Large areas near the early santa (Eriodictyon angustifolium). Understory grass settlements of Prescott and Globe, AZ, were reported to species, such as grama (Bouteloua spp.) and three-awn be grasslands in the 1860s and became dense stands of (Aristida spp.), occur throughout the range of interior interior chaparral by 1936 (Cable 1975). Aldo Leopold chaparral. (1924) reported a substantial increase in “brush” cover Interior chaparral is an important vegetation commu- since the 1880s at the expense of herbaceous plant cover nity for wildlife. Game animals such as javelina, deer, after 40 years of livestock grazing. and bighorn sheep use several plant species as forage and Aldo Leopold made additional observations at the in- others as cover. Distinct from the communities above terior chaparral–grassland ecotone in , and below it, interior chaparral provides a significant which sheds some light on the pre-settlement fire regime amount of wildlife habitat diversity. of this region. He noted during the early 1920s that Most chaparral species are adapted to a fire-prone there were multiple fire scars on ancient juniper stumps system, but methods of response vary. Turbinella live embedded in even-aged chaparral stands consisting of oak is well adapted to survive fire, typically resprout- shrubs <40 years old. This suggests that the fire scars ing vigorously from the root crown and in were created during low intensity grassland fires that response to fire or other disturbance (Pase 1969), pre-dated the current chaparral stands (Leopold 1924). while buckbrush and pointleaf manzanita regenerate Based on observations such as these, Leopold concluded from long-lived seeds that accumulate in the soil and that there had been no widespread fires in the chapar- germinate prolifically following fire. Areas dominated ral–grassland ecotone in southern Arizona between the by non-sprouting chaparral species, including pointleaf early 1880s and early 1920s. He further hypothesized manzanita, may develop a persistent cover of herbaceous that previous grassland fires at these same sites occurred species following fire, especially where Bromus spp. are at intervals of approximately once every 10 years before present. Interior chaparral dominated by turbinella live the advent of widespread livestock grazing. oak, have fire return intervals from 74 to 100 years. At Higher elevation interior chaparral sites likely did not least 20 years may be required before these sites can receive as much grazing pressure, but fire suppression, reburn (Cable 1975). especially at the interface with ponderosa pine forests, may have resulted in forest encroachment into chaparral shrublands. For example, where old chaparral stands Historical Conditions intergrade with woodlands or forests at higher elevations, chaparral species such as Pringle manzanita (Arcto- staphylos pringlei) and Fendler ceanothus (Ceanothus In some areas prior to the 1900s, interior chaparral fendleri) may be replaced by ponderosa pine, emory oak was considered good livestock range, but overgrazing (Quercus emoryi), or Arizona oak (Quercus arizonica) has removed much of the perennial grass component after long fire-free intervals (Pase and Brown 1994). since then (Nichol 1937). Most people now view interior Historical fire return intervals in interior chaparral chaparral as a nuisance or obstacle to human activity. were likely 50 to 100 years (Cable 1975). However, this Ranchers have routinely attempted to get rid of the brush is an average over its entire range, and local intervals that competes with forage grass and makes travel dif- probably vary widely. ficult. Livestock grazing and fire suppression have at least partly caused shrub encroachment into grassland and woodland/forest encroachment into shrublands during the 1900s in the southwestern Current Conditions (Hastings and Turner 1965; Leopold 1924; Miller and Rose 1999). Interior chaparral presents a more complex manage- Ma ny lower elevat ion i nt er ior chapa r ra l sit es have b e en ment challenge than the forests above or the deserts managed for livestock grazing since the 1880s (Pase and below, facing some of the challenges of both. Like the Brown 1994). Where fire was used to maintain grass ponderosa pine forests, chaparral communities are fire- forage, interior chaparral probably did not encroach into dependant. Exclusion of fire from interior chaparral can lower elevation grasslands. However, where fire was not lead to encroachments by woodland and forest species. used, and the removal of fine fuels by livestock grazing Like the creosotebush scrub and blackbrush desert

USDA Forest Service Gen. Tech. Rep. RMRS-GTR-202. 2007 107 Chapter 6—Creosotebush, Blackbrush, and Interior Chaparral Shrublands shrublands, non-native annual grasses can increase fire (20 ­percent of the Mojave Desert-Colorado plateau frequency to the point where even the fire-adapted inte- ecotone region). These sites typically retain significant rior chaparral cannot recover. Thus, interior chaparral amounts of area with late seral interior chaparral char- requires fire, but not too much fire. acteristics, but the trend is toward FRCC 3. Conventional wisdom in the fire suppression com- munity is that chaparral either does not burn, or when Fire Regime Condition Class 3 (FRCC 3) it does burn, it burns very intensely. Due to threats to FRCC 3 is characterized by vegetation and fire regime humans and their property, as well as to other high value attributes that have been significantly altered from their resources, full suppression remains the primary response natural range. The risk of losing key ecosystem com- to wildfires that occur under the hot, dry conditions of ponents, such as cover for wildlife, is high. Chaparral summer in the southwest. stands that have burned repeatedly and lost most of the shrub cover, have lost the shrub bank, and have significant amounts of Bromus spp. or other non-native Fire Regime Condition Classes grasses fall into this condition class. Non-native annu- als and early seral perennials typically dominate these Fire Regime Condition Class 1 (FRCC 1) stands. The fire regime for this condition class is typically FRCC 1 is characterized by vegetation and fire regime surface fire carried primarily by non-native annual attributes within the natural range of variation. The risk plants. Burns are patchy, fire intensity is low, and fire of losing key ecosystem components, such as cover for return intervals are <20 years. Re-establishment by wildlife, is low. These stands are typically late seral native interior chaparral shrub species is diminished with occasional early seral patches created by infrequent under this fire regime and becomes less likely as native stand-replacing fires. The fire regime for FRCC 1 is ac- chaparral seed banks disappear. tive crown fire carried primarily by turbinella live oak, Approximately 30 percent of the interior chaparral at buckbrush, and manzanita species. Burns are complete the Mojave Desert-Colorado plateau ecotone is in this and stand-replacing, fire intensity is high, and fire return condition class, but this percentage could increase if intervals are between 50 and 100 years. ignition rates increase with burgeoning human popula- Long fire return intervals allow for the re-establish- tions and if fine fuel continuity increases with increased ment of seed banks and the development of the fuel dominance of non-native annual grasses that could occur loads and spatial continuity necessary for fire to occur. if atmospheric CO and rainfall levels increase. Approximately 40 percent of the interior chaparral at 2 the Mojave Desert-Colorado plateau ecotone in southern Utah, southern Nevada, and northwestern Arizona is in this condition class. Recommended Treatments

Fire Regime Condition Class 2 (FRCC 2) In FRCC 1 areas suppress human-caused fires. Consider allowing lightning-caused fires to burn unless significant FRCC 2 is characterized by vegetation and fire regime populations of Bromus spp. are present, especially near attributes that have been moderately altered from their stands of non-sprouting chaparral species, or there are natural range. The risk of losing key ecosystem compo- other reasons for suppression. Prescribed fires should not nents, such as cover for wildlife, is moderate. There are be conducted except for small research burns designed two types of chaparral within FRCC 2: 1) sites where to evaluate fire behavior, fire effects, and fire manage- the fire return intervals are greater than the natural ment techniques and treatments. Apply fuel management range of variation (>100 years) and encroachment of treatments at the wildland urban interface to reduce fire interior chaparral by conifer woodlands has occurred (10 hazard and in wildland areas where fuel breaks are deemed percent of the Mojave Desert-Colorado plateau ecotone necessary to achieve management goals. Where possible, region) and 2) sites where fire return intervals, or other use indirect fire suppression tactics that provide a reason- landscape-scale disturbances, are within or slightly less able containment strategy to protect human life, property, ≤ than the natural range of variation ( 50 to 100 years) and other valuable resources while allowing some acres to and the post-disturbance community contains a signifi- burn during the high-intensity summer fire season where cant intermix of late seral unburned patches and early deemed appropriate. seral burned patches dominated by non-native grasses

108 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-202. 2007 Chapter 6—Creosotebush, Blackbrush, and Interior Chaparral Shrublands

Since this is a fire-dependent ecosystem, counter the disturbances. Control of non-native annual grasses and effects of fire suppression in FRCC 1 areas by imple- other invasive plants using herbicides immediately before menting burn treatments unless a significant threat of revegetation treatments may improve initial establish- conversion to a Bromus-dominated system is present. ment rates of revegetated plants and increase survival The goal of these treatments would be to replicate rates of regenerating plants. normal patch size/mosaic patterns to provide diversity We recommend research in adapted plant materials, and to reduce the potential size of wildfires. Treatment propagation techniques, and planting techniques for frequency should not occur more often than 20 years at restoration of these FRCC 3 sites. The grass/fire cycle any site. Treatment areas should not be reseeded with creates a feedback loop of decreasing habitat quality herbaceous vegetation unless necessary to compete with for wildlife and livestock. Livestock grazing to reduce non-native annual grasses. Treatments on sites dominated fuel loads may be counterproductive in the long run if by seed propagators (for example, pointleaf manzanita) it also hinders the re-establishment of late seral native may need to be seeded with chaparral species. plants. Realize that regular maintenance may be required to maintain FRCC 1 managed fuel zones because fuel treatments that involve replacement of late seral woody Acknowledgments fuels with early seral fine fuels will reduce fire intensity, but may increase susceptibility to ignition and rates of This document reflects many of the peer-review fire spread. comments and suggestions provided by Henry Bastian, Treat FRCC 2 sites that have had fire excluded and Curt Deuser, Karen Phillips, Louis Provencher, and are being encroached by conifer woodlands in a manner Tom Roberts. Financial support for the development of similar to FRCC 1, except where non-native grasses are this document was provided by grant #00-2-32 to Matt a significant threat. In other words, suppress human- Brooks from the Joint Fire Science Program. caused fires, but consider allowing lightning-caused fires to burn unless significant populations of Bromus spp. are present or there are other reasons for suppression. Prescribed fires should not be conducted except for small References research burns. Apply fuels management treatments at Anonymous. 1945. Artificial revegetation study plan for study the wildland urban interface to reduce fire hazard and B-108 near Elgin, Nevada, September, 27, 1945. United States in wildland areas where fuel breaks are deemed neces- Department of the Interior, Grazing Service, Nevada, Searchlight sary to achieve management goals. Where possible, use District, 9/27/1945. 8 p. Bates, P.A. 1984. The role and use of fire in blackbrush (Coleogyne indirect fire suppression tactics that provide a reasonable ramosissima Torr.) communities in California. Davis, CA: Uni- containment strategy to protect human life, property, versity of California. 56 p. Dissertation. and other valuable resources while allowing some acres Beatley, J.C. 1976. Vascular plants of the Nevada test site and ­Central-Southern Nevada: ecological and geographic distri- to burn during the high-intensity summer fire season. butions. Energy Research and Development Administration Treat FRCC 2 sites where disturbances have occurred, TID-26881. Technical Information Center, Office of Technical Information, Springfield Virginia. 308 p. but the post-disturbance community has changed to one Bowns, J.E. 1973. An autecological study of blackbrush (Coleogyne with a significant intermix of late seral unburned patches ramosissima Torr.) in southwestern Utah. Logan, UT: Utah State and early seral burned patches with non-native grasses, University. 115 p. Dissertation. Bowns, J.E .; West, N.E . 1976. Blackbr ush (Coleogyne ramosissima in a manner similar to FRCC 3. In other words, suppress Torr.) on southwestern Utah rangelands. Research Report 27. all fires; revegetate with live oak, buckbrush, manza- Logan, UT: Utah State University, Utah Agricultural Experi- ment Station. 27 p. nita, and other late seral shrubs and perennial grasses; Bradley, W.G.; Deacon, J.E. 1967. The biotic communities of exclude livestock grazing and other surface disturbing southern Nevada. Nevada State Museum Anthropological Papers. activities at least until plants become established, and 13: 202–295. Brooks, M.L. 1999a. Non-native annual grasses and fire in the control non-native annual grasses using herbicides). Mojave Desert. Madroño. 46: 13-19. In FRCC 3 areas suppress all wildfires. Prescribed Brooks, M.L 1999b. Habitat invasibility and dominance by non- native annual plants in the western Mojave Desert. Biological fires should not be conducted except for small research Invasions. 1: 325-337. burns. Revegetation may be necessary using turbinella Brooks, M.L. 2000a. Bromus madritensis subsp. rubens (L.) Husnot. live oak, Ceanothus spp., and manzanita species. and In: Bossard, C.; Hoshovsky, M.; Randall, J., eds. Invasive plants of California’s wildlands. Berkeley, CA: University of California other late seral shrubs and perennial grasses, along Press: 72-76. with exclusion of livestock grazing and other surface

USDA Forest Service Gen. Tech. Rep. RMRS-GTR-202. 2007 109 Chapter 6—Creosotebush, Blackbrush, and Interior Chaparral Shrublands

Brooks, M.L. 2000b. Schismus arabicus Nees, Schismus barbatus arid and semi-arid region. Tucson, AZ: University of Arizona (L.) Thell.�������������������������������������������������������������� In: Bossard, C.; Hoshovsky, M.; Randall, J., eds. Inva- Press. 317 p. sive plants of California’s wildlands. Berkeley, CA: University of Hereford, R.; Webb, R.H.; Longpré, C.I. 2006. history California Press: 287-291. and ecosystem response to multidecadal precipitation variability Brooks, M.L.; Berry, K.H. 2006. Dominance and environmental in the Mojave Desert region, 1893-2001. Journal of Arid Envi- correlates of alien annual plants in the Mojave Desert. Journal ronments. 67: 13-34. of Arid Environments. 67: 100-124. Holmgren, R.C. 1960. Inspection tour of old blackbrush burns Brooks, M.L.; Draper, J. V. 2006. Fire effects on seedbanks and in BLM District N-5, southern Nevada. Unpublished report, vegetation in the eastern Mojave Desert: implications for post- U.S. Department of Agriculture, Forest Service, Intermountain fire management. Proceedings of the Third International Fire Forest and Range Experiment Station, Reno Research Center, Ecology and Management Congress. 13-17 November 2006, San Reno, NV. 8 p. Diego, California. Humphrey, R.R. 1974. Fire in the deserts and desert grassland of Brooks, M.L.; Esque, T.C. 2002. Non-native plants and fire in desert North America. In: Kozlowski, T. T.; Ahlgren, C.E., eds. Fire tortoise (Gopherus agassizii) habitat of the Mojave and Colorado and . New York: Academic Press: 365-400. Deserts. Chelonian Conservation Biology. 4: 330-340. Jenson, D.E.; Buzan, M.E.; Dimock, D.E.; Holmgren, R. 1960. Brooks, M.L.; Matchett, J.R. 2003. Plant community patterns in Rep or t on f ield exa m i nat ion s, bla ckbr ush bu r n s, L a s Vega s G r a z- unburned and burned blackbrush (Coleogyne ramosissima) ing District (Nev. 5), April 1960. Unpublished report, Bureau of shrublands in the Mojave Desert. Western North American Land Management, Nevada State Office. 10 p. Naturalist. 63: 283-298. Keeley, J. E. 2000. Chaparral. In: Barbour, M.G.; Billings, W.D., eds. Brooks, M.L.; Matchett, J.R. 2006. Spatial and temporal patterns North American terrestrial vegetation, 2nd edition. Cambridge, of wildfires in the Mojave Desert. 1980-2004. Journal of Arid UK: Cambridge University Press: 203-253. Environments. 67: 148-164. Leopold, A.S. 1924. Grass, brush, timber, and fire in southern Brooks, M.L.; Minnich, R.A. 2006. Southeastern Deserts Bio­ Arizona. Journal of Forestry. 22: 1-10. region. In: Sugihara, Neil G.; van Wagtendonk, Jan W.; Shaffer, MacMahon, J. A. 2000. Warm Deserts. In: Barbour, M.G.; Billings, Kevin E.; Fites-Kaufman, JoAnn; Thode, Andrea E., eds. Fire W.D., eds. North American terrestrial vegetation, 2nd edition. in California’s ecosystems. Berkeley, CA: The University of Cambridge, UK: Cambridge University Press: 285-322. California Press: 391-414. Miller, R.F.; Rose, J.A. 1999. Fire history and western juniper Brooks, M.L.; Pyke, D. 2001. Invasive plants and fire in the deserts encroachment in sagebrush steppe. Journal of Range Manage- of Nor th A mer ica. I n: K. Ga lley, K.; Wilson, T., eds. P roceedings ment. 52: 550-559. of the workshop: the role of fire in the control Minnich, R.A. 2003. Fire and dynamics of temperate desert and spread of invasive species. Fire Conference 2000: The First woodlands in Joshua Tree National Park. Report submitted to National Congress on Fire, Ecology, Prevention and Manage- the National Park Service, Joshua Tree National Park. Contract ment. Miscellaneous Publications No. 11. Tallahassee, FL: Tall number P8337000034/0001. 32 p. Timbers Research Station: 1-14. Nichol, A.A. 1937. The natural vegetation of Arizona. University Brown, James K.; Smith, Jane Kapler, eds. 2000. Wildland fire in of Arizona, College of Agriculture, Agricultural Experiment ecosystems: effects of f i re on f lora. Gen. Tech Rep. R M RS- GRT- Station. Technical Bulletin No. 68. 42-vol. 2. Ogden, UT: U.S. Department of Agriculture, Forest O’Leary, J. F.; Minnich, R.A. 1981. Postfire recovery of creosote Service, Rocky Mountain Research Station. 257 p. bush scrub vegetation in the Western . Madroño. Brown, D.E.; Minnich, R.A. 1986. Fire and creosote bush scrub 28: 61-66. of the western Sonoran Desert, California. American Midland Pase, C. P. 1969. Survival of Quercus turbinella and Q. emoryi Naturalist. 116: 411-422. s e e d l i ngs i n a n A r i z ona chapa r r a l c om mu n it y. T he Sout hwest er n Cable, Dwight R. 1975. Range management in the chaparral type Naturalist. 14(2): 149-156. and its ecological basis: the status of our knowledge. Res. Pap. Pase, C.P. and D.E. Brown. 1994. Interior chaparral. In: Brown, RM-155. Fort Collins, CO: U.S. Department of Agriculture, D.E., ed. Biotic communities: Southwestern United States and Forest Service, Rocky Mountain Forest and Range Experiment Northwestern Mexico. , UT: University of Utah Station. 30 p. Press: 95-99. Carmichael, R. S.; O.D. Knipe; C.P. Pase; and W.W. Brady. 1978. Randall, D.C. 1972. An analysis of some desert shrub vegetation of Arizona chaparral: plant associations and ecology. Res. Pap. , California. Davis, CA: University of California. RM-202. Fort Collins, CO: U.S. Department of Agriculture, 186 p. Dissertation. Forest Service, Rocky Mountain Forest and Range Experiment Rowlands, P.G.; Johnson, H.B.; Ritter, E.; Endo, A. 1982. The ­Mojave Station. 16 p. Desert. In: Bender, G.L., ed. Reference handbook of North Croft, A.R. 1950. Inspection of black brush burn, May 12, 1950. ­American deserts. Connecticut: Greenwood Press: 103-159. Memorandum to the unpublished report, Bureau of Land Man­ Salo, L.F. 2003. Ecology and biogeography of red brome (Bromus agement, State Supervisor for Nevada, 6 p. plus photographs. madritensis rubens) in western North America. Tucson, Dimock, D.E. 1960. Report on blackbrush burn observations, April AZ: University of Arizona. Dissertation. 18-20, 1960. Memorandum to the Bureau of Land Management, Shreve, F. 1942. The desert vegetation of North America. Botanical State Supervisor for Nevada. 6p. Review. 8: 195–246. Esque, T.C. 1994. Diet and diet selection of the desert tortoise Turner, R.M. 1994. Great Basin desertscrub. In: Brown, D.E., ­( Gopherus agassizii) in the northeast Mojave Desert. Fort ­Collins, ed. Biotic communities: Southwestern United States and CO: Colorado State University. 243 p. Thesis. Northwestern Mexico. Salt Lake City, UT: University of Utah Esque, T.C.; Schwalbe, C.R. 2002. Non-native annual plants Press: 145-155. and their relationships to fire and biotic change in Sonoran Vasek, F.C.; Barbour, M.G. 1995. Mojave desert scrub vegetation. Desertscrub. In: Tellman, B., ed. Invasive exotic species in In: Barbour, M.G.; Major, J., eds. Terrestrial vegetation of the Sonoran ­region. Tucson, Arizona: Arizona- Desert California. Special Publication: No. 9. California Native Plant Museum and The University of Arizona Press: 165-194. Society: 835-868. Esque, T.C.; Schwalbe, C.R.; DeFalco, L.A.; Hughes, T.J.; ­Duncan, Webb, R.H.; Steiger, J.W.; Turner, R.M. 1987. Dynamics of Mojave R.B. 2003. Effects of wildfire on small desert vertebrates, Desert assemblages in the Panamint Mountains, California. ­especially desert tortoises (Gopherus agassizii). The Southwestern Ecology. 68: 478-490. Naturalist. 48: 103-110. Young, J.A. 2000. Bromus tectorum (L.). In: Bossard, C.; Hoshovsky, Hastings, J.R.; Turner, R.M. 1965. The changing mile: an ecologi- M.; Randall, J., eds. Invasive plants of California’s wildlands. cal study of vegetation change with time in the lower mile of an Berkeley, CA: University of California Press: 76-80.

110 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-202. 2007