Desert Mountain Chaparral

This ecological system occurs in mountains across southeastern New Mexico (Guadalupe Mountains), Trans-Pecos Texas (Chisos and Davis mountains) and Madrean Oriental in northern Mexico. It often dominates along the mid-elevation transition from the Chihuahuan Desert into mountains (1700-2500 m). It occurs on foothills, mountain slopes and canyons in drier habitats below the encinal and pine woodlands, and is often associated with more xeric and coarse-textured substrates such as limestone, basalt or alluvium, especially in transition areas with more mesic woodlands. The moderate to dense shrub canopy includes many shrub oak species, such as Quercus emoryi, Quercus grisea, Quercus intricata, Quercus invaginata, Quercus laceyi, Quercus mohriana, Quercus pringlei, Quercus pungens, and Quercus vaseyana, and several widespread chaparral species, such as Arctostaphylos pungens, Ceanothus greggii, Cercocarpus montanus, Fallugia paradoxa, and Garrya wrightii; other species characteristic of this system include Arbutus xalapensis, Fraxinus greggii, Fendlera rigida, Garrya ovata, Purshia mexicana, Rhus virens var. choriophylla, Salvia lycioides, Salvia roemeriana, and Salvia regla. In the Trans-Pecos of Texas, disjunct Quercus gambelii may occur as a significant component of this shrubland. In addition, Texas occurrences may also include Agave lechuguilla, Aloysia wrightii, Ceanothus greggii, Cercocarpus montanus, Chrysactinia mexicana, Dasylirion leiophyllum, Fallugia paradoxa, Fraxinus greggii, Garrya wrightii, Juniperus pinchotii, Nolina texana, Opuntia engelmannii var. engelmannii, Pinus cembroides or Pinus edulis (in the Guadalupe Mountain region), Quercus turbinella, Quercus x pauciloba, Rhus virens, and Viguiera stenoloba. Most chaparral species are fire-adapted, resprouting vigorously after burning or producing fire-resistant seeds. Stands occurring within montane woodlands are seral and a result of recent fires. Grass cover may be significant. Dominant grasses often include Bouteloua curtipendula, Bouteloua hirsuta, and Muhlenbergia emersleyi. In Texas, the herbaceous cover is patchy and bare rock is frequently visible. Where present, graminoids dominate the herbaceous layer with species such as Bouteloua curtipendula, Bouteloua hirsuta, Muhlenbergia emersleyi, Muhlenbergia pauciflora, Muhlenbergia setifolia, Achnatherum lobatum, Muhlenbergia dubia, and Heteropogon contortus.

The moderate to dense shrub canopy includes many shrub oak species, such as Quercus emoryi, Quercus grisea, Quercus intricata, Quercus invaginata, Quercus laceyi, Quercus mohriana, Quercus pringlei, Quercus pungens, and Quercus vaseyana, and several widespread chaparral species, such as Arctostaphylos pungens, Ceanothus greggii, Cercocarpus montanus, Fallugia paradoxa, and Garrya wrightii; other species characteristic of this system include Arbutus xalapensis (= Arbutus texana), Fraxinus greggii, Fendlera rigida (= Fendlera linearis), Garrya ovata, Purshia mexicana, Rhus virens var. choriophylla (= Rhus choriophylla), Salvia lycioides (= Salvia ramosissima), Salvia roemeriana, and Salvia regla. In the Trans-Pecos of Texas, disjunct Quercus gambelii may occur as a significant component of this shrubland. Most chaparral species are fire-adapted, resprouting vigorously after burning or producing fire-resistant seeds. Stands occurring within montane woodlands are seral and a result of recent fires. Grass cover may be significant. Dominant grasses often include Bouteloua curtipendula, Bouteloua hirsuta, and Muhlenbergia emersleyi.

This system occurs at elevations above desert shrublands on dry rocky habitats of foothills, mountains, and canyons. In Texas, it often occurs at elevations coincident with the occurrence of Madrean Encinal and Madrean coniferous woodlands, but typically occupies more xeric sites, often with steeper slopes and less soil development.

[from M091] Many of the communities in this macrogroup are dominated by fire-adapted shrubs. Quercus cornelius-mulleri sprouts vigorously from root crowns after fire. Since Quercus cornelius-mulleri chaparral occurs in areas of lower rainfall and sparser vegetation cover, it typically has less frequent fire and slower recovery rates than typical cismontane chaparral types elsewhere in California. Quercus turbinella in Arizona and New Mexico is a fire-type; it sprouts vigorously from the root crown and rhizomes. Typical fire intervals in Arizona exceed 74 years (Reid et al. 1999, Tirmenstein 1999d). Plants in the New York Mountains of California are treelike, suggesting that fires have been absent for perhaps greater than 100 years. Instead, flooding has initiated stem breakage and sprouting of some canyon bottom stands. Ceanothus greggii is an obligate seeder and germinates from seed after fire, and older stands will lose dominance of this shrub to other longer-lived sprouting shrubs.

Site conditions aside, the dynamics of fire within chaparral are still complex. In southern California, it has been suggested that the even-aged and large size of modern chaparral patches are a function of 20th century fire suppression feedbacks whereby intensive suppression has led to large fuel buildups over large areas of landscape leading to large stand-replacement fires of ever increasing size (Minnich 1983, 2001). Others contend that the large patch patterns are within that natural range of variability, and that they are driven more by climate trends, prevailing weather patterns, increased human ignition frequencies with increased population density, changes in land use, and landscape characteristics rather than suppression (Keeley and Fotheringham 2001a, 2001c, Moritz 2003). The pattern of chaparral distribution in southern New Mexico suggests that the latter scenario might be the case here. Because of the rugged country, effective suppression has been minimal. Hence, the large patches of chaparral may be representative of a more or less natural fire regime, but one possibly modified by increased human caused fires and fire suppression on neighboring forested lands. More frequent, intense fires leads to the decline of the grassy woodland savannas on the ridge top summits and a favoring of shrublands (possibly enhanced by increased fine fuels with the cessation of livestock grazing). In this type of fire regime, Keeley and Fotheringham (2001a) and Moritz (2003) contend that prescribed burning may be useless or even harmful and that fire suppression, at least in the short term, may be more appropriate for maintaining an ecosystem near its natural state. Minnich (2001) would likely argue the opposite saying it is fire suppression that generates the large patch pattern and that prescribed fire is needed to restore a small patch mosaic with imbedded natural fuel firebreaks. Detailed fire history studies that focus on chaparral patch age structure in a landscape context would be useful (and perhaps necessary) to help resolve these conflicting viewpoints and generate management options that are tailored to interior chaparral.

At the other end of the elevation spectrum, repeated burning of chaparral, particularly Pinchot juniper, has been suggested as a way to increase grass cover in shrubland communities (Ahlstrand 1982). Most of our understanding of how to manage of Pinchot juniper comes from the high Plains of Texas where it is seen as an invader of fine textured plains grasslands soils, and where management has focused on control and eradication to increase livestock forage. Research from the high plains indicates that the effectiveness of fire in controlling Pinchot juniper is a function of fire intensity, climatic conditions and position of the bud zone above or below the soil (Steuter and Britton 1983). Fire was particularly effective in inducing mortality in young plants with exposed buds on rocky sites, but this dropped off significantly with older plants. In addition, increased grass cover (grama grasses) can inhibit reproduction (Smith et al. 1975). As Ahlstrand (1982) has shown, fires can lead to at least short-term increases in grass cover, but because Pinchot juniper can recover 50% or more of its original cover within six or seven years of a burn, repeated prescribed fires at 10- to 15-year intervals would be needed to sustain a grassland type.

This system is found on mountains across southeastern New Mexico, Trans-Pecos Texas and northern Mexico. It often dominants along the mid-elevation transition from the Chihuahuan Desert into mountains (1700-2500 m elevation).