Physiognomy and Structure: No Data Available

Floristics: This plant association is characterized by a sparse to moderately dense tree canopy (5-65% cover) codominated by Pinus edulis and Juniperus osteosperma trees that are between 1 and 5 m tall. Juniperus deppeana may replace Juniperus osteosperma in southern stands. Other species of Juniperus, such as Juniperus scopulorum, may be present in higher elevation stands. Shrub cover is sparse (<10% cover). If Quercus gambelii is present, it has less than 5% cover. Other associated shrubs may be present, such as scattered Artemisia tridentata, Brickellia californica, Cercocarpus montanus, Chrysothamnus viscidiflorus, Ephedra viridis, Ericameria nauseosa, Eriogonum corymbosum, Eriogonum microthecum, Fallugia paradoxa, Gutierrezia sarothrae, Opuntia spp., Purshia stansburiana, Rhus trilobata, Ribes cereum, or Yucca spp. The herbaceous layer is typically moderately dense and is dominated by the warm-season, perennial short grass Bouteloua gracilis. Associated graminoids include Aristida spp., Achnatherum hymenoides (= Oryzopsis hymenoides), Bouteloua curtipendula, Elymus elymoides, Koeleria macrantha, Hesperostipa comata (= Stipa comata), Hesperostipa neomexicana (= Stipa neomexicana), and Pleuraphis jamesii (= Hilaria jamesii). Muhlenbergia montana is absent or scarce (<1% cover). Forb cover is typically low but may be moderately diverse. Species such as Artemisia dracunculus, Eriogonum spp., Hymenoxys richardsonii, and Oxytropis lambertii are common.

Dynamics:  Pinus edulis is extremely drought-tolerant and slow-growing (Powell 1988, Little 1987, Muldavin et al. 1998a). It is also non-sprouting and may be killed by fire (Wright et al. 1979). The effect of a fire on a stand is largely dependent on the tree height and density, fine fuel load on the ground, weather conditions, and season (Wright et al. 1979, Dwyer and Pieper 1967). Trees are more vulnerable in open stands where fires frequently occur in the spring, when the relative humidity is low, wind speeds are over 10-20 mph, and there are adequate fine fuels to carry fire (Wright et al. 1979). Under other conditions, burns tend to be spotty with low tree mortality. Large trees are generally not killed unless fine fuels, such as tumbleweeds, have accumulated beneath the tree to provide ladder fuels for the fire to reach the crown (Jameson 1962). Closed-canopy stands rarely burn because they typically do not have enough understory or wind to carry a fire (Wright et al. 1979).

Altered fire regimes, cutting trees for fencing, and improper grazing by livestock have significant impacts on the quality of sites. Grazing by livestock can modify the fire regime by removing the fine fuels that carry fire. Fire, livestock grazing, and trampling by recreationalists and vehicles disturb cryptogamic soil crusts that help maintain soil structure, reduce soil erosion, provide habitat for plants and preserve biological diversity (Ladyman and Muldavin 1996). More study is needed to understand and manage these woodlands ecologically.