Rocky Mountain Lower Montane Forest
Southern Rocky Mountain Lower Montane Forest
SWAP General Vegetation Type
ALPINE and MONTANE VEGETATION
The Rocky Mountain Lower Montane Forest [M022] is a mid-elevation (2,350-3300 m (7,700-10800 ft)) forest, woodland, and savanna habitat that occurs in the Southern Rocky and Arizona/New Mexico Mountains ecoregions, as well as isolated locations in the Colorado Plateaus and High Plains and Tablelands ecoregions. Characteristic trees are predominantly conifers and include white fir (Abies concolor), Douglas-fir, ponderosa pine, limber pine (Pinus flexilis), southwestern white pine (P. strobiformis), and Rocky Mountain juniper (Juniperus scopulorum). Cold-deciduous trees occasionally mix in the canopy or are dominant in some locations, e.g., quaking aspen and big-tooth maple (Acer grandidentatum). At the lower-elevation margins, Mexican piñon (Pinus cembroides), two-needle piñon (P. edulis), and alligator juniper (Juniperus deppeana) may be present in the subcanopy. Cold-deciduous, broad-leaved shrubs can be common in the undergrowth, e.g., Rocky Mountain maple (Acer glabrum), Gambel’s oak, and New Mexico locust (Robinia neomexicana). In closed-canopy conditions, grasses or forbs may be sparse. Under more open canopies, grasses in particular may be abundant, leading to the formation of savanna-like woodland. Representative graminoids include mountain muhly (Muhlenbergia montana), Arizona fescue (Festuca arizonica), fringed brome (Bromus ciliates), and Ross’ sedge (Carex rossii). This forest type occurs across a broad range of soils, geology, and topographical conditions. Fire regimes vary from mixed severity (surface and canopy fires) to low severity (mostly frequent surface fires, e.g., savannas). In general, fire suppression has led to encroachment of more shade-tolerant, less fire-tolerant species, resulting in an attendant increase in fire hazard.