Ponderosa pine forest
[3][4]: 2 Since ponderosa pine has a rather wide range of adaptability and can dominate some of the less mesic true forest sites, it occupies low mountains and foothills in many places; yet in mixtures with other species, it is found at moderate elevations.
[2] Local topography can be gentle, as on plateau tops and low mountains, or it can be steep, as on canyon walls and faces.
Semiarid, low mountain sites are common, but it is difficult to characterize the physiography of the ecosystem because it varies greatly.
Each of these sites can be characterized by its potential vegetation type (PVT) after succession reaches equilibrium or climax community.
[8][4]: 6 These ponderosa pine forests occur in the Rocky Mountains along the Front Range of Colorado, in Utah, and in southern Idaho.
These species, in particular, exemplify aggressive survivors after disturbance (e.g., fire, mechanical site preparation) and are strong competitors for light and nutrients which compete with ponderosa pine seedlings.
Pinegrass and ninebark are frequent associates, but tall shrubs such as Rocky Mountain maple (Acer glabrum) often occur.
[13][14][10][4]: 7 The western redcedar PVT is by far the most productive type on which ponderosa pine occurs, and lush and complex vegetation mixes may develop.
[7][15][4]: 7 Mid-seral shrubs include Rocky Mountain maple which readily survives disturbances and is joined by late-seral species such as huckleberry (Vaccinium spp.)
This ground-level vegetation can play critical roles in forests such as providing wildlife habitat, stabilizing soil, and capturing nutrients after disturbance.
This ecosystem is idealized as open and parklike with an excellent ground cover of grasses, sedges, and forbs or with an understory of shrubs of low to medium height.
In perhaps 60 percent of the area, the idealized open character of the ponderosa pine ecosystem has changed to that of a dense and growth-retarded stand, particularly in the Pacific Northwest.
[2] Bird species that live in the ponderosa pine ecosystem include the pygmy nuthatch, Steller's jay, sharp-shinned hawk, Rocky Mountain nuthatch, mountain chickadee, Cassin's finch, redshafted flicker, red-backed junco, northern goshawk, and western red-tailed hawk.
The high water tables associated with springs tend to increase site productivity regardless of the soil type and landform.
[1] Along the western edge of the Columbia Plateau and the east slope of the Cascade Mountains, common soil types are mollisols, inceptisols, entisols, and aridisols.
[19][20][4]: 7 In the northern Rocky Mountains of Idaho and western Montana, dry settings of ponderosa pine forests historically burned by low severity surface fires that did not kill overstory trees at 15 to 23 year mean return intervals.
[27][28][4]: 21 In the western United States domestic livestock grazing and harvesting of ponderosa pine forests was occurring by the mid-1800s.
[33][4]: 8 However, when heavy livestock grazing ceased in the early 1900s in the southwestern United States, dense stands of ponderosa pine seedlings became established.
[21][32][34][4]: 8 The dense stands that developed increased the abundance of insect and disease epidemics, and when combined with fire exclusion, significantly altered the composition and structure of these forests.
), fir engraver (Scolytus ventralis), Douglas-fir tussock moth (Orgyia pseudotsugata) were insects associated with regularly burned areas.
[36][4]: 8 In most years bark beetles occurred at endemic levels in ponderosa pine, Douglas-fir, and grand fir killing large and weakened trees that were struck by lightning, infected by root disease (Armillaria spp.
