Ecologically, park uplands are dominated by a subalpine forest on Promontory Ridge and Tremont Mountain. Lodgepole pine, mixed coniferous forest and ponderosa pine savanna are found on south-facing slopes and deeper canyons, aspen forests in moist and intermittent drainages, shrublands, mixed grasslands, forb meadows, riparian and wetland communities.
Nearly barren rock outcrops and cliffs support lichen and moss communities. Engelmann spruce and subalpine fir dominate the highest elevations. Nearly pure stands of lodgepole pine are present at slightly lower elevations along with mixed coniferous forest communities. Lodgepole pine, Douglas fir, Colorado blue spruce and ponderosa pine comprise the overstory. Several stands of Limber pine are present, mainly along the Mountain Base and Gap Road sections of Golden Gate State Park.
Ponderosa Pine, Rocky Mountain Juniper
Ponderosa pine and Rocky Mountain juniper are the dominant savanna trees on southern exposures. Douglas fir is the common tree at lower elevations on northfacing slopes, which have a sparse understory.
Conversely, aspen stands occur in relatively moist sites and support a very rich understory of flora. Common shrub and herbaceous species of the forests include Oregon grape, blueberry, thimbleberry, Woods' rose, snowberry, serviceberry, common juniper, kinnikinnick, nodding brome, western wheatgrass, pine dropseed, blue grama, prairie Junegrass, lupine, heart-leaved arnica, goldaster, and beard-tongue. Forb-dominated meadows are present among aspen stands and typically support bluegrass, meadowrue, lupine, black-eyed Susan, cinquefoil, valerian and yarrow. Common shrubs of lower elevation communities include mountain mahogany, skunkbrush, serviceberry and currant.
Grasslands at Golden Gate
Grasslands present are an interesting association of shortgrass prairie, tallgrass prairie, montane grassland and introduced species. Dominant grass species include Arizona fescue, mountain muhly, blue grama, needle-and-thread grass, prairie Junegrass, western wheatgrass, squirreltail and smooth brome. Riparian and wetland communities are limited, but are established along the creeks, tributary drainages and on seeps and springs.
Typically, riparian communities are dominated by narrowleaf cottonwood, aspen, Colorado blue spruce, Rocky Mountain maple, alder, bush honeysuckle, Woods' rose, blue-stem willow and currant.
Wetland communities are characterized by a number of shrubby willow species, Nebraska, beaked and aquatic sedge, Arctic rush and grass species such as bluejoint reedgrass and tufted hairgrass.