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Historic
Historic vegetation in the bottomland included ash-willow riparian forest and grassland. Upland prairie was dominated by grass and herbaceous species with a few scattered trees (likely yarrow, brome, blue wildrye, Roemer’s fescue, lupine, and oak) (Christy et al., 2000). Riparian vegetation around the historic Guilds Lake (filled in the early 1900s) was dominated by ash, cottonwood, and willow and most likely contained ninebark and other native scrub-shrub species. Interpretations of U.S. Coast Survey charts from 1870 to 1887 indicate a mix of emergent and forested wetland, open water, cottonwood-ash forests, and prairie (Graves et al., 1995).
According to reconstructions of land survey records from 1851 to 1865, the historic vegetation (circa 1850) of the hillsides in this subwatershed consisted of burned and unburned mixed coniferous forest as well as Douglas fir forest at the top of the West Hills (Hulse, et al., 2002). According to Christy et al. (2000), the burned, mixed conifer forest was similar to the unburned mixed forest and consisted of varying combinations of Douglas fir, western hemlock, red cedar, grand fir, scattered with big-leaf maple, red alder, dogwood, and white oak (Christy et al., 2000). The understory, ranging from sparse to dense, likely included vine maple, huckleberry, thimbleberry, rhododendron, yew, salal, hazel, sword fern, devil’s club, and Oregon grape. The Douglas fir forest lacked oak and contained big-leaf maple and grand fir with an understory of dogwood, ferns, vine maple, hazel, salal, viburnum, Oregon grape, rhododendron, and yew (Christy et al., 2000).
Current
Based on a visual estimate of 2002 aerial photography, Balch subwatershed consists of approximately 65% tree or shrub coverage, 5% residences and cleared areas, and 30% industrial use.
Vegetation cover types include mid-age conifer, mature hardwood, conifer topping hardwood forest, hardwood with a young conifer understory, shrubland, cultivated areas/city, and industrial areas. Cover types are delineated for only the central portion of the subwatershed. The composition of cover types was derived from Map 8 in the Northwest Hills Natural Areas Protection Plan (City of Portland Bureau of Planning, 1991b) and aerial photography.
Rare or uncommon vegetation species in this subwatershed include old conifers, western wahoo shrubs, and ornamental dawn redwoods (City of Portland Bureau of Planning, 1991). One area near Adams Park contains forests in a later stage of succession (Site 80, City of Portland, Bureau of Planning, 1991), with conifers surpassing the alder and maple canopy. Western cedar, Pacific yew, and hemlock occur in the understory of this area. Resource sites described in the Balch Creek Watershed Protection Plan contain the following vegetation types: late successional forest, mixed first and second growth conifer forest, park lawn, second growth mixed conifer and hardwood forest, gallery riparian forest, and artificial meadow (City of Portland, Bureau of Planning, 1991). Late successional Douglas fir forests in the west hills contain bigleaf maple, alder, and western Hemlock. Many of the steep sloped areas are late successional Douglas fir forests.
Invasive plant species that are prevalent in certain areas of Forest Park include English ivy, English holly, Clematis, morning glory, Himalayan blackberry, and laurel (City of Portland Bureau of Planning, 1991). English ivy is present in the riparian zone within Reach 1 (ODFW, 2001).
Assessment
Clearing, filing wetlands, logging, road building, and urban development disrupted native plant communities. Invasive and non-native species were introduced through landscaping, soil disturbance, and removal of native species.
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