|Abstract or Summary
- This dissertation describes patterns in epiphytic macrolichen community composition, diversity, and biomass across various stand types in the Blue River watershed of western Oregon. It first examines the relative importance of ecological factors such as stand age, remnant tree retention, and topography to lichen communities in the landscape. It then develops models for estimating epiphytic macrolichen biomass and uses these models to assess potential impacts of forest management strategies on future lichen biomass in the watershed.
Epiphytic macrolichen communities were sampled in 117 coniferous stands in uplands and riparian areas. Stands were typed by stand age (young, <20; pole, 21-80; mature, 81-200; and old-growth, >200 yrs) and by the degree of remnant tree retention (older trees that survived the most recent disturbance). Lichen biomass (oven-dried, kg/ha) was estimated for three functional groups: nitrogen-fixing cyanolichens, forage lichens, and matrix lichens in 63 of the 117 stands. Elevation was the leading factor related to differences in macrolichen communities and biomass. Cyanolichens (dominated by Lobaria oregana) were largely limited to lower elevations and were most abundant in old growth (median 1,377 kg/ha).
Lichen community composition changed with stand age. Remnant presence was related only to lichen community differences in young stands. Lichen biomass increased with stand age and with remnant retention. Stands along perennial streams were cyanolichen hotspots compared to uplands. Lichen biomass was unrelated to uplands and riparian areas.
Regression models estimating lichen biomass by functional group were developed from topography, stand structure, and lichen communities. The model for cyanolichen biomass had the strongest predictive power (R²= 0.85), whereas models for forage and matrix lichen biomass were less powerful (R² = 0.55 and R² = 0.58, respectively).
We estimated cyanolichen and forage lichen biomass in the present watershed and forecasted lichen biomass in 200 yrs for two different management scenarios: the Landscape Plan (LP) and the Northwest Forest Plan (NWFP). Under both scenarios, lichen biomass was predicted to increase substantially from current levels due to increased remnant tree retention and the elimination of clear-cutting. The LP scenario yielded 12% higher forage lichen biomass and 8% higher cyanolichen biomass than the NWFP.