Subject
- Oregon -- Antiquities4
- Indians of North America -- Oregon -- Antiquities3
- Natural resources -- Oregon3
- Buffer zones (Ecosystem management) -- Coast Ranges2
- Compost2
- Douglas fir2
- Excavations (Archaeology) -- Oregon -- Mission Lake Region2
- Fire ecology -- Oregon -- Willamette River Valley2
- Grazing -- Oregon2
- Groundwater -- Pollution -- Oregon -- Willamette River Valley2
- Irrigation efficiency2
- Lakes -- Oregon2
- Methodist Episcopal Church -- Oregon2
- Nitrates -- Environmental aspects -- Oregon -- Willamette River Valley2
- Oregon -- Climate2
- Plant-soil relationships2
- Ponderosa pine -- Climatic factors -- Oregon2
- Rain and rainfall2
- Riparian ecology -- Oregon2
- Soils -- Oregon2