Geology 264
Forest management 208
Mines and mineral resources 160
Oregon 145
Water quality 109
Outdoor recreation 86
Forest reserves 80
Groundwater 76
Public lands 72
Land use, Rural 70
Land titles Registration and transfer 68
Oregon Description and travel 55
Land use 46
Natural resources Management 44
Public lands Management 40
Water-supply 40
Wild and scenic rivers 39
Geology, Stratigraphic 36
Wildlife conservation 34
Environmental impact statements 33
Roads 33
Conservation of natural resources 31
Watershed management 31
Motor vehicles Recreational use 30
Land use Environmental aspects 29
Paleontology 29
Hydrology 28
Indians of North America 28
Mount Hood National Forest (Or.) 28
Willamette National Forest (Or.) 28
Wilderness areas Law and legislation 26
Ecosystem management 25
Land use Planning 25
Recreation areas 25
Siuslaw National Forest (Or.) 25
Stream measurements 25
Trails 25
Wildlife refuges 25
Wild and scenic rivers Law and legislation 24
Indians of North America Land tenure 23
Streamflow 23
Logging Environmental aspects 22
Water temperature 22
Hydrogeology 21
Umpqua National Forest (Or.) 21
Deschutes National Forest (Or.) 20
National parks and reserves 20
Wilderness areas 20
Crooked River National Grassland (Or.) 19
Malheur National Forest (Or.) Environmental conditions 19
Water resources development Law and legislation 19
Ochoco National Forest (Or.) 18
Overland journeys to the Pacific 18
Forests and forestry 17
Groundwater flow 17
Indians of North America Legal status, laws, etc 17
Range management 17
River sediments 17
Sediments (Geology) 17
Volcanic ash, tuff, etc 17
Forest roads Environmental aspects 16
Geochemical prospecting 16
Geothermal resources 16
Malheur National Wildlife Refuge (Or.) 16
Aquifers 15
Gold mines and mining 15
Oregon History 15
Sediment transport 15
Environmental impact analysis 14
Frontier and pioneer life 14
Fuelwood cutting 14
Mercury ores 14
Mines and mineral resources Environmental aspects 14
Missions 14
Oregon Public lands 14
Water Pollution 14
Watershed management Law and legislation 14
Fishery management 13
Forest ecology 13
Forest management Environmental aspects 13
Forest thinning Environmental aspects 13
Fremont National Forest (Or.) 13
Indians of North America Antiquities 13
Petrology 13
Plant communities 13
Real property, Exchange of 13
Vegetation management Environmental aspects 13
Wallowa-Whitman National Forest (Or.) 13
Water Dissolved oxygen 13
Water quality management 13
Crater Lake National Park (Or.) 12
Forest restoration 12
Habitat conservation 12
Land use Environmental aspects Planning 12
Management 12
Nutrient pollution of water 12
Wallowa National Forest (Or.) 12
Water resources development 12
Whitman National Forest (Or.) 12
Winema National Forest (Or.) 12