Forest-Range Environmental Study Ecosystems, known as FRES, is a system for the classification of ecosystems developed by the United States Forest Service as a management tool for the entire lower 48.Garrison, George A.; Bjugstad, A. J.; Duncan, D. A.; Lewis, M. E.; and Smith, D. R. (1977) Vegetation and environmental features of forest and range ecosystems (Forest Service Handbook Number 465) United States Department of Agriculture, Washington, D.C., Thirty four ecosystems were defined for grasslands, forests, and woodlands.
Forest and woodland classification FRES 10 White pine – red pine – jack pine FRES 11 Spruce – fir FRES 12 Longleaf – slash pine FRES 13 Loblolly – shortleaf pine FRES 14 Oak pine FRES 15 Oak – hickory FRES 16 Oak – gum – cypress FRES 17 Elm – ash – cottonwood FRES 18 Maple – beech – birch FRES 19 Aspen – birch FRES 20 Douglas-fir FRES 21 Ponderosa pine FRES 22 Western white pine FRES 23 Fir – spruce FRES 24 Hemlock – Sitka spruce FRES 25 Larch FRES 26 Lodgepole pine FRES 27 Redwood FRES 28 Western hardwoods FRES 29 Sagebrush FRES 30 Desert shrub FRES 31 Shinnery FRES 32 Texas savanna FRES 33 Southwestern shrubsteppe FRES 34 Chaparral – mountain shrub FRES 35 Pinyon – juniper
Grassland classification FRES 36 Mountain grasslands FRES 37 Mountain meadows FRES 38 Plains grasslands FRES 39 Prairie FRES 40 Desert grasslands FRES 41 Wet grasslands FRES 42 Annual grasslands
Alpine classification FRES 44 Alpine meadows and barren
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