Carbon storage and accumulation in United States forest ecosystems

Abstract

Annual mortality-The volume of sound wood in trees that died from natural causes during a specific year.Annual removals-The net volume of trees removed from the inventory during a specified year by harvesting, cultural operations such as timber stand improvement, or land clearing.Cull tree-A live tree.5.0 inches in diameter at breast height (d.b.h.) or larger, that is unmerchantable for saw logs now or prospectively because of rot.roughness, or species.(See definitions for rotten and rough trees.)Forest land-Land at least 10 percent stocked by trees of any size, including land that formerly had such tree cover and that will be naturally or artificially regenerated.Forestland includes transition zones, such as areas between heavily forested and nonforested lands that are at least 10 percent stocked with forest trees and forest areas adjacent to urban and built-up lands.Also included are pinyon-juniper and chaparral areas in the West and afforested areas.The minimum area for classification of forest land is 1 acre.Roadside, streamside, and shelterbelt strips of timber must have a crown width of at least 1 20 feet to qualify as forest land.Unimproved roads and trails, streams, and clearings in forest areas are classified as forest if less than 1 20 feet wide.Forest type-A classification of forest land based on the species presently forming a plurality of the live-tree stocking.Major eastern forest-type groups:White-red-jack-pine-Forests in which eastern white pine, red pine, or jack pine, singly or in combination, make up a plurality of the stocking.Common associates include hemlock, aspen, birch, and maple.Spruce-fir-Forests in which spruce or true firs, singly or in combination, make up a plurality of the stocking.Common associates include white-cedar, tamarack, maple, birch, and hemlock.Longleaf-slash pine-Forests in which longleaf or slash pine, singly or in combination, make up a plurality of the stocking.Common associates include other southern pines, oak.and gum.Loblolly-shortleaf pine-Forests in which loblolly pine, shortleaf pine, or southern yellow pines, except longleaf or slash pine, singly or in combination, make up a plurality of the stocking.Common associates include oak, hickory, and gum.Oak-pine-Forests in which hardwoods (usually upland oaks) make up a plurality of the stocking, but in which pine or eastern redcedar makes up 25-50 percent of the stocking.Common associates include gum.hickory, and yellow-poplar.Oak-hickory-Forests in which upland oaks or hickory, singly or in combination, make up a plurality of the stocking except where pines make up 25-50 percent, in which case the stand is classified as oak-pine.Common associates include yellow-poplar, elm, maple, and black walnut.Oak-gum-cypress-Bottomland forests in which tupelo.blackgum, sweetgum.oaks, or southern cypress, singly or in combination, make up a plurality of the stocking except where pines make up 25-50 percent, in which case the stand is classified as oak-pine.Common associates include cottonwood.willow, ash.elm.hackberry.and maple.Elm-ash-cottonwood-Forests in which elm. ash.or cottonwood, singly or in combination, make up a plurality of the stocking.Common associates include willow, sycamore, beech, and maple.Maple-beech-birch -Forests in which maple, beech, or yellow birch, singly or in combination, make up a plurality of the stocking.Common associates include hemlock, elm, basswood, and white pine.Aspen-birch-Forests in which aspen, balsam poplar, paper birch, or gray birch, singly or in combination, make up a plurality of the stocking.Common associates include maple and balsam fir.Major western forest-type groups: Douglas-fir-Forests in which Douglas-fir makes up plurality of the stocking.Common associates include western hemlock, western redcedar.the true firs, redwood, ponderosa pine, and larch.Hemlock-Sitka spruce-Forests in which western hemlock or Sitka spruce, or both, make up a plurality of the stocking.Common associates include Douglas-fir.silver fir.and western redcedar.Redwood-Forests in which redwood makes up a plurality of the stocking.Common associates include Douglas-fir.grand fir.and tanoak.Ponderosa pine-Forests in which ponderosa pine makes up a plurality of the stocking.Common associates include Jeffrey pine, sugar pine, limber pine, Arizona pine.Apache pine, Chihuahua pine.Douglas-fir, incense-cedar, and white fir.Western white pine-Forests in which western pine makes up a plurality of the stocking.Common associates include western redcedar.larch, white fir.Douglas-fir.lodgepole pine, and Engelmann spruce.Lodgepole pine-forests in which lodgepole pine makes up a plurality of the stocking.Common associates include alpine fir.western white pine.Engelmann spruce, aspen, and larch.