File:Carbon storage and accumulation in United States forest ecosystems (1992) (20580766851).jpg

Title: Carbon storage and accumulation in United States forest ecosystems
Identifier: CAT93989847 (find matches)
Year: 1992 (1990s)
Authors: Birdsey, Richard A; United States. Forest Service
Subjects: Carbon cycle (Biogeochemistry) United States; Plants Effect of carbon on; Trees Climatic factors United States; Forest ecology United States
Publisher: (Washington, D. C. ?) : U. S. Dept. of Agriculture, Forest Service
Contributing Library: U.S. Department of Agriculture, National Agricultural Library
Digitizing Sponsor: U.S. Department of Agriculture, National Agricultural Library

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Pacific Coast States, including Alaska, contain the highest average carbon in forest soils, 64 percent of the total. The lowest proportion of soil carbon is found in the Rocky Mountain States, with 49 percent of the total. Soil carbon is closely related to temperature and precipitation, with higher amounts of soil carbon found in regions with cooler tempera- tures and higher precipitation. The cooler temperatures slow the oxidation of soil carbon, while higher rainfall tends to produce more vegetation and thus the fine roots and litter that are the main sources of organic soil carbon. Carbon in the forest floor varies by region in a way similar to carbon in the soil. Western and Northern States contain the most carbon on the forest floor, and Southern States contain the least. There is a clear pattern of increasing forest carbon from Southern to Northern States (fig. 5). The two main factors are climate and average age of the forests. The cooler, wetter climates favor higher retention of carbon on the forest floor and in the soil, and northern forests tend to be older and less frequently disturbed than forests in the South. Carbon Storage by Forest Type There are significant differences in carbon storage among forest types. For example, selected eastern softwood types show large differences in total carbon storage and the relative storage by forest ecosystem component (fig. 6). Loblolly pine plantations are younger on average, so there is less carbon in the trees, and since they are mostly located in the South, the soil carbon is lower. Spruce - fir, common in the Northeast, has higher total carbon as a result of the large amount of carbon stored in the soil. Douglas - fir contains the highest average carbon because of the large quantity stored in the trees. Pinyon - juniper has the lowest amount of carbon because it occurs in dry climates that support lower vegetation densities. Changes in Carbon Storage U.S. forests are constantly changing. The total area of forest land declined by 4 million acres between 1977 and 1987 (Waddell and others 1989). Most of the loss was from forest clearing for urban and suburban development, highways, and other rights-of-way. Many more million acres were cleared for agricultural use, but this loss was roughly balanced by agricultural land that was planted with trees or allowed to revert naturally to forest. In addition to land-use changes, each year about 4 million acres of timberland are harvested for timber products and regenerated to forests, 4 million acres are damaged by wildfire, and 2.5 million acres are damaged by insects and diseases (estimates based on various unpublished Forest Service data sources). And of course, all forest lands change continually as trees and other vegetation germinate, grow, and die.
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