Hoover Coeli M, Smith James E
USDA Forest Service, Northern Research Station, 271 Mast Road, Durham, NH, 03824, USA.
Carbon Balance Manag. 2021 May 20;16(1):17. doi: 10.1186/s13021-021-00179-2.
With the introduction of the Trillion Trees Initiative and similar programs, forests' ability to absorb carbon dioxide is increasingly in the spotlight. Many states have mandates to develop climate action plans, of which forest carbon is an important component, and planners need current information on forest carbon stocks and rates of change at relevant spatial scales. To this end, we examine rates of average annual change in live aboveground tree carbon in different forest type groups and provide state-wide and regional summaries of current live tree carbon stock and rates of change for the forests of the conterminous United States. Forest carbon summaries are presented in a format designed to meet the needs of managers, policymakers, and others requiring current estimates of aboveground live tree carbon at state and regional scales.
Regional average aboveground live tree carbon stocks (represented on a per area basis) are generally between 40 and 75 tC/ha but range from 12.8 tC/ha in the Great Plains to 130 tC/ha in the Pacific Northwest West (west-side of Cascades). Regional average annual change in live aboveground tree carbon varies from a low of - 0.18 mtC/ha/y in the Rocky Mountain South to a high value of 1.74 mtC/ha/y in Pacific Northwest West. For individual states, carbon per unit area varies widely, from a low of 11.9 tC/ha in Nevada to a high of 96.4 tC/ha in Washington, with half the states falling between 50 and 75 tC/ha. Rates of average annual change in live aboveground tree carbon vary from a high of 1.82 tC/ha/y in Mississippi to a low of - 0.47 tC/ha/y in Colorado.
Aboveground live tree carbon stocks and rates of average annual change vary by forest type within regions. While softwood forest types currently exhibit a higher rate of increase in the amount of carbon in aboveground live tree biomass, the current standing stock of carbon per unit area does not consistently follow this pattern. For this reason, we recommend computing and considering both measures -standing stock and average annual change-of carbon storage. The relative importance of each component will depend on management and policy objectives and the time frame related to those objectives. Harvesting and natural disturbance also affect forest carbon stock and change and may need to be considered if developing projections of potential carbon storage.
随着“万亿树木倡议”及类似项目的推出，森林吸收二氧化碳的能力日益受到关注。许多州都有制定气候行动计划的要求，其中森林碳是重要组成部分，规划者需要有关森林碳储量及其在相关空间尺度上变化速率的最新信息。为此，我们研究了不同森林类型组中地上活立木碳的年均变化速率，并提供了美国本土森林当前活立木碳储量及变化速率的全州和区域汇总情况。森林碳汇总以一种旨在满足管理人员、政策制定者及其他需要州和区域尺度上地上活立木碳当前估算值的人员需求的格式呈现。
区域地上活立木碳储量（按单位面积计算）一般在40至75吨碳/公顷之间，但范围从大平原地区的12.8吨碳/公顷到太平洋西北地区西部（喀斯喀特山脉西侧）的130吨碳/公顷。地上活立木碳的区域年均变化量从落基山脉南部的低值 -0.18公吨碳/公顷/年到太平洋西北地区西部的高值1.74公吨碳/公顷/年不等。对于各个州，单位面积的碳含量差异很大，从内华达州的低值11.9吨碳/公顷到华盛顿州的高值96.4吨碳/公顷，一半的州处于50至75吨碳/公顷之间。地上活立木碳的年均变化速率从密西西比州的高值1.82吨碳/公顷/年到科罗拉多州的低值 -0.47吨碳/公顷/年不等。
地上活立木碳储量及其年均变化速率在各区域内随森林类型而异。虽然目前针叶林类型在地上活立木生物量中的碳含量增长速率较高，但单位面积的当前碳蓄积量并非始终遵循这一模式。因此，我们建议计算并考虑碳储量和年均变化这两项指标。每个组成部分的相对重要性将取决于管理和政策目标以及与这些目标相关的时间框架。采伐和自然干扰也会影响森林碳储量及其变化，如果要制定潜在碳储量的预测，可能需要予以考虑。
