Russell Matthew B, Domke Grant M, Woodall Christopher W, D'Amato Anthony W
Department of Forest Resources, University of Minnesota, St. Paul, MN 55108 USA.
USDA Forest Service, Northern Research Station, St. Paul, MN 55108 USA.
Carbon Balance Manag. 2015 Sep 4;10:20. doi: 10.1186/s13021-015-0032-7. eCollection 2015 Dec.
Refined estimation of carbon (C) stocks within forest ecosystems is a critical component of efforts to reduce greenhouse gas emissions and mitigate the effects of projected climate change through forest C management. Specifically, belowground C stocks are currently estimated in the United States' national greenhouse gas inventory (US NGHGI) using nationally consistent species- and diameter-specific equations applied to individual trees. Recent scientific evidence has pointed to the importance of climate as a driver of belowground C stocks. This study estimates belowground C using current methods applied in the US NGHGI and describes a new approach for merging both allometric models with climate-derived predictions of belowground C stocks.
Climate-adjusted predictions were variable depending on the region and forest type of interest, but represented an increase of 368.87 Tg of belowground C across the US, or a 6.4 % increase when compared to currently-implemented NGHGI estimates. Random forests regressions indicated that aboveground biomass, stand age, and stand origin (i.e., planted versus artificial regeneration) were useful predictors of belowground C stocks. Decreases in belowground C stocks were modeled after projecting mean annual temperatures at various locations throughout the US up to year 2090.
By combining allometric equations with trends in temperature, we conclude that climate variables can be used to adjust the US NGHGI estimates of belowground C stocks. Such strategies can be used to determine the effects of future global change scenarios within a C accounting framework.
精确估算森林生态系统中的碳储量是通过森林碳管理来减少温室气体排放和减轻预计气候变化影响的关键环节。具体而言，美国国家温室气体清单（US NGHGI）目前使用适用于单株树木的全国统一的物种和直径特定方程来估算地下碳储量。最近的科学证据表明气候是地下碳储量的驱动因素。本研究采用US NGHGI中使用的当前方法估算地下碳，并描述了一种将异速生长模型与基于气候的地下碳储量预测相结合的新方法。
经气候调整的预测因感兴趣的区域和森林类型而异，但在美国全国范围内，地下碳储量增加了368.87太克，与目前实施的NGHGI估算相比增加了6.4%。随机森林回归表明，地上生物量、林分年龄和林分起源（即种植与人工更新）是地下碳储量的有效预测指标。通过预测美国各地直至2090年的年平均温度，模拟了地下碳储量的减少情况。
通过将异速生长方程与温度趋势相结合，我们得出结论，气候变量可用于调整US NGHGI对地下碳储量的估算。此类策略可用于在碳核算框架内确定未来全球变化情景的影响。
