Moderate-resolution mapping of aboveground biomass stocks, forest structure, and composition in coastal Alaska and British Columbia

The forests of coastal Alaska and British Columbia are globally significant for their high carbon storage capacity and complex forest structure, hosting some of the densest values of aboveground biomass in the world. These ecosystems support biodiversity, provide critical habitat, and serve as long-term carbon sinks, offering resilience to climate change. However, comprehensive, spatially continuous estimates of forest structure across this region have been limited, particularly across political boundaries. In this study, we used a Gradient Nearest Neighbor (GNN) modeling approach to integrate extensive forest inventory plot data with satellite-derived environmental variables. This approach enabled us to produce high-resolution (30-meter) maps of aboveground biomass, species-specific biomass, forest age, basal area, and additional structural attributes. Our results indicate that climate and topography accounted for the majority of the explainable variation across all modeling regions. Predictions of aboveground live biomass were higher than previous estimates, particularly in Southeast Alaska, where estimates were 30-53% greater than previous studies. Forest structure varied across the region, with older forests found in Southeast Alaska and higher tree densities in British Columbia. Collectively, the coastal forests of Alaska and British Columbia store approximately 3.58 petagrams of carbon. These spatially explicit maps offer critical insights for forest management, carbon monitoring, and biodiversity conservation across this ecologically diverse and politically fragmented landscape. Citations for Forest Inventory and Analysis: Burrill, Elizabeth A.; DiTommaso, Andrea M.; Turner, Jeffery A.; Pugh, Scott A.; Christensen, Glenn; Perry, Carol J.; Lepine, Lucie C.; Walker, David M.; Conkling, Barbara L. 2024. The Forest Inventory and Analysis Database, FIADB user guides, volume database description (version 9.2), nationwide forest inventory (NFI). U.S. Department of Agriculture, Forest Service. 1042 p. [Online]. Available at web address: https://www.fs.usda.gov/research/products/dataandtools/datasets/fia-datamart Citation for Forest Analysis and Inventory Branch: Bourgeois, William; Brinley, Clark; LeMay, Valerie; Moss, Ian; Reynolds, Nick. 2018. “British Columbia Forest Inventory Review Panel Technical Background Report.” Office of the Chief Forester Division, British Columbia Ministry of Forests, Lands, Natural Resource Operations and Rural Development, December 2018. https://www2.gov.bc.ca/assets/gov/farming-natural-resources-and-industry/forestry/stewardship/forest-analysis-inventory/brp_technical_document_final.pdf. Distribution Liability: The USDA Forest Service manages resource information and derived data as a service to users of USDA Forest Service digital geographic data. The USDA Forest Service is in no way condoning or endorsing the application of these data for any given purpose. It is the sole responsibility of the user to determine whether or not the data are suitable for the intended purpose. It is also the obligation of the user to apply those data in an appropriate and conscientious manner. The USDA Forest Service provides no warranty, nor accepts any liability occurring from any incorrect, incomplete, or misleading data, or from any incorrect, incomplete, or misleading use of these data. Use Constraints: The USDA Forest Service makes no warranty, expressed or implied, including the warranties of merchantability and fitness for a particular purpose, nor assumes any legal liability or responsibility for the accuracy, reliability, completeness or utility of these geospatial data, or for the improper or incorrect use of these geospatial data. These geospatial data and related maps or graphics are not legal documents and are not intended to be used as such. The data and maps may not be used to determine title, ownership, legal descriptions or boundaries, legal jurisdiction, or restrictions that may be in place on either public or private land. Natural hazards may or may not be depicted on the data and maps, and users should exercise due caution. The data are dynamic and may change over time. The user is responsible to verify the limitations of the geospatial data and to use the data accordingly.阿拉斯加沿海与不列颠哥伦比亚省的森林凭借其极高的碳储存能力与复杂的森林结构，具有全球重要性，拥有全球范围内密度最高的地上生物量资源之一。这些生态系统支撑生物多样性，提供关键栖息生境，并作为长期碳汇发挥作用，为应对气候变化提供韧性。然而，该区域内全面且空间连续的森林结构估算研究始终有限，尤其是跨越行政边界的相关研究更为匮乏。 本研究采用梯度最近邻（Gradient Nearest Neighbor, GNN）建模方法，将大规模森林调查样地数据与卫星反演得到的环境变量进行整合。该方法成功生成了分辨率为30米的高分辨率地图，涵盖地上生物量、物种特异性生物量、林分年龄、胸高断面积及其他森林结构属性。 研究结果显示，气候与地形因素解释了所有建模区域中绝大部分可解释变异。地上活生物量的预测值高于此前的估算结果，尤其是在阿拉斯加东南部地区，其估算值较过往研究高出30%至53%。该区域的森林结构存在显著空间差异：阿拉斯加东南部以老龄林为主，不列颠哥伦比亚省则拥有更高的林木密度。综合来看，阿拉斯加与不列颠哥伦比亚省的沿海森林共储存约3.58拍克（petagrams, Pg）的碳。这些空间显式地图为这片生态多样且行政分割的区域的森林管理、碳监测与生物多样性保护提供了关键科学见解。 森林清查与分析引用文献： 伯里尔, 伊丽莎白·A.; 迪托马索, 安德烈亚·M.; 特纳, 杰弗里·A.; 普夫, 斯科特·A.; 克里斯滕森, 格伦; 佩里, 卡罗尔·J.; 勒平, 吕西·C.; 沃克, 戴维·M.; 康克林, 芭芭拉·L. 2024. 《森林清查与分析数据库、FIADB用户指南，第一卷：数据库描述（版本9.2），全国森林清查（NFI）》. 美国农业部森林服务局. 1042页. [在线]. 可通过以下网址获取：https://www.fs.usda.gov/research/products/dataandtools/datasets/fia-datamart 森林分析与清查分支引用文献： 布尔茹瓦, 威廉; 布林利, 克拉克; 勒梅, 瓦莱丽; 莫斯, 伊恩; 雷诺兹, 尼克. 2018. 《不列颠哥伦比亚省森林清查审查小组技术背景报告》. 不列颠哥伦比亚省森林、土地、自然资源运营与农村发展部首席林务官办公室分部, 2018年12月. https://www2.gov.bc.ca/assets/gov/farming-natural-resources-and-industry/forestry/stewardship/forest-analysis-inventory/brp_technical_document_final.pdf 分发免责声明： 美国农业部森林服务局管理资源信息与衍生数据，旨在为USDA森林服务局数字地理数据的用户提供服务。美国农业部森林服务局绝不认可或背书将这些数据用于任何特定用途。用户需自行判断数据是否适用于其预期用途，并负有以恰当、审慎的方式使用这些数据的义务。美国农业部森林服务局不提供任何担保，也不对因数据不准确、不完整或误导性，或因对这些数据的不当、错误使用而产生的任何责任承担责任。 使用限制： 美国农业部森林服务局不提供任何明示或暗示的担保，包括适销性及特定用途适用性的担保，也不对这些地理空间数据的准确性、可靠性、完整性或实用性，或因不当或错误使用这些地理空间数据承担任何法律责任或义务。这些地理空间数据及相关地图或图表并非法律文件，也不旨在用作法律文件。不得将这些数据与地图用于确定土地（公有或私有）的所有权、产权、法律描述或边界、法律管辖范围或相关限制。数据与地图中可能未标注自然灾害，用户应保持谨慎。数据是动态的，可能随时间变化。用户需自行核实地理空间数据的局限性，并据此使用数据。