One of the primary conservation threats surrounding sagebrush (Artemisia spp.) ecosystems in the Intermountain West of the United States is the expansion and infilling of pinyon pine (Pinus edulis, P. monophylla) and juniper (Juniperus spp.) woodlands. Woodland expansion into sagebrush ecosystems has demonstrated impacts on sagebrush-associated flora and fauna, particularly the greater sage-grouse (Centrocercus urophasianus). These impacts have prompted government agencies, land managers, and landowners to ramp up pinyon-juniper removal efforts to maintain and restore sagebrush ecosystems. Accurately quantifying and analyzing management activities over time across broad spatial extents still poses a major challenge. Such information is vital to broad-scale planning and coordination of management efforts. To address this problem and aid future management planning, we applied a remote sensing change detection approach to map reductions in pinyon-juniper cover across the sage-grouse range and developed a method for rapidly updating maps of canopy cover. We found total conifer reduction over the past several yr (2011−2013 to 2015−2017) amounted to 1.6% of the area supporting tree cover within our study area, which is likely just keeping pace with estimates of expansion. Two-thirds of conifer reduction was attributed to active management (1.04% of the treed area) while wildfire accounted for one-third of all estimated conifer reduction in the region (0.56% of the treed area). Our results also illustrate the breadth of this management effort—crossing ownership, agency, and state boundaries. We conclude by identifying some key priorities that should be considered in future conifer management efforts based on our comprehensive assessment.

在美国西部山间地区的鼠尾草（Artemisia spp。）生态系统周围的主要保护威胁之一是松树（Pinus edulis，P. monophylla）和杜松（Juniperus spp。）林地的扩张和填充。林地向鼠尾草生态系统扩展已显示出对鼠尾草相关动植物的影响，尤其是更大的鼠尾草（Centrocercus urophasianus）。这些影响促使政府机构，土地经理和土地所有者加大了对松柏的清除工作，以维护和恢复鼠尾草的生态系统。在广泛的空间范围内，随着时间的推移准确量化和分析管理活动仍然是一个重大挑战。这些信息对于大规模规划和协调管理工作至关重要。为了解决此问题并帮助制定未来的管理计划，我们应用了遥感变化检测方法来减少鼠尾草范围内的松树杜松覆盖图，并开发了一种快速更新树冠覆盖图的方法。我们发现过去几年（2011-2013年至2015-2017年）的针叶树总减少量占研究区域内支持树木覆盖的面积的1.6％，这很可能与扩展估计保持一致。针叶树减少的三分之二归因于积极管理（占树木面积的1.04％），而野火占该地区所有估计的针叶树减少的三分之一（占树木面积的0.56％）。我们的结果还说明了这种管理工作的广度–跨越所有权，代理和州边界。最后，我们根据综合评估结果，确定了在未来针叶树管理工作中应考虑的一些关键优先事项。