Better living through conifer removal: A demographic analysis of sage-grouse vital rates

Sagebrush (Artemisia spp.) obligate wildlife species such as the imperiled greater sage-grouse (Centrocercus urophasianus) face numerous threats including altered ecosystem processes that have led to conifer expansion into shrub-steppe. Conifer removal is accelerating despite a lack of empirical evidence on grouse population response. Using a before-after-control-impact design at the landscape scale, we evaluated effects of conifer removal on two important demographic parameters, annual survival of females and nest survival, by monitoring 219 female sage-grouse and 225 nests in the northern Great Basin from 2010 to 2014. Estimates from the best treatment models showed positive trends in the treatment area relative to the control area resulting in an increase of 6.6% annual female survival and 18.8% nest survival relative to the control area by 2014. Using stochastic simulations of our estimates and published demographics, we estimated a 25% increase in the population growth rate in the treatment area relative to the control area. This is the first study to link sage-grouse demographics with conifer removal and supports recommendations to actively manage conifer expansion for sage-grouse conservation. Sage-grouse have become a primary catalyst for conservation funding to address conifer expansion in the West, and these findings have important implications for other ecosystem services being generated on the wings of species conservation.

专性依赖鼠尾草灌丛（Artemisia spp.）的野生动物类群（如濒危的艾草榛鸡（greater sage-grouse, Centrocercus urophasianus））面临诸多威胁，其中包括生态系统过程改变导致针叶林向灌丛草原扩张。尽管目前尚无关于榛鸡种群响应的实证依据，针叶林清除工作仍在加速推进。本研究采用景观尺度的前后对照影响（before-after-control-impact, BACI）实验设计，于2010至2014年间在大盆地北部追踪监测了219只雌性艾草榛鸡与225个巢穴，以此评估针叶林清除对两项关键种群统计参数的影响：雌性个体年存活率与巢存活率。最优处理模型的估算结果显示，相较于对照区域，处理区域的种群参数呈现正向变化趋势；至2014年时，处理区域的雌性年存活率较对照区域提升6.6%，巢存活率提升18.8%。基于本研究的估算结果与已发表的种群统计数据开展随机模拟后，本研究估算得到处理区域的种群增长率较对照区域提升25%。本研究首次建立了艾草榛鸡种群统计特征与针叶林清除之间的关联，支持了为保护艾草榛鸡而主动管控针叶林扩张的相关建议。艾草榛鸡已成为美国西部针对针叶林扩张申请保护资金的核心催化因素，本研究结果对依托物种保护工作催生的其他生态系统服务亦具有重要参考价值。