Greater sage-grouse general use relative abundance in the Wyoming Basins Ecoregional Assessment area

Greater sage-grouse (Centrocercus urophasianus) have been declining both spatially and numerically throughout their range due to anthropogenic disturbance and loss and fragmentation of sagebrush (Artemisia spp.) habitats. Understanding how sage-grouse respond to these habitat alterations and disturbances, particularly the types of disturbances and extent at which they respond, is critical to designing management actions and prioritizing areas of conservation. To address these needs, we developed this spatially explict model of the relationship between occurrence and abundance of greater sage-grouse and multi-scaled measures of vegetation, abiotic, and disturbance in the Wyoming Basins Ecoregional Assessment (WBEA) area. Sage-grouse occurrence was strongly related to the amount of sagebrush within 1 km. Proximity to anthropogenic disturbance including energy development, power lines, and major roads was negatively associated with sage-grouse occurrence. General use sites were identified by presence of single sage-grouse fecal pellets. The information here was developed using a generalized ordered logistic regression with study sites assigned into absent, low, and high abundance classes. The models for low and high abundance were combined into a three-class relative abundance surface (absent, low, and high). The bin breakpoint separating absent from low/high abundance habitat was based on the sensitivity-specificity equality threshold to maximize prediction success for each model. Within low/high abundance habitat, the threshold was set at the point where the predicted probability of being high abundance habitat exceeded the probability of being low abundance habitat This map correctly predicted active lek locations as either low or high abundance with >75% accuracy and the mean number of sage-grouse at leks increased with each class (Absent: 17.57 males, Low: 29.75 males, High: 46.61 males).艾草松鸡（Greater sage-grouse，学名Centrocercus urophasianus）在其分布范围内的种群数量与空间分布均呈下降趋势，诱因包括人为干扰、蒿属（Artemisia spp.）栖息地的丧失与破碎化。明晰艾草松鸡对这类栖息地改变与干扰的响应模式，尤其是其响应的干扰类型与程度，对于制定管理措施、划定保护优先区域至关重要。为满足上述研究需求，本研究在怀俄明盆地生态区域评估（Wyoming Basins Ecoregional Assessment, WBEA）区域内，构建了艾草松鸡出现率与种群丰度，以及多尺度下植被、非生物因子与干扰因子度量指标之间关系的空间显式模型（spatially explicit model）。研究结果显示，艾草松鸡的出现概率与1公里范围内的蒿属植被覆盖量呈显著正相关；人为干扰源（包括能源开发设施、输电线与主要道路）的邻近性与艾草松鸡的出现概率呈显著负相关。本研究通过单个艾草松鸡粪便颗粒识别出普通利用位点，所用数据基于广义有序logistic回归（generalized ordered logistic regression）构建，将研究位点划分为未出现、低丰度与高丰度三个等级。随后将低丰度与高丰度对应的模型整合，得到包含未出现、低丰度、高丰度三个类别的相对丰度表面。区分未出现栖息地与低/高丰度栖息地的分界阈值，采用各模型中最大化预测成功率的灵敏度-特异度相等阈值；而在低/高丰度栖息地范围内，阈值设定为高丰度栖息地的预测概率超过低丰度栖息地预测概率的临界点。该模型对活跃求偶场的低/高丰度类别预测准确率超过75%，且求偶场内的艾草松鸡平均数量随丰度等级升高而增加（未出现类：17.57只雄鸟，低丰度类：29.75只雄鸟，高丰度类：46.61只雄鸟）。