Data from: Linking landscape-scale differences in forage to ungulate nutritional ecology

Understanding how habitat and nutritional condition affect ungulate populations is necessary for informing management, particularly in areas experiencing carnivore recovery and declining ungulate population trends. Variations in forage species availability, plant phenological stage, and the abundance of forage make it challenging to understand landscape-level effects of nutrition on ungulates. We developed an integrated spatial modeling approach to estimate landscape-level elk (Cervus elaphus) nutritional resources in two adjacent study areas that differed in coarse measures of habitat quality and related the consequences of differences in nutritional resources to elk body condition and pregnancy rates. We found no support for differences in dry matter digestibility between plant samples or in phenological stage based on ground sampling plots in the two study areas. Our index of nutritional resources, measured as digestible forage biomass, varied among landcover types and between study areas. We found that altered plant composition following fires was the biggest driver of differences in nutritional resources, suggesting that maintaining a mosaic of fire history and distribution will likely benefit ungulate populations. Study area, lactation status and year affected fall body fat of adult female elk. Elk in the study area exposed to lower summer range nutritional resources had lower nutritional condition entering winter. These differences in nutritional condition resulted in differences in pregnancy rate, with average pregnancy rates of 89% for elk exposed to higher nutritional resources and 72% for elk exposed to lower nutritional resources. Summer range nutritional resources have the potential to limit elk pregnancy rate and calf production, and these nutritional limitations may predispose elk to be more sensitive to the effects of harvest or predation. Wildlife managers should identify ungulate populations that are nutritionally limited and recognize that these populations may be more impacted by recovering carnivores or harvest than populations inhabiting more productive summer habitats.阐明生境与营养状况对有蹄类动物（ungulate）种群的影响机制，可为野生动物管理提供科学依据，尤其在食肉动物种群恢复、有蹄类动物种群数量呈下降趋势的区域，该研究尤为重要。饲草物种可获得性、植物物候期与饲草丰度的空间变异，使得解析营养因子对有蹄类动物种群的景观尺度效应极具挑战。本研究构建了一套集成空间建模方法，用于估算两个相邻研究区的景观尺度马鹿（elk, Cervus elaphus）营养资源状况；这两个研究区的生境质量粗尺度评估结果存在差异，且我们将营养资源差异的生态后果与马鹿体况及妊娠率相关联。基于两个研究区的地面样方调查结果，我们未发现植物样本间干物质消化率或物候期存在显著差异。本研究以可消化饲草生物量为指标构建的营养资源指数，在不同土地覆被类型间以及两个研究区之间均存在显著差异。研究发现，火灾后植物群落组成的改变是导致营养资源差异的最主要驱动因子，这表明维持火灾历史与火点分布的镶嵌格局，或将有助于有蹄类动物种群的存续。研究区域、泌乳状态以及调查年份，均会影响成年雌性马鹿的秋季体脂含量。夏季栖息地营养资源供给水平较低的研究区内的马鹿，越冬前的营养体况更差。体况差异进一步导致妊娠率的分化：营养资源供给水平较高区域的马鹿平均妊娠率为89%，而营养资源供给水平较低区域的马鹿平均妊娠率仅为72%。夏季栖息地的营养资源状况可能会限制马鹿的妊娠率与产仔量，而这类营养限制效应可能会使马鹿更易受到狩猎或捕食作用的影响。野生动物管理者应甄别出受营养限制的有蹄类动物种群，并意识到相较于栖息于夏季栖息地生产力更高区域的种群，这类种群受食肉动物种群恢复或狩猎活动的影响可能更为显著。