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.明确生境与营养状况对有蹄类动物种群的影响机制，可为野生动物管理提供科学支撑，尤其在正经历食肉动物恢复、且有蹄类种群数量呈下降趋势的区域中，该研究尤为关键。 饲草物种可获得性、植物物候期以及饲草丰度的差异，使得解析营养因子对有蹄类动物的景观尺度效应颇具挑战。 本研究开发了一种集成空间建模方法，在两个生境质量粗尺度指标存在差异的相邻研究区内，估算景观尺度的马鹿（Cervus elaphus）营养资源，并将营养资源差异的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，本研究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衡量指标的营养资源指数，在不同土地覆盖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素，这表明维持火灾历史与分布的镶嵌格局，或将显著有益于有蹄类动物种群。 研究区、泌乳状态以及年份，会显著影响成年雌性马鹿的秋季体脂水平。 夏季栖息地营养资源较低的研究区内的马鹿，其进入冬季时的营养状况更差。 这类营养状况差异进而导致了妊娠率的差异：营养资源更充足的研究区马鹿平均妊娠率为89%，而营养资源较低的研究区则为72%。 夏季栖息地的营养资源有可能限制马鹿的妊娠率与幼鹿生产，这类营养限制可能会使马鹿对狩猎或捕食的影响更为敏感。 野生动物管理者应识别出存在营养限制的有蹄类种群，并意识到相较于栖息于生产力更高的夏季栖息地的种群而言，这类种群受恢复中的食肉动物或狩猎活动的影响可能更为显著。