Goosey Hayes B, Smith Joseph T, O'Neill Kevin M, Naugle David E
Department of Animal and Range Sciences, Montana State University, Bozeman, MT.
Wildlife Biology Program, University of Montana, Missoula, MT.
Environ Entomol. 2019 Aug 5;48(4):856-866. doi: 10.1093/ee/nvz074.
Terrestrial arthropods are a critical component of rangeland ecosystems that convert primary production into resources for higher trophic levels. During spring and summer, select arthropod taxa are the primary food of breeding prairie birds, of which many are imperiled in North America. Livestock grazing is globally the most widespread rangeland use and can affect arthropod communities directly or indirectly through herbivory. To examine effects of management on arthropod community structure and avian food availability, we studied ground-dwelling arthropods on grazed and ungrazed sagebrush rangelands of central Montana. From 2012 to 2015, samples were taken from lands managed as part of a rest-rotation grazing program and from idle lands where livestock grazing has been absent for over a decade. Bird-food arthropods were twice as prevalent in managed pastures despite the doubling of overall activity-density of arthropods in idle pastures. Activity-density on idled lands was largely driven by a tripling of detritivores and a doubling in predators. Predator community structure was simplified on idled lands, where Lycosid spiders increased by fivefold. In contrast, managed lands supported a more diverse assemblage of ground-dwelling arthropods, which may be particularly beneficial for birds in these landscapes if, for example, diversity promotes temporal stability in this critical food resource. Our results suggest that periodic disturbance may enhance arthropod diversity, and that birds may benefit from livestock grazing with periodic rest or deferment.
陆生节肢动物是牧场生态系统的重要组成部分，它们将初级生产转化为更高营养级的资源。在春季和夏季，某些节肢动物类群是繁殖期草原鸟类的主要食物，其中许多鸟类在北美面临濒危。在全球范围内，牲畜放牧是最普遍的牧场利用方式，它可以通过食草直接或间接地影响节肢动物群落。为了研究管理措施对节肢动物群落结构和鸟类食物可利用性的影响，我们在蒙大拿州中部放牧和未放牧的鼠尾草牧场上研究了地面节肢动物。从2012年到2015年，我们从作为轮牧计划一部分进行管理的土地以及十多年来一直没有牲畜放牧的闲置土地上采集样本。尽管闲置牧场中节肢动物的总体活动密度增加了一倍，但在管理牧场中作为鸟类食物的节肢动物的数量却是其两倍。闲置土地上的活动密度主要是由食腐动物数量增加两倍和捕食者数量增加一倍所驱动的。在闲置土地上，捕食者群落结构简化，狼蛛数量增加了五倍。相比之下，管理土地上支持着更为多样的地面节肢动物群落，如果例如多样性促进了这种关键食物资源的时间稳定性，那么这对这些景观中的鸟类可能特别有益。我们的结果表明，周期性干扰可能会增强节肢动物的多样性，并且鸟类可能会从定期休牧或延期放牧的牲畜放牧中受益。
