Mammalian responses to changed forest conditions resulting from bark beetle outbreaks in the southern Rocky Mountains
Mammalian responses to changed forest conditions resulting from bark beetle outbreaks in the southern Rocky Mountains
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哺乳动物对落基山脉南部树皮甲虫爆发导致的森林条件变化的反应
作者：
Jacob S. Ivan;A. Seglund;Richard L. Truex;Eric S. Newkirk
云杉甲虫（Dendroctonus rufipennis）和山地松甲虫（Dendroctonus ponderosae）的爆发影响了从阿拉斯加到北方墨西哥数百万英亩的针叶林。这些物种原产于北美，几千年来，周期性的爆发塑造了针叶林的结构和组成。然而，由于有利的气候条件和森林易感性的增加，目前疫情的范围和严重程度在有记录的历史上是无与伦比的。为了描述一系列哺乳动物物种对落基山脉南部甲虫引起的植被变化的反应，我们在2013-2014年夏季在300个随机选择的地点部署了摄像机。选定的网站跨越梯度年过去了，因为树皮甲虫爆发（YSO）和严重程度。我们将单季占用模型拟合到为每个物种收集的检测/未检测数据，以检查给定林分的使用与YSO，严重程度或两者之间的各种合理关系。有蹄类动物表现出积极的关联与树皮甲虫的活动，虽然这些协会的性质因物种而异。麋鹿（Cervus canadensis）与严重程度呈正相关，但不是YSO;黑尾鹿（Odocoileus hemionus）表现出相反的关系。驼鹿（Alces alces）在二次响应的方式，使用森林看台附近的首选杨柳栖息地达到峰值后3-7年爆发开始，但只有在高严重性。类似地，黄腹土拨鼠使用邻近岩石露头的受影响林分遵循二次趋势，但仅在高严重性下。红松鼠（Tamiasciurus hudsonicus）的使用下降，在严重影响的立场，可能是作为一个响应减少锥作物。金背地松鼠（Callospermophilus lateralis）和花栗鼠（Neotamias spp.）与YSO表现出浅的负相关，郊狼（犬latrans）。与我们的假设相反，黑熊（Ursus americanus），美国貂（Martes americana），雪鞋野兔（Lepus americanus），豪猪（Erethizon dorsatum）似乎没有受到甲虫活动的实质性影响。赤狐（Vulpes vulpes）的使用与YSO呈正相关，但总体使用随着严重程度的增加而下降。请注意，这里描述的使用概率的变化可能反映了丰度、家域大小、栖息地使用或某种组合的变化，在某些情况下，竞争模型之间存在相当大的不确定性。
Spruce beetle (Dendroctonus rufipennis) and mountain pine beetle (Dendroctonus ponderosae) outbreaks have impacted millions of acres of conifer forest from Alaska to northern Mexico. These species are native to North America, and periodic outbreaks have shaped the structure and composition of conifer forests for millennia. However, the extent and severity of current outbreaks, fueled by favorable climatic conditions and increased susceptibility of forests, are unmatched in recorded history. To characterize the response of a suite of mammalian species to beetle‐induced changes in vegetation in the southern Rocky Mountains, we deployed cameras at 300 randomly selected sites during summer 2013–2014. Selected sites spanned gradients of years elapsed since bark beetle outbreaks (YSO) and severity. We fit single‐season occupancy models to detection/non‐detection data collected for each species to examine a variety of plausible relationships between use of a given stand and YSO, severity, or both. Ungulates exhibited a positive association with bark beetle activity, although the nature of these associations varied by species. Elk (Cervus canadensis) were positively associated with severity, but not YSO; mule deer (Odocoileus hemionus) exhibited the opposite relationship. Moose (Alces alces) responded in a quadratic fashion; use of forest stands adjacent to preferred willow habitat peaked 3–7 yr after an outbreak commenced, but only at high severity. Similarly, yellow‐bellied marmot use of impacted stands adjacent to rock outcroppings followed a quadratic trend, but only at high severity. Red squirrel (Tamiasciurus hudsonicus) use declined in severely impacted stands, likely as a response to diminished cone crops. Golden‐mantled ground squirrels (Callospermophilus lateralis) and chipmunks (Neotamias spp.) exhibited a shallow negative relationship with YSO, as did coyotes (Canis latrans). Contrary to our hypotheses, black bears (Ursus americanus), American marten (Martes americana), snowshoe hares (Lepus americanus), and porcupines (Erethizon dorsatum) did not appear to be substantially influenced by beetle activity. Red fox (Vulpes vulpes) use was positively associated with YSO, but overall use declined as severity increased. Note that changes in probability of use described here could reflect changes in abundance, home range size, habitat use, or some combination, and in several cases, there was considerable uncertainty across competing models.