THE PERILS OF HAVING TASTY NEIGHBORS: GRAZING IMPACTS OF LARGE HERBIVORES AT VEGETATION BOUNDARIES
THE PERILS OF HAVING TASTY NEIGHBORS: GRAZING IMPACTS OF LARGE HERBIVORES AT VEGETATION BOUNDARIES
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DOI：
10.1890/02-0245
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发表时间：
2003-11
期刊：
影响因子：
4.8
通讯作者：
S. Palmer;A. Hester;D. Elston;I. Gordon;S. Hartley
中科院分区：
文献类型：
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作者：
S. Palmer;A. Hester;D. Elston;I. Gordon;S. Hartley
植被斑块之间的边界是植物群落之间动态相互作用的焦点，特别是在放牧生态系统中，其中植被类型对食草动物的可接受性可能不同。在这里，我们表明，关键植被资源吸引食草动物，并且周围的植被受到的影响比与不太喜欢的植被斑块相关的影响更大（明显竞争的例子）。我们在英国苏格兰凯恩戈姆山脉的一系列空间尺度上研究了靠近偏好的草丛对马鹿 (Cervus elaphus) 和羊 (Ovis aries) 使用不太偏好的矮灌木石南花 (Calluna vulgaris) 的影响。随着距草丛边缘距离的增加，石南花利用率急剧下降。草在当地景观中（1 km 以内）的比例对草-石南花边界以及距离草斑 5 m 以外的石南花利用具有显着的积极影响。优势草种对草斑边缘 50 厘米范围内的石南花利用率也有显着影响，其中，在地头草/羊茅斑块（最优选）周围的利用率大于以水松为主的斑块周围，而在莫利尼亚斑块周围的利用率最低。对石南花利用变化的最大贡献是在最小尺度上，并且方差分量随着空间尺度的增加而减少，使得无法仅根据大尺度参数（例如食草动物密度）来预测局部石南花利用（即在单个植物和觅食有蹄类动物的单个叮咬的规模上）。这些发现强调，植被与食草动物的相互作用局限于景观范围内，而这些热点正是植被动态的关键支点。
The boundaries between vegetation patches are focal points for dynamic interactions between plant communities, particularly in grazed ecosystems where vegetation types may differ in their acceptability to herbivores. Here we show that key vegetation resources attract herbivores, and the surrounding vegetation receives a higher impact than if it is associated with patches of less preferred vegetation (an example of apparent competition). We studied the influence of proximity to preferred grass patches on utilization of the less preferred dwarf shrub, heather (Calluna vulgaris) by red deer (Cervus elaphus) and sheep (Ovis aries) at a range of spatial scales in the Cairngorm Mountains of Scotland, UK. There was a sharp decline in heather utilization with increasing distance from the edges of grass patches. The proportion of grass in the local landscape (within 1 km) had a significant positive effect on heather utilization both at the grass–heather boundary and beyond 5 m from the grass patch. There was also a significant effect of dominant grass species on the utilization of heather within 50 cm of the grass-patch edge, with utilization around Agrostis/Festuca patches (most preferred) being greater than around Nardus-dominated patches, and lowest around patches of Molinia. The greatest contribution to variation in heather utilization was at the smallest scale, and variance components decreased as spatial scale increased, making it impossible to predict local heather utilization (i.e., at the scale of individual plants and of individual bites by foraging ungulates) from large-scale parameters alone, such as herbivore density. These findings emphasize that vegetation–herbivore interactions are localized within the landscape, and that it is these hot spots which are the key fulcrum for vegetation dynamics.