Influences of chronic and current season grazing by collared pikas on above-ground biomass and species richness in subarctic alpine meadows
Influences of chronic and current season grazing by collared pikas on above-ground biomass and species richness in subarctic alpine meadows
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DOI：
10.1007/s00442-005-0127-z
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发表时间：
2005-09-01
期刊：
影响因子：
2.7
通讯作者：
Hik, DS
中科院分区：
文献类型：
--
作者：
McIntire, EJB;Hik, DS
为了研究不同放牧水平对高寒冻土带鼠兔地上生物量（AGB）和物种丰富度（SR）的影响，研究了一种小型中心觅食鼠兔建立的高山草食梯度。研究了季节内（4个采样期）、多季节（3个夏季）和长期动态（从相对于鼠兔干草群的植被空间位置推断）的影响。在放牧梯度上，我们发现了支持和反对草食双相、增加或减少草食反应的假设，无论是在AGB还是sr方面。我们的结果表明，植物-草食的可预测性仍然很弱。为了进一步研究草食对鼠兔的影响，我们实验性地在离鼠兔所占据的土场边缘越来越远的地方放置了网格遮挡物，以清除鼠兔。与距距足距6英寸的高度放牧区域的对照区相比，连续第二年排除草食动物后，AGB增加了125%。与那些没有放牧历史的鼠兔相比，以前被鼠兔放牧过的草地斑块的AGB最高，但这种反应仅在草食释放后的两个季节后观察到。这些结果表明，在生产力较低的地区，以长寿命多年生植物为主的生态系统中，多年生长测量尤其相关。偶尔出现的草食动物空缺可能会在当地短期释放鼠兔的放牧，从而有助于维持高产、美味的植被。
We studied an alpine herbivory gradient established by collared pikas, a small central place foraging lagomorph, to examine the effects of multiple grazing levels on above-ground live biomass (AGB) and species richness (SR) in alpine tundra. The effects of within-season (four sampling periods), multi-season (across three summers) and longer-term dynamics (inferred from spatial location of vegetation with respect to pika haypiles) were examined. Along the grazing gradient, we found support for and against hypotheses that propose biphasic, increasing, or decreasing responses to herbivory, both in terms of AGB and SR. Our results suggest that plant-herbivore predictability is still weak. To further examine the impact of herbivory, we experimentally removed pikas using mesh exclosures placed at increasing distance from the edge of talus occupied by pikas. AGB after the second consecutive year of herbivore exclusion increased by 125% compared to control plots in highly grazed areas adjacent to talus ( 6 in from talus. AGB was highest in meadow patches previously grazed by pikas compared to those with little grazing history, but this response was only observed after two seasons following release from herbivory. Grazed sites at distances of 1-6 m had the highest SR. These results indicate that multi-year measurements of growth are particularly relevant in ecosystems dominated by long-lived perennials in regions where productivity is low. Infrequent herbivore vacancies may provide local short-term release from pika grazing, thereby contributing to the persistence of productive, highly palatable vegetation.