Effects of fragmentation and trampling on carabid beetle assemblages in urban woodlands in Helsinki, Finland
Effects of fragmentation and trampling on carabid beetle assemblages in urban woodlands in Helsinki, Finland
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DOI：
10.1007/s11252-006-5526-3
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发表时间：
2006-01-01
期刊：
影响因子：
2.9
通讯作者：
O'Hara, Bob
中科院分区：
文献类型：
--
作者：
Lehvavirta, Susanna;Kotze, D. Johan;O'Hara, Bob
我们研究了碎片化(边缘效应和斑块大小)和践踏(路径覆盖)对芬兰赫尔辛基城市林地斑块中步甲群落的影响。我们预计(1)开阔的栖息地和多面手物种将受益，森林物种将因林地碎片化程度增加而受损，(2)大多数步行动物物种将对更高水平的践踏做出负面反应。共采集步甲类37种2088只。聚类分析表明，大片林地斑块内部具有低或中等路径盖度的样地有别于其他样地。其他地点没有有意义的集群，这表明随着人类影响的增加，步甲动物区系的多样性增加。随着林缘距离林地内部距离的增加和斑块大小的增加，所有物种和生态种组均减少。这种格局符合我们对开阔栖息地和多面手物种的期望，但与我们对森林物种的期望相反。这些令人惊讶的结果的原因可能是：(1)我们收集的物种不是真正的森林内部物种，(2)城市林地边缘是许多森林步行动物的最佳栖息地，或(3)边缘实际上是次优的，高捕获量只是反映了甲虫离开边缘的活动增加。践踏并没有像假设的那样对步行动物产生全面的负面影响。与潮湿森林栖息地相关的物种如预测的那样做出反应：它们的数量随着路径覆盖率的增加而减少。此外，开放栖息地物种随着路径覆盖度的增加而减少，但比我们预测的更直接。通过从分析中删除高度被践踏的站点，模型精化表明我们的高度被践踏的数据可能太稀缺：没有这些站点的结果更符合我们的预测，而不是完整的数据集。
We studied the effects of fragmentation (edge effects and patch size) and trampling (path cover) on carabid beetle assemblages in urban woodland patches in Helsinki, Finland. We expected that (1) open habitat and generalist species would benefit and forest species would suffer from increased woodland fragmentation, and (2) most carabid species would respond negatively to increased levels of trampling. A total of 2088 carabid individuals representing 37 species were collected. A cluster analysis distinguished sites in the interior of large woodland patches, with low or moderate path cover, from the other sites. The other sites did not cluster meaningfully, suggesting increased variation in the carabid fauna with increasing human impact. All species and ecological species-groups decreased with increasing distance from the edge toward the woodland interior and with increasing patch size. This pattern is in accordance with our expectation for open habitat and generalist species but opposite to what we expected for forest species. The reason for these surprising results may be that (1) the species we collected are not true forest interior species, (2) urban woodland edges are optimal habitats for many forest carabids, or (3) edges are actually suboptimal, and high catches simply reflect increased activity of beetles moving away from the edge. Trampling did not have an overall negative effect on carabids as hypothesized. Species associated with moist forest habitat responded as predicted: they decreased in abundance with increasing path cover. Furthermore, open habitat species decreased with increasing path cover but more straight forward than we had predicted. Model elaboration, by dropping the highly trampled sites from the analyses, suggested that our data of high trampling may be too scarce: the results without these sites were more in accordance with our predictions than with the full dataset.