Local Dynamics of Bird Assemblages in Small Forest Habitat Islands in Australia and North America
Local Dynamics of Bird Assemblages in Small Forest Habitat Islands in Australia and North America
复制标题
澳大利亚和北美小森林栖息地岛屿鸟类群落的局部动态
作者：
R. Howe
小孤立的森林补丁（0.1-7公顷）在新南威尔士州东部和威斯康星州南部定期调查至少1年之间的1977年和1981年。这两个地区的森林和林地在过去世纪被大规模砍伐。本文分析了森林生境的破碎化如何影响当地鸟类群落的组成和动态。森林岛屿中的物种进行了比较，相当于“控制地块”附近的一个大的，连续的森林的边缘。显然，连续带的破坏不仅影响森林内部的鸟类，而且也影响那些发生在森林边缘沿着或附近的鸟类。新南威尔士州和威斯康星州的鸟类在森林岛屿之间表现出共同的分布模式，尽管在分类关系、季节性和栖息地方面存在相当大的差异。(1)面积是岛屿和对照区物种丰富度的最佳预测因子。其他生境变量（隔离除外）是相对统一的网站之间，并没有一贯的物种数量的变化。(2)森林岛屿中常见的物种也往往是常见的大型附近的森林，但森林岛屿中的鸟类组合有统计学差异，从森林控制地块。(3)在森林岛屿的物种组合一般是更可预测的空间和时间比当地的组合在较大的森林。虽然瞬态或定期游客通常观察到在森林岛屿，非居民物种发生更频繁的控制地块。鸟类栖息地破碎化改变了原生森林鸟类群落的时空动态.反过来，这可能有利于某些物种，而使其他物种处于不利地位。森林岛屿和控制地块的物种组合之间的差异最明显的是在威斯康星州。森林或林缘物种的数量在威斯康星州森林岛屿比相应的控制地块低得多。孤立的森林岛屿与物种丰富度呈负相关，只有在威斯康星州。新南威尔士州森林破碎化的长期影响可能尚未实现，因为相对较大面积的森林仍然靠近现有的生境岛屿。
Small isolated forest patches (0.1-7 ha) in eastern New South Wales and southern Wisconsin were surveyed regularly for at least 1 yr between 1977 and 1981. Forests and woodlands in both regions have been cleared extensively during the past century. This analysis examines how fragmentation of forest habitat has affected composition and dynamics of local bird assemblages. Species in forest islands are compared with those in equivalent "control plots" near the edge of a large, continuous forest. Disruption of continuous tracts apparently affects not only birds of the forest interior, but also those occurring along or near the edge. Birds in New South Wales and Wisconsin show common patterns of distribution among forest islands, despite considerable differences in taxonomic relationships, seasonality, and habitat. (1) Area was the best predictor of species richness in islands and control plots. Other habitat variables (except isolation) were relatively uniform among sites and did not contribute consistently to variation in numbers of species. (2) Species common in forest islands also tended to be common in large nearby forests, but bird assemblages in forest islands were statistically different from those in forest control plots. (3) Species assemblages in forest islands generally were more predictable over space and time than were local assemblages in larger forests. Although transients or regular visitors commonly were observed in forest islands, nonresident species occurred even more frequently in control plots. Ap- parently habitat fragmentation alters the spatial and temporal dynamics of native forest bird com- munities. This, in turn, may favor some species and leave others at a disadvantage. Differences between species assemblages of forest islands and control plots were most pronounced in Wisconsin. Numbers of forest or forest edge species were much lower in Wisconsin forest islands than in corresponding control plots. Isolation of forest islands was associated negatively with species richness only in Wisconsin. Long-term effects of forest fragmentation in New South Wales might not yet be realized, because relatively large areas of forest remain near existing habitat islands.