Habitat Associations and Community Structure of Birds in Shrubsteppe Environments
Habitat Associations and Community Structure of Birds in Shrubsteppe Environments
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DOI：
10.2307/2937305
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发表时间：
1981-02
影响因子：
6.1
通讯作者：
J. Wiens;J. Rotenberry
中科院分区：
文献类型：
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作者：
J. Wiens;J. Rotenberry
通过对北美大盆地西北部灌丛草原9个地点的14个样地连续3年的调查，研究了区域调查尺度下鸟类分布与丰度和栖息地特征的关系。双变量和多变量分析表明，没有大型鸟类种群在分布和丰度上存在相关性，物种对之间也几乎没有关联，这表明该系统中的鸟类种群在很大程度上是相互独立的。鸟类与生境地貌的双变量和多变量相关分析表明，在该灌丛系统中广泛分布的鸟类物种与生境特征的相关性较小，而分布较局部化的物种确实表现出生境亲缘关系，最显著的是与岩石露头的出现有关的一系列特征。主要分布和栖息地亲和力位于东部草原地区的鸟类种类与该灌丛地区的生境地貌特征相关性最大，随着植被盖度和身高的增加，鸟类的丰度增加，生境的水平异质性降低。然而，一些鸟类与我们测量的栖息地特征没有相关性，比较鸟类丰度变化与栖息地地貌特征变化的多元分析占鸟类丰度矩阵总变化的17%。然而，考虑到不同种类灌木的盖度，通常与鸟类数量的变化产生了更显著的相关性，特别是对于分布广泛的灌丛物种。不同调查地点的鸟类群落结构特征不同。布鲁氏麻雀是大多数地点数量最多的物种，其丰度的变化占总鸟类密度变化的86%。物种多样性与总密度呈负相关(可能是由于一个物种对密度的压倒性影响)，但与物种丰富度呈正相关。丰富度的变化反过来又是几个当地分布的灌丛或草原物种丰富度变化的结果。丰富度随生境水平异质性和总体植被稀疏度的增加而降低，随生境结构多样性的增加而增加。鸟类群落生物量的变化在很大程度上是广布或外围物种丰富度的函数；对物种丰富度贡献如此大的当地灌丛形式中，没有一种与总生物量变化相关。我们将这些区域尺度的分析结果与大陆尺度的研究结果进行了比较，该研究包括了从灌木草原到高草草原的栖息地范围。鸟类在两个空间尺度上表现出不同的栖息地相关性。特别是在大陆分析中，特征灌丛物种与生境地貌特征表现出很强的相关性，但在区域研究中，这种相关性普遍缺乏，这些鸟类反而与各种灌木物种的盖度相关。这表明，在大范围、栖息地之间的分析水平上，这些鸟类可能会对一般栖息地配置的某些元素做出反应，但它们的栖息地内反应可能与栖息地植物群的细节更密切相关。这些结果使鸟类群落/栖息地关系的研究复杂化：完全了解生态格局显然需要植被区系和地貌的知识；鸟类对栖息地特征的反应以及重要的栖息地特征可能在不同的空间分辨率尺度上有所不同。然而，在考虑栖息地特征后，在这两个空间尺度上，鸟类丰度变化的很大一部分仍然无法解释。因此，出现的显著相关性相对较少，增加了那些被揭示的很可能是虚假的可能性，并强化了这样一种观点，即竞争等生物相互作用可能在构建这些群落方面发挥次要作用。
We studied the relations between bird distribution and abundance and habitat characteristics at a regional scale of investigation, using surveys conducted over three consecutive years on 14 plots at nine locations in the shrubsteppe of the northwestern Great Basin of North America. Bivariate and multivariate analyses revealed no large suites of bird species that were correlated in their distribution and abundance, and few associations existed between pairs of species, suggesting that bird populations in this system vary largely independently of one another. Both bivariate and multivariate correlational analyses between birds and habitat physiognomy indicated that the bird species that were widely distributed in this shrubsteppe system had few significant associations with habitat features, while species with more localized distributions did exhibit habitat affinities, most notably with a suite of characters associated with the occurrence of rocky outcrops. Bird species whose primary distributions and habitat affinities lie in grassland regions to the east demonstrated the greatest degree of correlation with features of habitat physiognomy in this shrubsteppe region, increasing in abundance as vegetation coverage and stature increased and horizontal heterogeneity of habitats decreased. Some bird species, however, exhibited no correlations with the habitat features we measured, and multivariate analyses comparing variation in the bird abundances with variation in features of habitat physiognomy accounted for <17% of the overall variation in the bird abundance matrix. Consideration of coverages of different species of shrubs, however, generally produced more significant correlations with variations in bird abundances, especially for the widespread shrubsteppe species. Attributes of avian community structure varied among the locations surveyed. Variations in the abundance of Brewer's Sparrows, the most abundant species at most sites, accounted for 86% of the variation in total avian density. Species diversity was negatively correlated with total density (presumably because of the overwhelming influence of one species on density) but positively correlated with species richness. Richness variations, in turn, were a consequence of variations in the abundances of several locally distributed shrubsteppe species or grassland species. Richness decreased with increasing horizontal habitat heterogeneity and general vegetation sparseness, but increased with increasing structural diversity of the habitat. Variations in avian community biomass were largely a function of abundances of the widespread or peripheral species; none of the local shrubsteppe forms that contributed so much to species richness was correlated with total biomass variations. We compare the findings of these regional—scale analyses with those of a continental—scale study that included a habitat spectrum ranging from shrubsteppe through tallgrass prairies. Bird species exhibited different patterns of habitat correlations on the two spatial scales. In particular, the characteristic shrubsteppe species showed strong correlations with features of habitat physiognomy in the continental analysis, but in the regional study such associations were generally lacking and these birds instead were correlated with the coverages of various shrub species. This suggests that at a large scale, between—habitat level of analysis these birds may respond to some elements of general habitat configuration, but their within—habitat responses may be more strongly associated with details of habitat floristics. These results complicate studies of avian community/habitat relationships: complete understanding of ecological patterns apparently requires knowledge of vegetational floristics as well as physiognomy; the response of birds to habitat characteristics, and the habitat features that are important, may differ at different scales of spatial resolution. At both spatial scales, however, a substantial portion of the variation in avian abundance remains unexplained after consideration of habitat features. Relatively few significant correlations thus emerge, increasing the probability that those that are revealed may well be spurious, and reinforcing the view that biotic interactions such as competition probably play a minor role in structuring these communities.