Clarke Peter J
Botany, University of New England, Armidale, NSW 2351, Australia.
Oecologia. 2002 Aug;132(4):582-591. doi: 10.1007/s00442-002-0962-0. Epub 2002 Aug 1.
Rock outcrops are landscape features that may form habitat islands in a matrix of more widespread vegetation. The patterns of floristics, reproduction, gender, life span, growth forms, and fire response traits were compared between rock outcrops and matrix sclerophyll vegetation to test for insularity in taxon composition and functional traits. The outcrops and matrix had similar reproduction, gender, life span, and growth form traits, being dominated by co-sexual sclerophyll shrubs. The outcrops, however, were dissimilar in species composition and functional traits forming an archipelago of habitat islands in a forest matrix. Rank abundance curves were less even on rock outcrops than in adjacent forests, being dominated by shrubs that were killed by fire (obligate seeders). The ratio of shrubs killed by fire (obligate seeders) to resprouters was 70:30 on the outcrops compared with 38:62 in the matrix. Evidence for functional convergence in fire response traits comes from 27 genera, in 17 families, which have congeners in each habitat. Most shrub congeners on or near rocky outcrops were killed by fire whereas related taxa in the forests resprout after fire. Functional convergence can be related to disturbance frequency and/or differences in regeneration niche among habitats. A resprouting response appears to be related to more frequent fires in the matrix as outcrops experience fires less often. The dominance of obligate seeding shrubs on high rainfall outcrops may also be related to better resources in an environment where allocation to growth rather than storage could be advantageous. In drier and shadier habitats, however, resprouting may be promoted over seedling recruitment as the risks of recruitment failure are higher.
岩石露头是一种景观特征，可能在更广泛的植被基质中形成栖息地岛屿。为了测试分类群组成和功能性状的岛屿性，我们比较了岩石露头和基质硬叶植被之间的植物区系、繁殖、性别、寿命、生长形式和火灾响应性状的模式。露头和基质具有相似的繁殖、性别、寿命和生长形式性状，以雌雄同体的硬叶灌木为主。然而，露头在物种组成和功能性状上有所不同，在森林基质中形成了一个栖息地岛屿群岛。岩石露头上的秩多度曲线比相邻森林中的更不均匀，以被火烧死的灌木（专性种子植物）为主。露头上被火烧死的灌木（专性种子植物）与萌生植物的比例为70:30，而基质中的这一比例为38:62。火灾响应性状功能趋同的证据来自17个科的27个属，这些属在每个栖息地都有同属植物。岩石露头或其附近的大多数灌木同属植物被火烧死，而森林中的相关分类群在火灾后会重新萌生。功能趋同可能与干扰频率和/或不同栖息地再生生态位的差异有关。由于露头遭遇火灾的频率较低，萌生响应似乎与基质中更频繁的火灾有关。在高降雨量的露头上，专性种子灌木的优势也可能与资源更好有关，在这种环境中，分配给生长而非储存可能更有利。然而，在更干燥和更阴暗的栖息地，由于招募失败的风险更高，可能会促进萌生而非幼苗招募。
