Edge-mediated compositional and functional decay of tree assemblages in Amazonian forest islands after 26 years of isolation
Edge-mediated compositional and functional decay of tree assemblages in Amazonian forest islands after 26 years of isolation
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DOI：
10.1111/1365-2745.12371
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发表时间：
2015-03-01
影响因子：
5.5
通讯作者：
Peres, Carlos A.
中科院分区：
文献类型：
--
作者：
Benchimol, Maira;Peres, Carlos A.
大型水电站大坝上游形成的岛屿是评估栖息地破碎化对生物多样性影响的绝佳实验景观。我们研究了样地、斑块和植被尺度变量对34个森林岛屿植物多样性格局的影响，这些岛屿自巴西亚马逊河流域中部4437 km（2）的巴尔比纳水电水库建成以来经历了26年的隔离。此外，在邻近大陆地区的三个未受干扰的连续森林网站也在一个可比的海拔梯度采样。我们确定了所有活的树木10厘米直径在物种水平上的87个四分之一公顷的森林地块内，并进行了全面的汇编每个树种的功能属性。然后，我们研究了种-面积关系（SAR）和斑块和斑块尺度指标对树木组合异质性模式的额外影响，无论是在分类和功能多样性方面。尽管有一个明确的积极的SAR，边缘介导的森林干扰是岛屿内的物种组成和丰富的单一最重要的驱动程序。我们的研究结果表明，岛屿地块内的非随机植物区系过渡遵循可预测的模式，不同的生活史特征惩罚或奖励当地的持久性不同的功能群。到边缘的距离介导的概率树木死亡率引起的意外收获和偶发性的表面火灾，显然导致更快的物种周转和单向变化的行业协会结构内的小岛屿，轻树木繁茂的快速增长的先驱者在很大程度上取代了树木繁茂的物种的古老的生长flora. Synthesis。同时26年后隔离的历史，我们解开的影响，栖息地丧失和岛屿化的树木组合在一个大的亚马逊河流域真正的森林岛屿，大小不等，共享一个统一的开放水域矩阵。面积效应是通过对边缘效应的反应来表达的，较小岛屿上的树木更容易受到与边缘有关的表面火灾和风的影响。此外，森林边缘效应可以是一个强大的驱动程序的非随机植物区系过渡的巴尔比纳群岛内的岛屿通过一个过程中的快速先锋增殖，极大地影响了岛屿树木群落的分类和功能组成。最后，我们的研究结果表明，由水电大坝引起的森林破碎化的不利影响是相当强的嵌入在陆地植被基质中的森林斑块。
Islands formed upstream of mega hydroelectric dams are excellent experimental landscapes to assess the impacts of habitat fragmentation on biodiversity. We examined the effects of plot-, patch- and landscape-scale variables on the patterns of floristic diversity across 34 forest islands that had experienced 26years of isolation since the creation of the 4437km(2) Balbina Hydroelectric Reservoir of central Brazilian Amazonia. In addition, three undisturbed continuous forest sites in neighbouring mainland areas were also sampled across a comparable elevational gradient. We identified all live trees 10cm DBH at species level within a total of 87 quarter-hectare forest plots and conducted a comprehensive compilation of functional attributes of each tree species. We then examined species-area relationships (SARs) and the additional effects of patch and landscape-scale metrics on patterns of tree assemblage heterogeneity, both in terms of taxonomic and functional diversity. Despite a clearly positive SAR, edge-mediated forest disturbance was the single most important driver of species composition and abundance within islands. Our results suggest that non-random floristic transitions within island plots followed a predictable pattern, with different life-history traits either penalizing or rewarding local persistence of different functional groups. Distance to edges mediated the probability of tree mortality induced by windfalls and episodic surface fires, clearly resulting in faster species turnover and unidirectional changes in guild structure within small islands where light-wooded fast-growing pioneers largely replaced heavy-wooded species of the old-growth flora.Synthesis. Following a simultaneous 26-year post-isolation history, we disentangle the effects of habitat loss and insularization on tree assemblages within a large set of Amazonian true' forest islands, of variable sizes, sharing a uniform open-water matrix. Area effects are expressed via a response to edge effects, with trees in smaller islands being more vulnerable to edge-related surface fires and wind-throws. Additionally, forest edge effects can be a powerful driver of non-random floristic transitions across islands within the Balbina archipelago via a process of rapid pioneer proliferation, drastically affecting both the taxonomic and functional composition of insular tree communities. Finally, our results indicate that detrimental effects of forest fragmentation induced by hydroelectric dams are considerably stronger than those of forest patches embedded within a terrestrial vegetation matrix.