Department of Conservation Ecology and Entomology and Centre for Invasion Biology, University of Stellenbosch, Private Bag X1, Matieland, 7602, South Africa.
Conserv Biol. 2010 Feb;24(1):267-77. doi: 10.1111/j.1523-1739.2009.01427.x.
Because dragonflies are very sensitive to alien trees, we assessed their response to large-scale restoration of riparian corridors. We compared three types of disturbance regime--alien invaded, cleared of alien vegetation, and natural vegetation (control)--and recorded data on 22 environmental variables. The most significant variables in determining dragonfly assemblages were percentage of bank cover and tree canopy cover, which indicates the importance of vegetation architecture for these dragonflies. This finding suggests that it is important to restore appropriate marginal vegetation and sunlight conditions. Recovery of dragonfly assemblages after the clearing of alien trees was substantial. Species richness and abundance at restored sites matched those at control sites. Dragonfly assemblage patterns reflected vegetation succession. Thus, initially eurytopic, widespread species were the main beneficiaries of the removal of alien trees, and stenotopic, endemic species appeared after indigenous vegetation recovered over time. Important indicator species were the two national endemics (Allocnemis leucosticta and Pseudagrion furcigerum), which, along with vegetation type, can be used to monitor return of overall integrity of riparian ecology and to make management decisions. Endemic species as a whole responded positively to restoration, which suggests that indigenous vegetation recovery has major benefits for irreplaceable and widespread generalist species.
由于蜻蜓对外来树木非常敏感，我们评估了它们对大规模河岸林恢复的反应。我们比较了三种干扰模式——外来入侵、清除外来植被和自然植被（对照），并记录了 22 个环境变量的数据。决定蜻蜓类群的最重要变量是河岸植被覆盖率和树冠覆盖率，这表明植被结构对这些蜻蜓的重要性。这一发现表明，恢复适当的边缘植被和光照条件非常重要。清除外来树木后，蜻蜓类群的恢复幅度很大。恢复地点的物种丰富度和丰度与对照地点相当。蜻蜓类群的模式反映了植被演替。因此，最初广泛分布的广域种是清除外来树木的主要受益者，而随着时间的推移，本地植被恢复后，特化的特有种出现了。重要的指示物种是两种国家特有种（Allocnemis leucosticta 和 Pseudagrion furcigerum），它们与植被类型一起可用于监测河岸生态整体完整性的恢复，并做出管理决策。特有种整体上对外来树木的清除做出了积极的响应，这表明本地植被的恢复对不可替代的广泛分布的一般性物种具有重大益处。
