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首页> 外文会议> >Large-scale Manipulations Reveal That Top-downand Bottom-up Controls Interact To Alter Habitat utilization By Saltmarsh Fauna
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Large-scale Manipulations Reveal That Top-downand Bottom-up Controls Interact To Alter Habitat utilization By Saltmarsh Fauna

机译：大型操作揭示了自上而下和自下而上的控件相互作用以改变Saltmarsh动物区系的生境利用

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We used ecosystem-wide predator removal and nutrient enrichment to examine top-down and bottom-up forces on saltmarsh fauna. We reduced the killifish Fundulus heteroclitus by ～60%, which elicited significant increases (2 to 4×) in hydrobiid snails Hydrobia spp., suggesting top-down control. The talitrid amphipod Uhlorchestia spartinophila was the most abundant species of epifauna in the creek-bank Spartina alterniflora habitat. Our elevated water column nutrients (～70 μmol 1~(-1), ～10× background) and predator reduction treatments alone both yielded nonsignificant increases in amphipod abundance, suggesting weak top-down and bottom-up control over this species. However, treatments interacted antagonistically in this habitat such that amphipod abundances were lower than would be expected by an additive response to both treatments. We found corresponding amphipod abundance increases in the adjoining creek-wall habitat, suggesting that amphipods move under the influence of our treatments from the marsh edge onto the creek wall, possibly as a result of an increased incidence of a parasitic (i.e. trematode Levinseniella sp.) infection. Coincident to increased amphipods on creek walls, semipalmated sandpipers Calidris pusilla, amphipod predators, increasingly foraged in creek channels in combined treatments (～30× higher than controls based on unreplicated creek systems). Our results suggest that top-down and bottom-up effects may at times be difficult to detect in small, single-factor studies because of inter-habitat movements of target species and redundant predation. Because the effects of stressors may not be limited to one part of the landscape even for small, motile fauna, landscape-level studies may generally be needed to capture responses to anthropogenic activities.
机译：我们使用了整个生态系统中的捕食者去除和营养物质富集的方法来研究盐沼动物群的自上而下和自下而上的作用力。我们减少了约60％的致死鱼类Fundulus heteroclitus，这引起了水生螺Hydro Hydrobia spp。的显着增加（2至4倍），表明自上而下的控制。在河岸互花米草生境中，滑石纲两栖纲Uhlorchestia spartinophila是表生动物中最丰富的物种。单独使用我们升高的水柱养分（〜70μmol1〜（-1），〜10x背景）和捕食者减少处理，两栖动物的丰度均无明显增加，表明该物种自上而下和自下而上的控制力较弱。但是，处理在该生境中产生拮抗作用，因此两栖动物的丰度低于对两种处理的加和反应所预期的水平。我们发现相邻的小溪壁栖息地中的两栖类动物数量相应增加，这表明两栖类动物在我们的处理作用下从沼泽边缘移动到小溪壁上，这可能是由于寄生虫（即吸虫Levinseniella sp。 ） 感染。巧合的是，在小溪壁上的两栖动物数量增加，半棕榈sand，卡利德里斯（Cadriss pusilla），两栖动物捕食者在小溪渠道中的联合处理中觅食的数量越来越多（比基于无复制小溪系统的对照高约30倍）。我们的研究结果表明，由于目标物种的栖息地之间的运动和多余的捕食，有时在小型单因素研究中有时很难检测到自上而下和自下而上的影响。因为压力源的影响可能不仅仅局限于景观的一部分，即使对于小型，活动的动物也是如此，因此通常可能需要进行景观层面的研究来捕捉对人为活动的响应。

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