The coupling between grazing and detritus food chains and the strength of trophic cascades across a gradient of nutrient enrichment
The coupling between grazing and detritus food chains and the strength of trophic cascades across a gradient of nutrient enrichment
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DOI：
10.1007/s10021-008-9174-8
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发表时间：
2008-09-01
期刊：
影响因子：
3.7
通讯作者：
Ripa, Joergen
中科院分区：
文献类型：
--
作者：
Attayde, Jose Luiz;Ripa, Joergen
构建了一个最小食物网模型，包括一个放牧和一个碎屑食物链耦合营养循环和通才食肉动物，以研究食肉动物的猎物偏好如何影响营养级联的强度在梯度的营养富集。平衡或平均丰度的每个食物网组件和食肉动物的影响，对较低的营养水平的幅度计算不同值的猎物的偏好和营养输入参数。我们的模型预测，营养丰富的食肉动物，自养生物和碎屑的平均丰度增加，但这种影响的大小是依赖于猎物的偏好项。另一方面，食草动物和非食草动物相对不受富集的影响，但强烈影响食肉动物的偏好。食肉动物对食草动物有负面影响，对自养生物和碎屑有正面影响，而对食草动物的影响既有正面也有负面。在高度偏好食草动物，食肉动物对食草动物有积极的影响，因为减少食草动物放牧增加碎屑可用性的积极影响超过了捕食的负面影响。在高度偏好食草动物的情况下，平衡向另一个方向改变。我们认为，在autochtonous初级生产是碎屑的主要来源的系统中，食草动物可以控制碎屑生产的速率，并对食草动物产生间接影响，这可能会反馈到食草动物通过他们共同的敌人的影响。这种正反馈可能是影响浅水湖泊中替代稳定状态恢复力的一种机制。
A minimal food web model was constructed comprising one grazing and one detritus food chain coupled by nutrient cycling and generalist carnivores to investigate how prey preference by carnivores may affect the strength of trophic cascades across a gradient of nutrient enrichment. The equilibrium or mean abundance of each food web component and the magnitude of the carnivore effect on lower trophic levels were calculated for different values of the prey preference and nutrient input parameters. Our model predicts that nutrient enrichment increases the mean abundances of carnivores, autotrophs and detritus, but the magnitude of this effect is dependent on the prey preference term. On the other hand, herbivores and detritivores are relatively unaffected by enrichment but are strongly affected by carnivore preference. Carnivores have a negative effect on herbivores and a positive effect on autotrophs and detritus, whereas the effect on detritivores can be both positive and negative. At high preference for herbivores, carnivores have a positive effect on detritivores, because the positive effect of increased detritus availability due to reduced herbivore grazing outweighs the negative effect of predation. At high preference for detritivores, the balance is changed in the other direction. We argue that in systems where authochtonous primary production is the major source of detritus, herbivores can control the rates of detritus production and have indirect effects on detritivores, which may feed back into effects on herbivores through their shared enemies. This positive feedback is probably one mechanism affecting the resilience of alternative stable states in shallow lakes.