Interactions between marsh plant species vary in direction and strength depending on environmental and consumer context
Interactions between marsh plant species vary in direction and strength depending on environmental and consumer context
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DOI：
10.1111/j.1365-2745.2007.01314.x
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发表时间：
2007-11
影响因子：
5.5
通讯作者：
C. Crain
中科院分区：
文献类型：
--
作者：
C. Crain
物种之间的积极相互作用预计在环境梯度的极端末端会增加重要性，在那里，邻居在恶劣环境中提供压力改善，或在良性环境中提供消费者的联合防御。然而，这个模型从未在消费者的单一环境梯度下对同一物种进行过测试。从咸水到潮汐淡水的景观尺度上，河口沼泽植被经历了很强的物理（盐度）压力梯度，但在强地形控制下的这些系统中很少考虑消费者效应。在这里，我提供的证据表明，小型哺乳动物是美国新英格兰沿海沼泽的重要消费者，在所有盐碱度高的沼泽中，它们通过保持开放的跑道来减少植被覆盖，但在盐碱度低的沼泽中，它们对植物物种的自上而下的影响增加。在不同的环境胁迫（盐沼、半咸水和低盐沼泽）和消费者压力（有和没有哺乳动物食草）条件下，对有或没有邻近基质草的样地进行的幼苗移栽试验表明，盐沼中幼苗与基质的相互作用是积极的，在半咸水沼泽中是消极的，而在低盐沼泽中则因物种而异。虽然竞争相互作用在低盐沼泽中占主导地位，但在消费者存在的情况下，一个移植物种的负面邻居相互作用较少，这表明由于联想防御，相互作用的积极成分正在增加。4的合成。这些结果表明，在恶劣的物理环境中，积极的相互作用可能比在有压力的生物环境中更一致，因为消费者的压力可能因物种和空间和时间而异，而环境压力通常更持续地施加。结果表明，同一物种之间的相互作用可能会根据环境和消费者背景而发生方向逆转或强度变化，这提醒人们，在日益变化的气候和消费者环境中，单点研究可能无法准确预测群落变化。
1 Positive interactions between species are predicted to increase in importance at extreme ends of environmental gradients where neighbours offer either stress amelioration in harsh environments or associational defence from consumers in benign environments. However, this model has never been tested with the same species across a single environmental gradient in light of consumers. 2 Estuarine marsh vegetation, at a landscape‐scale from salt to tidal freshwater, experiences strong gradients in physical (salinity) stress, but consumer effects are rarely considered in these systems under strong edaphic control. Here, I present evidence that small mammals are important consumers in coastal marshes of New England, USA, reducing vegetative cover by maintaining open runways in all salinity marshes, but whose top‐down influence on plant species increases in less saline marshes. 3 A seedling transplant experiment into plots with and without neighbouring matrix grasses, and with varying environmental stress (salt, brackish and oligohaline marshes) and consumer pressure (with and without mammal herbivory), showed that seedling–matrix interactions were positive in salt marshes, negative in brackish marshes, and varied in oligohaline marshes depending on species. While competitive interactions predominated in oligohaline marshes, one transplant species had less negative neighbour interactions in the presence of consumers, indicating an increasing positive component of the interaction due to associational defence. 4 Synthesis. These results suggest that positive interactions may occur more consistently in harsh physical environments than in stressful biotic environments because consumer pressure is likely to vary by species and over space and time, while environmental stress is generally applied more constantly. Results show that interactions between the same species can reverse in direction or change in strength depending on environmental and consumer context, cautioning that single‐site studies may not accurately predict community changes in increasingly altered climatic and consumer environments.