Plant-herbivore interactions in Alaskan arctic tundra change with soil nutrient availability
Plant-herbivore interactions in Alaskan arctic tundra change with soil nutrient availability
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DOI：
10.1111/j.0030-1299.2007.15449.x
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发表时间：
2007-03-01
期刊：
影响因子：
3.4
通讯作者：
Johnson, David R.
中科院分区：
文献类型：
--
作者：
Gough, Laura;Ramsey, Elizabeth A.;Johnson, David R.
在营养有限的系统中，如北极苔原，食草动物被认为在控制植物生长方面起着次要的作用，这仅仅是因为它们的数量相对较少。然而，理论预测，随着净初级生产力（NPP）的增加，因为更多的营养物质或能量的投入，草食动物可能对植物生长产生更大的影响。这一预测尚未在北极苔原气候变暖的背景下进行测试，这可能会增加土壤养分的可用性，从而增加NPP。我们研究了一个长期的实验，排除小型和大型哺乳动物食草动物和增加土壤养分在两个北极阿拉斯加苔原社区：干燥的石楠（DH）和潮湿的酸性草丛（MAT）。在第九年的操作，我们测量了三种植物的三种生长形式：丛生形成禾本科，根茎状禾本科，和矮落叶灌木，在每个社区的每周增长。所有的物种都在受精后生长得更好。在DH中，当植物受到草食动物的保护时，这种生长的增加被夸大了，证实了草食动物在营养增加的条件下对植物生长有负面影响，但在环境土壤条件下并不重要。然而，在MAT中，植食性的重要性不同的物种与受精。草丛形成莎草在MAT，Eriophorum vaginatum，生长得更好，开花更多时，围栏下的环境和修正的营养相比，植物暴露于草食动物。当哺乳动物存在时，这种物种在长期施肥的地块中丰度减少，我们的研究结果表明，除了竞争关系的变化之外，食草动物可能至少占了部分损失。虽然我们只关注这里的个别植物而不是整个群落，但我们的研究结果表明，在北极气候持续变暖的情况下，预计土壤养分会增加，食草动物可能会在影响几个丰富的苔原植物种群方面变得更加重要，不应被忽视。
Herbivores in nutrient-limited systems such as arctic tundra have been suggested to play a minor role in controlling plant growth simply because they are relatively few in number. However, theory predicts that as net primary productivity (NPP) increases because of greater inputs of nutrients or energy, herbivores may have greater effects on plant growth. This prediction has not been tested in the context of climate warming in arctic tundra, which may increase soil nutrient availability and thus NPP. We examined a long-term experiment that excluded small and large mammalian herbivores and increased soil nutrients in two arctic Alaskan tundra communities: dry heath (DH) and moist acidic tussock (MAT). In the ninth year of manipulations, we measured weekly growth of three plant species of three growth forms: tussock-forming graminoid, rhizomatous graminoid, and dwarf deciduous shrub, in each community. All species grew better when fertilized. In DH, this increase in growth was exaggerated when plants were protected from herbivores, confirming that herbivory had a negative effect on plant growth under increased nutrient conditions, but was unimportant under ambient soil conditions. However, in MAT, the importance of herbivory differed among species with fertilization. The tussock-forming sedge at MAT, Eriophorum vaginatum, grew better and flowered more when fenced under both ambient and amended nutrients compared to plants exposed to herbivores. This species decreases in abundance in long-term fertilized plots when mammals are present, and our results suggest that herbivory may be accounting for at least some of that loss, in addition to shifts in competitive relationships. Although we only focused on individual plants here rather than the entire community, our results suggest that under the increased soil nutrient conditions expected with continued climate warming in the Arctic, herbivores may become more important in affecting several abundant tundra plant populations, and should not be ignored.