Strong Responses of Subarctic Plant Communities to Long-Term Reindeer Feces Manipulation
Strong Responses of Subarctic Plant Communities to Long-Term Reindeer Feces Manipulation
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DOI：
10.1007/s10021-015-9856-y
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发表时间：
2015-08-01
期刊：
影响因子：
3.7
通讯作者：
Olofsson, Johan
中科院分区：
文献类型：
--
作者：
Barthelemy, Helene;Stark, Sari;Olofsson, Johan
粪便沉积是食草动物影响土壤养分循环和植物生产的重要机制，但由于缺乏实验证据，对其在植物生产和群落结构中的重要性的认识仍处于初级阶段。在两种不同养分有效性的冻土带植被类型上进行了为期7年的驯鹿粪便处理试验，分析了处理对植物群落组成和土壤养分有效性的影响。尽管粪便营养相当贫乏，但粪便处理对营养贫乏的荒原和营养丰富的草甸都有很强的影响。以高密度加粪效果最强，两个群落维管植物总生产力和谷粒素含量均有显著提高。驯鹿粪便的自然沉降增加一倍，促进了初生产量和落叶灌木的生长。相比之下，粪便的清除只减少了禾本科植物和落叶灌木的产量。虽然在营养丰富的草甸中对粪便添加的响应更快，但7年后在营养贫乏的荒原中更为明显。粪便处理对土壤养分有效性的影响较低，且呈暂时性变化。我们的研究为草食动物数量充足时，草食动物粪便在调节初级生产中的核心作用提供了实验证据。然而，粪便的沉积本身并不会引起植被的剧烈变化；为了将贫瘠的荒地变成多产的草为主的状态，可能还需要食草动物的践踏和放牧。
Deposition of feces is a key mechanism by which herbivores influence soil nutrient cycling and plant production, but the knowledge about its importance for plant production and community structure is still rudimental since experimental evidence is scarce. We thus performed a 7-year long reindeer feces manipulation experiment in two tundra vegetation types with contrasting nutrient availability and analyzed effects on plant community composition and soil nutrient availability. Despite feces being fairly nutrient poor, feces manipulation had strong effect on both the nutrient-poor heath and the nutrient-rich meadow. The strongest effect was detected when feces were added at high density, with a substantial increase in total vascular plant productivity and graminoids in the two communities. Doubling natural deposition of reindeer feces enhanced primary production and the growth of deciduous shrubs in the heath. By contrast, removal of feces decreased only the production of graminoids and deciduous shrubs in the heath. Although the response to feces addition was faster in the nutrient-rich meadow, after 7 years it was more pronounced in the nutrient-poor heath. The effect of feces manipulation on soil nutrient availability was low and temporarily variable. Our study provides experimental evidence for a central role of herbivore feces in regulating primary production when herbivores are abundant enough. Deposition of feces alone does, however, not cause dramatic vegetation shifts; to drive unproductive heath to a productive grass dominated state, herbivore trampling, and grazing are probably also needed.