Impact of simulated moose densities on abundance and richness of vegetation, herbivorous and predatory arthropods along a productivity gradient
Impact of simulated moose densities on abundance and richness of vegetation, herbivorous and predatory arthropods along a productivity gradient
复制标题
模拟驼鹿密度对沿生产力梯度的植被、草食性和掠食性节肢动物的丰度和丰富度的影响
DOI：
--
复制
发表时间：
2008
期刊：
影响因子：
--
通讯作者：
J. Pastor
中科院分区：
文献类型：
--
作者：
Otso Suominen;I. Persson;K. Danell;R. Bergström;J. Pastor
大型食草动物通过选择性取食、排便、践踏等方式影响植被结构和物种组成，影响生态系统的物质和能量流动。这些变化具有间接影响其他营养水平的巨大潜力，但其机制尚不清楚。通过实验模拟4种不同驼鹿密度，研究了驼鹿在不同种群密度下对生境生产力梯度的影响。在这里，我们表明驼鹿可以通过复杂的直接和间接影响来影响瑞典北方针叶林中三个营养水平的丰富度和丰度，但根据营养水平的物理栖息地或食物资源如何受到影响，其影响方式在质量上有所不同。植被丰富度随驼鹿密度的增加呈驼峰型（单峰型）响应。凋落叶的产生随着觅食的增加而减少，这反过来又降低了蜘蛛飞行猎物的丰度。结果表明，蜘蛛的丰度和丰富度呈单调下降趋势。蜘蛛丰富度对驼鹿密度的响应进一步受到场地生产力的制约，在生产性场地为正响应，在非生产性场地为负响应。相比之下，食草半翅目动物没有受到驼鹿的影响，很可能是因为它们的食物植物的丰度没有受到影响。即使经过几年的处理，最高的模拟驼鹿密度也会对所有变量产生影响，并且可以被认为是过剩的。我们还表明，低或中等驼鹿密度的影响可能对一些受高密度影响的生物产生积极影响。草食动物种群密度水平对群落的影响还取决于场地因素，如生产力。
Large herbivores can affect vegetation structure and species composition as well as material and energy flows in the ecosystem through their selective feeding, defecation, urination and trampling. These changes have a large potential to indirectly affect other trophic levels, but the mechanisms are poorly known. We studied the impacts of moose Alces alces browsing along a gradient of site productivity by experimentally simulating four different moose densities. Here we show that moose can affect the richness and abundance of three trophic levels in Swedish boreal forests through complex direct and indirect impacts, but in qualitatively different ways depending on how the physical habitat or food resources of a trophic level are affected. Vegetation richness had a hump-shaped (unimodal) response to increased moose density. Leaf litter production decreased when browsing increased, which in turn depressed the abundance of flying prey for spiders. Consequently, spider abundance and richness declined monotonically. The responses of spider richness to moose density were further conditioned by site productivity: the response was positive at productive and negative at unproductive sites. In contrast, herbivorous Hemiptera were not affected by moose, most likely because the abundance of their food plants was not affected. The highest simulated moose density had an impact on all variables responding to moose even after a few years of treatment and can be considered as overabundance. We also show that the impacts of low or moderate moose density can be positive to some of the organisms negatively affected by high density. The level of herbivore population density that leads to substantial community impacts also depends on site factors, such as productivity.