Takada Mayura, Asada Masahiko, Miyashita Tadashi
Laboratory of Biodiversity Science, School of Agriculture and Life Sciences, The University of Tokyo, Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.
Natural History Museum and Institute, Chiba, Aoba-Cho, Chuou-ku, Chiba, 260-8682, Japan.
Oecologia. 2002 Nov;133(3):389-394. doi: 10.1007/s00442-002-1037-y. Epub 2002 Nov 1.
We demonstrated the effect of cross-habitat foraging by sika deer (Cervus nippon) on plant communities under the hypothesis that the intensity of herbivory on a plant community is changed by the presence of a preferable habitat for deer nearby. To investigate this landscape-level effect, we examined two types of forest understory; "adjacent site" was located near agricultural fields where deer prefer to forage, and "remote site" was far from fields. We compared plant community structures between adjacent and remote sites in areas with high deer densities, and found that plant species richness and plant coverage were significantly higher in adjacent sites than in remote sites. We hypothesized that this difference was caused by the lower intensity of browsing at adjacent sites due to the higher use of fields by the deer at these sites. The following four results supported this hypothesis. First, in areas with no deer, plant species richness and plant coverage did not differ significantly between adjacent and remote sites. Second, we demonstrated a lower intensity of herbivory at adjacent sites by experimentally transplanting a preferred plant species, Aucuba japonica. Third, we detected no difference in the number of deer fecal pellets found in adjacent and remote sites, indicating that the difference in browsing intensity between the two sites was not due to differences in the frequency of site use by the deer. Fourth, fecal analysis showed that deer at adjacent sites consumed more graminoids, suggesting that deer at these sites used fields to forage because graminoids were abundant in fields. All of these results support the notion that the intensity of herbivory on forest understorys becomes lower in the presence of agricultural fields nearby. This also implies the importance of the indirect effects at the landscape level in that the two ecosystems are linked by the consumers moving between them.
我们在以下假设下，证明了梅花鹿（Cervus nippon）跨栖息地觅食对植物群落的影响：鹿附近存在适宜栖息地会改变植物群落的食草强度。为了研究这种景观层面的影响，我们考察了两种类型的林下植被；“邻近地点”位于鹿喜欢觅食的农田附近，“偏远地点”则远离农田。我们比较了鹿密度高的地区邻近地点和偏远地点的植物群落结构，发现邻近地点的植物物种丰富度和植物覆盖度显著高于偏远地点。我们推测，这种差异是由于鹿在邻近地点更多地利用农田，导致这些地点的啃食强度较低。以下四个结果支持了这一假设。第一，在没有鹿的地区，邻近地点和偏远地点的植物物种丰富度和植物覆盖度没有显著差异。第二，通过实验性移植一种受欢迎的植物物种——日本桃叶珊瑚，我们证明了邻近地点的食草强度较低。第三，我们在邻近地点和偏远地点发现的鹿粪粒数量没有差异，这表明两个地点啃食强度的差异不是由于鹿使用地点的频率不同。第四，粪便分析表明，邻近地点的鹿消耗了更多的禾本科植物，这表明这些地点的鹿利用农田觅食，因为农田里禾本科植物丰富。所有这些结果都支持了这样一种观点，即附近存在农田时，林下植被的食草强度会降低。这也意味着景观层面间接影响的重要性，即两个生态系统通过消费者在它们之间移动而相互联系。
