Is deer herbivory directly proportional to deer population density? Comparison of deer feeding frequencies among six forests with different deer density
Is deer herbivory directly proportional to deer population density? Comparison of deer feeding frequencies among six forests with different deer density
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DOI：
10.1016/j.foreco.2011.04.009
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发表时间：
2011-08-01
影响因子：
3.7
通讯作者：
Fujita, Noboru
中科院分区：
文献类型：
--
作者：
Koda, Ryosuke;Fujita, Noboru
直接影响森林生态系统的不是鹿的种群密度，而是鹿的食草强度，但一般认为这两个因素之间存在线性关系。为了评估它们之间的关系，我们在日本屋久岛的6个不同鹿密度的森林中调查了鹿种群密度和树苗植被。以取食频率作为鹿的草食性指标。适口树苗呈高取食频率，在鹿多地区较少取食；不适口树苗呈低取食频率，随鹿密度增加而增加。此外，幼树植被的取食次数并没有随着鹿群的增加而持续增加，在鹿群丰富的地区（≥20只/km），取食次数仅为0.24 ~ 0.32次(2)。这些数据表明，鹿将其主要食物从美味的活树苗转移到其他食物，如落叶，而不是不美味的活树苗。鹿群密度与草食对森林植被的非线性关系可能是由鹿群的食物变化引起的，因此有必要根据鹿群的数量和直接草食的强度来评估鹿群对森林植被的影响。(C) 2011 Elsevier B.V.版权所有
The intensity of deer herbivory, rather than simply the deer population density, directly affects the forest ecosystem, but a linear relationship between these two factors has generally been assumed. To assess their relationship, we investigated deer population density and tree sapling vegetation in six forests with different deer density on Yakushima Island, Japan. The feeding frequency was used as an index of deer herbivory. Palatable saplings showed high feeding frequency and became rare in deer-abundant areas, while unpalatable saplings showed low feeding frequency and increased with increasing deer density. In addition, feeding frequency on sapling vegetation did not continue to increase with increasing deer population and was limited to only 0.24-0.32 in deer-abundant areas (more than 20 deer/km(2)). These data suggest that deer shift their main food items from living palatable saplings to other alternatives such as litter fall rather than living unpalatable saplings. Clearly, the nonlinear relationship between deer density and deer herbivory on forest vegetation could result from a change in the food eaten by deer, and it is therefore necessary to assess the impacts of deer based on not only the size of the deer population but also the intensity of direct herbivory. (C) 2011 Elsevier B.V. All rights reserved.