Estimate of the seed shadow created by the Asiatic black bear Ursus thibetanus and its characteristics as a seed disperser in Japanese cool-temperate forest
Estimate of the seed shadow created by the Asiatic black bear Ursus thibetanus and its characteristics as a seed disperser in Japanese cool-temperate forest
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DOI：
10.1111/j.1600-0706.2010.18626.x
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发表时间：
2011-02-01
期刊：
影响因子：
3.4
通讯作者：
Kaji, Koichi
中科院分区：
文献类型：
--
作者：
Koike, Shinsuke;Masaki, Takashi;Kaji, Koichi
为了评估亚洲黑熊作为种子传播者的有效性，我们估计了亚洲黑熊（Ursus thibetanus）产生的种子阴影。我们结合了由GPS遥测确定的熊运动数据和肠道滞留时间（GRT）数据。我们通过两种方法估计植物种子阴影：从直接运动数据中得到实际种子阴影（ASS），从累积运动数据中得到潜在种子阴影（PSS）。本研究的目的是回答以下问题：(1)GRT在季节或内容大小上是否存在差异？(2)种子阴影在性别、季节、估计方法（ASS或PSS）和年份之间是否存在差异？(3)悬挂对种子影有影响吗？中位GRT在季节和种子维度之间没有差异。结合这些数据，长GRT（中位数15.2-19.7小时，最大值44.0小时）和大的每日移动产生的种子阴影表明，熊有效地将它们消耗的40%的种子移动到距离母树500米以上的距离，并且可能将种子移动到距离母树22000米以上的最大距离。研究结果还表明，由于多次排便和长时间的日常活动，熊会产生复杂的种子阴影。综上所述，PSS在两性之间没有差异，但每年秋季的PSS都比夏季大。然而，可以预期雄性比雌性更大，秋季比夏季更大。与良好的桅杆年份相比，在糟糕的桅杆年份，桅杆可能会变得特别大。这些结果表明，在秋季果实产量低的年份，熊可能是更有效的种子传播者。熊的种子阴影比其他种子传播者长，因此在森林生态系统的维护和更新中发挥了独特的作用。
We estimated the seed shadow created by the Asiatic black bear Ursus thibetanus in order to evaluate the bears effectiveness as a seed disperser. We combined data from bear movements, determined by GPS telemetry, with data from gut retention time (GRT). We estimated plant seed shadows in two ways: from direct movement data to give the actual seed shadow (ASS), and from cumulative movement data to give the potential seed shadow (PSS). The purpose of this study was to answer the following questions: (1) does GRT differ between seasons or in the size of contents? (2) Does seed shadow vary among sex, seasons, estimation method (ASS or PSS), and years? (3) Does the masting affect seed shadows? There were no differences in median GRT among seasons or seed dimensions. Combining these data, the seed shadows produced by long GRT (median; 15.2-19.7 hours, maximum; 44.0 hours) and large daily movements suggest that the bears effectively move 40% of the seeds they consume to a distance greater than 500 m from the parent tree and can potentially move the seeds up to a maximum distance of more than 22 000 m from the parent tree. The results also indicate that bears make complex seed shadows caused by multiple defecations and long periods of daily movement. In summary, PSS did not differ between sexes, but PSS can be expected to be larger in autumn than in summer of each year. ASS, however, can be expected to be larger in males than females, and to be larger in autumn than in summer. ASS may become especially large during a poor masting year as compared to good masting years. These results indicate that bears are potentially more effective seed dispersers during years of poor fruit production in autumn. The bears have longer seed shadows than other seed disperser and consequently may play a unique role in the maintenance and renewal of forest ecosystem.