Oscillatory characteristics of young mangroves exposed to short-period waves
Oscillatory characteristics of young mangroves exposed to short-period waves
复制标题
暴露于短周期波的幼年红树林的振荡特性
DOI：
10.1016/j.scitotenv.2021.148157
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发表时间：
2021
影响因子：
9.8
通讯作者：
Sreeranga Sindhu
中科院分区：
文献类型：
--
作者：
Takagi Hiroshi;Shirai Rikuo;Sreeranga Sindhu
周期<1 s的超重力波由于对海岸结构的影响较小，在海岸工程中往往被忽略。在这项研究中，我们证明了即使短周期波的高度很小，波也会引起年轻红树林的剧烈振荡。通过室内和现场红树林生长试验、振荡试验、波浪实验和理论分析，确定了一种红树林（Kandelia obovata）幼树在小波浪作用下的振荡特性。红树幼芽的自然振荡周期小于0.5 s。当波浪周期是红树林枝条自然振荡周期的倍数时，它们发生共振。由于共振，红树林树叶的水平加速度被计算为重力加速度的两倍。如果这些波浪持续很长时间，嫩叶就会掉落。在日本奄美岛的红树林中进行的一项试验表明，尽管红树林的高度增长迅速，但它们的茎粗却没有实质性的变化。因此，年轻的红树林需要在短时间内获得刚性，以承受短时间的波浪。为了提高红树幼树的成活率，可以通过设置小型防波堤来避免与红树茎的自然振荡周期接近的短周期波浪。然而，茎的摆动可能会对叶片的光合作用产生积极的影响，因为小波浪和微风有同样的作用，可以促进小红树林的生长。因此，需要进一步研究超重力波和红树林幼树的生长情况。
Ultragravity waves with a period of <1 s are often ignored in coastal engineering because they have little effect on coastal structures. In this study, we demonstrate that even though the height of short-period waves is small, the waves cause young mangroves to oscillate greatly. Indoor and onsite mangrove growth tests, oscillation tests, wave experiments, and theoretical analyses were conducted on a mangrove species (Kandelia obovata) to determine the oscillatory characteristics of young mangroves when exposed to small waves. Natural period of oscillation of the young mangrove shoots was less than 0.5 s. Their resonance occurred when the wave period was a multiple of the natural period of oscillation of the mangrove shoots. Because of resonance, the horizontal acceleration of the mangrove leaves was calculated to reach twice the acceleration of gravity. If these waves act for a long time, young leaves can fall. A test performed on a mangrove forest in Amami Island in Japan revealed that although the mangrove heights grew rapidly, their stem thickness did not change substantially. Thus, the young mangroves need to gain rigidity in a short period to withstand short-period waves. To increase the survival rate of the young mangroves, short-period waves, whose period is close to the natural period of oscillation of the mangrove stems, could be avoided by installing a small breakwater. However, stem oscillations may positively affect leaf photosynthesis because small waves have the same effect as a gentle breeze and can promote the growth of young mangroves. Therefore, further studies on ultragravity waves and the growth of young mangroves are required.