Fluvial seed dispersal of riparian trees: transport and depositional processes
Fluvial seed dispersal of riparian trees: transport and depositional processes
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DOI：
10.1002/esp.3850
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发表时间：
2016-04
影响因子：
3.3
通讯作者：
Adrienne Cunnings;E. Johnson;Y. Martin
中科院分区：
文献类型：
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作者：
Adrienne Cunnings;E. Johnson;Y. Martin
河流种子传播考虑了种子的运输和沉积，其中通道地貌结构、水文和种子传播特性对运输时间和沉积位置有影响。本文采用一维输运模型研究了水流模式对漂浮的白色桤木种子在河流中扩散的影响。从概念上讲，该模型将河流分为两个部分：（i）种子向下游运输的主要通道;以及（ii）种子暂时滞留或沉积在河岸上的临时存储区。传输过程的特点是由一个对流-弥散方程耦合到一个瞬态存储模型，使用指数衰减项。模型参数：根据在北方加州沿海具有池浅滩形态的封闭基岩砾石河床中进行的现场试验，估算了纵向弥散（DL）、交换系数（α）、主河道面积（A）和蓄水区（As）。河岸带居住着Alnus rhombifolia，它们在仲春与潮湿的地中海季节结束时散布漂浮的种子。人工种子，具有相似的性状的浮力和密度的桤木种子，被用来量化运输时间和沉积位置。优先沉积导致河流河段具有较大的As，高As/A比和更快的交换系数，对应于由地貌结构（如沙洲/浅滩特征的末端和河流中的弯曲）引起的发散水流（回流，再循环流，流量扩张）。结果表明，种子运输和沉积过程中的瞬态存储的重要性。增加通道复杂性的形态特征产生了复杂的流动结构，这些流动结构滞留种子并为沉积发生提供了更大的机会。该模型提供了一个简化的河流水力学代表扩散动力学，并有助于进一步了解水文过程和相关的人口结构。版权所有© 2015约翰威利父子有限公司.
Fluvial seed dispersal considers both the transport and deposition of seeds where channel geomorphic structures, hydrology and seed dispersal traits contribute to transport times and depositional locations. This study examines the influence of stream flow patterns on fluvial seed dispersal of buoyant white alder (Alnus rhombifolia) seeds by applying a one‐dimensional transport model. Conceptually, the model separates the stream into two components: (i) the main channel where the seeds are transported downstream; and (ii) the transient storage zone where seeds are temporarily detained or deposited on the river bank. Transport processes are characterized by an advection–dispersion equation which is coupled to a transient storage model using an exponential decay term. The model parameters: longitudinal dispersion (DL), exchange coefficient (α), main channel area (A) and storage zone (As) are estimated based on field experiments conducted in a confined, bedrock‐gravel bed river with pool‐riffle morphology located in coastal northern California. The riparian zone is inhabited by Alnus rhombifolia that disperse buoyant seeds in mid‐spring coinciding with the end of the wet, Mediterranean season. Artificial seeds, with similar traits of buoyancy and density to alder seeds, were used to quantify transport times and depositional locations. Preferential deposition resulted in stream reaches with larger As, high As/A ratios, and faster exchange coefficients corresponding to divergent stream flow (back‐eddies, re‐circulating flow, flow expansions) caused by geomorphic structures such as the ends of bar/riffle features and bends in the stream. The results demonstrate the importance of transient storage for seed transport and depositional processes. Morphological features that increase a channel's complexity create complex flow structures that detain seeds and provide a greater opportunity for deposition to occur. The model provides a simplification of river hydraulics to represent dispersal dynamics and lends itself to further understanding of hydrochory processes and associated population structure. Copyright © 2015 John Wiley & Sons, Ltd.