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The role of sediment transportation and deposition for seed dispersal and vegetation development on gravel-bed river floodplain.

沉积物输送和沉积对砾石河漫滩上种子传播和植被发育的作用。

基本信息

批准号：
18580326
负责人：
HOSHINO Yoshinobu
金额：
$ 1.67万
依托单位：
Tokyo University of Agriculture and Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

This study aimed to clarify the role of seed dispersal by sediment transportation through riverbed for vegetation development on newly deposited sediments after flooding. The fall velocities through water of plant seeds were determined for herbaceous species that grow on the floodplain of the Tama River. Furthermore, The seeds deposited with the alluvial materials were detected by the seedling germination method, and the composition was compared with the species composition of the plant communities developed on the floodplain. Consequently, following results were obtained.1. 55 herbaceous species in 70 species had non-buoyant seeds that subsided in water within 24 hours. The fall velocities through water of the non-buoyant seeds were corresponded to the fall velocity of sediment particles of very fine sand (0.075-0.125mm) or fine sand (0.125-0.25mm).2. Seedlings of 60 species were germinated from the plant debris sampled after the flooding. It means that debris includes a number of plant seeds. Most of the seeds were buoyant and had spine or pappus.3. Seedlings of 76 species were germinated from the sediment sampled on the floodplain after the flooding, showing that sediments includes many plant seeds. Germinated seedling number and species number were higher in the samples those contain higher ratio of very fine sand and fine sand, suggesting that many seeds accumulated with the sediment particles that had same fall velocities.4. 50-70% of the component species of the pioneer plant communities on the floodplain germinated from the sediment samples. This fact suggested that plant seeds contained in alluvial materials had great contribution to development of the plant communities on the newly deposited sediments.For accurate sediment management of the river basin regarded as a sediment transportation system, it is necessary to progress the study about the seed dispersal through the sediment transportation.

本研究的目的是阐明种子传播的作用，通过河床泥沙输移的植被发展后，洪水新沉积的沉积物。通过水的植物种子的下降速度，确定草本植物的品种，生长在多摩河漫滩。此外，还采用种子萌发法对沉积于冲积物中的种子进行了检测，并与河漫滩植物群落的物种组成进行了比较。结果表明：1. 70种草本植物中有55种种子无浮力，在水中24小时内下沉。非浮性种子在水中的下落速度与极细砂（0.075-0.125mm）或细砂（0.125-0.25mm）泥沙颗粒的下落速度相对应. 60种植物的幼苗从洪水后取样的植物残体中发芽。这意味着碎片包括一些植物种子。多数种子具有浮力，有刺或冠毛.从洪水后的河漫滩上取样的沉积物中萌发出76种植物的幼苗，表明沉积物中含有许多植物种子。极细砂和细砂比例较高的样品，其种子萌发数和种类数均较高，说明许多种子随沉降速度相同的泥沙颗粒而积累.河漫滩先锋植物群落的组成种有50-70%是从沉积物中萌发出来的。这表明，冲积物中的植物种子对新沉积物上植物群落的发育具有重要贡献，因此，为了准确地管理作为输沙系统的流域泥沙，有必要开展泥沙输移过程中种子扩散的研究。