Secondary seed dispersal in hydro‐fluctuation belts and its influence on the soil seed bank

Abstract

The completion of the Three Gorges project altered the water level fluctuations from "summer submersion and winter exposure" to "summer exposure and winter submersion." The reverse seasonal flooding has dramatically changed both the time and duration of exposure and submergence of reservoir banks. Secondary seed dispersal by water is the primary method of dispersal in hydro-fluctuation belts. This study conducted field sampling and germination experiments to evaluate the effects of reverse seasonal flooding on species composition, diversity, and density of the secondary seed dispersal system and the soil seed bank, and their changes with elevation, in the Xiangzi River. The results indicate that that the secondary seed dispersal system and soil seed bank were associated with 42 and 50 plant species, respectively, and their average seed densities were 1,876.27 and 7,322.18 seeds/m 2 , respectively.The quantity of seeds from secondary seed dispersal accounted for 20.40% of the soil seed bank. The species life-form composition of both consisted mainly of annual and perennial grasses. Among these grasses, the dominant species in the secondary seed dispersal system were Cynodon dactylon and Paspalum distichum, whereas the dominant species in the soil seed bank were Solanum nigrum and Rumex dentatus. Due to the effects of reverse seasonal water level fluctuations, the species composition and quantity of the soil seed bank and secondary seed dispersal system largely exhibited similar spatial distribution characteristics, but some differences were observed. The species quantity, species diversity index, and seed density in the soil seed bank were the highest in the middle section of the hydro-fluctuation belt, followed by the top section and then the bottom section. Conversely, the species quantity, species diversity index, and seed density in the secondary seed dispersal system were highest at the top section, followed by the middle section and then the bottom section.

Diversity of soil seed bank and influencing factors in the nascent wetland of the Yellow River Delta

“…In the estuary wetland, the initial vehicle of dispersal is wind ( Chen et al., 2019 ; Zhu et al., 2022 ). When seeds fall to the ground, they will dispersal again faraway under the action of tides and surface runoff ( Kim et al., 2022 ; Wang et al., 2022 ).…”

Effects of soil water conditions on seedling regeneration in Myricaria laxiflora remnant populations

“…Remnant M. laxiflora populations exist between 41 and 46 m altitude. The soil type of this site is Haplic Alisol (depth, 30–40 cm), the soil organic matter content ranged 10.0–16.0%, and the soil bulk density and porosity ranged 35.52–61.81% and 1.05–1.81 g cm −3 , respectively (Chen, Guan, et al, ; Chen, Wu, et al, ; Chen & Xie, ; Wang et al, ).…”

“…Construction of the Three Gorges Project disrupted M. laxiflora habitats in the reservoir area, leaving only a small number of remnant populations downstream of the dam (Chen & Wang, ). The remnant population structure of M. laxiflora featured sparse seedlings and difficulty in population regeneration (Bao et al, ; Chen et al, ; Chen et al, ). Construction of the Three Gorges‐Gezhouba cascade hydropower stations considerably changed downstream water level fluctuation patterns in the habitats of M. laxiflora remnant populations.…”