Data from: Hydrology, shore morphology and species traits affect seed dispersal, germination and community assembly in shoreline plant communities

1.Seed dispersal and germination are two primary processes influencing plant community assembly. On freshwater shores, water levels regulate both processes. However, it is still unclear how water levels, shore morphology and species traits interactively affect seed dispersal and germination, and how these interactions determine plant community assembly. We hypothesize that a drawdown water regime enhances seed establishment compared to a year-round stable water level, that this increases species richness and diversity, and that this is modulated by species traits and shore morphology. 2.Germination of 20 wetland plant species with different dispersal capacities (floating capacity expressed as seed floatation half-time) and soil moisture preferences for germination (Ellenberg F) was tested on artificial shores in 24 outdoor ponds in 2 complementary experiments over 8 weeks. The “dispersal experiment” tested the effect of water regime on recruitment of hydrochorously dispersing seeds. The “seed bank experiment” tested the effect of water regime on germination from a sown seed bank, on steep and gradual shores. 3.In the dispersal experiment, the drawdown regime increased recruitment and species richness. Longer floating species colonised a larger shoreline section. Soil moisture preference for germination did not determine colonisation patterns. 4.In the seed bank experiment, the drawdown regime increased the number of seedlings on gradual sloping shores, but not on steep shores. The number of germinating seedlings corresponded to the area subjected to the drawdown regime in both shore types. Species richness was not affected by water regime or shore morphology, and species traits did not determine shoreline colonisation. Most seeds germinated in moist soil conditions for all species. 5.Synthesis. A spring drawdown instead of stable water regime stimulates establishment of hydrochorously dispersing seeds in temperate wetlands, leading to higher species richness and diversity. Germination from the seed bank is more affected by water regime and shore surface than by the tested species traits. Species traits, water levels and shore morphology together determine wetland plant community assembly, with dispersal as the main driver of seedling community diversity. Water level regulations and shore morphology can be used to influence plant communities in wetland restoration.

1. 种子扩散（seed dispersal）与种子萌发（germination）是调控植物群落构建（plant community assembly）的两个核心过程。在淡水岸带，水位（water levels）会对这两个过程均产生调控作用。然而目前仍未明确：水位、岸带形态（shore morphology）与物种性状（species traits）如何共同交互影响种子扩散与萌发，以及这些交互作用如何决定植物群落构建。本研究提出如下假说：相较于全年稳定水位条件，水位消落（drawdown water regime）处理可提升种子定植成功率，进而提高物种丰富度（species richness）与物种多样性（species diversity），且该效应会受到物种性状与岸带形态的调控。
2. 本研究在24个室外池塘的人工岸带开展了两项互补性实验，实验周期为8周，共测试了20种具有不同扩散能力（以种子漂浮半衰期表征漂浮能力）且萌发偏好土壤湿度各异的湿地植物的萌发情况，其中土壤湿度偏好采用埃伦贝格湿度指数F（Ellenberg F）标注。其中“扩散实验”旨在探究水位节律对水力传播（hydrochory）种子定植的影响；“种子库实验”则在陡坡与缓坡岸带上，测试水位节律对播种种子库萌发过程的影响。
3. 在扩散实验中，水位消落处理可提升种子定植率与物种丰富度。漂浮时长更长的物种可定植的岸带范围更广，而物种的萌发土壤湿度偏好并未对其定植模式产生决定性影响。
4. 在种子库实验中，水位消落处理仅在缓坡岸带提升了幼苗数量，而陡坡岸带未出现该效应。两类岸带上的萌发幼苗数量均与处于水位消落处理下的岸带面积呈对应关系。物种丰富度不受水位节律与岸带形态的影响，且物种性状也未决定岸带定植模式。所有物种的多数种子均在湿润土壤条件下完成萌发。
5. 综合分析结果表明：在温带湿地中，采用春季水位消落替代全年稳定水位的处理方式，可促进水力传播种子的定植，进而提升物种丰富度与多样性。相较于实验测试的物种性状，种子库萌发过程更易受到水位节律与岸带表面特征的影响。物种性状、水位与岸带形态共同决定了湿地植物群落构建，其中种子扩散是幼苗群落多样性的核心驱动因子。在湿地修复实践中，可通过调控水位与岸带形态来影响植物群落结构。