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. 种子扩散与萌发是影响植物群落构建的两个核心过程。在淡水岸带，水位调控着这两个过程。然而目前尚不清楚水位、岸带形态与物种性状如何通过交互作用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，水位消落情势可提升种子定植成功率，进而提高物种丰富度与多样性，且该效应受物种性状与岸带形态的调控。
2. 本研究依托24处室外池塘的人工岸带，通过两项互补实验、历时8周，针对20种具有不同扩散能力（漂浮能力以种子漂浮半衰期（seed floatation half-time）表征）和萌发土壤湿度偏好（埃伦伯格F值（Ellenberg F））的湿地植物开展萌发实验。其中，“扩散实验”探究了水文情势对水媒扩散种子定植的影响；“种子库实验”则针对陡坡与缓坡岸带，探究了水文情势对播种种子库萌发的影响。
3. 在扩散实验中，水位消落情势提升了幼苗定植成功率与物种丰富度。漂浮时长更长的物种可定植的岸带范围更广，而萌发的土壤湿度偏好并未决定物种的定植格局。
4. 在种子库实验中，水位消落情势仅在缓坡岸带提升了幼苗萌发数量，陡坡岸带则无此效应。两类岸带的萌发幼苗数量均与经历水位消落的区域面积呈对应关系。物种丰富度不受水文情势或岸带形态的影响，物种性状也未决定岸带定植格局。所有物种的多数种子均在湿润土壤条件下萌发。
5. 研究总结：相较于稳定水位，春季水位消落情势可促进温带湿地中水媒扩散种子的定植，进而提升物种丰富度与多样性。种子库的萌发过程受水文情势与岸面形态的影响程度大于受试物种性状。物种性状、水位与岸带形态共同决定湿地植物群落构建，其中扩散过程是幼苗群落多样性的核心驱动因子。水位调控与岸带形态可用于调控湿地修复中的植物群落组成。