Data from: Seed banks are biodiversity reservoirs: species-area relationships above versus below ground

Soil seed banks offer plants the possibility to disperse through time. This has implications for population and community dynamics, as recognised by ecological and evolutionary theory. In contrast, the conservation and restoration literature often find seed banks to be depauperate, weedy and without much conservation value or restoration potential. One explanation for these contrasting views might lie in a systematic bias in the sampling of seed banks versus established plant communities. We use the species–area relationship as a tool to assess and compare the per-area species richness and spatial structuring of the diversity of the established plant community versus soil seed banks. To allow this direct comparison we extensively survey the species–area relationship of the vegetation and underlying seed bank of a grassland community across twelve sites spanning regional bioclimatic gradients. We also compile a global dataset of established vegetation and seed banks from published sources. We find that seed banks have consistently higher intercepts and slopes of the relationship, and hence higher diversity at any given spatial scale, than the vegetation both in the field and literature study. This is consistent across habitat types, climate gradients, and biomes. Similarity indices are commonly used to compare vegetation and seed bank, and we find that sampling effort (% of the vegetation area sampled for seed bank) was the strongest predictor of vegetation–seed bank similarity for both the Sørensen (R2 = 0.70) and the Raup–Crick (R2 = 0.25) index. Our study suggests that the perception that seed banks are intrinsically less diverse than established plant communities has been based more on inadequate sampling than on biological reality. Across a range of ecosystems and climatic settings, we find high diversity in seed banks relative to the established community, suggesting potentially important roles of seed banks in population dynamics and diversity maintenance.土壤种子库（soil seed banks）为植物提供了通过时间实现扩散的可能。这一特性对种群与群落动态具有重要意义，已为生态学与进化生物学理论所证实。与之相反，保护与修复领域的相关研究往往认为土壤种子库物种贫乏、多为杂草类群，且兼具较低的保护价值与修复潜力。造成这两种观点分歧的原因之一，或许在于土壤种子库与现存植物群落的采样方式存在系统性偏差。 我们以种-面积关系（species–area relationship）作为分析工具，评估并对比现存植物群落与土壤种子库的单位面积物种丰富度，以及多样性的空间结构特征。为实现这一直观对比，我们对覆盖区域生物气候梯度的12个草地群落样地，分别开展了植被与下伏土壤种子库的种-面积关系全面调查。此外，我们从已发表文献中整合得到一套涵盖现存植被与土壤种子库的全球数据集。 研究结果显示，无论是野外实地调查还是文献数据分析，土壤种子库的种-面积关系截距与斜率均显著高于现存植被，因此在任意给定空间尺度下，其物种多样性均更高。这一规律在不同生境类型、气候梯度以及生物群区中均保持一致。相似性指数是对比植被与土壤种子库的常用工具，我们发现，采样投入（即用于种子库采样的植被样地面积占比）是影响索伦森（Sørensen）相似度指数（R²=0.70）与劳普-克里克（Raup–Crick）相似度指数（R²=0.25）的最强预测因子。 本研究表明，认为土壤种子库物种多样性本质上低于现存植物群落的主流认知，更多是源于采样不足而非生物学实际。在多种生态系统与气候环境下，我们均发现土壤种子库的物种多样性显著高于现存群落，这暗示土壤种子库在种群动态与多样性维持中可能发挥着关键作用。