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性，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。与之形成鲜明对比的是，保育与修复领域的相关研究通常认为土壤种子库物种贫乏、杂草化，且几乎不具备保育价值或修复潜力。针对这两种截然相反的观点，一种可能的解释是：相较于原生植物群落，土壤种子库的采样存在系统性偏差。本研究以种-面积关系（species–area relationship）为工具，评估并对比原生植物群落与土壤种子库的单位面积物种丰富度及多样性空间结构特征。为实现二者的直接对比，我们针对横跨区域生物气候梯度的12个草原群落样地，全面调查了其植被与下层土壤种子库的种-面积关系；此外，我们从已发表文献中整合得到一套涵盖原生植被与土壤种子库的全球数据集。研究发现，无论是野外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原生植被，因此在任意给定空间尺度下，其多样性均高于植被，且这一规律在不同生境类型、气候梯度及生物群区中均保持一致。相似度指数常被用于对比植被与土壤种子库的组成，我们发现，采样强度（即用于种子库采样的植被面积占比）是影响索伦森（Sørensen）指数与劳普-克里克（Raup–Crick）指数的最强预测因子，二者的决定系数R²分别为0.70与0.25。本研究表明，‘土壤种子库固有多样性低于原生植物群落’这一认知，更多源于采样不足而非生物学现实。在多种生态系统与气候背景下，我们均发现土壤种子库的多样性高于原生群落，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。