论文标题
土壤种子库可以缓冲年度植物社区的长期组成变化
The soil seed bank can buffer long-term compositional changes in annual plant communities
论文作者
论文摘要
生态理论预测，面对环境变异性，土壤种子库稳定了年度植物群落的组成。但是，需要关于种子库中社区动态的长期数据和常规植被来测试这一预测。我们检验了以下假设：在地中海，半干旱和干旱生态系统的一项为期9年的研究中，种子库的成分比常规植被的时间变化低。种子库的组成是通过每年从研究地点收集土壤核心来估算的。在最佳浇水条件下，在每个土壤核心连续三年测量了幼苗的出现，以考虑种子休眠状态。在所有地点，种子库的组成与多年来的植被不同。小种子和休眠种子的种子在种子库中的频率高于站立植被。相反，在控制种子质量和种子休眠中草与福布斯之间的差异之后，功能群体的成员资格（草与FORBS）无法解释种子库和植被之间物种频率的差异。与预测相反，种子库中逐年变异性（连续几年之间的平均组成差异）的幅度并不低于所有地点的植被。但是，种子库中的长期成分趋势比地中海和半干旱场所的植被弱。在逐年变异性最高的干旱地点，未观察到长期趋势。总体而言，种子库对年度社区植被时间变化的影响取决于现场条件和时间尺度。尽管种子库的逐年变异与植被相似，但土壤种子库可以缓冲长期趋势。
Ecological theory predicts that the soil seed bank stabilises the composition of annual plant communities in the face of environmental variability. However, long-term data on the community dynamics in the seed bank and the standing vegetation are needed to test this prediction. We tested the hypothesis that the composition of the seed bank undergoes lower temporal variability than the standing vegetation in a nine-year study in Mediterranean, semi-arid, and arid ecosystems. The composition of the seed bank was estimated by collecting soil cores from the studied sites on an annual basis. Seedling emergence under optimal watering conditions was measured in each soil core for three consecutive years, to account for seed dormancy. In all sites, the composition of the seed bank differed from the vegetation throughout the years. Small-seeded and dormant-seeded species had a higher frequency in the seed bank than in the standing vegetation. In contrast, functional group membership (grasses vs. forbs) did not explain differences in species frequency between the seed bank and the vegetation after controlling for differences between grasses and forbs in seed mass and seed dormancy. Contrary to predictions, the magnitude of year-to-year variability (the mean compositional dissimilarity between consecutive years) was not lower in the seed bank than in the vegetation in all sites. However, long-term compositional trends in the seed bank were weaker than in the vegetation in the Mediterranean and semi-arid sites. In the arid site where year-to-year variability was highest, no long-term trends were observed. Overall, the effect of the seed bank on the temporal variability of the vegetation in annual communities depends on site conditions and time scale. While the year-to-year variability of the seed bank is similar to the vegetation, the soil seed bank can buffer long-term trends.
