Cross Adam T, Turner Shane R, Renton Michael, Baskin Jerry M, Dixon Kingsley W, Merritt David J
School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Perth, Australia, Kings Park and Botanic Garden, Fraser Avenue, West Perth WA 6005, Perth, Australia and Department of Biology, University of Kentucky, Lexington, KY 40506, USA School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Perth, Australia, Kings Park and Botanic Garden, Fraser Avenue, West Perth WA 6005, Perth, Australia and Department of Biology, University of Kentucky, Lexington, KY 40506, USA
School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Perth, Australia, Kings Park and Botanic Garden, Fraser Avenue, West Perth WA 6005, Perth, Australia and Department of Biology, University of Kentucky, Lexington, KY 40506, USA School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Perth, Australia, Kings Park and Botanic Garden, Fraser Avenue, West Perth WA 6005, Perth, Australia and Department of Biology, University of Kentucky, Lexington, KY 40506, USA.
Ann Bot. 2015 Apr;115(5):847-59. doi: 10.1093/aob/mcv014. Epub 2015 Feb 7.
Rock pools are small, geologically stable freshwater ecosystems that are both hydrologically and biologically isolated. They harbour high levels of plant endemism and experience environmental unpredictability driven by the presence of water over variable temporal scales. This study examined the hypothesis that the sediment seed bank in monsoon tropical freshwater rock pools would persist through one or more periods of desiccation, with seed dormancy regulating germination timing in response to rock pool inundation and drying events.
Seeds were collected from seven dominant rock pool species, and germination biology and seed dormancy were assessed under laboratory conditions in response to light, temperature and germination stimulators (gibberellic acid, karrikinolide and ethylene). Field surveys of seedling emergence from freshwater rock pools in the Kimberley region of Western Australia were undertaken, and sediment samples were collected from 41 vegetated rock pools. Seedling emergence and seed bank persistence in response to multiple wetting and drying cycles were determined.
The sediment seed bank of individual rock pools was large (13 824 ± 307 to 218 320 ± 42 412 seeds m(-2) for the five species investigated) and spatially variable. Seedling density for these same species in the field ranged from 13 696 to 87 232 seedlings m(-2). Seeds of rock pool taxa were physiologically dormant, with germination promoted by after-ripening and exposure to ethylene or karrikinolide. Patterns of seedling emergence varied between species and were finely tuned to seasonal temperature and moisture conditions, with the proportions of emergent seedlings differing between species through multiple inundation events. A viable seed bank persisted after ten consecutive laboratory inundation events, and seeds retained viability in dry sediments for at least 3 years.
The persistent seed bank in freshwater rock pools is likely to provide resilience to plant communities against environmental stochasticity. Since rock pool communities are often comprised of highly specialized endemic and range-restricted species, sediment seed banks may represent significant drivers of species persistence and diversification in these ecosystems.
岩池是小型的、地质稳定的淡水生态系统，在水文和生物方面均处于隔离状态。它们拥有大量的植物特有种，并且在不同的时间尺度上，由于水的存在而经历环境的不可预测性。本研究检验了这样一个假设：季风热带淡水岩池中的沉积物种子库能够在一个或多个干涸期持续存在，种子休眠会根据岩池的淹没和干涸事件调节萌发时间。
从七种优势岩池物种中收集种子，并在实验室条件下，针对光照、温度和萌发刺激剂（赤霉素、卡里金内酯和乙烯）评估萌发生物学和种子休眠情况。对西澳大利亚金伯利地区淡水岩池中的幼苗出土情况进行了实地调查，并从41个有植被的岩池中采集了沉积物样本。确定了多次干湿循环后幼苗出土和种子库的持久性。
单个岩池的沉积物种子库很大（所研究的五个物种为13824±307至218320±42412粒种子·平方米⁻²）且空间上存在差异。这些相同物种在野外的幼苗密度为每平方米13696至87232株幼苗。岩池分类群的种子处于生理休眠状态，后熟以及暴露于乙烯或卡里金内酯可促进萌发。不同物种间的幼苗出土模式各不相同，并且与季节性温度和湿度条件精确匹配，在多次淹没事件中，不同物种的出土幼苗比例有所不同。经过连续十次实验室淹没事件后，仍存在有活力的种子库，并且种子在干燥沉积物中至少保持3年的活力。
淡水岩池中的持久性种子库可能为植物群落提供抵御环境随机性的恢复力。由于岩池群落通常由高度特化的特有种和分布范围受限的物种组成，沉积物种子库可能是这些生态系统中物种持久性和多样化的重要驱动因素。
