Institute for Conservation Biology & Environmental Management, School of Biological Sciences, University of Wollongong Wollongong, New South Wales, 2522, Australia.
Institute for Conservation Biology & Environmental Management, School of Biological Sciences, University of Wollongong Wollongong, New South Wales, 2522, Australia ; Office of Environment & Heritage P.O. Box 1967, Hurstville, New South Wales, 2220, Australia.
Ecol Evol. 2014 Mar;4(5):656-71. doi: 10.1002/ece3.973. Epub 2014 Feb 12.
Variation in dormancy thresholds among species is rarely studied but may provide a basis to better understand the mechanisms controlling population persistence. Incorporating dormancy-breaking temperature thresholds into existing trait frameworks could improve predictions regarding seed bank persistence, and subsequently species resilience in response to fire, climate change and anthropogenic management. A key ecological strategy for many species from fire-prone ecosystems is the possession of a long-lived seed bank, ensuring recovery after fire. Physical dormancy is dominant in these ecosystems and maintaining this dormancy is directly linked to seed bank persistence. We identified a suite of seed-related factors relevant to maintaining populations in fire-prone regions for 14 co-occurring physically dormant species. We measured variation in initial levels of dormancy and then applied experimental heating treatments, based on current seasonal temperatures and those occurring during fires, to seeds of all study species. Additionally, higher seasonal temperature treatments were applied to assess response of seeds to temperatures projected under future climate scenarios. Levels of germination response and mortality were determined to assess how tightly germination response was bound to either fire or seasonal cues. Six species were found to have dormancy cues bound to temperatures that only occur during fires (80°C and above) and were grouped as having obligate pyrogenic dormancy release. The remaining species, classified as having facultative pyrogenic dormancy, had lower temperature dormancy thresholds and committed at least 30% of seeds to germinate after summer-temperature treatments. Evidence from this study supports including dormancy-breaking temperature thresholds as an attribute for identifying functional types. High temperature thresholds for breaking dormancy, found in our obligate pyrogenic group, appear to be a fire-adapted trait, while we predict that species in the facultative group are most at risk to increased seed bank decay resulting from elevated soil temperatures under projected climate change.
物种休眠阈值的变化很少被研究，但它可能为更好地理解控制种群生存的机制提供依据。将休眠打破温度阈值纳入现有的特征框架中，可以提高对种子库持久性的预测，并随后提高物种对火灾、气候变化和人为管理的恢复力。许多来自易发生火灾生态系统的物种的一个关键生态策略是拥有一个长寿的种子库，以确保在火灾后能够恢复。这些生态系统中以物理休眠为主，维持这种休眠与种子库的持久性直接相关。我们确定了一套与易发生火灾地区种群维持相关的种子相关因素，这些因素与 14 种同时具有物理休眠的共存物种有关。我们测量了初始休眠水平的变化，然后根据当前季节性温度和火灾期间的温度，对所有研究物种的种子进行实验加热处理。此外，还应用了较高的季节性温度处理来评估种子对未来气候情景下预测温度的反应。通过测定发芽响应和死亡率来评估发芽响应与火灾或季节性线索的紧密程度。有 6 个物种被发现具有与火灾期间（80°C 及以上）发生的温度相关的休眠线索，被归类为具有强制性火引发休眠释放。其余物种被归类为具有兼性火引发休眠，它们具有较低的温度休眠阈值，在夏季温度处理后至少有 30%的种子能够发芽。本研究的证据支持将休眠打破温度阈值作为识别功能类型的一个属性。在我们的强制性火引发组中发现的打破休眠的高温阈值似乎是一种适应火灾的特征，而我们预测在兼性组中，由于预计气候变化下土壤温度升高导致种子库衰减增加，物种面临最大的风险。
