Predicting seed germination in the field is a critical part of anticipating the impact of climate change on the timing of wild species regeneration. We combined thermal time and soil heat sum models of seed germination for three endemic Mediterranean mountain species with endospermic seeds and morphophysiological dormancy: Aquilegia barbaricina, Paeonia corsica, and Ribes sandalioticum. Seeds were buried in the soil within the respective collection sites, both underneath and outside the tree canopy, and their growth was assessed regularly and related to soil temperatures and estimates of the thermal characteristics of the seeds. The thermal thresholds for embryo growth and seed germination of A. barbaricina assessed in previous studies under controlled conditions were used to calculate soil heat sum accumulation of this species in the field. Thermal thresholds of seed germination for P. corsica and R. sandalioticum were not previously known and were estimated for the first time in this field study, based on findings of previous works carried out under controlled conditions. Critical embryo length and maximum germination for A. barbaricina were reached in April, and in December for R. sandalioticum. Seeds of P. corsica stay dormant in the ground until the following summer, and the critical embryo length and highest germination were detected from September to December. Soil heat sum models predicted earlier germination by one month for all three species under two Intergovernmental Panel on Climate Change (IPCC) scenarios, based on the assumption that the estimated thermal thresholds will remain constant through climate changes. This phenological shift may increase the risk of mortality for young seedlings. The models developed provide important means of connecting the micro-environmental niche for in situ seed germination and the macro-environmental parameters under a global warming scenario.

中文翻译：

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三种特有物种的胚乳种子对山地温度的差异解释影响原位发芽的时间


预测田间种子发芽是预测气候变化对野生物种再生时间影响的关键部分。我们将三种具有胚乳种子和形态生理休眠的地中海特有山地物种的种子萌发的热时间和土壤热和模型结合起来：耧斗菜、芍药和山茶藨子。种子被埋在各自收集地点的土壤中，包括树冠下方和外部，并定期评估它们的生长情况，并将其与土壤温度和种子热特性的估计相关。之前的研究中在受控条件下评估的A. barbaricina胚胎生长和种子萌发的热阈值用于计算该物种在田间的土壤热总积累。 P. corsica和R. sandalioticum种子萌发的热阈值以前并不为人所知，并且在本次实地研究中首次根据先前在受控条件下进行的工作的结果进行了估计。 A. barbaricina在 4 月份达到了临界胚胎长度和最大发芽率，而R. sandalioticum在 12 月份达到了临界胚胎长度和最大发芽率。科西嘉种子在地下休眠直至次年夏季，9月至12月检测到临界胚长度和最高发芽率。 土壤热和模型预测，在政府间气候变化专门委员会 (IPCC) 的两种情景下，所有三个物种的发芽时间提前了一个月，其基础是估计的热阈值在气候变化过程中保持不变的假设。这种物候变化可能会增加幼苗死亡的风险。开发的模型提供了在全球变暖情景下将原位种子萌发的微环境生态位与宏观环境参数联系起来的重要手段。