Biology Department, University of Wisconsin Oshkosh, Oshkosh, Wisconsin, USA.
Institute for Arctic and Alpine Research, University of Colorado - Boulder, Boulder, Colorado, USA.
Ecology. 2024 Aug;105(8):e4361. doi: 10.1002/ecy.4361. Epub 2024 Jul 15.
In many regions, the climate is changing faster during winter than during the other seasons, and a loss of snow cover combined with increased temperature variability can expose overwintering organisms to harmful conditions. Understanding how species respond to these changes during critical developmental times, such as seed germination, helps us assess the ecological implications of winter climate change. To address this concern, we measured the breaking of seed dormancy and cold tolerance of temperate grassland species in the lab and field. In the lab, we ran germination trials testing the tolerance of 17 species to an extreme cold event. In the field, we deployed seeds of two species within a snow manipulation experiment at three locations and measured germination success biweekly from seeds subjected to ambient and reduced snow cover from winter into spring. From lab trials, cold tolerance varied among species, with seed germination decreasing <10%-100% following extreme cold events. Cold tolerance was related to seed traits, specifically less round seeds, seeds that required cold stratification, and seeds that mature later in the season tended to be more impacted by extreme cold temperatures. This variation in seed cold tolerance may contribute to altered community composition with continued winter climate change. In the field, germination increased through late winter, coinciding with the accumulation of days where temperatures were favorable for cold stratification. Through spring, germination success decreased as warm temperatures accumulated. Collectively, species-specific seed cold tolerances and mortality rates may contribute to compositional changes in grasslands under continued winter climate change.
在许多地区，冬季的气候变化速度比其他季节都要快，而积雪的减少和温度变化的增加会使越冬生物暴露在有害的环境条件下。了解物种在种子发芽等关键发育时期对这些变化的反应，有助于我们评估冬季气候变化对生态系统的影响。为了解决这个问题，我们在实验室和野外测量了温带草原物种的种子休眠打破和耐寒性。在实验室中，我们进行了发芽试验，测试了 17 个物种对极端寒冷事件的耐受性。在野外，我们在三个地点进行了雪地处理实验，部署了两个物种的种子，并从冬季到春季每隔两周测量一次处于自然和减少的积雪覆盖下的种子的发芽成功率。从实验室试验来看，不同物种的耐寒性存在差异，在经历极端寒冷事件后，种子发芽率下降了 10%-100%。耐寒性与种子特性有关，具体来说，较圆的种子、需要低温层积的种子以及在季节后期成熟的种子更容易受到极端寒冷温度的影响。随着冬季气候的持续变化，这种种子耐寒性的差异可能导致群落组成发生变化。在野外，随着适合低温层积的天数的积累，种子发芽率在整个冬季逐渐增加。到了春季，随着温暖天气的积累，发芽成功率下降。总的来说，特定物种的种子耐寒性和死亡率可能会导致在持续的冬季气候变化下草原的组成发生变化。
