Institute of Arctic Biology and Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, 99775-7000, USA.
Department of Wildland Resources, Utah State University, Logan, Utah, 84322, USA.
Glob Chang Biol. 2017 Feb;23(2):801-814. doi: 10.1111/gcb.13386. Epub 2016 Jul 4.
Summer temperature on the Cape Churchill Peninsula (Manitoba, Canada) has increased rapidly over the past 75 years, and flowering phenology of the plant community is advanced in years with warmer temperatures (higher cumulative growing degree days). Despite this, there has been no overall shift in flowering phenology over this period. However, climate change has also resulted in increased interannual variation in temperature; if relationships between phenology and temperature are not linear, an increase in temperature variance may interact with an increase in the mean to alter how community phenology changes over time. In our system, the relationship between phenology and temperature was log-linear, resulting in a steeper slope at the cold end of the temperature spectrum than at the warm end. Because below-average temperatures had a greater impact on phenology than above-average temperatures, the long-term advance in phenology was reduced. In addition, flowering phenology in a given year was delayed if summer temperatures were high the previous year or 2 years earlier (lag effects), further reducing the expected advance over time. Phenology of early-flowering plants was negatively affected only by temperatures in the previous year, and that of late-flowering plants primarily by temperatures 2 years earlier. Subarctic plants develop leaf primordia one or more years prior to flowering (preformation); these results suggest that temperature affects the development of flower primordia during this preformation period. Together, increased variance in temperature and lag effects interacted with a changing mean to reduce the expected phenological advance by 94%, a magnitude large enough to account for our inability to detect a significant advance over time. We conclude that changes in temperature variability and lag effects can alter trends in plant responses to a warming climate and that predictions for changes in plant phenology under future warming scenarios should incorporate such effects.
过去 75 年来，加拿大曼尼托巴丘吉尔角半岛的夏季气温迅速升高，随着温度升高（累积生长度日数增加），植物群落的开花物候期也提前了。尽管如此，在这段时间内，开花物候期并没有整体变化。然而，气候变化也导致了温度的年际变化增加；如果物候与温度之间的关系不是线性的，温度方差的增加可能会与平均值的增加相互作用，从而改变群落物候随时间的变化方式。在我们的系统中，物候与温度之间的关系呈对数线性，导致在温度谱的冷端斜率比暖端陡峭。由于低于平均温度对物候的影响大于高于平均温度，因此长期以来物候的提前期减少了。此外，如果前一年或两年前夏季温度较高（滞后效应），当年的开花物候会延迟，进一步减少随时间的预期提前。早期开花植物的物候仅受前一年温度的影响，而晚期开花植物的物候主要受前两年温度的影响。亚北极植物在开花前一年或多年就形成了叶片原基（预形成）；这些结果表明，温度会影响开花原基在这个预形成期的发育。总之，温度方差和滞后效应的增加相互作用，导致预期的物候提前减少了 94%，这一幅度足以解释我们无法检测到随时间显著提前的原因。我们得出结论，温度可变性和滞后效应的变化会改变植物对气候变暖的反应趋势，未来变暖情景下植物物候变化的预测应该考虑到这些影响。
