Leaf-out in northern ecotypes of wide-ranging trees requires less spring warming, enhancing the risk of spring frost damage at cold range limits

Aim. Trees need to avoid frost damage to their young leaves by leafing out after the occurrence of the last frost, yet they also need to start photosynthesis early in the season to achieve sufficient growth. This trade-off leads to the hypothesis that ‘safety margins’ against spring frost should become shorter, the longer the winter duration, perhaps reaching an asymptotic limit where frost damage would occur in most years. Physiologically, shorter safety margins in high-latitude ecotypes might be achieved by lower degree-day requirements for leaf-out, compared to low-latitude ecotypes. Location. Europe Time period. 1902–2009 Major taxa studied. Temperate trees. Methods. Using herbarium collections of Acer platanoides, Carpinus betulus, Fagus sylvatica, and Prunus spinosa made over 108 years at 40 to 60o N latitude, we related historic leaf-out dates to winter and spring temperatures (chilling and degree-days), winter duration, and date of last frost occurrence in the rele...研究目的：树木需在终霜发生后展叶，以避免幼叶遭受霜害，但同时又需在季初尽早启动光合作用以获得充足生长。这一权衡关系催生了如下假说：冬季时长越长，春季霜害的安全边际（safety margins）应越短，甚至可能达到渐近极限，导致多数年份均会发生霜害。从生理学角度而言，相较于低纬度生态型，高纬度生态型可通过降低展叶所需的积温（degree-days）需求，来实现更短的安全边际。 研究区域：欧洲 研究时段：1902年至2009年 研究类群：温带树木 研究方法：本研究采集了1902至2009年（跨度108年）、北纬40°至60°范围内的挪威槭（Acer platanoides）、欧洲鹅耳枥（Carpinus betulus）、欧洲山毛榉（Fagus sylvatica）以及黑刺李（Prunus spinosa）的蜡叶标本馆藏，并将历史展叶日期与冬春气温（冷积温与积温）、冬季时长以及研究区域内终霜发生日期进行关联分析……