Strong warming can stop budburst advance and reduce leaf number

This data supplements the manuscript: “Strong warming can stop budburst advance and reduce leaf number in temperate forest trees”by Beil, I; Vorjans, M; Piesk, H.; Malyshev, AV

Abstract:The acceleration of global warming over the last decades has led to historically unprecedented advances in spring phenology of trees. However, this advancing trend is slowing down, mainly due to reduced chilling during shorter winters. We ask how shifts in phenology will continue under progressive warming and if budburst success will be affected.Using seedlings of two common temperate tree species, Betula pendula and Fagus sylvatica, we tested how strong warming by 4.4°C form late summer till spring affects autumn and spring leaf phenology and budburst success. For mechanistic understanding, we tracked dormancy progression over the entire period, assessing the dynamics in dormancy depth and percent budburst.Autumn senescence was delayed by 30 days, spring budburst was not altered and leaf unfolding advanced by only 6.5 days (1.48 days/°C). This weak spring advancement could be attributed to delayed dormancy induction, caused by warm autumn temperatures. Most importantly, the lack of chilling reduced budburst success by 13% in Betula and 17% in Fagus.With further climate warming the advance in spring phenology is likely to saturate and reduced budburst might cause fewer leaves and lower carbon uptake. Strongly elevated autumn temperatures might therefore counteract possible warming induced increase in carbon uptake.