Climate‐driven intraspecific shifts in seed germination phenology: Consequences for native temperate woodland restoration and regeneration

Societal Impact Statement
As climate change alters seasonal patterns, temperate tree populations face a growing risk of phenological mismatch, where seed dispersal and germination no longer align with favourable conditions for survival. This study predicted how warming by the end of the century will affect seed dormancy breaking and germination in populations of three UK tree species across environmental gradients. Results reveal potential misalignments between seed behaviour and environmental conditions, which may reduce seedling recruitment and hinder forest regeneration. These findings support forestry, conservation and policy efforts to develop climate‐resilient woodlands and promote long‐term ecosystem sustainability.


Summary




Shifts in seasonal cues, as a result of human‐driven changes in climate, can impact tree species germination phenology and, consequently, woodland regeneration and the benefits they provide. In this study, we investigated the intraspecific variation in seed germination traits of three native trees of forestry interest in the UK (

Alnus glutinosa

,

Betula pubescens

and

Pinus sylvestris

) to predict the timing of their field germination under different future climate scenarios.



We tested seeds from six populations of each species to represent environmental gradients across the country. Germination tests were conducted at a range of constant temperatures, with and without cold stratification, to test for dormancy for each population, and results were modelled using a thermal time approach to predict shifts in germination phenology.



Although none of the populations were projected to experience temperatures outside the ranges that yield high germination percentages, several of them showed substantial phenological shifts between present and future climates, mostly driven by changes in local temperatures and month of seed dispersal. The largest shifts occurred in

B. pubescens

when warming altered dormancy dynamics, either because milder winters failed to satisfy cold stratification requirements or because warmer environmental temperatures triggered germination upon dispersal.



Phenological mismatch in germination under altered seasonal cues can exhibit seemingly irregular patterns, arising from interactions among local climate conditions, timing of seed dispersal, dormancy depth and stratification requirements. These dynamics have important implications for the potential of native seeds to restore and regenerate woodlands.