Format: ORAL

Roberta L.C. Dayrell1,Charlotte Seal1,Efisio Mattana1,Kaitalin White1,Pablo Gmez-Barreiro1,Ted Chapman1

1 RBG Kew, Millennium Seed Bank, Ardingly, UK

Expanding and connecting woodlands to capture atmospheric carbon and enhance resilience to environmental change is garnering support as a climate change mitigation action. This requires an unprecedented increase in tree planting, which demands the efficient use of limited native seed resources. Thus, there is a need to develop improved practices to overcome hurdles posed by the variable quality, dormancy states, and germination requirementsof nativeseeds. Moreover, as the climate changes, species germination requirements may no longer be fulfilled or be met at an unfavourable time for seedling establishment, impacting woodland regeneration and ecosystem diversity and services. We aimed to investigate intra-specific variation in seed germination traits of two native broad-leafed species of forestry importance in the UK: Alnus glutinosa and Betula pubescens. We tested seeds from six populations of each species collected in the wild and stored at the RBG Kews Millennium Seed Bank, to represent the latitudinal gradient across the country. Germination tests were conducted on collections of each population at a range of constant temperatures, both with and without a cold stratification pre-treatment to alleviate dormancy. The collected data were then used in a modelling approach to estimate thermal thresholds for seed germination (base, optimum and ceiling temperatures; sub- and supra-optimal thermal time) and determine the requirement for cold stratification for all collections. In addition, we modelled germination parameters under different climate change scenarios to identify plant populations at the greatest risk. Finally, we explored the potential of morphological traits serving as predictors of germinative behaviour. This information helps evaluate the impact of climate change on woodland regeneration and allows for informed adaptive 'climate-smart' seed sourcing to enhance reforestation practices. The results also provide insights on how climate and provenance shape the functional diversity of tree seeds.