Limits to reproduction and seed size-number trade-offs that shape forest dominance and future recovery

The relationships that control seed production in trees are fundamental to understanding the evolution of forest species and their capacity to recover from increasing losses to drought, fire, and harvest. A synthesis of fecundity data from 714 species worldwide allowed us to examine hypotheses that are central to quantifying reproduction, a foundation for assessing fitness in forest trees. Four major findings emerged. First, seed production is not constrained by a strict trade-off between seed size and numbers. Instead, seed numbers vary over ten orders of magnitude, with species that invest in large seeds producing more seeds than expected from the 1:1 trade-off. Second, gymnosperms have lower seed production than angiosperms, potentially due to their extra investments in protective woody cones. Third, nutrient-demanding species, indicated by high foliar phosphorus concentrations, have low seed production. Finally, sensitivity of individual species to soil fertility varies widely, limiting the response of community seed production to fertility gradients. In combination, these findings can inform models of forest response that need to incorporate reproductive potential.

Belmont Forum 1854976

NASA AIST16-0052, AIST18-0063

Programme d’Investissement d’Avenir 18-MPGA-0004

National Science Foundation DEB-1754443, DEB 0963447, LTREB 11222325, LTREB 1754647, LTER DEB-1440409

Polish National Science Foundation 2019/33/B/NZ8/0134

Polish National Science Centre 2019/35/D/NZ8/ 00050

Polish National Agency for Academic Exchange Bekker programme PPN/BEK/ 2020/1/00009/U/00001