Plant carbohydrate storage: intra- and inter-specific trade-offs reveal a major life history trait

Trade-offs among carbon sinks constrain how trees physiologically, ecologically, and evolutionarily respond to their environments. These trade-offs typically fall along a productive growth to conservative, bet-hedging continuum. How nonstructural carbohydrates (NSCs) stored in living tree cells (known as carbon stores) fit in this trade-off framework is not well understood. We examined relationships between growth and storage using both within species genetic variation from a common garden, and across species phenotypic variation from a global database. We demonstrate that storage is actively accumulated, as part of a conservative, bet-hedging life history strategy. Storage accumulates at the expense of growth both within and across species. Within the species Populus trichocarpa, genetic trade-offs show that for each additional unit of wood area growth (in cm(2) yr(-1)) that genotypes invest in, they lose 1.2 to 1.7 units (mg g(-1) NSC) of storage. Across species, for each additional unit of area growth (in cm(2) yr(-1)), trees, on average, reduce their storage by 9.5% in stems and 10.4% in roots. Our findings impact our understanding of basic plant biology, fit storage into a widely used growth-survival trade-off spectrum describing life history strategy, and challenges the assumptions of passive storage made in ecosystem models today.

Automated summary

Trade-offs among carbon sinks constrain how trees respond to their environments. This study examines the relationship between growth and storage in trees using genetic and phenotypic data. The findings show that storage is actively accumulated at the expense of growth, both within and across species. This challenges the assumptions of passive storage in current ecosystem models.