To spend or to save? Assessing energetic growth-storage tradeoffs in native and invasive woody plants.

Many non-native woody plants invade low-light forest understories but differ from native species in leaf phenology and seasonality of photosynthesis. It is unknown whether such differences in assimilation patterns are due to contrasting strategies of energy allocation. In a group of native and invasive species in Eastern North America, we hypothesized that invaders employ a grow-first strategy, prioritizing allocation to new structural biomass over carbon storage compared to native congeners. We also hypothesized that species producing a single spring leaf flush exhibit a more conservative carbon storage strategy than species with continuous leaf production. We measured sugar and starch concentrations (non-structural carbohydrates; NSCs) in spring and fall in the stems and roots of 39 species of native and non-native shrubs in a common garden, and compared these to patterns of leaf production across species. Native species had higher soluble sugar concentrations than invaders, but invaders tended to store more root starch in spring. We found no difference in leaf production between natives and invaders. Determinate species had more soluble sugars than indeterminate species but had lower root starch. We found no relationship between aboveground productivity and carbon storage. Our results suggest that closely related species with contrasting evolutionary histories have different carbon storage strategies, although not necessarily in relation to their growth potential. The higher soluble sugar concentrations of native species may reflect their evolutionary response to historical disturbances, or different interactions with soil microbes, while increased spring root starch in invaders may support fine root or fruit production.