To spend or to save? Carbon allocation strategies in native and invasive woody plants
Invasive woody plant species from Europe and Asia are a common management problem in deciduous forests in the Eastern US. High productivity and extended leaf display in autumn relative to native species likely contribute to invader success, but we know little about how native and invasive plants allocate carbon resources to growth and storage, and how this relates to overall resource-use strategies. We hypothesize that increased carbon gain in invaders allows them to invest more in growth at the expense of storage, whereas natives allocate more to storage as part of a more conservative survival-based strategy in response to defoliation. We carried out partial and full defoliation treatments on saplings of two native/invasive pairs to understand how disturbance affects carbon allocation to growth and storage. We used a hierarchical model to estimate the effects of species, light level, and sapling diameter on refoliation probability and extent. This is part of a three-year defoliation experiment that will conclude with a harvest of the saplings for biomass allocation measurements and the determination of storage pool sizes.
Results from the first growing season suggest that in one native/invasive pair, invaders have a higher probability of refoliating in response to repeated, complete defoliation than native plants. This supports the hypothesis that invasive plants allocate more toward growth than natives. However, in the other native/invasive pair within the genus Acer, invasive species identity had only an 80% chance of increasing refoliation probability. This similarity in response may be due to phylogenetic constraint. Increased light availability had a negative effect on refoliation probability, perhaps because individuals occurring under high light require less time to accumulate adequate carbon to initiate leaf-out in spring. Increased refoliation probability in invasive saplings may support superior performance relative to natives given current environmental conditions. Continuation of defoliation treatments will reveal whether these results hold over multiple years, and how refoliation affects carbon storage pools.