Interspecific and intraspecific variation in tree seedling survival: effects of allocation to roots versus carbohydrate reserves

We examined interspecific and intraspecific variation in tree seedling surv ival as a function of allocation to carbohydrate reserves and structural ro ot biomass. We predicted that allocation to carbohydrate reserves would var y as a function of the phenology of shoot growth, because of a hypothesized tradeoff between aboveground growth and carbohydrate storage. Intraspecifi c variation in levels of carbohydrate reserves was induced through experime ntal defoliation of naturally occurring, 2-year-old seedlings of four north eastern tree species - Acer rubrum, A, saccharum, Quercus rubra, and Prunus serotina - with shoot growth strategies that ranged from highly determinat e to indeterminate. Allocation to root structural biomass varied among spec ies and as a function of light, but did not respond to the defoliation trea tments. Allocation to carbohydrate reserves varied among species, and the t wo species with the most determinate shoot growth patterns had the highest total mass of carbohydrate reserves, but not the highest concentrations. Bo th the total mass and concentrations of carbohydrate reserves were signific antly reduced by defoliation. Seedling survival during the year following t he defoliation treatments did not vary among species, but did vary dramatic ally in response to defoliation. In general, there was an approximately lin ear relationship between carbohydrate reserves and subsequent survival, but no clear relationship between allocation to root structural biomass and su bsequent survival. Because of the disproportionate amounts of reserves stor ed in roots, we would have erroneously concluded that allocation to roots w as significantly and positively related to seedling survival if we had fail ed to distinguish between reserves and structural biomass in roots.