Winter deciduous trees are thought to be more dependent than evergreens on carbon storage to meet their growth demands. Recent studies have found, however, that the amount of carbohydrates withdrawn from major carbon storage sites in spring is actually a very small fraction of the total carbon storage, and that annual variation in carbon storage is similar between broadleaved winter deciduous species and evergreen conifers. It remains unclear whether deciduous species are also more dependent on nutrient storage. Here I examined the seasonal dynamics of carbon and nutrient storage in Angiosperm sympatric tree species of contrasting leaf type (deciduous versus evergreen). The aims of this study were to determine if winter deciduous species experience more pronounced annual variations of carbon storage than evergreens, and to explore potential coordination between the seasonal dynamics of carbon and nutrient storage. In four locations of southern Chile, I selected mature trees of two winter-deciduous species and at least four evergreen species, and performed a seasonal sampling of coarse roots, cores, branches, and new shoots to determine concentrations of non-structural carbohydrates, phosphorous, and nitrogen. Data were analyzed with linear mixed-models, with the leaf type and date as fixed factors, and location as the random effect.
Results/Conclusions
Winter deciduous and evergreen species differed in the seasonal dynamics of non-structural carbohydrates concentrations, with the former showing a decrease in spring and the latter exhibiting maximum accumulation in spring and minimum levels in summer. Seasonal variations of non-structural carbohydrates were not more pronounced in winter deciduous than in evergreen species; indeed, for all tissues but roots evergreens showed higher magnitudes of seasonal variations. Seasonal variations in nitrogen and phosphorous were, in general, similar between deciduous and evergreen species, with the new shoots exhibiting the strongest variation. This variation was driven by a decrease of nutrients in spring and an increase during fall, thus indicating some coordination between the seasonal storage of carbon and the nutrients in deciduous species. These results do not support the long standing view of deciduous trees being more dependent on carbon storage than evergreens to meet their growth demands. Results are consistent with the hypothesis that winter deciduous species keep high levels of storage in spring to tolerate disturbances like herbivory. Funding: Fondecyt 1160330.