Leaf traits, shoot growth and seed production in mature Fagus sylvatica trees after 8 years of CO2 enrichment

Background and Aims Masting, i.e. synchronous but highly variable interannual seed production, is a strong sink for carbon and nutrients. It may, therefore, compete with vegetative growth. It is currently unknown whether increased atmospheric CO2 concentrations will affect the carbon balance (or that of other nutrients) between reproduction and vegetative growth of forest species. In this study, reproduction and vegetative growth of shoots of mature beech (Fagus sylvatica) trees grown at ambient and elevated atmospheric CO2 concentrations were quantified. It was hypothesized that within a shoot, fruiting has a negative effect on vegetative growth, and that this effect is ameliorated at increased CO2 concentrations. Methods Reproduction and its competition with leaf and shoot production were examined during two masting events (in 2007 and 2009) in F. sylvatica trees that had been exposed to either ambient or elevated CO2 concentrations (530 µmol mol−1) for eight consecutive years, between 2000 and 2008. Key Results The number of leaves per shoot and the length of terminal shoots was smaller or shorter in the two masting years compared with the one non-masting year (2008) investigated, but they were unaffected by elevated CO2 concentrations. The dry mass of terminal shoots was approx. 2-fold lower in the masting year (2007) than in the non-masting year in trees growing at ambient CO2 concentrations, but this decline was not observed in trees exposed to elevated CO2 concentrations. In both the CO2 treatments, fruiting significantly decreased nitrogen concentration by 25 % in leaves and xylem tissue of 1- to 3-year-old branches in 2009. Conclusions Our findings indicate that there is competition for resources between reproduction and shoot growth. Elevated CO2 concentrations reduced this competition, indicating effects on the balance of resource allocation between reproduction and vegetative growth in shoots with rising atmospheric CO2 concentration

Biomass Allocation and Chemical Defense in Defoliated Seedling of Quercus serrata with Respect to Carbon-Nitrogen Balance

東北大学金沢大学大学院自然科学研究科Scedule:17-18 March 2003, Vemue: Kanazawa, Japan, Kanazawa Citymonde Hotel, Project Leader : Hayakawa, Kazuichi, Symposium Secretariat: XO kamata, Naoto, Edited by:Kamata, Naoto

Limits to reproduction and seed size-number trade-offs that shape forest dominance and future recovery

International audienceThe relationships that control seed production in trees are fundamental to understanding the evolution of forest species and their capacity to recover from increasing losses to drought, fire, and harvest. A synthesis of fecundity data from 714 species worldwide allowed us to examine hypotheses that are central to quantifying reproduction, a foundation for assessing fitness in forest trees. Four major findings emerged. First, seed production is not constrained by a strict trade-off between seed size and numbers. Instead, seed numbers vary over ten orders of magnitude, with species that invest in large seeds producing more seeds than expected from the 1:1 trade-off. Second, gymnosperms have lower seed production than angiosperms, potentially due to their extra investments in protective woody cones. Third, nutrient-demanding species, indicated by high foliar phosphorus concentrations, have low seed production. Finally, sensitivity of individual species to soil fertility varies widely, limiting the response of community seed production to fertility gradients. In combination, these findings can inform models of forest response that need to incorporate reproductive potential

Dynamics of non-structural carbohydrates following a full masting event reveal a role for stored starch in relation to reproduction in Fagus crenata

Although mature trees have substantial non-structural carbohydrate (NSC) storage that is well documented with respect to its capacity to buffer the asynchrony of supply and demand at the whole-plant level, its role in reproduction remains poorly understood, especially in mast seeding species. In order to elucidate whether masting depletes the whole-tree NSC storage pool, seasonal and inter-annual variations in starch and soluble sugar (SS) concentrations in branchlets, stems and coarse roots of Fagus crenata were measured in two stands over 5 years after a full masting event. Full masting reduced individual storage pools to 72% and 49% of the maxima in the two stands; this was observed 2−3 years after full masting. In addition, temporary reduction in starch concentration in summer due to moderate fruiting was found in roots and deep sapwood cores of stems, representing tree rings formed 20 years ago, but not in branchlets. Together with a higher starch storage pool in roots than in branchlets, these results indicate that starch stored in roots and stems is available and supports life-history traits, such as masting events, that occur irregularly. Moreover, limited rainfall in the late growing season caused a reduction in both organ NSC concentration and individual storage irrespective of masting, which further complicated the masting–NSC relationship. These findings have important implications for interpreting the role of carbon resources in masting events