Title Leaf traits, shoot growth and seed production in mature Fagus sylvatica trees after eight years’ CO2 enrichment
Author/s Han Q, Kabeya D, Körner Ch, Hoch G
Year 2011
Journal Annals of Botany 107:1405-1411
Abstract 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 con- centrations 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 concen- trations (530 mmol mol21) 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 allo- cation between reproduction and vegetative growth in shoots with rising atmospheric CO2 concentrations.
Keywords Beech, carbon autonomy, CO2 enrichment, Fagus sylvatica, mast seeding, nitrogen, resource allocation, trade-off, vegetative growth
Contact Günter Hoch: email | webpage