Shifts in spruce and beech flushing in the context of global climate change

POKORNÝ RADEK, TOMASKOVA IVANA, AC ALEXANDER: Shi s in spruce and beech fl ushing in the context of global climate change. Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 2013, LXI, No. 1, pp. 163–167 Bud phenology and development of needle nitrogen content were monitored on Norway spruce (Picea abies [L.] Karst) and European beech (Fagus sylvatica [L.]) trees grown inside glass-domes for fi ve years under ambient (385 μmol(CO2) mol −1) and elevated (700 μmol(CO2) mol −1) atmospheric CO2 concentrations ([CO2]). The spruce to beech ratio was 35:65 in both treatments. At the beginning of the experiment mean age of investigated trees was 5 years. Elevated [CO2] was responsible for premature growth of both spruce and beech buds in the E treatment (not signifi cantly, by 3–7 days). Nevertheless the fl ushing of neither beech nor spruce was not signifi cantly hastened in E treatment during the fl ushing within the 5 years. During the second half of fl ushing faster development of terminal beech buds comparing to spruce was found (Chi-square = 65, p << 0.01). While the trajectory of beech buds development proceeded in the line – terminal – apical – lateral, the development of apical and lateral buds in spruce was fi nished before fi nalization of terminal buds development. At the beginning of the growing season the lowest value of nitrogen in spruce needles from E treatment (mean ± standard deviation 1.20 ± 0.18 %) was found. This could be a reason of weak diff erences between A and E treatment in both tree species. Elevated [CO2] acts as growth stimulator but the nitrogen insuffi ciency eliminates a positive eff ect of [CO2]. As the global climate change express itself in many ways and relationship’s consequences among plants and/or animals are hard to forecast. elevated [CO2], forest phenology, global climate change, needle nitrogen Plant phenology studies the onset and duration of periodic vegetation cycles such as sprouting, foliage, fl owering, fructifi cation and leaf cast. Temperature is regarded to be an important environmental factor inducing bud fl ushing (Hannerz, 1999). Higher air CO2 concentration, which rose from 316 ppm in 1956 to 394 ppm now, is associated with global temperature increase during previous 100 years of about 0.8 °C (IPCC 2007). Under elevated [CO2] conditions, an acceleration of bud phenology (Repo et al., 1996; Jach and Ceulemans, 1999) is reported, others studies showed a dilution response (Linkosalo, 2000), or no eff ects (Olszyk et al., 1998; Roberntz, 1999; Kilpelainen et al., 2006; Slaney et al., 2007). Except fl ushing, climate change aff ects size of tree foliage and even changes the chemical composition (C/N ratio) of leaves – leaves contain less nitrogen and leaf-eating insects therefore have to consume more leaves to cover their nourishment needs (DeLucia et al., 2008). Shi s in tree phenology may aff ect synchrony of insects and the reproduction of birds, and the time discrepancy between the gradation of caterpillars and the occurrence of birds can reduce bird population (Strode, 2003). Indeed, phenological changes are considered to be an early indicator of climate change due to their sensitivity to temperature changes (Chuine et al., 2004). Goal of this investigation was evaluate fl ushing of spruce and beech under elevated [CO2] conditions and compare them with regard to needle/leaf needle nitrogen content in the course of fi ve years. Possible consequences of phenological shi s on forest ecosystem are formulated. 164 Radek Pokorný, Ivana Tomaskova, Alexander Ac