Long-term effects of CO2 enrichment on bud phenology and shoot growth patterns of Norway spruce juvenile trees

Abstract

Bud phenology and shoot elongation growth were monitored on Norway spruce (Picea abies [L.] Karst.) trees grown inside glass domes with adjustable windows for six years under ambient (355 μmol CO2-mol-1) and elevated (700 μmol CO2-mol-1tmospheric CO2 concentrations CO2. Each treatment consisted of two stand densities - sparse (5,000 trees-a-1)nd dense (10,000 trees.ha-1). The age of spruce trees was 10 years at the beginning of the experiment. Elevated CO 2 slightly accelerated the consequential bud germinating phases and it significantly induced shoot elongation growth, especially of sun-exposed shoots in a stand with sparse density. This accelerated growth lasted one to three weeks after full bud development in E compared to A. At the end of the growing season the total shoot length did not show any differences between the treatments. We supposed that limiting nitrogen supply to needles slowed down subsequent shoot elongation growth in E treatment. Nevertheless, faster shoot growth in elevated CO2 conditions can enhance the carbon sink in spruce due to prolongation of the growing season.