21 - Impact of Elevated CO2 Concentration on Interactions between Seedlings of Norway Spruce (Picea abies) and a Perennial Grass Calamagrostis epigejos

Abstract

This chapter presents the results of some experiments focused on the determination of shade tolerance of spruce seedlings and grasses of the genus Calamagrostis at ambient and elevated CO2 concentration in the air. The chapter also discusses the possible consequences of elevated CO2 for changes in competitive interactions between spruce seedlings and the grasses. The results indicate that the relative values of responses of spruce seedlings and Calamagrostis epigejos to elevated CO2 are unexpectedly similar in most parameters measured, despite substantial differences in morphology and growth potential of the two species. Elevated CO2 concentration in the air enhances the potential growth rate of spruce seedlings even in the forest understory with very low values of incident radiation. The relative increase in the growth rate of these seedlings is of a similar magnitude as a growth stimulation of the competing grass C. epigejos. Because of the inherently higher absolute growth rate of C. epigejos, the increase in its biomass and leaf area is much higher than in spruce seedlings. As derived from the experiments in simplified conditions, the light compensation point of whole-plant carbon gain (CPCG) of spruce seedlings is not expected to be lower at elevated CO2.