A comparative analysis of foliar chemical composition and leaf construction costs of beech (Fagus sylvatica L.), sycamore maple (Acer pseudoplatanus L.) and ash (Fraxinus excelsior L.) saplings along a light gradient

Abstract

Construction cost (g glucose g(-1)), chemical composition and morphology of leaves of beech (Fagus sylvatica L.) and two co-occurring valuable broadleaved species (sycamore maple - Acer pseudoplatanus L. - and ash - Fraxinus excelsior L.) were investigated along a horizontal light gradient (3-60% of above canopy radiation) and from top to bottom within the crowns in a fairly even-aged mixed-species thicket established by natural regeneration beneath a patchy shelterwood canopy. Construction cost and carbon concentration increased with irradiance in ash and sycamore maple and were independent of irradiance in beech. Leaf traits expressed on an area basis, like construction cost, nitrogen content and leaf mass (LMA) increased significantly with irradiance in all three species and decreased from top to bottom within crowns. The shade tolerant beech invested more glucose to produce a unit foliar biomass, but less to build a unit foliar area due to lower LMA. Thereby beech was able to display a greater total leaf area, what at least in parts counterbalanced the lower values of N(a) as compared to ash and sycamore maple.