Litter quality and litter decomposition of Acer pseudoplatanus L. after growth in elevated CO2-atmosphere

In acrylic greenhouse chambers, which were climatized according to outside conditions, seedlings of Acer pseudoplatanus L. were exposed to CO2-concentrations of 520, 650 (both enriched) and 390 (ambient, control) mu mol mol(-1) over a period of three years. The dry matter weights of the trees were enhanced by the elevated CO2-concentrations. The elevated CO2 levels resulted also in a dilution of nitrogen, phosphorous, potassium, calcium, iron, magnesia and manganese in the green plant material. Leaf litter of Acer pseudoplatanus L. was filled in mesh containers (1 mm) and placed in the litter-layer of a Pino-Quercetum forest topsoil at the Grunewald in Berlin and, subsequently, retrieved 3, 5, 6, 9, and 11 months later for analysis. After nearly one year, mass loss rates of leaf litter cultivated under elevated CO2-concentrations were significantly lower (t-test, alpha less than or equal to 0.05) than those of control (45 % and 65 % respectively). The elevated CO2-concentrations resulted also in a reduced N-concentration in the tree leaf litter and hence lower C/N-ratios. Concentrations of potassium, manganese, iron and magnesia in the accumulation matrices showed a decline of up to 40 %. Only a few studies examined quality and decomposition of natural litter. Modified litter quality and decreased decomposition rates could possibly affect the nutrient cycle within the respective ecosystems.