Does fertilizer application alter the effects of elevated CO2 on Carex leaf litter quality and in situ decomposition in an alpine grassland?

The purpose of our investigation was to determine: (1) whether fertilization with NPK would result in an improvement in leaf litter quality of the dominant species (Carer curvula) in a high alpine grassland in Switzerland; and especially (2) if fertilization improves the quality of leaf litter produced under elevated atmospheric CO2 and compensates for the suppressive effects of high CO2 on the in situ decomposition rates of C. curvula litter, observed at this site in an earlier study. Fertilizer application (40 k(g) N ha(-1) yr(-1)) resulted in 34% higher leaf litter [N] but did not change C:N or lignin N ratios, when viewed across both CO2 treatments. Improvement in the mean N quality of litter produced under elevated CO2 resulting from fertilization appeared to lead to a significantly faster mean decomposition rate (+ 60%), but fertilization had no significant effect on decomposition of litter produced under ambient CO2. We conclude that the potential stimulatory effect of an increase in atmospheric N deposition on litter quality and decomposition rates may partially compensate for the inhibitory effects of rising atmospheric CO2 in these high alpine grassland ecosystems.