Does fertilizer application alter the effects of elevated CO 2 on Carex leaf litter quality and in situ decomposition in an alpine grassland?

Abstract

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 ( Carex curvula) in a high alpine grassland in Switzerland; and especially (2) if fertilization improves the quality of leaf litter produced under elevated atmospheric CO 2 and compensates for the suppressive effects of high CO 2 on the in situ decomposition rates of C. curvula litter, observed at this site in an earlier study. Fertilizer application (40 kg 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 CO 2 treatments. Improvement in the mean N quality of litter produced under elevated CO 2 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 CO 2. 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 CO 2 in these high alpine grassland ecosystems.