Root and root-lignin degradation in a Norway spruce stand: Effects of long-term nitrogen addition

Abstract Mass loss, degradation of lignin and the qualitative change of the organic C structures of spruce root litter (2 – 5 mm in diameter) in O-horizon were studied for a period of 6 years (1995 – 2001) in a Norway spruce stand with a current deposition of 13 kg N and 12 kg S ha−1 yr−1. The stand was fertilized annually by addition of 100 kg N and 114 kg S ha−1 (NS). Litterbags, acid detergent lignin (ADL), CuO-oxidation as well as 13C-NMR were used for measurements of mass loss, lignin concentration, degradation of lignin and changes of the organic C structures, respectively. The roots originating from the NS-treated plots lost 20% of their mass in the first year while in control (CON) plots the corresponding value was 10%. After 1879 days of decomposition the fertilized roots had a cumulative mass loss of 54% compared with the CON roots of 44%. The C/N ratios were significantly lower in the NS roots (35) than in the CON roots (59) after 1879 days of decomposition. The initial concentrations of ADL we...