CHEMICAL-COMPOSITION AND CARBON MINERALIZATION POTENTIAL OF SCOTS PINE NEEDLES AT DIFFERENT STAGES OF DECOMPOSITION

Chemical changes in decomposing Scots pine needles exposed for 22 mont hs in litter bags in central France forest were determined using near infrared reflectance spectroscopy (NIRS). Concentrations of N, P, cell ulose, lignin, lignin-C and lignin-N content were related to accumulat ed mass loss. Litters from the litter bags exposed for 2, 4, 8, 12 and 16 months in situ were incubated for I additional year in the laborat ory under controlled conditions, and CO2 release was measured (carbon mineralisation potential). Asymptotic and exponential functions were f itted to these data and defined respirometric fractions with low, inte rmediate and high decomposition rates. In addition, litter (L), fermen tation (F) and humus (H) layers from the site were incubated in the la boratory under the same conditions. The correspondence analysis, using the parameters of the asymptotic functions as variables, showed that the carbon mineralisation potential of the naturally-decomposing litte r collected at the site was similar to the mineralisation potential of the material in the litter exposed in bags for about 1 yr in the fiel d. Nevertheless the decomposition rates observed under laboratory cond itions should be interpreted with caution since they were considerably lower than the decomposition rates of the same Litter exposed in situ . (C) 1998 Elsevier Science Ltd. All rights reserved.