LIGNIN DECOMPOSITION IN DECAYING LEAVES OF FAGUS-SYLVATICA L AND NEEDLES OF ABIES-ALBA MILL

Lignin decomposition in litter of beech leaves and fir needles as rela ted to litter N concentration and litter mass loss was studied for 7 y in two forests at Mount Taburno (41 degrees 05'N., 12 degrees 07'E.; Campania Apennines). Both types of litter showed a pattern of decompos ition characterized by two stages with significantly decreasing decomp osition rates. Litter N concentration did not appear to influence the rate of litter decomposition in either the early or the late stage of the process. On the contrary mass loss rates of litter were influenced by lignin concentrations at the beginning of the late stage: the lowe r the lignin concentration the higher was mass loss rate. Both in beec h and fir litter lignin degradation started immediately during incubat ion. Lignin degradation throughout the study was less in fir needles t han in beech leaves with lignin losses of 60-67% and 73-87% of initial amount, respectively. Both in beech and fir litter, lignin loss rate was negatively correlated to the initial N concentration. Lignin loss rate of both beech and fir litter was correlated to litter mass loss r ate during the early as well as during the late phase of decomposition . Different dynamics of lignin decomposition between the two species w ere observed with a higher lignin decomposition rate in the early stag e than in the late stage in beech litter, and rates of lignin decompos ition increasing from early to late phase in fir litter.