DECOMPOSITION OF NOTHOFAGUS FALLEN WOODY DEBRIS IN FORESTS OF TIERRA-DEL-FUEGO, ARGENTINA

We report the decay constants of fallen fine (<1 cm in diameter) and c oarse (greater than or equal to 1 cm) woody debris of the southern bee ches lenga (Nothofagus pumilio (Poepp. et Endl.) Krasser), nire (Notho fagus antarctica (Forst.) Oerst.), and guindo (Nothofagus betuloides ( Mirb.) Oerst.) in Tierra del Fuego, Argentina. The decomposition of sm all branches (<1 cm) was assessed with the nylon mesh bag technique. A tethered-branch method was used for the decomposition of branches 1-1 6 cm in diameter of hire and guindo incubated in the field for a perio d of approximately 4 years. For large lenga branches (8-17 cm) and bol es (19-60 cm), we used a chronosequence method, using a 3.5- to 55-yea r series of natural. field incubations. Small lenga branches decayed f aster (k=0.47 year(-1)) than those of nire (k=0.23.year(-1)) and guind o (k=0.17.year(-1)). For branches 1 cm, decomposition rates of the spe cies were not significantly different, but diminished with diameter in crease. The rate of change of k versus diameter was significantly grea ter for lenga. In the full range of lenga wood diameters studied, k de creased exponentially with diameter (k=0.553.exp(-0.177.diameter)) att aining a nearly constant value (k=0.010.year(-1)) between 30 and 60 cm . Residence time increased from 2 to 100 years for small branches to l arge boles, respectively. There was no lag time for decomposition init iation. The decay constants for large lenga branches and boles appeare d similar to or slightly greater than those of cold temperate conifers and less than those of hardwoods of the cold and warm temperate zones of the Northern Hemisphere.