Fine fuel dynamics of old-growth redwood forests

Litterfall and litter decomposition were measured for two years at four sites in old-growth redwood (Sequoia sempervirens) forests. Sites were selected to represent sloped and flat areas at inland and coastal locations. Both a litterbag and an in situ, mass balance style of analysis were used to determine decomposition rates. Litterfall, decomposition rates and, forest floor litter layer loadings were used to model equilibrium (decomposition=litterfall) litter loads and the time required to attain them. Average annual litterfall at the four sites ranged from 3122 kg ha-1 yr-1 to 4687 kg ha-1 yr-1. Pseudotsuga menziesii litter exhibited the fastest decomposition rates, losing an average of 55 per cent of its original weight at the end of two years. Lithocarpus densiflorus lost 50 per cent and S. sempervirens, 42 per cent. Decomposition rate constants (k) calculated from the litterbag analysis ranged from .273 to .405. Values of k estimated from the mass balance analysis were slightly lower, ranging from .210 to .262. Equilibrium litter loads estimated with the modeling procedure ranged from 7760 kg/ha to 14,500 kg/ha. In comparison, samplings of existing forest floor litter loads resulted in estimations of 14,340 kg/ha to 22,300 kg/ha. Times required for the litter layers to reach equilibrium were estimated to be 7 to 11 years with the litterbag analysis and from 11 to 20 years with the mass balance study. Statistical analysis suggested that, for the two year period, S. sempervirens litterfall at the sloped, inland site was significantly lighter (p.05) than the other three sites. No statistically significant differences (p.05) in decomposition rates were found among the four sites in the litterbag analysis. In the mass balance study, the existing litter layer at the coastal flat site was significantly thinner (p.05) than the inland flat and coastal sloped sites while the litter at the inland sloped site was significantly thicker.