LEAF-LITTER DECOMPOSITION IN THE PICEA-TSUGA FORESTS OF OLYMPIC NATIONAL-PARK, WASHINGTON, USA

The factors controlling litter decomposition of eleven species of leaf litter were examined in the Hoh Rain Forest, Olympic National Park, Washington, using the litter-bag method. Leaching of litter decreased the decay rate-constant as compared to unleached litter. This decrease was in proportion to the readily leachable fraction (rlf) in the litter. Decay of both leached and unleached litter was highly correlated (P <0.001) with lignin: nitrogen ratio, although the regressions differed significantly between leached and unleached litter. Of the unleached litters used, Cornus nutallii decayed fastest (k=2.35-2.46/year), and Pinus monticola decayed slowest (k=0.38/year). A double-exponential regression was used to fit decay time-series from four species. This analysis indicated that species differed markedly in the proportion of fast and slow components and that the fast component was correlated with rlf for three of four species tested. Fast components decayed an order of magnitude faster than slow components. The rate at which these components decayed varied between species, indicating that both the amount and decay rate-constant of fast and slow components must be estimated to use the double-exponential equation. © 1990.