Litterfall and forest floor dynamics in Eucalyptus pilularis forests

Calculations relating the input of litterfall to litter or forest floor mass in forests generally assume that the forest floor reaches an equilibrium state. Based on this assumption, a decomposition factor (k') can be calculated. In the present paper, this basic assumption is questioned and the implications considered. Data on litterfall and forest floor from blackbutt (Eucalyptus pilularis) regrowth forests and plantations were collated from publications and the authors' studies to evaluate both assumptions and relationships. Blackbutt grows over a wide environmental range but its main distribution is in mild temperate to subtropical conditions. Data were from single-plot studies, sequential studies and chronosequences in both plantations and native regrowth forests. Stands ranged in age from 3 years to maturity in the case of pure, or almost pure blackbutt stands. The forest floor biomass increased up to 12.3 t ha(-1) at 33 years of age with no evidence of steady state. Litterfall increased up to 7.8 t ha(-1) year(-1) and was correlated with crown biomass. Regrowth stands were relatively undisturbed and more than 20 years of age, and litterfall ranged from 4.1 to 11.6 t ha(-1) year(-1) and was correlated with stand basal area. Forest floor mass in regrowth forests was variable between the different aged stands but did not exceed 18 t ha(-1) , and there was no evidence that steady state was achieved. The forest floor mass was related to, and approximately 1.7 times the input of litterfall. Although the assumption of steady state was not valid, a k' factor was estimated that related input to forest floor mass and this was relatively constant across all stands and correlated with generalized environmental data. Although assumptions of forest floor equilibrium cannot be supported for E. pilularis, it still should be possible to predict forest floor mass and decomposition from stand conditions and general environmental data.