MICROBIAL DECOMPOSITION (RESPIRATION) OF LITTER IN EUCALYPT FORESTS OF SOUTH-WESTERN AUSTRALIA - AN EMPIRICAL-MODEL BASED ON LABORATORY INCUBATIONS

Rate of respiration (CO2 production) from litter of two species of eucalypt. jarrah (Eucalyptus marginata Donn ex Sm.) and karri (E. diversicolor F. Muell.), was determined. Laboratory incubations of litter under controlled moisture and temperature conditions were used to define the relationship between microbial activity and environmental variables. A model relating rate of respiration to moisture content and temperature of litter explained 93-94% of the variation in rates of CO2 production. Respiration was relatively constant at moisture contents > 100% ODW but decreased markedly when moisture <80% ODW. The optimum temperature for respiration was 33-34°C. The model was used as a basis for explaining seasonal patterns of respiration of field samples of litter from jarrah and karri forest. Production of CO2 which is strongly influenced by the Mediterranean climate of south-western Australia, is highest in autumn and spring. During summer, when moisture content of the litter is low, respiration is near zero. Higher average daily rates of litter respiration in karri forest (1.5mg CO2 g-1 litter day-1) than in jarrah forest (0.9mg CO2 g-1 litter day-1) were due partly to the longer period during which moisture content of the litter was adequate for microbial activity in karri forest and partly to differences in substrate quality. © 1990.