EFFECTS OF LEAF-LITTER MIXTURES ON THE DECOMPOSITION OF QUERCUS-SERRATA AND PINUS-DENSIFLORA USING FIELD AND LABORATORY MICROCOSM METHODS

The decay rate, respiration rate and nitrogen dynamics of mixed Quercu s serrata Murray and Pinus densiflora Sieb et. Zucc. leaf litter were studied for 1 year using field and greenhouse microcosms (GM) and litt erbag (LB) methods. The study aimed to determine the effect of mixing two types of litter with contrasting physical and chemical properties. It also evaluated the suitability of using laboratory microcosms in d ecomposition studies using mixed litter. Results indicate that combine d weight losses were affected by both litter mixtures and incubation c hambers, Decay rate of Quercus was enhanced in field microcosms (FM) c ompared to LBs while that of Pinus was not. The decay rates of both li fter types were significantly suppressed in GM as compared to field se t up (FM and LB) which were comparable. Observed combined weight losse s of mixed litter were higher than predicted based on single litter de composition assays, suggesting a positive enhancement effect. Mixed li tter had higher biological activities, indicated by litter respiration rates and mediated the decay process. Observed N contents of Pinus li tter were higher than predicted, while the observed values of Quercus were lower than predicted based on data from pure litter, due to inter active effect of mixed litter. Nutrient translocation from nutrient-ri ch litter (Quercus) to nutrient-poor (Pinus) litter had occurred. It i s then inappropriate to use data derived from pure litter decompositio n studies to estimate the nutrient dynamics of mixed forest stands bec ause it may be either under-or over-estimated, depending on the type o f litter and the rate of mixture. (C) 1998 Elsevier Science B.V. All r ights reserved.