Effects of leaf litter mixtures on the decomposition of Quercus serrata and Pinus densiflora using field and laboratory microcosm methods

Abstract

The decay rate, respiration rate and nitrogen dynamics of mixed Quercus serrata Murray and Pinus densiflora Sieb et. Zucc. leaf litter were studied for 1 year using field and greenhouse microcosms (GM) and litterbag (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 decomposition studies using mixed litter. Results indicate that combined weight losses were affected by both litter mixtures and incubation chambers. Decay rate of Quercus was enhanced in field microcosms (FM) compared to LBs while that of Pinus was not. The decay rates of both litter types were significantly suppressed in GM as compared to field set up (FM and LB) which were comparable. Observed combined weight losses of mixed litter were higher than predicted based on single litter decomposition assays, suggesting a positive enhancement effect. Mixed litter had higher biological activities, indicated by litter respiration rates and mediated the decay process. Observed N contents of Pinus litter were higher than predicted, while the observed values of Quercus were lower than predicted based on data from pure litter, due to interactive effect of mixed litter. Nutrient translocation from nutrient-rich litter ( Quercus) to nutrient-poor ( Pinus) litter had occurred. It is then inappropriate to use data derived from pure litter decomposition studies to estimate the nutrient dynamics of mixed forest stands because it may be either under- or over-estimated, depending on the type of litter and the rate of mixture.