Decomposition of Cistus incanus leaf litter in a Mediterranean maquis ecosystem: mass loss, microbial enzyme activities and nutrient changes

The decomposition of leaf litter from the summer deciduous shrub, Cistus in canus, in a low Mediterranean maquis was followed for 18 months. Microbial activity in the decaying materials was evaluated by measuring respiration, as well as cellulase, xylanase, alpha- and beta -amylase activities. Fungal biomass, pH, water soluble substances and nutrient content (N, S, P, Ca, K , Na, Mg, Mn) were also measured. Litter incubated in the field in autumn a nd in spring evidenced similar decay constants (k(a) = 0.36 +/- 0.02 yr(-1) and k(s) = 0.32 +/- 0.03 yr(-1), respectively). Mass loss rate was not aff ected by the dry summer. Microbial activity showed seasonal changes, with t he highest values (150 mu mol CO2 g(-1) d.w. d(-1)) in autumn and winter an d the lowest ones in summer (30 mu mol CO2 g(-1) d.w. d(-1)) when the litte r water content was around 10% d.w.). Litter water content was strongly cor related to microbial respiration, cellulase and xylanase activities. The al pha -amylase and, to a lesser extent, beta -amylase activities occurred at the highest level (0.78 and 0.35 mu mol glucose g(-1) d.w. h(-1), respectiv ely) during the initial stages of decomposition, when residual starch was s till present in the litter, but rapidly declined. Total fungal biomass was significantly and positively correlated with mass loss throughout the exper iment. Water soluble substances decreased in the first 4 months of decompos ition and increased thereafter. The elements N, S, K, P, Ca, Na decreased, while Mg and Mn increased. (C) 2001 Elsevier Science Ltd. All rights reserv ed.