DECOMPOSITION OF C-14-LABELED CELLULOSE SUBSTRATES IN LITTER AND SOILFROM A BEECHWOOD ON LIMESTONE

The decomposition of three different C-14-labeled cellulose substrates (plant holocellulose, plant cellulose prepared from C-14-labeled beec h wood (Fagus sylvatica) and bacterial cellulose produced by Acetobact er xylinum) in samples from the litter and mineral soil layer of a bee chwood on limestone was studied. In a long-term (154 day) experiment, mineralization of cellulose materials, production of C-14-labeled wate r-soluble compounds, and incorporation of C-14 in microbial biomass wa s in the order Acetobacter cellulose > holocellulose > plant cellulose in both litter and soil. In general, mineralization of cellulose, pro duction of C-14-labeled water-soluble compounds, and incorporation of C-14 in microbial biomass were more pronounced, but microbial biomass C-14 declined more rapidly in litter than in soil. In short-term (14 d ay) incubations, mineralization of cellulose substrates generally corr esponded with cellulase and xylanase activities in litter and soil. Pr e-incubation with trace amounts of unlabeled holocellulose significant ly increased the decomposition of C-14-labeled cellulose substrates an d increased cellulase activity later in the experiment but did not aff ect xylanase activity. The SUM of (CO2)-C-14 production, C-14 in micro bial biomass, and C-14 in water-soluble compounds is considered to be a sensitive parameter by which to measure cellulolytic activity in soi l and litter samples in short-term incubations. Shorter periods than 1 4 days are preferable in assays using Acetobacter cellulose, because t he decomposition of this substrate is more variable than that of holoc ellulose and plant cellulose.