MICROBIAL-C AND MICROBIAL-N, AND RESPIRATORY ACTIVITY, IN LITTER AND SOIL OF A SOUTHERN BEECH (NOTHOFAGUS) FOREST - DISTRIBUTION AND PROPERTIES

Microbial biomass C and N, and respiratory activity (CO2 production), declined with sample depth in the strongly acid litter and soil of a southern beech (Nothofagus spp) forest, at which annual precipitation is about 2000 mm and mean annual air temperature 9.5-degrees-C. Microbial C, and generally N, did not differ significantly between spring and autumn samples, possibly because of spatial variability. As a percentage of total C, microbial C was highest (c 4.5%) in leaf (L) litter, similar (c 2.1%) in FH material and the topmost soil depths (0-20 cm), but declined to 0.6% in 50-60 cm depth soil; microbial N, as a percentage of total N, declined similarly with sample depth. Microbial C: N ratios were also highest (c 13) in L material, but were generally similar (mean 6.7) in all other samples. On an area basis, the mass of microbial C and N to 60 cm soil depth was c 4220 and 605 kg ha-1, respectively, with c 14% occurring in the litter layers. The contribution of litter to total CO2 production on an area basis with roots excluded was, however, c 42%. Temperature coefficients (Q10 values) for CO2 production, determined with 5 and 13-degrees-C data, averaged 3.0. Metabolic quotients (qCO2 values) were highest in L and FH materials, and were low and similar in the different depths of soil. Generally, qCO2 values in this old-growth forest were compatible with other values reported for a late stage of ecosystem succession.