Microbial biomass-N was extracted using the chloroform fumigation-extraction technique (Vance et al., 1987). Ninhydrinreactive N released by fumigation was converted to biomass-C using a conversion factor of 20.6 (Joergensen and Brookes, 1990). Soil dehydrogenase activity (DHA) was determined following the Tabatabai method (Tabatabai, 1994). Soil respirationwas determined bymeasuring O2 absorption by microorganisms using OxiTop Control BM6 containers with
an OxiTop Control OC 110 measurement system (WTW, Weilheim, Germany).