Soil microbial properties and nutrients in pure and mixed Chinese fir plantations

An investigation on soil organic carbon,total N and NO3--N,available microbial biomass C,N and basal respiration and metabolic quotients(qCO2)was conducted to compare diferences in soil microbial properties and nutrients between 1 5-year-old pure Chi— nese fir(Cunninghamia lanceolata)and two mixed Chinese fir plantations(mixed plantations with A/nus cremastogyne,mixed plantations with Kalopanax septemlobus)at Huitong Experimental Station of Forest Ecology(26。45'N latitude and 109。30'E longitude),Chinese Academy of Sciences in May,2005.Results showed that the concentrations of soil organ ic carbon,total N,NO3一N,total P and available P in mi xed plantations were higher than that in pure plantation.Soil microbial biomass N in tw o mi xed plan tations was averagely higher 69% and 61% than that in pure plantation at the 0__10 cm and 1 0-20 cm soil depth,respectively.Soil mi crobial biomass C,P an d basal respiration in mi xed plantations were higher 1 l%,14% and 4% at the O—l0 cm soil dep th and 6%,3% and 3% at the 1020 cm soil depth compared with pure plantation.However,soil microbial C:N ratio and qCO2 were averagely lower 34% an d 4% in mixed plan tations than pure plantation.Addi— tionally,there was a closer relation betw een soil microbial biomass and soil nutrients than betw een basal respiration.microbial C:N ratio and qCO2 and soil nutrients.In conclusion,introduction of broad-leaved tree species into pure coniferous plantation improved soil mi crobial properties and soil fertility,and can be helpful to restore degraded forest soil.