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

Abstract

An investigation on soil organic carbon, total N and P. NO3(superscript -)-N, available P, microbial biomass C, N and P, basal respiration and metabolic quotients (qCO2) was conducted to compare differences in soil microbial properties and nutrients between 15-year-old pure Chinese fir (Cunninghamia lanceolata) and two mixed Chinese fir plantations (mixed plantations with Alnus 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 organic carbon, total N, NO3(superscript -)-N, total P and available P in mixed plantations were higher than that in pure plantation. Soil microbial biomass N in two mixed plantations was averagely higher 69% and 61% than that in pure plantation at the 0-10 cm and 10-20 cm soil depth, respectively. Soil microbial biomass C, P and basal respiration in mixed plantations were higher 11%, 14% and 4% at the 0-10 cm soil depth and 6%, 3% and 3% at the 10-20 cm soil depth compared with pure plantation. However, soil microbial C: N ratio and qCO2 were averagely lower 34% and 4% in mixed plantations than pure plantation. Additionally, there was a closer relation between soil microbial biomass and soil nutrients than between 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 microbial properties and soil fertility, and can be helpful to restore degraded forest soil.