Comparative studies on functional diversity of soil microbial community of larch plantations with different ages in black soil region，northeastern China

Metabolism diversity of soil microbial carbon sources of surface soil (0-20 cm) from 21, 30, 40, and 52-year-old larch (Larix gmelini) plantations in typical black soil region of northeastern China was studied by using the method of Biolog-ECO microplate culture. Results showed that the average well color development (AWCD) increased gradually with forest age increasing, varying from 0.41 to 1.40 and 0.20 to 0.69 (cultured for 168 hrs) for 0-10 cm and 10-20 cm soil depth, respectively. The peak value of microbial functional diversity was found in 52-year-old plantations, followed by 40, 30, 21-year-old in consequence. The microbial functional diversity indices in shallower soil depth all showed higher values: for soil in 0-10 cm and 10-20 cm depth, richness index was 12-25 and 6-14, ShannonWeiner diversity index was 2.55-3.12 and 1.83-2.62, Simpson diversity index was 0.89-0.95 and 0.76-0.91, McIntosh index was 4.22-9.49 and 2.52-6.18, respectively. The utilization efficiency of six carbon sources by the soil microbial community also increased when plantations grew from 21 to 52-year-old. Sensitive carbon sources to cause microbial metabolic differences were carbohydrates, polymers and amines for soil of 0-10 cm, and carboxylic acids in addition to carbohydrates and amines for 10-20 cm also. The significant relationships were observed between the metabolic diversity of microbial communities and soil physical and chemical properties. We conclude that functional diversity of soil microbial community in larch plantations increases gradually with the increase of forest age, and soil microbial functional diversity can be improved by implementing plantation vegetations recovery. The results presented in this paper could further suggest a reference for revealing transmutation of soil quality under plantations of black soil region, northeastern China.