Abstract: [Objective] This paper aimed to study the differences in soil physical and chemical properties and utilization of carbon source by microbial communities, and the influences of stand age of Chinese fir plantationson soil microbial functional diversities, so as to provide a theoretical basis for sustainable management of Chinese fir plantation.[Method] The 3-, 12-and 38-year-old Chinese fir plantations were targeted in Wuyi Mountain, Fujian Province. Biolog-ECO method was used to study the characteristics of carbon utilization by soil microorganisms in the topsoil layer (0-20 cm) of Chinese fir plantations at different stand ages. The heatmap analysis, principal component analysis (PCA) and correlation analysis were used to reveal the differences in use of various carbon sources by microorganisms and the main influencing factors that cause differences.[Result] The results showed that the metabolic activity, Shannon-Wiener diversity index (H'), Pielou evenness index (J),Simpson diversity index (D), McIntosh Diversity Index (U) and McIntoshevenness index(E) all gradually increased with the increase of stand age. The metabolic activity of soil microbial community in 38-year-old Chinese fir plantation was significantly higher than that of 12-and 3-year-old Chinese fir plantation (P<0.05). And the utilization intensity of phenolic acids, amines and amino acids in 38-year-old Chinese fir plantation was higher, that of phenolic acids, polymers and amino acids in 12-year-old Chinese fir plantation was higher, and that of polyphenols, carboxylic acids and carbohydrates in 3-year-old Chinese fir plantation was higher. In 38-year-old Chinese fir plantation, the utilization intensity of carbohydrates, amino acids, carboxylic acids and amines was significantly higher than that in 3-year-old Chinese fir plantation, while there was no significant difference in the utilization intensity of the six types carbon sources by soil microbial communities between 12-year-old and 3-year-old (P>0.05). The results of heatmap analysis showed that soil microbial community of 38-and 12-year-old Chinese fir plantations could metabolize 31 kinds of carbon sources, while the soil microbial community of 3-year-old Chinese fir plantation could only metabolize 19 kinds of carbon sources. Among environmental factors, soil pH, total nitrogen and carbon to nitrogen ratio (C:N) had significant effects on the metabolic function of microbial communities.[Conclusion] The results showed that the soil microbial community of 38-year-old Chinese fir plantation had the highest metabolic activity and diversity, and the 3-year-old had the lowest among the three forest ages. The pH and total N content increased with the increase of forest age, and the carbon to nitrogen ratio decreased with the increase of forest age, indicating that the stand age was an important factor driving soil biotic and abiotic changes in Chinese fir plantations.

Key words: Chinese fir plantation, Biolog-ECO, soil microorganism, metabolic functional diversity