Effects of single and mixed species forest ecosystems on diversity and function of soil microbial community in subtropical China

The objective of the present study was to evaluate soil microbial community function and diversity among eight single and mixed species forest ecosystems (18-year-old restoration) in subtropical China. Soil samples of the 0-10 cm depth were taken from each of the eight forest ecosystems: Masson pine (CP1); Pitch pine (CP2); Slash pine and Sweetgum (CBMP1); Slash pine and Camphortree (CBMP2); Masson pine and Sweetgum and Chinese Gugertree (CBMP3); Sweetgum and Chinese Gugertree (BMP); Chinese Gugertree (BP1); and Sweetgum (BP2). Potential soil bacterial catabolic activities were assessed by the MicroResp (TM), and bacterial and fungal community diversities were analyzed by using the polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) technique. Substrate-induced respiration (SIR) rates and catabolic evenness of the SIR values for 15 carbon (C) sources under the broadleaved forest ecosystems (BP2, BMP, BP1) were much higher than those under the mixed conifer-broadleaved forest ecosystem (CBMP1 and CBMP2), and then under the pure conifer forest ecosystems (CP2 and CP1). Value of Shannon-Weaver index in the MicroResp (TM) was similar to that in the DGGE method, but the value of evenness was lower than that in the DGGE method. Principal component analysis, using all 15 C sources in the MicroResp (TM), 39 bands of fungi and 21 main bands of bacteria in the DGGE profiles, revealed a separation of all the soil samples, indicating that they had different patterns of potential C utilization and different microbial communities. The scores of the first principal component appeared to reflect the variation of soil microbial functional and structural communities associated with different forest ecosystems. Results from this study showed that forest ecosystems have significantly influenced the composition and function of soil microbial community. Catabolic diversity and function of soil microbial community under broadleaf tree species and mixed broadleaf-conifer plant species are much better than under conifer tree species. This may indicate that the efficiency of soil quality restoration is higher under broadleaf species than under coniferous species. Further study is needed for investigating the consequences of the changes seen in this study on soil microbial functional diversity.