松嫩草地4种植物功能群土壤微生物碳源利用的差异

为了探讨草地不同植物功能群土壤微生物碳源利用差异,利用Biolog-ECO微平板检测法,研究了松嫩放牧草地禾草(Grass)、羊草(Leymus chinensis)、杂类草(Forb)和豆科牧草(Legume)4种植物功能群土壤微生物碳源代谢的多样性变化特征。结果表明,在培养的240h内,4种不同植物功能群的土壤微生物对碳源的利用程度均随着时间的延长而升高,表明微生物代谢活性随着时间而增强;不同植物功能群土壤微生物总体活性(AWCD)(P0.001)、Shannon-Wiener指数(H)(P0.001)、物种丰富度(R)(P=0.005)、Pielou均匀度指数(E)(P0.001)差异显著;其中禾草的各项指数明显高于其他3种(P0.01),杂类草的各指标均最低。禾草、羊草对糖类、氨基酸类、羧酸类、多聚物类有较好的利用,豆科牧草除羧酸类外对其他碳源都有更好的利用,杂类草只对酚类碳源利用率最高,而对其他碳源利用率极低。总体得出4种功能群土壤微生物的碳源利用率顺序为:禾草羊草豆科牧草杂类草。

Utilization of carbon sources by soil microbial communities of four plant functional groups in Songnen Steppe

The soil physical-chemical properties and the soil microbial functional diversity for carbon source utilization may vary depending on plant functional groups and be susceptible to soil surface disturbance. The objective of this study was to assess the effect of plant functional groups on the potential activities of soil microbial communities and to evaluate the association with soil properties under different plant functional groups (grass, Leymus chinensis, forb, and legume) in Songnen steppe. Soil samples were collected in August 2011. Physiological profiles (CLPP) (Biolog Ecoplates^TM) at community levels were measured for each plot to determine the capability of soil microorganisms in utilizing 31 types of carbon source. Furthermore, soil physiochemical properties (pH, electrical conductivity EC], soil water SW], soil organic carbon SOC], total nitrogen TN], and C : N ratio C/N]) were determined in rhizosphere soil under different plant functional groups. The results showed that carbon source utilization and microbial metabolic activity increased with time from 36 to 180 hours. There was a significant difference in the soil microbial community structure among plant functional groups. Significant difference was observed in AWCD (the average well color development) (P < 0.001), Shannon-Wiener index (P < 0.001), richness (P = 0.005) and Pielou evenness index (P < 0.001), and they were significantly higher for grass than other functional groups at the latest stage of incubation (P < 0.01). Carbon source utilization was highest for microbial community under grasses, and it was lowest under forbs. The difference in microbial community structure may result in the difference in utilization of the six types of carbon sources. Grasses and Leymus chinensis had higher utilization ability for sugar, amino acids, carboxylic acids, and polymers, and legumes had higher utilization ability for carbon sources except for carboxylic acids. Forbs had highest utilization ability for phenolic compounds but had lower utilization ability for other carbon sources. SOC and TN of the soil were closely associated with the value of AWCD, Shannon-Wiener index, Richness and Pielou evenness index, and EC of the soil was associated with AWCD and richness, while the effect of SW, pH, and C/N were not significant. For further determination of microbial communities under different plant functional groups, Biolog data after 180 h were subjected to redundancy analysis (RDA), and the results showed that TN, SOC, and EC were the most important indices to represent soil quality under the four plants functional groups in this steppe. Carbon source utilization of soil microbial function changed among the four plant functional groups as follows: grass > Leymus chinensis > legume > forb. This result will improve the understanding of the underground carbon cycle and will benefit the grassland management in Songnen steppe by providing a scientific guide for preservation and improvement of soil quality, soil fertility, and nutrient use efficiency, and for enhancing protection of the ecological environment.