小叶锦鸡儿根际微生物群落功能多样性对环境变化的响应

利用Biolog技术对内蒙古草原灌丛优势种小叶锦鸡儿(Caragana microphylla)根际土壤微生物群落功能多样性特征及其对大气CO2浓度、土壤氮水平和土壤水分3个环境因子变化的响应进行了研究。结果表明:(1)小叶锦鸡儿根际土壤微生物利用碳源总量在整个培养过程中呈逐渐增加的趋势。其利用比例较高的碳源类型为聚合物、糖类和氨基酸。(2)主成分分析表明,8个处理组的微生物群落功能多样性差异显著,其中与主成分1显著相关的碳源有14种,分别属于聚合物、糖类、氨基酸和羧酸。(3)加倍CO2浓度极显著提高平均颜色变化率(AWCD)以及丰富度指数和Shannon均匀度。(4)氮素添加使AWCD、丰富度指数和Shannon均匀度均极显著降低,其抑制效应在加倍CO2浓度时有所缓解。(5)加水处理对上述指标均有一定的促进作用,但是差异未达显著水平。(6)加倍CO2浓度和氮素添加联合处理下,小叶锦鸡儿根际微生物活性高于对照处理,说明加倍CO2浓度对微生物活性的促进效应强于添加氮素的抑制效应。(7)CO2和氮素对上述指标有交互作用。综上所述,小叶锦鸡儿根际土壤微生物群落的功能在很大程度上受到外界环境因子的影响,对环境变化较敏感的碳源类型为聚合物、糖类、氨基酸和羧酸,与利用比例较高的碳源类型基本一致。

Response of microbial community functional diversity in the rhizosphere of Caragana microphylla to environmental change

Functiona1 diversity of soil microbia1 communities in rhizosphere of Caragana microphylla, a dominant shrubby leguminous species in the Inner Mongolia Grassland Ecosystem, was examined using the Biolog method to evaluate the effects of environmental changes in atmospheric CO2 concentration, soil nitrogen level and water level on soil microbia1 community. The results showed that total amount of carbon sources utilized by microbes in rhizosphere of C. microphylla increased with the incubation time. The main types of carbon sources utilized were polymers, carbohydrates and amino acids. Principal Component Analysis indicated that microbial community functional diversity varied significantly among 8 treatment groups. Fourteen categories of carbon sources were significantly related to the principal component 1, which belonged to polymers, carbohydrates, amino acids, and carboxylic acids. Elevated CO2 significantly increased the value of average well colour development (AWCD), richness index and Shannon evenness. Under nitrogen addition treatments, AWCD, richness index and Shannon evenness were significantly decreased, but this inhibition was slightly alleviated under elevated CO2. Water addition showed no significant effect on AWCD and diversity indices of soil microbial community. Rhizospheric microbial activity were higher under combined treatments of elevated CO2 and nitrogen addition than CK, which implied that the positive effect of elevated CO2 on microbial activity of C. microphylla was larger than the negative effect of nitrogen addition on it. There was significant CO2 nitrogen interaction on AWCD, richness index and Shannon evenness. In conclusion, microbial community functional diversity in rhizosphere of C. microphylla was sensitive to environmental changes, with the sensitive carbon source types being polymers, carbohydrates, amino acids, and carboxylic acids, essentially those carbon sources that are also the most heavily used.