秭归张家冲坡耕地作物类型对土壤微生物功能多样性的影响

Effects of crop types on soil microbial functional diversity in sloping agricultural land of Zhangjiachong in Zigui County

湖北省秭归县张家冲小流域位于三峡库区,土地资源贫瘠,生态环境脆弱。为探讨相似土壤环境下,种植不同作物的坡耕地土壤微生物的碳源代谢是否有差异,我们选择该地水土保持站试验田坡耕地3种典型作物(柑橘、茶树、花生)及有无树篱搭配共计6种处理的6块样地,采得18个土样,测定了土壤理化性质,通过Biolog ECO微平板技术研究土壤微生物功能多样性,并运用多元统计方法,探索土壤微生物功能多样性与土壤理化性质的关系。结果表明,土壤理化性质及土壤微生物受种植作物类型的影响。花生样地速效养分含量最低(P<0.001)。柑橘无树篱样地土壤微生物活性最高,即Biolog培养的平均颜色变化率(AWCD)最大(P<0.05)。不同作物样地土壤微生物功能多样性顺序为:柑橘地>花生地>茶树地(P<0.05)。总体来看,样地土壤微生物主要代谢碳源类型为多聚物类和氨基酸类。芳香类和胺类碳源代谢在不同作物样地间存在显著差异(P<0.05),有无树篱对糖类和羧酸类碳源代谢有较大的影响(P<0.01)。柑橘样地土壤微生物碳源代谢受土壤理化因子影响较小,茶树样地土壤微生物的代谢与土壤pH、碱解氮、速效磷等相关性较高,而花生样地土壤微生物的代谢却与总氮、速效钾相关性较高。研究表明:在该地贫瘠的土壤中,不同作物土壤理化性质、土壤微生物代谢活性、多样性及碳源代谢类型存在差异;土壤微生物代谢特征与土壤理化性质有关。

To assess the effect of crops on the utilization of carbon sources by soil microorgan- isms, we chose one piece of sloping agricultural land in Zhangjiachong, part of the Three Gorges Reservoir area in Zigui County, Hubei Province as the study site. An experiment was designed considering three types of crops, including tea, orange and peanuts, with or without hedges. In total, 18 soil samples were collected from 6 plots with 3 replicates in each plot. Soil physicochemical properties were determined, and soil microbial functional diversity was measured by Biolog ECO plates. Effects of crops and hedges on soil microbes, soil physicochemical properties and the relationships between them were explored by multivariate statistical analysis. The results indicated that hedge had no significant effects on soil physicochemical properties, but crops did. Soil sam- ples from the peanut plots showed lowest availability of nitrogen, phosphorus and potassium （P〈 0.001）. Soil microbial activity was higher in the orange plot （without hedge） than that in the other plots （P〈0.05）. The functional diversity indices were in order of： orange plots 〉 peanut plots 〉 tea plots （P〈0.05）. Amino acids and polymers were the dominant carbon sources of soil microbial metabolism from all sample plots （P〈0.05）. The utilization of aromatic and amine car- bon significantly differed among different crop lands （P〈0.01）, while hedge greatly affected the utilization of carbohydrates and carboxylic acids. The soil physicochemical variables had minor influence on the carbon source utilization by soil microbes in the orange plots. The utilization of car- bon sources in the tea plots was highly affected by the soil factors such as soil pH, available ni- trogen and available phosphorus, and that of soil microorganisms in the peanut plots was correla- ted with total nitrogen and available potassium. The results indicated that in nutrient-poor soil, soil physicochemical properties, soil microbial activities and carbon source utilization were different among different crop plots, and soil microbial metabolism of carbon sources was correlated with soil physicochemical properties.