In this study, the effects of intercropping with alfalfa and nitrogen application on the functional diversity of soil microbial community in mulberry rhizosphere were examined by Biolog-EcoplateTM technique, and principal component and canonical analyses. Compared to monoculture with no nitrogen (N) addition, monoculture with N application and intercropping with alfalfa remarkably reduced soil pH and significantly increased the contents of soil organic matter, soil available N, soil water content, and activities of peroxidase and urease. Monoculture with N application and intercropping with alfalfa (with or without N application) increased the AWCD values, diversity index, and the carbon source utilization ratios of soil microbes. Higher increments of these parameters were detected in the treatment of intercropping plus N application. The results of principal component analysis showed that N application and intercropping changed the capacity of the rhizosphere microbial community for utilizing carbon sources. The utilization of carbon sources highly related to the principal components by the rhizosphere microbial communities was similar in the treatments of monoculture with N application and intercropping without N application. The utilization of itaconic acid and D-glucamaminic acid in the latter was more than 4% and was significantly higher than that in the former. The results from redundancy analysis showed that the soil microbial diversity in mulberry rhizosphere of the treatment of monoculture without N application was positively correlated with polyphenol oxidase activity and negatively correlated with soil water content, whereas that of monoculture with N application and intercropping without N application was significantly positively correlated with soil pH and soil water content and negatively correlated with soil N avalaibility. The diversity of the microbes in the rhizosphere soil of mulberries under the treatment of intercropping with N application showed positive correlation with soil N availability and was significantly negatively correlated with soil pH.
利用Biolog-EcoplateTM结合主成分与冗余分析法,研究与苜蓿间作和施氮对桑树根际土壤微生物功能多样性及其与环境因子的影响.结果表明: 与单作无氮相比,单作施氮和间作(无氮和施氮)明显降低桑树根际土壤pH值,显著提高有机质含量、有效氮、含水量和过氧化物酶、脲酶的活性.同时,单作施氮和间作(无氮和施氮)提高了桑树根际土壤微生物的AWCD值、多样性指数和利用碳源比例,且间作施氮增加其提高的程度.主成分分析表明,施氮和间作改变了根际土壤微生物利用碳源强度和种类,其中单作施氮和与间作无氮处理的碳源利用情况相似,但后者对衣康酸和D-葡糖胺酸的利用率(>4%)显著高于前者.冗余分析表明,单作无氮桑树根际土壤微生物多样性与土壤多酚氧化酶活性呈正相关,与土壤含水量呈负相关.单作施氮与间作无氮处理的桑树根际微生物多样性与土壤pH值和含水量呈显著正相关,与土壤氮素营养呈负相关.间作施氮处理的桑树根际微生物多样性与土壤氮素营养呈正相关,而与土壤pH值呈显著负相关.
Keywords: carbon source; intercropping; mulberry; principal component analysis; redundancy analysis.