外源氮素添加对森林土壤氨基糖转化的影响

Effect of nitrogen addition on transformation of amino sugars in forest soil

采用室内模拟培养法研究了不同数量氮素添加条件下森林土壤中3种微生物来源的氨基糖含量的动态变化,并且利用氨基葡萄糖和胞壁酸的比值分析了氮素添加条件下土壤真菌和细菌对土壤氮素转化和积累的相对贡献。结果表明:土壤中氨基糖含量的动态变化与土壤中的养分状况密切相关;当向土壤中添加氮源时,微生物会利用外加氮源合成自身的细胞壁物质,并且高氮处理胞壁酸含量高于低氮处理,而高氮处理氨基葡萄糖含量则低于低氮处理,说明随施氮量的增加更有利于以胞壁酸为代表的细菌残留物在土壤中的积累,不利于以氨基葡萄糖为代表的真菌残留物的积累,氨基半乳糖对氮素添加的响应较小;当土壤中养分缺乏时,氨基糖能够发生不同程度的分解;添加氮源条件下,真菌和细菌来源氨基糖的比值发生变化,细菌对土壤氮素转化的贡献大于真菌,并且高氮处理细菌的贡献更大。本研究表明,氮素添加改变了以氨基糖为代表的土壤氮素的微生物转化过程。

A laboratory incubation of soil samples was conducted to study the dynamics of three kinds of microbial-derived amino sugars in forest soil after adding different amounts of nitrogen.The relative contribution of soil fungi and bacteria to soil nitrogen transformation and accumulation was also investigated by the ratio of glucosamine to muramic acid. The results showed that,dynamics of the soil amino sugar contents were closely related to the nutrient status of the soil.When nitrogen was added to the soil,the microorganisms could use the extraneous nitrogen to synthesize their own cell wall material,and the content of muramic acid in the high nitrogen treatment was higher than that in the low nitrogen treatment,while the content of glucosamine in the high nitrogen treatment was lower than that in the low nitrogen treatment. Our study indicated that increased nitrogen addition was more beneficial to the accumulation of bacteria-derived muramic acid. However,high nitrogen addition was detrimental to the accumulation of fungi-derived glucosamine. The response of galactosamine to nitrogen addition was weak. When soil nutrient was deficient,the amino sugars could be decomposed with different degrees. In addition,the ratio of bacteria-derived amino sugar to fungi-derived amino sugar was changed. We found that the contribution of bacteria to soil nitrogen transformation in soil was greater than that of fungi,and the contribution of bacteria to soil nitrogen transformation was greater under high nitrogen addition.This study indicated that nitrogen addition changed the microbial transformation of amino sugarderived soil nitrogen.