土壤微生物数量对模拟氮沉降增加的早期响应

The short-term response of soil microorganism number to simulated nitrogen deposition

通过以南亚热带森林三种主要树种即荷木、锥栗和黄果厚壳桂为主的苗圃试验地的苗圃控制实验,初步探讨土壤微生物数量对模拟氮沉降增加的响应。结果表明,施氮增加对土壤微生物数量的影响根据类群和氮处理水平不同而异。总的来说,施氮增加对土壤微生物数量具有促进作用,这种促进作用对放线菌数量仅在一定(中氮)处理水平以下,超过此水平施氮增加则表现为抑制作用,而施氮对真菌数量则始终表现为抑制作用,尤其以中N处理水平的抑制作用最强。但目前细菌仍占微生物总量的绝对优势,放线菌次之,真菌则占微生物总量的比例最小。分析结果还表明,有效氮与放线菌、有效氮与细菌数量变化呈显著相关关系。

The short-term response of soil microorganism number to simulated nitrogen deposition was studied in a nursery of Dinghushan Biosphere Reserve. The species of seedlings in the nursery were Schima superba,Castanopsis chinensis and Cryptocarya concinna. The simulated elevated N depositions were equivalent to 0（Control） ,5（T5）, 10 （T10）, 15（T15） and 30（T30）gN·m^-2·a^-1. Dissolved NH4NO3 was sprayed in the field of the nursery twice every month and began in January 2003. Results indicated that microorganism number responded to N treatment in all groups（bacteria,actinomycetes and mould） but varied depending on different group and nitrogen treated level. Overall,nitrogen addition significantly increased soil bacteria number, but significantly decreased soil mould number. Meanwhile,nitrogen addition showed accelerated effect to the actinomycetes at the nitrogen treated levels lower than middle and restrained effect higher than that level. Available N in the field was significantly correlated with the number of soil bacteria and of actinomycetes.