中文摘要：

以不施肥与休闲处理为对照,通过对土壤微生物磷脂脂肪酸（PLFA）、中性磷脂脂肪酸（NLFA）、NLFA/PLFA比值及各菌群特定PLFA比值的测定,研究不同氮肥处理条件下东北黑土微生物群落变化规律.PLFA测定结果表明,氮磷配施能促进土壤微生物生长;氮磷钾配施未表现出促进土壤微生物生长的作用;单施氮肥处理因有效磷等养分过度消耗而抑制真菌生长.不同菌群之间PLFA比值表明,真菌较细菌更能适应养分贫瘠条件,而氮肥与磷肥的施入则能促进细菌生物量增加.不同氮肥处理NLFA含量及个别NLFA/PLFA比值存在较大差异,可用来说明土壤微生物生理状态和土壤养分水平.

英文摘要：

Effects of long-term application of N fertilizer on microbial communities in Mollisol, in Northeast China, were investigated by determining phospholipid fatty acid（ PLFA） and neutral lipid fatty acid（ NLFA）of soil microbes, NLFA/PLFA ratio, and PLFA composition in soil samples different in nitrogen treatment with or without phosphorus and potassium fertilizer. Treatments Nil-fertilizer and Fallow were set as controls. Results of PLFA determination show that application of nitrogen coupled with phosphorus promoted microbial growth and immobilization of nitrogen in the soil, while application of nitrogen coupled with phosphorus and potassium did not show any similar effect. Application of nitrogen alone, however, inhibited growth of fungi, probably due to the excessive consumption of nutrients such as available phosphorus. Comparison between different microbial groups in PLFA ratio demonstrates that fungi were better adapted to nutritional stress than bacteria, while the latter accumulated more rapidly in biomass than the former in Treatment N or Treatment NP. NLFA content and NLFA/PLFA ratio varied sharply between treatments different in N rate, suggesting that they could be used as indicators of bio-physiological conditions of soil microorganisms and nutrient level of the soil.