黄瓜连作对土壤微生物区系的影响Ⅰ——基于可培养微生物种群的数量分析

利用平板培养法对黄瓜连作根系微生物种群连续性变化进行了跟踪研究。结果表明,黄瓜连作导致土壤可培养微生物数量减少,其中细菌数量降低最为明显,对连作表现出较高的敏感性,根际根外细菌数目减幅分别在第三、四茬时达显著水平。放线菌数量对黄瓜连作反应较小,根际到第四茬减幅才达到了显著水平,而根外在连作四茬过程中均未达显著水平。黄瓜连作致使少数真菌种群富集,同时多种真菌类群数量减少,种群变化呈现单一化趋势。根际土壤微生物主要生理群分析表明,连作导致根际自生固氮菌与好气性纤维素分解菌数目明显下降,硝化细菌数量大幅增加,而氨化细菌数量变化不大。土壤酶活性测定结果表明,土壤过氧化氢酶、酸性磷酸酶活性随连作茬次增加而降低,脲酶活性稍有上升。

The Effects of Continuous Cucumber Cropping on Microbial Communities Structure Ⅰ--Based on Quantitative Analysis of Culturable Microbial Population

Variation of culturable microbial population structure and essential soil enzyme activities were investigated with continuous cucumber cropping. The results indicated that culturable microbial population gradually decreased with continuous cucumber cropping. Bacteria showed a greater decrease trend in population than actinomyces and fungi. The decrease of bacterial population in rhizosphere and bulk soil reached a significant level when the third and the fourth cucumber crop were planted. The number of actinomyces occured a decline tendency in the third cropping season. Data in this paper also indicated that continuous cucumber cropping could induce a few fungal population increasing as well. The fungi species in rhizosphere decreased. The major rhizospheric microbial physiological groups were also analyzed. The results indicated that there was significant decrease in the number of rhizosphere azotobacter and aerobic cellulose-decomposing microbes, and great increase in nitrobacteria population. However, there was little variation in the number of ammonifying bacteria population when cucumber cropping continued. Soil enzyme activities showed Catalase and acid phosphotase activities declined, and Urease activities rose slight as intensive mono cucumber cropping was conducted.