【作者】 陈秀蓉；

【导师】 任继周； 南志标；

【作者基本信息】 甘肃农业大学 ， 草业科学， 2003， 博士

【摘要】 土壤微生物是草地农业生态系统的重要组成部分,在能量流动、物质循环以及土壤的形成与熟化过程中均起重要作用,也是反应环境变化的敏感指示生物,其数量种群和组成是评价草地土壤环境质量的重要参数。因此,研究土壤微生物的数量、多样性以及病原微生物对牧草生产力的影响具有重要意义。本文针对目前草地退化严重这一突出问题,应用土壤微生物学和植物病理生态学原理,采用田间试验、室内分离培养、生理生化分析以及16S rDNA分子技术等试验方法,选择农牧交错带的陇东典型草原中不同退化程度的草地,设计3个处理:处理1(CG),退耕7年,2001年围栏封育;处理2(WS),天然草地,2001年围栏封育;处理3(CK),天然草地,自由放牧,对其土壤微生物数量的季节动态、生理类群、优势种群以及牧草病害对草地生产力的影响等进行了较为系统的研究,3年的研究结果表明:1.土壤理化性状及年际变化试验区土壤状况总体表现为:有机质、全氮及全磷含量低,碱解氮含量中等,速效磷极低,且C/N、C/P和N/P比例失调;2002～2003年同期土壤含水量测定结果表明:CG样地2年变化不明显,WS样地由5.23%提高到7.25%,CK则由7.04%下降到2.56%;土壤有机质、全氮、全磷、碱解氮的测定发现:WS样地分别提高2.15g/kg、0.181g/kg、0.274g/kg、3.3mg/kg,CG与CK样地基本无差异。说明,天然草地围栏封育后对改善土壤水份状况、恢复土壤肥力具有较明显的作用。2.土壤微生物年际及季节变化2002年土壤微生物种群数量变化表现为6月和9月份数量多,5月份和10月份数量少,而2003年则为5月和7月份为全年高峰期,9月份最低。不同年份、不同样地间,各类微生物数量变化为:(1)细菌:2002年各月份各样地均以细菌占绝对优势,全年平均总数量在CG、WS、CK样地分别占76.16%、84.51%和69.45%,2003年各样地总数依次为52.75%、62.07%和58.28%,且变化幅度较2002年小,种群数量稳定。(2)放线菌:2002年数量最高的样地CK仅占微生物总数的30.40%,最少的WS只占17.5%,不同月份的比例变化分别为:CG 11.47%~33.23、WS为8.15%~29.99%、CK为8.05%~39.80%。2003年数量比例大幅度提高,甚至上升为优势种群,在CG、CK样地上7、9月份约占微生物数量50%或略高。年际间数量变化极大。(3)真菌:2002年～2003年数量只占微生物比例的0.09%~0.20%。总体趋势与细菌基本一致,但2002年表现为6月至7月份数量最多,10月份数量最少;2年均以CK样地数量最多,CG、WS数量较少。微生物的年际和季节动态变化受多种因素的影响,主要受降雨量和温度的影响,尤其是水份对微生物种群数量具有限制作用。更多还原

【Abstract】 The soil microorganisms, a main part of the agricultural ecosystem of grassland, play vital roles in energy conversion,substance cycling, and soil development and maturation.They are sensitive indicatives of any variation in environmental conditions. Both constitution and quantity of each member come to be the key parameters for evaluating the soil quality. Thus investigatina the diversity and member quantity of microorganisms in grassland soil as well as effects of pathogenic ones on grassland productivity are of indispensably significance.In this paper, aiming a solution to the serious degradation of present grassland, based on principles of soil microbiology and plant pathologic ecology, combined technologies such as, field test, lab isolation and cultivation,physiochemical analysis and molecular confirmation based on 16S rDNA were employed. plots of steppe grassland at different level of degradation in the east of Gansu Province were selected and administered with three different treatments. Treatment No 1 (CG), enclosed grassland in 2001 after a 7-year-cultivation-withdrawal; No 2 (WS), enclosed natural grassland in 2001; and No 3 (CK), natural grassland free to graze. Systematic studies on seasonal quantitative kinetics of soil microorganisms, physiological flora,dominant genera species and effects of pathogenic ones on productivity of grassland were conducted. Findings of the 3-year researches are as follows:1. Physicochemical properties and yearly variation of grassland soil General characteristics such as low content of organic substance, total nitrogen and phosphorus, medium of alkaline hydrolytic nitrogen, extreme low of available phosphorus, and accompanying unbalanced ratio of C/N, C/P and N/P were detected. Water content detection of sample soil collected in 2003 showed, compared with 2002, no obvious variation in sample CG, an increase from 5.23% to 7.25% in WS, while a decrease from 7.04% to 2.56% in CK. During the same period, tests revealed an rise by 2.15g/kg of organics content, 0.181g/kg of total nitrogen, 0.274g/kg of total phosphorus, and 3.3 mg/kg of alkaline hydrolytic nitrogen in sample WS, whereas little change in CG and CK. These data suggest that enclosed natural grassland is significantly effective in humidity improvement and fertility rehabilitation of grassland soil.2.Yearly and seasonal variation pattern of soil microorganism In 2002, flourishing of soil microorganisms in June and September is contrasted with their small quantity May and October, while in 2003, a peak showed in May and July contrasted with their nadir in September. Quantitative pattern of various microorganisms among different samples and years were compared. (1) Bacteria were dominant regardless of the months and samples in 2002. Its annual average proportion against total soil related microorganisms reached 76.16%, 84.51% and 69.45% in CG, WS and CK samples respectively. However in 2003, it slightly reduced to 52.75%, 62.07% and 58.28% with relatively a smaller fluctuation against different time periods compared with 2002. (2) Actinomyces, with a quantitatively steep change between years, peaked its proportion as 30.40% in CK sample grassland and showed its least as 17.5% in WS in 2002, meanwhile with its inter-monthly fluctuation range as 11.47～33.23 %, 8.15～29.99% and 8.05～39.80% in CG, WS and CK respectively. However, in 2003, Actinomyces showed a great rise in its proportion against total soil microorganisms, even became dominant by accounting for about 50% or more both in CG and CK in July and September. (3) Fungi comprised only 0.09～0.20% against total soil microorganisms, always higher in CK than either CG or WS in both 2002 and 2003, showing a resemble variation patterns as bacteria except for peak showed in June and July and lowest in October in 2002. Kinetics of microorganisms either yearly or quarterly were affected by various factors including soil physiochemical conditions, microbiological ecosystem, vegetation flora, and mainly by rainfall and temperature. The humidity exerted a restriction to quantity of microorganism.更多还原