黄土高原子午岭天然油松林土壤微生物生态学研究

【作者】 王金成；

【导师】 梁健；

【作者基本信息】 陕西师范大学 ， 微生物学， 2010， 硕士

【摘要】 天然油松林是黄土高原森林群落自然演替过程的重要环节,是黄土高原植被保护和恢复的重要森林植被类型之一。土壤是植物群落演替过程中重要的环境因子,是生态系统功能恢复与维持的关键指标。研究天然油松林土壤微生物群落结构特征及其与土壤养分、土壤酶和植被演替等关系,将有助于进一步认识和明确土壤微生物在天然油松林演替过程中地位和作用,这对于黄土高原退化生态系统的恢复和重建具有重要的借鉴意义。本文以黄土高原子午岭处于不同演替阶段的天然油松林为研究对象,测定了土壤有机质、全N、碱解N、速效P、速效K、pH和土壤含水量等土壤肥力指标,以及土壤过氧化氢酶、脲酶、转化酶、蛋白酶、纤维素酶、多酚氧化酶、碱性磷酸酶等土壤微生物生理活性指标；利用“平板培养法”、“MPN法”和“末端标记限制性片段长度多态性法(Terminal Restriction Fragment Length Polymorphism, T-RFLP)"分别测定了土壤微生物三大类群、主要功能群以及遗传多样性组成；利用“熏蒸提取-容量分析法”测定了土壤微生物生物量碳(MBC)组成。研究结果显示：随着天然油松林的演替,1)十壤有机质、全N,碱解N,速效K及含水昔增加,土壤速效P和pH下降。2)土壤过氧化氢酶含量逐渐下降,土壤纤维素酶、转化酶及脲酶含量上升,土壤多酚氧化酶及碱性磷酸酶呈先升后降趋势。3)土壤可培养微生物数量及土壤MBC增加；基于可培养微生物组成的微生物群落多样性随着油松林的演替而递增,放线菌数量的变化对多样性的影响作用更大。4)辽东栎、油松及白桦凋落叶单独或组合处理70a油松林土壤后,土壤微生物三大类群数量均不同程度的增加；经白桦和辽东栎凋落物分别处理的土壤,其微生物数量均明显高于油松凋落物处理的土壤。5)40a林和70a林土壤微生物群落T-RFLP图谱相似性较大,二者与25a林相似性较小,与10a林相似性最小；由10a油松林发展到40a油松林,土壤微生物群落遗传多样性增加,由40a林发展到70a油松林,多样性明显下降。以上结果表明：1)天然油松林演替过程中,伴随着油松凋落物等物质的积累,土壤有机质和总N等肥力指标增加,有机质分解过程中产生的有机酸导致土壤pH下降,并抑制了土壤P的有效化过程,造成土壤速效P含量下降。2)天然油松林的演替过程中,随着林下凋落物的增加,土壤转化酶、脲酶及碱性磷酸酶含量增加,土壤肥力进一步改善；土壤脲酶含量的增加提高了土壤N素含量,而N素的积累有助于土壤蛋白酶的合成；由于油松凋落物纤维化程度较高,土壤纤维素酶活性随油松林演替增加；随着天然油松林演替的进行,土壤过氧化氢酶含量降低,缓解了土壤的自毒效应。3)随着天然油松林的演替,林下凋落物逐年积累,为土壤微生物提供了大量的C源,土壤微生物量及可培养微生物数量增加,微生物三大类群分布愈加均匀。4)凋落叶处理土壤的结果表明,不同凋落物都能促进土壤微生物数量的增长,其中,阔叶树种优于针叶树种,因此,在森林恢复实践中,应注意合理搭配树种,以更好地改善土壤性质。5) T-RFLP结果反映了土壤可培养和未培养微生物组成状况,演替早期阶段,土壤微生物组成变化较大,随着演替的进行,土壤微生物组成愈加相似。微生物群落遗传多样性随着油松群落演替而增加,但到了70a林阶段,多样性急剧下降,个中原因值得进一步研究。更多还原

【Abstract】 Natural Chinese pine forests, which is one of the important forest plant species in forest recovery and protection in the Loess Plateau, is also the significant links of forest community natural succession process in this region. Soil, which is the vital important environment factor during plant succession, is the key index of function recovery and maintain of the eco-system. Study on the relationship among soil community structure characteristic and soil fertility as well as enzyme activity could further understand the statue and effect of soil microbe in the process of natural Chinese pine forests during different succession stages, which also play an important role in the process of function recovery and maintain of the eco-system in this region.Therefore, taking the natural Chinese pine forests with different growth years in Ziwuling forest region of the Loess Plateau as research object; organic matter, total nitrogen, available nitrogen, available phosphorus, available potassium, pH,water content Catalase, Urease,Protease. lnvertase, Cellulose and Polyphenol oxidase as well as Alkaline phosphatase of soil samples were determined by traditional methods so as to investigate the change law of soil physical and chemical properties and soil enzyme activity along plant succession; the three main micro-groups and major functional groups of soil microbe was investigated based on the method of plate cultivation and MPN method, besides, the soil microbial biomass carbon (MBC) was also determined through the method of chloroform fumigation; the soil micro-community composition was studied with the method of terminal restriction fragment length polymorphism (T-RFLP), which would be helpful to further understand status and function of function recovery and maintain of the eco-system in this region.Results show that:1) Total nitrogen, organic matter, available nitrogen and available potassium as well as water content of soil samples showed an increasing trend but available phosphorus and pH were reduced as the succession prolonged.2) Catalase showed a decreasing trend but cellulose, urease and invertase increased, and polyphenol oxidase as well as alkaline phosphatase of soil samples showed forword increase and decrease afterword trend along the succession.3) Both total number of soil microbe and soil MBC showed an increasing trend as the succession prolonged. Addinationally, soil actinomycetes play the determining effect on community diversity than soil becteria.4) The three main micro-groups number of soil microbe form the natural Chinese pine forests with the growth year of 70, determined by effective components extracted form the litter fall in this region, showed an increasing trend separately; System cluster result showed that the number treated by birch and liaodong oak is extremely higher than of the chniese pine.5) There is a higher T-RFLP maps similarity between soil samlple of 40a and 70a, and both of them shows a middle similarity with 25a soil sample, and they has a lower similarity with the 10a; the soil genetic diversity show a increasing trend from 10a to 40a but decreas till70a.The results above represent that:1) As the the forest litter fall accumulation increased, the feritility, including soil organic and total N improved, show an increasing trend as the succession prolonged; Organic acid form the organic acid decomposition make the soil pH stay at lower level, which could restrict the availability of P.2) The complex the plants community structure and increased litter fall under the forest plants which are benefit for the accumulation of soil Urease and Invertase, it indicate that the soil fertility here is getting better and better; besides, the improvement of soil Urease would be helpful to the level of N, which consequently improve the Protease level; according to Chinese pine litter fall of itself characteristic, it would be benefit for the accumulation of soil Cellulose, moreover, the litter fall itself could produce more organic acid, which would interrupt the level of soil Alkaline Phosphatase.3) The distribution of three main micro-groups number of soil microbe is getting more averaged and the number of Actinomycetes play more significant role than the Bacterium in the micro-diversity; The increased litter fall under the forest plants would offer the rich C to the microbe growth, thus, the MBC level at the preliminary stage improved slowly but it showed an increasing trend as the succession time prolonged.4) Soil microbe number form the soil of natural Chinese pine forests with the growth year of 70, determined by effective components extracted form the litter fall in this region, showed an increasing trend separately; System cluster result showed that the number form hardwood litter fall is extremely higher than of the conifer and the litter fall from coriaceous was located between them; it tells us that reasonably plants setting would be extremely important to the plantation growth.5) The soil micro-community genetic diversity was studied with the method of terminal restriction fragment length polymorphism (T-RFLP), it represented that there is high diversity similarity during the earlier succession, and it shows a higher similarity as the succession develops but it sharply decreased till 70a, its pricinple is valuable and necessary to be further studied.更多还原