论文标题:黄河源区高寒草地土壤微生物数量动态及其与土壤养分关系研究
Studies on Quantity Dynamics of Soil Microorganism and the Relation with Soil Nutrients of Alpine Meadow in the Headwater Area of Yellow River
论文作者
论文导师 龙瑞军,论文学位 硕士,论文专业 草业科学
论文单位 甘肃农业大学,点击次数 72,论文页数 70页File Size1487K
2007-05-20论文网 http://www.lw23.com/lunwen_347046577/
Headwater area of Yellow River;; alpine meadow;; artificial grassland;; soil microorganism;; soil nutrients
以青藏高原黄河源区不同退化程度高寒草地(末退化高寒草地、中度退化草地、严重退化的“黑土滩”草地)以及建植于“黑土滩”不同种植年限人工草地(人工2龄草地、人工4龄草地和人工6龄草地)为研究对象,应用土壤微生物学和土壤学原理,采用传统的土壤微生物分离培养方法和土壤农化分析方法,对6个样地的土壤微生物三大类群和土壤养分在不同季节、不同草地和土壤剖面分布进行研究,并结合相关分析和通径分析等统计方法对微生物与土壤养分之间的关系进行分析,研究结果如下: 1.土壤微生物季节分布动态微生物总数量随着季节的变化呈现出递减的趋势,即5月份(牧草返青不久)数量最高,8月份有所下降,11月份的数量最少。细菌数量的季节动态变化与微生物总数量的变化一致。放线菌数量随着月份的增加呈现先降低后升高的变化趋势,最低值出现在8月份。真菌数量随着月份的增加呈上升的趋势,即5月份数量最低,8月份数量略高于5月份,11月份数量最高。 2.土壤微生物不同类型草地间分布动态从微生物数量组成来看,6种草地土壤三大微生物类群的组成比例略有不同,但大体上一致。其中,细菌数量最多,占微生物总数的87%～99%,放线菌数量次之,占总量的1%～11%,真菌数量最少,约占总量的0.01%～0.3%。对于不同退化程度的天然草地而言,土壤细菌和放线菌数量随着草地退化程度的加剧呈现降低的趋势,真菌数量随着退化程度的加剧而升高;人工草地细菌、放线菌数量随着建植年限增加呈先降低后升高趋势变化,且2龄草地细菌、放线菌数量明显的高于“黑土滩”退化草地,人工2龄草地真菌数量虽较未退化高寒草地高,但低于“黑土滩”退化草地。 3.土壤微生物数量剖面分布动态土壤微生物数量的垂直分布呈现随土层的加深数量逐渐降低的趋势:0～10cm土层微生物数量最多,10～20cm土层微生物数量次之,20～30cm土层微生物数量最少。一般0～10cm土层微生物总量是10～20cm土层的2～7倍,是20～30cm土层的2～13倍。 4.土壤养分含量季节分布动态随着草地类型和土壤养分指标不同、土壤养分含量的季节变化表现出多样性。土壤有机质除了人工2龄和4龄草地呈倒“V”型变化外,其余4样地均呈“V”字型规律变化。全磷含量的变化较大,各样地全磷含量均为8月份最高,5月份、11月份较低,呈倒“V”字型规律变化。全氮含量的季节性变化在未退化高寒草地、中度退化草地、“黑土滩”退化草地和人工2龄草地与全磷的变化趋势一致,均是8月份含量最高,只有人工4龄和6龄草地全氮含量在8月份最低,呈先降低后升高的规律变化。土壤碱解氮的季节动态变化规律与全氮基本一致,只有6龄草地的碱解氮含量在8月份最低,呈“V”字型规律变化。未退化高寒草地和中度退化草地的速效钾含量呈先升高后降低的单峰曲线变化,在8月份达到峰值,其余样地速效钾含量呈“V”型规律变化。6个样地土壤均为中性偏碱土壤,其季节变化除人工4龄土壤pH值呈现“V字型变化规律外,其余草地土壤pH值均表现为随着月份的增加呈现先升高后降低的变化趋势,并在8月份达到峰值。6个样地土壤水分含量季节变化均呈现先升高后降低的趋势,在8月份达最大值。 5.土壤养分含量不同类型草地间分布动态不同月份、不同草地类型土壤养分、水分含量不同,但其在6个样地中分布规律基本一致,即随着退化程度的增加,土壤养分、水分含量均呈现降低的趋势,人工2龄草地土壤养分较“黑土滩”退化草地高,但随着建植年限的增加有降低的趋势,4龄草地土壤养分含量最低,随着建植期的继续延长,6龄草地的各项养分含量又有所回升。对土壤pH值而言,未退化草地各土层pH值最低,中度退化草地表层土壤pH值较“黑土滩”退化草地低,中下层较高。人工草地之间土壤pH值变化不明显,只是在8月份人工4龄草地土壤pH值较2龄和6龄草地低,但其较未退化草地的高。在垂直分布上均表现为,土壤养分随着土层深度增加而降低的趋势,即土壤养分各项指标含量在0-10cm土层最高,10-20cm土层其次,20-30cm土层养分含量最低。各样地土壤pH值均表现表层最低,并且随深度增加而逐渐增加。 6.土壤微生物数量与土壤养分的关系除真菌数量与pH值呈负相关外,其余土壤营养因子与细菌、放线菌和真菌数量均呈正相关关系。其中,细菌数量与有机质、全氮、全磷、碱解氮和速效钾之间呈极显著正相关关系,与土壤含水量呈显著正相关关系,与pH值呈正相关关系,但相关性不显著。放线菌数量与有机质、全氮、碱解氮、速效钾含量和土壤含水量呈极显著的正相关关系,与pH值呈显著的正相关关系,与全磷呈正相关关系,但相关性不显著。真菌数量与有机质、全氮和速效钾含量呈极显著的正相关关系,与碱解氮含量、全磷和土壤含水量呈正相关关系,与p H值负相关关系,但相关性均不显著。经通径分析表明:碱解氮、全磷、速效钾是影响细菌数量的主要因子,有机质、全氮、碱解氮、速效钾是影响放线菌数量的主要因子,全氮和速效钾是影响真菌数量的主要因子。
Six different type of representative grasslands in the headwater area of yellow river were selected to investigate their soil properties including microorganism communities, soil nutrients, pH value and soil containing water in May (spring), August (summer) and November (late autumn). They are undegraded alpine meadow, medium degraded pasture, "Black- soil-patch" degraded meadow, 2 years-old artificial grassland, 4 years-old artificial grassland and 6 years-old artificial grassland. The quantity of soil microorganism, content of soil nutrients, pH value and soil moisture content, and their relationships were analyzed, which based on principles of soil microbiology and pedology. The main research results are as follows: 1. The seasonal dynamics of soil microorganism With season changing the total soil microorganism presents the degressive tendency. Compare of the three seasons, there are the most microorganism in May, and the least microorganism in November. So did the tendency of bacteria. Actinomycete quantity decreases then increases regularly with change of season, and the minimum value appears in August. But the quantity of fungi increases as the season progresses, and it is lowest in May and highest in November. 2. The distributing of soil microorganism in different type of grassland Compositive proportion of Soil microbial species of six grasslands have the difference slightly, but consistent on the whole. Among them, bacteria quantity is the most, actinomycete quantity is less and fungi quantity is the least. The proportions of them in total microorganism are 87%-99%, 1%-11% and 0.01%-0.3% respectively. For the different degeneration of natural meadow, the quantities of soil bacteria and actinomycete present the reducing tendency along with the degeneration of meadow, but the tendency of fungi quantity elevate with the degeneration aggravating of meadow. However, in artificial grassland, the quantities of bacteria and actinomycetes firstly decreased then increased. Campared with‘black-soil-patch’degraded meadow, the quantities of bacteria and actinomycetes of 2 years-old artificial grassland were obviously higher, and the quantity of Fungi was lower, though it was higher when compared with undegraded meadow. 3. The quantitive distribution of soil microorganism in soil section The vertical quantitive distribution of soil microorganism has a degressive tendency when the depth increased: the quantity of soil microorganism in 0-10cm soil layer is the most, less in 10-20cm soil lay, and the least in 20-30cm soil layer. In general, the quantity of soil microorganism in 0-10cm soil layer is 2-7 times more than in 10-20cm soil layer, and is 2-13 times more than in 20-30cm soil layer. 4. The seasonal dynamics of soil nutrients The seasonal change of soil nutrients in six grasslands are different, also display multiplicity with changing of grassland type and soil nutrients. Soil organic matter in 2 years-old and 4 years-old grassland show a reversed‘v’model, the rest of four grasslands all show a‘v’model. Total phosphorus of six grasslands is highest in August and lower in May and November. The seasonal change of total nitrogen in native meadow has the same change with medial degenerative meadow,‘black-soil-batch’degraded grassland and 2 years-old grassland. All of them had the most total nitrogen in August except for 4 years-old and 6 years-old grassland. Available N of soil in all samples ascend and then descend except for 6 years-old grassland. Available K of soil change with unimodal curve which firstly increases and then reduces and the peak value appears in august. Available K of other grasslands presents a‘v’model. The soil of six grasslands is the neutral leaning alkali soil. The seasonal variation of soil pH value presents a‘V’model only in 4 years-old grassland and displays a reversed‘v’model in other grasslands, whose peak appears in August. Soil moisture content of six grasslands increases firstly then reduces with seasonal variation, finally reaches the maximum in August. 5.The dynamic distribution of soil nutrients in different grasslands soil nutrients and moisture content of six grasslands differ in different month, but their distribution rule is basically consistent, that was to say, as the degree of degradation increased, soil nutrients presente the degressive tendency. Compared with "Black-soil-patch" degraded meadow, the soil nutrients and moisture content of 2 years-old grassland are higher, and 6 years-old grassland is lower than 2 years-old, however higher than 4 years-old. The soil nutrient and moisture content present reducing tendency as the depth of soil layer increases, namely the content of each index is the highest in 0-10cm soil layer and the lowest in 20-30cm soil layer. In terms of the potential hydrogen of soil, the pH value of native meadow is thelowest in each soil layers; the pH value of medial degenerative meadow is lower in surface layer and higher in middle-layer and under-layer than‘Black-soil-patch’degraded meadow. The change of soil pH value is not obvious among artificial grasslands. The soil pH value of 4 years-old grassland is lower than 2 years-old and 6 years-old grassland in the August, but it higher than native meadow. For vertical distribution, soil nutrients present reducing tendency along with increasing of soil layer depth, namely they are highest in 0～10cm soil layer, and lower in 10～20cm soil layer, and lowest in 20～30cm soil layer. Soil acidity of six grasslands is lowest in surface layer, and increases along with the depth increases gradually. 6. The relation between microorganism quantity and soil nutrients except pH value is negatively correlated with fungi quantity; other soil nutrients are positively correlated with bacteria quantity, actinomycete quantity and fungi quantity. Among them, bacteria quantity is extremely significantly positively correlated with organic matter, total N, total P, available N and available K, and it is significantly positively correlated with moisture content, and it is positively correlated with pH value, but the correlation is not significant. Actinomycete quantity is extremely significantly positively correlated with organic matter, total N, available N, available K and moisture content, and it is significantly positively correlated with pH value, and it is positively correlated with total P, but the correlation is not significant. Fungi quantity is extremely significantly positively correlated with organic matter, total N and available K, and it is significantly positively correlated with available N, and it is positively correlated with total P and soil moisture content, and it is negatively correlated with pH value, but the correlation are not significant. After the pathway analysis was done between soil factors and microbial factors, the conclusion was reached: available N, total P and available K is the most important factor affecting the bacteria quantity; the organic matter, total N, available N and available K are the most factors affecting actinomycete quantity; the total N and available K are the most factors affecting fungi quantity.
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