毛乌素沙地生物结皮物种组成及氮动态研究

发布时间：2018-04-11 23:06

本文选题：生物结皮 + 藻类　；参考：《北京林业大学》2015年博士论文

【摘要】：氮素养分的匮乏严重制约着荒漠生态系统的净初级生产力。生物土壤结皮(下称“生物结皮”)在荒漠生态系统广泛分布,是主要的氮源。生物结皮因其土壤理化性质和生物群落结构的改变,强烈地影响着表层土壤氮素动态,进而影响着表层土壤可利用氮素的供给,以及植被的生长和发育,对于荒漠生态系统土壤改良和植被恢复具有重要的实践指导意义。目前,相关研究不够系统和深入,一定程度上制约着对荒漠生态系统氮动态过程的理解以及荒漠化防治工作的开展。鉴于此,本研究以毛乌素沙地普遍存在的不同类型生物结皮为研究对象,进行了野外调查、室内模拟实验、化学试验和生物学实验,对其物种群落结构、固氮能力、矿质氮积累和氮损失的等方面进行了研究,结果表明：(1)生物结皮的物种群落结构对固氮活性有着重要的贡献。随着生物结皮从低级到高级阶段,固氮物种丰富度和多度与固氮活性呈现相同的变化趋势,即单峰曲线。生物结皮的固氮物种,尤其是蓝藻,对固氮活性具有显著的的贡献(90.9%)。并且蓝藻对于固氮活性的贡献又因水分和温度条件不同而不同。水分和温度条件越适宜,蓝藻对于固氮活性的解释量越高,在最适条件下(含水量25%,25℃),其解释量高达96.9%。在不同类型的生物结皮当中,蓝藻结皮的年固氮量估算值最高,为14.43±1.18mgN2m-2a-1。生物结皮中可能存在一些高多度且对温度水分高敏感度的蓝藻,它们只在温度水分最适的环境条件下表现出高固氮活性。(2)随着生物结皮从低级阶段到高级阶段,土壤物理结构得到改良和土壤养分不断积累,微生物数量也大体上呈增加趋势,这些都为土壤氮矿化作用提供了良好的条件,有利于提高土壤矿质氮含量。生物结皮矿质氮的积累与生物结皮的水分和温度呈正相关；随着土壤有机碳、全氮、有效氮含量和土壤体积分形维数的增加而增加,随着土壤C/N和pH的降低而增加；与细菌、放线菌和真菌的数量呈正相关。在不同季节中,由于6-8月温度水分条件较好,生物结皮碳氮养分含量较高,可以为氮矿化作用提供良好的条件和原料,因而该季节的矿质氮含量最高。(3)随着生物结皮从低级阶段到高级阶段,土壤结构不断改良,土壤透气性不断增加,碱性危害逐渐降低,进而有效地抑制了土壤气体氮损失。生物结皮从低级阶段到高级阶段,土壤体积分析形维数和土壤孔隙度的增加抑制了氮损失,C/N和pH的下降减少了氮损失。本研究表明生物结皮对于荒漠生态系统表层土壤氮动态有显著的影响,生物结皮的出现和发育总体上有利于土壤可利用氮的积累和气体氮损失的减轻,为荒漠化防治工作中的生物措施提供了理论和实验基础。微生物和隐花植物是生物结皮实现氮动态过程的主要执行者,其群落结构与固氮功能和矿质氮积累密切相关。后续研究可以采用新技术来检测参与氮动态过程的功能微生物群落,以期阐明生物结皮氮素动态的生物机制。
[Abstract]:The lack of nitrogen seriously restricts the net primary productivity of desert ecosystem. The biological soil crust (hereinafter referred to as "biological crust") are widely distributed in the desert ecosystem, is the main source of nitrogen. The skin microbiotic soil physicochemical properties and biological community structure changes, strongly influence the dynamics of nitrogen in surface soil. And the effects of soil available nitrogen supply, and vegetation growth and development, are important for ecosystem restoration of desert vegetation and soil improvement. At present, the related research is not systematic and in-depth, to a certain extent restricts on desert ecosystem nitrogen dynamic process of understanding and carry out the prevention and control of desertification. In view of this, different types of biological crusts in Maowusu sandland generally exist in this study as the research object, conducted a field survey, indoor simulation experiment, test and biochemical studies Experimental study on the species, community structure, nitrogen fixation ability, mineral nitrogen accumulation and nitrogen loss were studied, results showed that: (1) species community structure of biological crusts are important contributors to the nitrogenase activity. With the biocrusts from elementary to advanced stage, species richness and nitrogen fixation and the nitrogenase activity showed the same trend, namely the single peak curve. The nitrogen fixing species of biological crusts, especially cyanobacteria, nitrogen fixation activity has significant contribution (90.9%). And the contribution to the nitrogenase activity of cyanobacteria due to moisture and temperature conditions are different. The more suitable conditions of moisture and temperature, the higher the cyanobacteria the nitrogenase activity explained, under the optimum conditions (25% water, 25 C), the amount of up to 96.9%. in the biological crusts of different types, in the amount of nitrogen fixing cyanobacterial crusts of the estimated value of the highest, 14.43 + 1.18mgN2m-2a-1. There may be some high degree of temperature and moisture sensitive cyanobacterial crusts, they are only in the most suitable temperature and moisture conditions showed high nitrogenase activity. (2) with biological crust from the lower stage to the higher stage, improved soil physical structure and soil nutrient accumulation, microbial number generally showed an increasing trend, provide a good condition for the soil nitrogen mineralization, is conducive to the improvement of mineral nitrogen content of soil moisture and temperature were positively biocrusts accumulation and biological crusts of mineral nitrogen related; with soil organic carbon, total nitrogen, available nitrogen content increased and the fractal dimension of soil volume increased and decreased with increasing soil C/N and pH; and the number of positive bacteria, actinomycetes and fungi. In different seasons, 6-8 months due to temperature and moisture conditions are better, higher biological carbon and nitrogen nutrient content of skin, Can provide good conditions and raw materials for nitrogen mineralization, and mineral nitrogen content of the season. The highest (3) with biological crust from the lower stage to the higher stage, improving soil structure, soil permeability increased, alkaline harm gradually reduced, thus effectively restrain soil nitrogen gas losses. Biocrusts from the lower stage to the higher stage, analysis of fractal dimension and porosity of soil can inhibit the nitrogen loss of soil volume, decreased C/N and pH reduced the nitrogen loss. This study shows that biological crusts have significant influence on soil nitrogen dynamics of desert ecosystem, biological crust and development to reduce the soil available the loss of nitrogen accumulation and nitrogen gas on the whole, provides theoretical and experimental basis for the prevention and control of desertification in microbial and biological measures. Cryptogamic crusts are nitrogen dynamic The main executors of the process are closely related to their community structure and nitrogen fixation function and mineral nitrogen accumulation. Subsequent research can use new technology to detect functional microbial communities involved in nitrogen dynamic process, with a view to elucidate the biological mechanism of nitrogen dynamics in biological crusts.

【学位授予单位】：北京林业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：S154

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