【作者】 李为；

【导师】 余龙江； 袁道先；

【作者基本信息】 华中科技大学 ， 生物医学工程， 2004， 博士

【摘要】 国家虽然已将推进“西南岩溶地区石漠化综合治理”列为重要目标,但目前对石漠化形成以及良性生态恢复的机理研究滞后于国家目标。本文选择代表西南不同类型岩溶生态系统的重庆金佛山、六盘水米苏嘎、广西弄拉、桂林岩溶试验场等四个岩溶区,研究比较土壤微生物和酶活性特征,探讨其与岩溶环境的相关性及生态作用,同时研究碳酸酐酶在岩溶生态环境中的分布,探明其稳定性,并探索微生物碳酸酐酶活性表达的环境条件以及微生物碳酸酐酶与岩溶生态系统元素迁移之间的关系。本文研究成果将为揭示土壤微生物和土壤酶在岩溶生态系统中的作用,以及碳酸酐酶在自然界风化作用中的地位及其岩溶生态效应提供科学依据,并为岩溶石漠化综合治理提供科学支撑。 首先研究比较西南不同类型岩溶生态系统土壤微生物的数量、分布和组成,结果表明其与具有不同地形和植被条件的岩溶生态系统的特性高度相关。在考察的几种岩溶生态系统中, 代表石漠化生态环境的六盘水米苏嘎的微生物数量最低。以岩溶试验场为例,研究不同地貌部位的微生物生理群数量分布和土壤酶活性的时空特征及其与土壤肥力因子的关系,结果表明洼地和垭口土壤水解酶类活性较高,与这两个地貌部位微生物生理群数量较多的结果相对应,同时,土壤微生物数量和土壤水解酶类活性一般与不同地貌部位的土壤有机质、全氮、有效氮、速效磷之间呈显著或极显著正相关, 这既说明土壤微生物数量或土壤酶活性可作为评价岩溶土壤肥力水平的重要指标之一,而且也为不同地貌部位的土地利用方式提供了一定的理论依据。 对能加速石灰岩溶解的碳酸酐酶的来源及分布进行了研究,发现碳酸酐酶不仅广泛存在于西南岩溶区的植物(包括植物新鲜叶片和枯落叶)和微生物中,而且广泛存在于自然岩溶土壤环境中。根据土壤碳酸酐酶活性呈现明显的垂直分布和季节变化以及植物根际附近土壤碳酸酐酶活性较高的结果,认为植物根系及土壤微生物是土壤碳酸酐酶的主要来源。通过监测不同季节典型岩溶生态系统土壤中的碳酸酐酶活性,探明了碳酸酐酶在岩溶土壤环境中的相对稳定,为进一步深入研究碳酸酐★ 国家自然科学基金重大研究计划项目(No.90202016),国家自然科学基金面上项目(No.40152002),国家自然科学基金青年基金项目(No.40302034)及国土资源部岩溶动力学开放研究实验室资助项目 I<WP=4>酶与岩溶生态系统脆弱程度的相关性奠定了基础。 通过室内模拟实验研究了植物碳酸酐酶以及微生物胞外碳酸酐酶的稳定性,结果表明,植物碳酸酐酶和微生物胞外碳酸酐酶均具有良好的热稳定性,钙、镁、锌、钴等岩溶环境主要金属离子和SO4 、H2PO4 、NO3 、NO2 、Cl-、Br-、I-等几种阴离 2- - - -子分别对碳酸酐酶活性有一定的影响,但在一定离子浓度范围内酶活性基本稳定。同时,以从西南岩溶生态系统土壤中分离出的细菌GLRT102Ca为代表,研究了微生物胞外碳酸酐酶活性表达的环境条件,结果表明岩溶环境中的土壤微生物能够表达胞外碳酸酐酶活性,活性高低则因岩溶环境条件(如温度、pH以及金属离子和阴离子的种类和浓度等)的不同而不同。 不同微生物和不同温度处理条件下的土柱模拟试验表明,有微生物作用的土柱的Ca2+和Mg2+的总淋失量都大于对照(P<0.01),说明微生物对岩溶系统的Ca、Mg元素迁移具有较大促进作用,同时温度的影响也比较大,较高的温度环境有利于Ca、Mg元素的迁移。扫描电镜显示埋入经微生物处理土柱的试片表面较对照(未埋入土柱和埋入灭菌土柱的试片)有明显侵蚀现象。另一方面,各处理的淋出液中均检测出不同程度的碳酸酐酶活性,说明土柱中的微生物产生了胞外碳酸酐酶并被淋出。相关分析表明淋出液中碳酸酐酶活性与Ca2+总淋失量关系密切,呈显著正相关,说明碳酸酐酶是影响Ca2+淋失的主要因素之一。此外通过微生物离体模拟溶蚀试验,进一步证明了微生物胞外碳酸酐酶对石灰岩溶蚀的显著驱动作用,碳酸酐酶粗酶液体系对石灰岩溶解释放的Ca2+量分别是碳酸酐酶活性受抑制体系的2.4倍和双蒸水体系的11.73倍。 综上所述,土壤微生物数量和土壤酶活性可作为西南岩溶生态系统脆弱程度的评价指标。本文弄清了能加速灰岩溶解速率的碳酸酐酶的来源与分布,探明了碳酸酐酶在岩溶生态环境中的稳定性,以及岩溶土壤典型微生物表达胞外碳酸酐酶活性的环境条件,为研究碳酸酐酶的岩溶作用机理奠定了基础,同时,也为进一步从碳酸酐酶的分子多态性角度探索岩溶地质环境的演变提供了新思路。室内模拟试验发现微生物胞外碳酸酐酶是岩溶动力系统的重要驱动力,这对于阐明微生物碳酸酐酶在岩溶作用及元素迁移中的地位具有重要意义。更多还原

【Abstract】 One of the important national object is to promote comprehensive treatment of rockydesertification in karst regions of Southwest China. However, studies on mechanisms ofrocky desertification formation and ecological rehabilitation are lagged behind the nationalobject. Four karst areas including Jinfu Mountain in Chongqing, Misuga in Liu Panshui,Nongla in Guangxi and the Guilin Yaji Karst Experimental Site in Guangxi, were selectedas representing different types of karst ecosystem in this thesis. Through analyzingcharacteristics of soil microorganisms and enzyme activities, their relationship with karstenvironment and their ecological effects would be discussed. At the same time, thedistribution and stability of carbonic anhydrase in karst environment wereinvestigated.The environmental factors in expressing extracellular activities of microbialcarbonic anhydrase, and its relationship with element migration in karst ecosystem wereexplored. The results in this thesis will provide scientific bases for opening out the roles ofsoil microorganism and enzymes in karst ecosystem, and the roles of carbonic anhydrasein natural weathering and its karst ecological effects. The results in this thesis will alsohelp to provide scientific support for comprehensive treatment of rocky desertification. The comparative study on the amount, distribution and composition of soilmicroorganisms in different types of karst ecosystem of Southwest China was conducted.The results showed that the amount, distribution and composition of soil microorganismscorrelated highly with characteristics of the karst ecosystems, including their differentgeochemical environments and vegetation. Of the four kinds of karst ecosystemsinvestigated, the amount of soil microorganism at Misuga in Liu Panshui representingenvironment of rock desertification was the lowest. Exemplified by the Yaji KarstExperimental Site, the distribution of soil microbial physiological community as well asthe seasonal and spatial characteristics of soil enzyme activities at different★ Jointly supported by the Major Research Plan of the National Natural Science Foundation(No.90202016), the General Program of the National Natural Science Foundation (No.40152002), theYouth Foundation Program of the National Natural Science Foundation (No.40302034), and the KarstDynamics Laboratory, Ministry of Land and Resources III<WP=6>geomorphological locations and their relationship with soil fertility factors wereinvestigated. The results indicated that there were higher activities of soil hydrolase inDepression and Saddle, which were consistent with the result of more amount of soilmicrobial physiological community in these two geomorphological locations. Moreover,the amount of soil microorganisms and soil enzyme activities correlated highly with soilnutrients such as soil organic matter, total nitrogen, available nitrogen, and availablephosphorus in different geomorphological locations. These results illuminated that theamount of soil microorganisms and soil enzyme activities could not only be made as theimportant indicators in evaluating karst soil fertility level, but also provide a certaintheoretical base for land use in different geomorphological locations. The origin and distribution of carbonic anhydrase, which could accelerate limestonedissolution, were explored. It was found that carbonic anhydrase activity could be detectedwidespread not only in plants (including plant fresh leaves and litters) and microorganismsfrom karst ecosystems of Southwest China, but also in natural karst soil environments.Moreover, the variation of carbonic anhydrase activity in soils with season was almost inaccordance with seasonal changes in the quantities of soil microorganisms in karstecosystems, and that higher carbonic anhydrase activities could be detected in soils of plantrhizosphere. These facts implied that plant roots and soil microorganisms serve asimportant source更多还原