【作者】 朱志梅；

【导师】 杨持；

【作者基本信息】 内蒙古大学 ， 生态学， 2004， 博士

【摘要】 沙漠化是制约我国干旱、半干旱地区社会经济可持续发展的重要因素。研究地多伦县由于其独特的地理位置和地形地貌，在中国北方沙漠化研究领域尤其是草原沙漠化研究中起着十分重要的作用。本文从土壤、植物群落、种群、个体、形态、生理角度出发，通过连续三年(2001．2003年)的野外生态学观测，结合室内生理生化分析，在不同层次、不同尺度上系统地运用生态系统生态学、群落生态学、种群、个体生态学、生理生态学的科学理论和方法，整合研究沙漠化这一大尺度干扰问题，探讨自然条件下沙质草原沙漠化过程中植被的受损过程和适应对策。研究结果如下： 1．随着草原沙漠化的加剧，土壤粘粒含量趋于减少，砂粒增多。土壤含水量下降尤其是上层(0-20cm)下降明显，且深层含水量逐渐高于表层。土壤容重呈上升趋势。土壤有机质、C、N含量极显著下降，且土壤N的衰减要快于C。土壤C／N比呈增加趋势，表明植物N素供应不足较为突出。土壤的颗粒组成状况与土壤营养元素之间显著正相关，粘粒与N的关系比粘粒与C和C、N间的关系密切，因此土地沙漠化过程中细颗粒物的减少导致土壤N素衰减十分明显。 2．随着沙漠化的进展，群落盖度、密度、物种丰富度、生物量和相邻两个梯度间p多样性指数均呈下降趋势，地上生物量／地下生物量比值变化不大。与土壤的相关性表明土壤C／N比与群落的关系最密切。 3．随着沙漠化的进展，共有种群株高、密度、植物比叶面积、叶面积指数、地上千物质累积、生殖分配多项指标均随之变化。 ①株高、密度的变化总体上呈降低趋势。其中羊草梯度间差异很明显，糙隐子草和冷蒿分别在潜在、中度沙漠化和潜在、轻度沙漠化阶段的增加，既与种群所处的阶段性优势地位有关，又与其抗逆性、适应性增强有关，而扁蓿豆在中度沙漠化以前升高，生长渐趋旺盛，重度沙漠化时下降，其形态生长同其它共有种群一样受到限制，与其地上生物量变化相一致。扁蓿豆密度梯度间差异性只表现在随沙漠化梯度的增加而增大方面，而糙隐子草差异性只表现在随沙漠化梯度的增加而下降方面，冷蒿差异性则既表现在下降方面又表现在增大方面。不同种群各沙漠化梯度间差异的不同及其高度、密度变化的不同，表明植物在恶化环境的受损程度和适应性的差异，羊草受损较重，适应性差，糙隐子草和冷蒿受到一定程度的损伤，但抗性、适应性较强，扁蓿豆对沙漠化较迟钝，适度的沙漠化反而有利于其生长，但过度的沙漠化也会导致与其它种群表现一致的生长不利。 ②多数被调查的植物比叶面积呈降低趋势，形态生长受到抑制，只有冷蒿和扁蓿豆呈上升趋势，但冷蒿的增大程度不及扁蓿豆：扁蓿豆叶面积及其高度、密度的增加，是长期适应环境的表型特征。 ③叶面积指数总体上呈下降趋势，扁猎豆变化不大，中度沙漠化阶段前略增，而到重度沙漠化阶段下降。共有种群叶面积指数均受土壤的理化性质影响，其中冷篙和扁楷豆的影响较小。 ④地上干物质累积的变化与叶面积指数相似。羊草和糙隐子草的地上干物质累积随土壤理化性质的衰减显著降低;扁稽豆的地上干物质累积随土壤粘粒、C含童的减少却显著增加，其与土壤含水量、全N含量和土壤C入比不相关:冷篙的地上干物质累积随土壤理化性质的衰减虽也降低，但未达显著水平。 ⑤种群生殖分配降低过程中，羊草降幅最大，冷篙和扁稽豆降幅较小;均受土壤理化性质影响较小。种群地上部分C含量及C加比均增大，N含量均减少。羊草和糙隐子草沙漠化初期地上C素增加明显，而冷篙与扁楷豆在沙漠化中、后期地上C素才显著增加。因此，羊草和糙隐子草的敏感性可能要大于冷篙与扁稽豆，另一方面冷篙与扁楷豆的抗性可能要大于羊草和糙隐子草。 4.草原沙漠化过程中伴随着共有种群叶片含水量、叶绿素含量的降低，其质膜相对透性、游离脯氨酸含量上升，MDA含量增加，SOD、CAT活性升高，而POD活性下降，表现出沙漠化过程中植物受损的生理共性。不同植物在不同阶段对沙漠化的响应不同，表现出植物受损程度的不同及对沙漠化抗性、适应性的差异。扁稽豆、糙隐子草和冷篙叶绿素确均呈上升趋势，且梯度间差异性冷高>扁楷豆>糙隐子草>羊草，所以冷篙叶绿素水平的抗性较强，羊草抗性较弱。结合膜透性、脯氨酸及MDA累积t看，扁箱豆受损最少。羊草脯氨酸及ABA的累积有伤害症状，而糙隐子草和冷篙脯氨酸及ABA的累积有适应性倾向，扁楷豆脯氨酸及ABA的累积表现为对沙漠化环境的不敏感。 ①羊草的膜透性与脯氨酸、MDA、ABA含量、SOD活性呈极显著正相关，与CAT活性呈极显著负相关，说明SOD活性升高，CAT活性降低，脯氨酸、MDA、ABA含量的增加，导致了膜透性的增大，最终使膜受损。而脯氨酸与ABA含量、SOD活性呈极显著正相关，与POD、CAT活性呈极显著负相关，说明ABA诱导了脯氨酸累积，SOD活性的增强，POD、CAf活性的减低，也是导致脯氨酸累积的原因。MDA含量与SOD、POD活性极显著正相关，表明在沙漠化过程中，随着羊草SOD、POD活性的增高，清除ROS的能力并没有提高，因此引起MDA的显著积累。POD、CAT活性与ABA含量呈极显著负相关，而POD又与CAI，呈显?更多还原

【Abstract】 The social and economic sustainable development in the arid and semiarid area in China has been restricted by sandy desertification heavily. The studied site (DUOLUN county) has distinct geographical position and special terrain and geomorphic, so studying in this area plays the important role in the research on the sandy desertification in northern China, especially for grassland. It was studied integratedly on sandy desertification interference according to the principle and methods of community ecology, population ecology and physiological ecology through observation outdoors and analysis indoors in 3 years. The damage and adaptation strategy of the vegetation during sandy desertification process in natural conditions were discussed through variations of community, population and individual, morphological and physiological characters under different gradients of sandy desertification. The results were as follows:1. With the process of the sandy desertification in grassland, the contents of clay decreased. The soil moisture decreased, especially in 20-30cm layer. The soil moisture in deeper was higher than the super. The soil bulk density increased. The contents of organic matter, carbon and nitrogen in the soil decreased very significantly, the reduction of nitrogen was more rapid than that of carbon, thus C/N in the soil increased. It shows that the provided nitrogen in the plant was scarce heavily. The positive correlation was significant between the granular composition and the nutrient element in the soil. The correlation between the clay and N was nearer than that of the clay and C, C and N. Therefore the reduction of the fine particle resulted in the reduction of N very significantly during sandy desertification.2. With the process of the sandy desertification, the coverage, density, number of species, biomass and diversity index of community decreased. The ratio of biomass aboveground- biomass underground did not changed significantly. C/N in the soil was the nearest to community through their correlation analysis.3. With the process of the sandy desertification, individual height, density, leaf area index(LAX), biomass aboveground, reproductive allocation(RA) of the common populations and the specific leaf area(SLA) of the main plant changed alternatively.(1)Individual height, density decreased overall. Leymus chinensis had Very significantdifferences in the different gradients of desertification. Cleislogenes squarrosa and Artemisia frifida increased in potential desertification stage (PD), light desertification stage (LD) or moderate desertification stage (MD) because of their phasic statuses of dominant species and their stronger stress resistances. Melilotoides ruthenica increased before MD, and after MD its morpha growth reduced along with the others, only that it had no significance. This change was the same as biomass aboveground of M: ruthenica. The significance of density of M. ruthenica in the different gradients of desertification was only in the increase with the development of the sandy desertification. The significance of density of C. squarrosa was only in the decrease with the development of the sandy desertification. The significance of A. frifida was both in the increase and in the decrease with the development of the sandy desertification. The variances in the different gradients of desertification and the changes of individual height, density of different populations showed the variance of the damage and adaptability of different plants in the worse environment. L. chinensis was damaged heavily, thus its adaptability was little. C. squarrosa and A. frifida were damaged to certain extent, but they had the stronger stress resistances. Responses of M. ruthenica to sandy desertification were weak, moderate sandy desertification made for its growth, but its reduce of growth resulted in exorbitant sandy desertification as the same as other populations.(2)The specific leaf area of majority investigated plants decreased, thus their morpha growth reduced. Then A. frigida and M.更多还原