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题名	古尔班通古特沙漠生物结皮的微结构特征及结皮对种子植物萌发和生长的影响
作者	陈荣毅
学位类别	博士
答辩日期	2007
授予单位	中国科学院．新疆生态与地理研究所
导师	魏文寿，中国科学院新疆生态与地理研究所/中国气象局乌鲁木齐沙漠气象研究所
关键词	古尔班通古特沙漠
其他题名	The effect of biological crust on plant germination, growth and survival in Gurbantunggut Desert
中文摘要	古尔班通古特沙漠位于温带气候条件下的准噶尔盆地，是中国最大的固定和半固定沙漠。该沙漠广泛发育的生物结皮, 是除种子植物以外固定沙面的重要生物因子。结皮影响土壤养分的积累和土壤水分分配特征，从而对种子植物定居产生重要影响。然而国内外的研究在结皮的微形态与矿物风化，结皮对种子植物定居等方面存在争议。本文以古尔班通古特沙漠生物结皮为研究对象，通过扫描电镜和制作土壤薄片，探讨生物结皮的微结构特征以及结皮在矿物风化中的作用；通过室内、野外萌发试验，结合微结构研究结果研究生物结皮对植物种子的捕获、萌发以及对植物生存和生长的影响；通过调查沙漠边缘到腹地的结皮、土壤养分和植被的空间分异与干扰的关系，结合人为对结皮的干扰，研究结皮存在条件下干扰对土壤理化性质和植被格局的影响。综合以上研究结果，探讨古尔班通古特沙漠生物结皮对种子植物多样性的影响。本文主要研究结果如下： 1.生物结皮早期阶段的微结构特征去除结皮后，恢复1年形成的结皮是通过粘性菌体及其多糖等分泌物对沙粒的粘结作用来维持结构, 此时的抗压强度较低为13.42±1.38Pa。组成胞外多糖的各单糖组成中以葡萄糖、甘露糖和一种葡萄糖的同分异构体为主。经过4年的恢复, 藻类结皮逐渐形成, 抗压强度增加至32.53±3.08Pa。藻结皮以陆生蓝藻具鞘微鞘藻(Microcoleus vaginatus)为优势种。 此时, 沙粒间维持藻结皮结构的主要是丝状藻体更紧密和高强度的机械束缚作用以及藻体胞外分泌物对沙粒的粘结作用。 2.不同演替阶段生物结皮的形态特征与矿物学变化随着结皮演替结皮中生物体数量及在土壤中分布深度逐步增加，表层土壤矿物组成中不易风化的原生矿物石英和长石含量减少而易风化原生矿物辉石和角闪石含量增加。次生矿物水云母在结皮发育后期出现而在流沙和浅色藻结皮中缺乏。表层土壤机械组成随着结皮演替改善，粘粒和粉砂粒均在结皮形成时出现。藻类、地衣和苔藓生物对矿物有明显的生物侵蚀作用。发育后期的生物结皮比早期的结构复杂，生物活性更高，并且有更好的水分条件，因此更有利于荒漠表层土壤原生矿物的风化。 3.结皮存在下古尔班通古特沙漠养分空间分异与干扰的关系结皮存在下干扰对沙漠土壤养分空间分异特征产生了影响。沙漠边缘至腹地，全N、全P和全K含量、EC、总盐，可溶性离子HCO3-、SO42-及Ca2+呈增加趋势，而干扰因子数呈现减少趋势。干扰因子数与结皮盖度呈显著负相关，除与pH值呈正相关外，干扰因子数与土壤养分指标都呈负相关，其中与全K、全P、全N和EC的负相关接近于显著或极显著水平。该段沙漠放牧活动影响的最大范围为里程125-145km，而随着引水渠通水以及沙漠腹地交通条件的改善，人类在沙漠活动可能增加，会增加干扰源及其强度，最终降低沙漠腹地土壤的养分条件。 4.生物结皮与沙丘部位对种子库的影响不同结皮类型和沙丘部位上种子分布特征有一定的规律性。藻类结皮上的种子数量、丰富度和多样性均显著高于地衣和苔藓结皮，生物结皮从藻类到地衣和苔藓的演替，有降低种子的数量和多样性的现象。在不同沙丘部位，顶部流沙的种子数量和多样性较低，与丘顶流沙相比沙丘底部的藻类结皮上种子显示出较高的丰富度和多样性，但沙丘底部的地衣和苔藓结皮与丘顶流沙相比种子多样性和丰富度未表现出明显的差异。背风坡中部的藻类结皮上种子多样性较高，显著高于迎风坡中部的藻类结皮。 5.生物结皮对种子萌发、生长和生存的影响生物结皮减少了种子的萌发速度，最终减少了种子萌发和出苗率，而室内和野外的萌发、出苗试验表明，覆沙处理能显著提高种子的出苗率。相对于流沙，生物结皮的存在能够提高植物幼苗的营养条件，结皮较高的营养条件有利于短命植物生长，但发育良好的结皮减少了夏秋季土壤深层的水分条件会对深根系的多年生草本和灌木的生存带来不利影响。 6.生物结皮对古尔班通古特沙漠种子植物多样性的影响发育后期的结皮相对早期阶段对植物多样性有降低作用，特别对于深根系的植物不利。对结皮进行适度干扰，使之保持在早期阶段有利于增加植物多样性。然而严重干扰使土壤变成流沙会导致养分缺乏，致使浅根系植物不能正常发育，从而减少植物的多样性。植被的覆盖度、种类、多样性指数H以及干扰因子数从沙漠边缘到内部都呈波动性的减少趋势，分析表明植被变化与干扰因素有关。与流沙相比，生物结皮由于在土壤养分固定、保持及成土作用上具有重要意义，有利于荒漠植物的多样性，在对生物结皮采取干扰措施以提高植物多样性之前需要谨慎考虑可能的不利影响。As the largest fixed and semi-fixed desert in China, the Gurbantonggut Desert is located in the Junggar Basin, which is typical of temperate deserts in the world. There is an abundant biological crust (BC) on the sand surface of the desert, which serves as one of the biological factors contributing to the sand fixation besides plant. The BC has a profound impact on the soil hydrological processes, soil water environment and soil fertility, thus it affect the establishment and survival of vascular plants. The available data from international research shows, however, varied results about microstructure and mineral weathering of BC and it having either positive, inhibitory, or no effect on vascular plant establishment and cover. This paper studied microstructure and mineralogical composition of BC with thin soil section and Scanning Electron Microscope (SEM), discuss the effect of BC on soil formation and mineral weathering in desert area. Under laboratory and field conditions, we experimentally investigate the effect of BC on vascular plant seed bank, seed germination, plant growth and establishment. A field investigation was conducted to test the correlation between disturbance with the distribution of BC, soil nutrient and plant structure from the verge to center of desert, and it based on the result of manmade disturbance to discuss the effect of disturbance on soil nutrient and plant structure in present of BC. In summarize all the above results, the paper discuss the effect of BC on plant diversity in the Gurbantonggut Desert. The mean conclusions are followed as: 1. The microstructure of early stage of biological crust One year after removal of biological soil crusts, the exposed surface could be fixed by bacteria, which make sand particles cohere by exopolysaccharides. The intension of pressure for this kind of crust is 13.42±1.38 Pa. The exopolysaccharides were mainly composed of glucose, mannitol, arabinose and galactose. After four year recovery of the disturbance, the biological soil crust resulting from the colonization of soil surface by communities of filamentous cyanobacteria were mainly dominated by Microcoleus, which occurred as a cluster of filaments surrounded by a gelatinous sheath. At this developmental stage, the main contributors for sand fixation were changed from bacteria to filamentous cyanobacteria. These effects enhance soil cohesion and resistance to erosion. The intension of pressure for this kind of crust is 32.53±3.08Pa. 2. Morphology and mineralogical component changed with successional crusts It is showed that crust had greater organism biomass and deeper location of organism in soil with crust successions. The minerals which resist weathering like quartz and feldspar decreased with crust succession, but the pyroxene and hornblende that are susceptible to weathering increased with crust development. Neogenic mineral as hydrous mica is found in late stages of crust (dark cyanbacterial crust, lichen and moss), whereas it is not found in shifting sand and light cyanobacterial crust. The silt and clay are found when shifting sand evolved into cyanobacterial crust and the soil mean particle-size value tended to become finer with crust succession. The cyanobacteria, lichen and moss erode minerals based on soil section observation. The late stages of crust which have more activities and complexities as well as better moisture condition than early stage, thus may have more ability to accelerate mineral weathering. 3. The relation between disturbance and spatial heterogeneity of soil nitration in the gurbantunggut desert The trend of soil nutrient distribution in the Gurbantunggut desert which covered by BC is influenced by disturbance. The results show that the total N, total P, total K and soluble salt, such as HCO31-, SO42-and Ca2+, increase from the verge to center of desert while the value of disturbance factors has a decreasing trend. All soil nutrient parameters have negative correlation with disturbance factors aside from pH which has a positive correlation with that. The human activities will increase when the aqueduct was used to transport water as well as the traffic condition was improved, which will fortify the disturbance factors and intensity in desert, which decrease the soil nutrient in desert. 4. The effect of biological crusts and sand dune position on soil seed bank The soil seed banks on different biological crust and different position of representative sand dune have interesting phenomena. The results show that the seed density, species richness (Margalet index) and the species diversity (Simpson’s diversity index and Shannon-Winner index) are higher on algal crust than lichen and moss crust. The seed density and diversity decrease with the crust evolve from algal crust to lichen and moss crust. The seed density and diversity are lowest on the top of sand dune without crust. The seed density and diversity of seed bank on algal crust are significantly higher than that sand crest. In comparison with the algal crust, the seed density and diversity on lichen and moss crust are not significantly different with soil at crest without crust. The seed density and diversity on algal crust were significant higher on leeward slope than windward slope. 5. The effect of biological crusts on plant germination, growth and survival We have conducted a field investigation and greenhouse experiments to test the effect of crusts on plant seeding. Our results suggest that BC have a negative effect on the speed of seed germination, however, sand burying can significantly improve seed germination. In contrast to shifting sand, BC have positive effect on nutrient of the early seeding. But well developed BC decreased soil water condition of deep soil, and has a negative impact on the survival of deep-rooted grass and shrubs. 6. The effect of biological crust on plant diversity in the Gurbantunggut Desert In comparison with early stage of crust, late stages of crust have a negative effect on plant diversity, and have an especially negative impact on deep-rooted plant. Moderate disturbance can maintain the BC at an early-successional stage, which will improve the plant diversity. However, heavy disturbance changed soil into shifting sand and the soil will become too poor to suit for growth of shallow-root plant, which will decrease the plant diversity. The results show that the plant species, vegetation cover, the species diversity (Simpson’s diversity index) and the disturbance factors have a decreasing trend from the verge to center of desert. The change of plant structure is influenced by disturbance. The BC has a significant role in contributing to the soil formation and soil nutrient fixation and hold, which will contribute the plant diversity. Before taking manmade disturbance to improve plant diversity in the regions, all the negative effects should be carefully considered.
语种	中文
学科主题	微生物学
公开日期	2010-11-12
页码	共128页
内容类型	学位论文
源URL	[http://ir.xjlas.org/handle/365004/7982]
专题	新疆生态与地理研究所_中国科学院新疆生态与地理研究所(2010年以前数据)
推荐引用方式 GB/T 7714	陈荣毅. 古尔班通古特沙漠生物结皮的微结构特征及结皮对种子植物萌发和生长的影响[D]. 中国科学院．新疆生态与地理研究所. 2007.

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