Knowledge Resource Center for Ecological Environment in Arid Area
| 沙坡头人工固沙植被稳定性研究 | |
| 其他题名 | Study on the stability of artificial sand-fixing vegetation in Shapotou |
| 马风云 | |
| 出版年 | 2003 |
| 学位类型 | 博士 |
| 导师 | 李新荣 |
| 学位授予单位 | 中国科学院寒区旱区环境与工程研究所 |
| 中文摘要 | 稳定性是生态系统最重要的特性，是生态学界研究的核心和最复杂的问题之一。自上世纪初至今相关的研究已有大量的报道，其内容涉及稳定性的定义、机理、测度、评价及稳定性研究的尺度等一系列重要的问题。但是，截止目前对干早区半干旱区生态系统，特别是人工植被系统的稳定性的研究报道尚不多见。本文以属于草原化荒漠过度带的沙坡头人工固沙植被作为研究对象，从植被动态、土壤微生物结皮、土壤水分变化、土壤物理化学性质变化与植被关系等多个角度探讨了人工植被系统的稳定性及其机理，并在此基础上提出了人工固沙植被系统稳定性评价的标准和方法以及维持固沙植被稳定性的对策。初步得出如下结论：人工固沙植被动态：沙坡头人工固沙植被建立后，在40多年的演变中发生了很大的变化：在群落结构上由人工植建立初期的一个层片（灌木层片）发展到目前的三个层片（layer）灌木、草本和隐花植物层片）；群落的种类组成上表现为，随固沙时间的增长，人工栽植的植物种类在群落中逐渐减少，而天然侵入的植物种类在增加。并且灌木的盖度和生物量在下降，草本的盖度和生物量在增加。人工植被的演变可分为以下几个阶段：固沙植被建立9-10年后灌木覆盖度达到最高峰（30-40％），15-16年后群落成为以油篙占优势的人工一天然植被组合。在无人为干扰的情况下，大约经过20年左右的时间，人工植被由最初的纯人工植被，经过人工一天然植被组合，既可演变到以天然植被为主的天然一人工植被阶段。人工植被下一步的演替可能有两种趋势：第一种情况是随着人工植被土壤层的不断加厚，灌木和半灌木必将逐渐衰退或保持在一个较低的盖度水平。草本植物将占绝对优势。植被向草原化荒漠类型方向演变。在极端干旱的情况下有可能形成以非维管束植物（no-ascular或cryptogams）为优势的群落；第二种情况是在适度干扰微生物结皮的情况下，土壤深层水分得以改善，植被形成以油篙和草本为主的偏途顶级群落。微生物结皮的发育：对沙坡头固沙植区微生物结皮的研究表明微生物结皮的形成改变了土壤水分的传输特点，有限的降水在沙土层的时空分布发生了变化，使深根系的灌木因得不到较多土壤水分的补给而逐渐退化，浅根系的草本植物因易获得降水的补给而得以定居、繁衍。微生物结皮的进一步增厚，对一年生植物的定居和生长将产生不利的影响，但其形成的致密的抗蚀层，能减轻土壤表面的风蚀和水蚀，增加了土壤表面的稳定性。对沙坡头人工固沙植被区微生物结皮的轻度和重度干扰试验结果表明，微生物生物结皮在受到轻度千扰的情况下有利于草本植物的生长。因此微生物结皮的存在和发育在一定程度上影响了固沙植被的\n组成、结构和功能。微生物结皮的地表气候学特征在20年左右达到一个相对稳定状态，20年前变化非常迅速，之后变化相对缓慢。这一特征和植被的演变时间进程相一致。人工固沙植被土壤水分变化特点：沙坡头地区固沙植被土壤水分在时间尺度上的变化表现为：随着固沙植被建立、发展和演变时间进程的增加，固沙区沙丘土壤水分呈明显的下降趋势：固沙植被建立初期，土壤水分因受降水的影响而季节变化明显，尔后趋于不明显；当固沙植被建立9-10年后，较深沙层（100-30Ocm）的含水量从植被建立初期的3.8-3.5％下降至2％左右，15年后沙层（100-300cm）含水量接近1％。较深沙层含水量的这种变化规律与固沙植被中深根性的灌木种的盖度大小密切相关，当其盖度从30-40％下降至6％-9％时，100300cm沙层能够维持一个相对稳定的较低含水量（1％-1.5％）。对土壤水分空间异质性的研究表明，土壤水分除15-30cm层没有明显的空间依赖性外，其余被分析的各层土壤水分均存在明显的空间依赖性，结构性方差占样本方差的比例从75.7％到99.9％，说明各层土壤水分除15-30cm层外均具有较高的空间依赖性。土壤水分的有效变程从上层到下层有逐渐减小的趋势（15-30cm层除外），O-15cm层有效变程为28.8米，80-120cm层与120-200cm层土壤水分有效变程则分别下降到8.4米和10.8 米。人工植被区土壤水分空间依赖性的变化可能与植物根系对不同层水分的利用有关。人工固沙植被土壤变化特征：沙坡头地区固沙植被建立后，植被区不断积累的降尘使沙面原有的粒度特征发生了变化：随着固沙植被年限的增长，粉粒和粘粒的含量总的趋势是在不断的增加，而砂粒的含量则在逐渐下降；土壤表层(O-15cm)容重在减小，空隙度和毛管持水量的垂直变化与容重正好相反；从流沙到固定沙地，土壤的化学性质也发生了巨大的变化：1956年人工固沙植被表层土壤电导率和流沙相比较增加了几乎13倍。表层土壤PH值和流沙相比有降 低的趋势，稍下层的土壤PH值则高于流沙。和流沙相比较土壤有机质增加明显。氮、磷、钾具有类似于有机质积累过程的总趋势。对人工植被区土壤上下两层（O-15，15-30cm）土壤容重、空隙度和毛管持水量的空间变异性分析表明，O-15cm层土壤容重、毛管持水量和空隙度在13.8-28.8m的有效变程范围内较高的自相关度，结构性方差占样本方差的比例在83.5％以上。在15-30cm层，容重、毛管持水量和空隙度半方差函数为线形模型，表明它们的自相关度存在于更大的尺度上。该结果表明固沙植被的演变过程增加了上层土壤（O-15cm）的空间异质性，对深层土壤物理性质的影响较小。人工固沙植被稳定性评价：在分析沙坡头固沙植被及生境演变特征的基础上，提出了影响其稳定性的关键因子，并作为评价植被稳定性的指标，它们依次是：植被盖度（分别为灌木盖度、草本盖度和隐花植物盖度）、生物量、生物多样性、植物更新能力、结皮厚度、土壤水分、土壤理化性状、植被及土壤特性空间异质性。通过用稳定性指数的方法来评价人工固沙植被的稳定性，进而提出人工固沙植被维持的对策。总之，沙坡头人工固沙植被建立后，沙面得以稳定，大气中的降尘沙面上不断的积累，为微生物结皮的产生创造了物质条件。而微生物结皮的产生、发育和发展使固沙植被系统发生了一系列深刻的变化。首先微生物结皮的存在改变了植被区有限的降水在土壤中的再分配，造成人工固沙植被深层土壤水分不断下降，从而影响了深根系灌木的生长。其次微生物结皮形成的初期为一年生草本植物的生长创造了良好的环境，大批草本植物的入侵提高了人工植被区的物种丰富度和生物多样性。而微生物结皮的进一步增厚，对一年生植物的定居和生长将产生不利的影响。再次微生物结皮的进一步发育促进了植被区成土过程，生境进一步向良性化发展，最终也决定着人工固沙植被的发展方向。人土固沙植被建立约20年后，植被变化趋于缓慢。植被区土壤深层水分含量比较稳定，灌木盖度虽然还在逐步减小，但幅度不大，且随降雨的变化出现一定波动。微生物结皮的组成和性质趋于稳定，生长在结皮上的植物种类和植被盖度可能还会有少量的增加，但不会出现剧烈变化。从这时起，固沙植被及其环境逐渐趋于稳定。如果在这个阶段遇到对结皮的干扰会出现两种情况：轻度的干扰可能会有利于植被的稳定性；而重度的干扰则会出现逆行演替，使人工固沙植重新沙化。因此，要维持固沙植被的稳定性，就要根据其自身发展的规律性，采取人为的措施来科学的管理该系统，便该系统的群落始终保持具有良好防风固沙的结构，实现固沙植被系统健康发暖，长久地发挥其生态功能和效益。 |
| 英文摘要 | Stability is one of important characteristics of ecosystem, but so far, there have been little reports on the stability of ecosystem in arid and semi-arid regions, especially the stability of artificial sand-fixing vegetation ecosystem. Taken the artificial sand-fixing vegetation in Shapotou as a object, this paper explored its stability as well as its mechanism of stability by studying the evolvement of vegetation, macrobiotics crusts, soil moisture changes, the changes of soil physical and chemical properties, and so on. On the basis of these studies, the criterions and methods have been put forward to evaluate the stability of artificial sand-fixing vegetation and also, strategies of maintaining its stability have been proposed. Some results are as follow: The marked changes have happened during more than 40 years since the establishment of sand-fixing vegetation: one layer (shrub layer) in community structure in early stage have turned into three layers; with the time of sand-fixing vegetation extending, shrubs species planted by man decline and herbs invaded increase. Moreover, shrub cover and biomass decline and herb cover and biomass enhance. The change of sand-fixing vegetation can be divided into these stages as follow: the first stage is the period of 9-10 years after the establishment of sand-fixing vegetation. In this period the shrub cover reaches the highest; the second stage is the period of 15-16year after the establishment of sand-fixing vegetation. In this period the community becomes artificial-natural vegetation dominated by artemisia ordosica; after about 20 years, sand-fixed vegetation turns into natural-artificial vegetation dominated by natural species from pure artificial vegetations. Sand-fixed vegetation has two possible trend of evolvement: one is that sand-fixing vegetation will turn into steppe-desert vegetation or communities dominated by non-vascular plants in the situation of extreme drought; the other is the vegetation will become the disclimax communities dominated by artemisia ordosica and herbs under the circumstance that microbiotic crusts are properly disturbed. Studies on the microbiotic crusts in the sand-fixing vegetation region show that microbiotic crusts change the transportation characteristics of soil moisture, and the distribution of limited precipitation in sand soil layers changes. As a result, the deep-rooted shrubs gradually declined due to lack of soil moisture, and shallow-rooted herbs quickly establish and multiply because of precipitation available. With microbiotic crusts thickness in sand-fixing vegetation regions increasing, it has disadvantage influences on establishment and growth of annual herbs, but its compact layer can alleviate erosion caused by wind and water on the surface of soil and augment the stability of soil surface. The experiment results of microbiotic crusts disturbed by means of slightness severe show that microbiotic crusts disturbed by means of slightness is in favor of growth of herbs. Thus, existence and development of microbiotic crusts affect the composition, structure and function to some extent. After 20 year since establishment of sand-fixing vegetation, the climatic characteristics of microbiotic crusts reaches a state of relative stability, that means that there is swift changes before 20 years and slow changes after 20 years. This trait is consistent with the course of vegetation evolvement. Based on observation data during about 40 years, the characteristics of soil water changes in time and in spatial and its effects on vegetation in different sand-fixing areas were analyzed. The results showed that soil water obviously decreased after 9-10 years since vegetation was planted. Especially, the soil water in deeper soil layer remarkably reduced. There is a good corrective relationship between precipitation and soil water in 0-40cm layer, but the relationship between precipitation and soil water in deeper layer (from 40 to 300) was not obvious. The soil moisture in deeper layer further worsened resulted from plants with deep roots system absorbing water around roots, which restrained the plant growth and existing and affected directly on the composition and stability of sand-fixing vegetation. After 40 years, the shrub cover in sand-fixing vegetation decreased from maximum 47.6% to 6%-9% presently. The soil moisture content will keep a constant value (l-%-1.5%) when shrub cover reduced to 6%-9%. Study on soil moisture heterogeneity showed soil moisture in layer analyzed has significant auto-relation except in 15-30cm layer. The proportion of structure variance in total variance ranged from 75.5%-99.9% which means soil moisture except in 15-3Ocm layer have high auto-relation. Effective ranges a trend of decline from 28.8m in upper soil to 10.8m in substrate layers. The change of soil moisture heterogeneity may be related to utilization of water by plant roots in different layers. The increasing accumulation of dust from air on surface of desert altered the original particle characteristics of soil after establishment of sand-fixing vegetation. With the time extension, the content of silt and clay particles in upper soil increasingly enhanced and the content of sand particles gradually descended. Soil bulk density in layer of 0-15cm descended, whereas the vertical change of porosity and capillary moisture capacity were opposite in comparison with bulk density. Soil chemical properties changed a lot from blown.-sand to sand-fixing vegetation. Soil electric conduct in upper layer in sand-fixing vegetation established in 1956 was 13 times in comparison with blown-sand. Soil PH in upper layer was less than that of the blown-sand and soil PH in substrate layers were more than that of blown-sand. Organic matter increased obviously in comparison with blown-sand, and N, P, K had the similar general trend with accumulation of organic matter. Using principle and methods of geo-statistics, spatial heterogeneity of soil physical properties of upper layer soil (0-15, 15-30cm) in Shapotou artificial vegetation area was studied. The results of traditional statistics analysis reveal the mean of soil moisture, bulk density in 0-15cm layer are less than that of 15-3 Ocm layer, the mean of capillary moisture capacity and porosity are reversed, whereas the coefficients of variation are more than that of 15-3 Ocm layer. Results of semivariogram analysis show that there are high degrees of spatial heterogeneity in soil moisture bulk density, capillary moisture and porosity in 0-15cm layer. The scale of spatial heterogeneity is 13.8-28.2m. The spatial heterogeneity of autocorrelations in total spatial heterogeneity are 83.5-99.9%, which are far more than the spatial heterogeneity of stochastic in total spatial heterogeneity. There is no spatial heterogeneity for each soil physical factor in l5-30cm layer. The semivariance function of soil moisture is stochastic model, and the semivariance function of bulk density, capillary moisture capacity and porosity are linear modals. On the basis of Kriging interpolation, the colorful contour maps are produced, from which the distributions of each soil physical factors can be seen clearly. The relationship between spatial heterogeneity and vegetation is discussed. On the basis of analyzing the changes of sand-fixing vegetation and its habitats, the key factors affecting the stability were proposed and were used as criterions to evaluate sand-fixing vegetation stability. These factors are vegetation cover, biomass, biodiversity, macrobiotics crusts, soil moisture, soil physical and chemical properties uncl vegetation as well as soil spatial heterogeneity. The method of evaluating sand-fixing vegetation stability with stability index were used to evaluate the stability of sund-fixing vegetation established indifferent year. Moreover, strategies of muintuining sand-ilxing stability were put forward. To sum up, after the establishment of sand-fixing vegetation, sand surface was stabilized and dusts from air increasingly accumulated on surface of desert, which created conditions for the form of macrobiotics crusts. The development of miemhintie crusts made system of sand-fixing vegetation take place a series of profound changes. First, microbiotic crusts alter the re-distribution of limited precipitation in soil, which caused decline in soil moisture in deeper layer soil and influenced the growth of the growth of deep-rooted plants. Second, microbiotic crusts utlcret! a favorable condition for establishment and growth of annual herbs, and settlement of large number of herbs in sand-fixing vegetation region greatly increased species richness and biodiversity. Third, the further development of microbiotic crusts quickened the production of soil and made environment in a better condition, which incd the cvolvcment direction of sand-fixing vegetation. 20 year after tcm ol suml-Hxing vegetation, its changes tended to slow. In this period, soil moisture in deeper layers was stable, and so is the shrub covers. Also, composition and trait of microbiotic crusts tend to stable. Herbaceous species and its cover may increase slightly, but abrupt changes will not occur. From then on, sand-fixing vegetation as well as its environments gradually tended to stable. If some disturbances to microbiotic crusts occur, two circumstances may take place: slight disturbances may extend sand-fixing vegetation stability; severe disturbances may cause adverse evolvement and make the vegetation re-desertification. Therefore, adopting contrived methods to manage this system scientifically could maintain its stability. |
| 中文关键词 | 人工固沙植被 ; 植被演变 ; 生物多样性 ; 土壤水分 ; 土壤理化性质 ; 空间异质性 ; 稳定性评价 ; 对策 |
| 英文关键词 | artificial sand-fixing vegetation evolvement of vegetation biodiversity soil moisture soil physical and chemical properties spatial heterogeneity |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286324 |
| 推荐引用方式 GB/T 7714 | 马风云. 沙坡头人工固沙植被稳定性研究[D]. 中国科学院寒区旱区环境与工程研究所,2003. |
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