【作者】 张庆；

【导师】 牛建明；

【作者基本信息】 内蒙古大学 ， 生态学， 2011， 博士

【摘要】 生物多样性是生态系统功能和服务的必然前提,是自然生态系统和人类社会发展和维持的基本保障,它不仅可以直接为人类提供物质资源而具有巨大的直接价值,而且还为人类提供生态、科学、美学等间接价值。然而近年来,人类不合理的活动加速了生境丧失和物种绝灭的速率,对生态系统构成了严重破坏,日益威胁到人类的生存和发展,因而生物多样性问题引起国际社会的广泛关注。本文以内蒙古短花针茅草原为研究对象,从基因、物种及群落三个层次探讨了其多样性特征、格局及其与环境因子的关系,在加深对植被生态学及生物多样性若干理论理解的同时,亦可以为科学、合理利用短花针茅草原提供指导,并为短花针茅草原受损生态系统恢复和重建提供科学依据和理论支持。主要研究结果如下：1内蒙古短花针茅种群遗传多样性采用RAPD (Random Amplified Polymorphism DNA, RAPD)分子标记技术,从102条10碱基随机引物中筛选出28条有效引物,共扩增出308条DNA带,多态性DNA带151条,占49.03%,特异性DNA带45条,占14.61%,遗传多样性较为丰富(49.03%),但低于同种方法获得的大针茅(54.75%)和克氏针茅(74.67%)的遗传多样性；等级聚类、PCA(Principal Component Analysis, PCA)分析和UPGMA (Unweighted Pair-Group Method with Arithmetic mean, UPGMA)聚类三种不同方法都将8个不同地理种群分为同样的两类：暖温性种群和中温性种群,聚类结果与种群的空间分布相吻合,经Mantel检验发现,遗传距离与地理距离存在显著相关性；DCCA (Detrended Canonical Correspondence Analysis, DCCA)与Pearson相关分析表明,短花针茅种群的遗传分化与热量因子(≥10℃积温、≥0℃积温、最冷月平均气温、年平均气温、最热月平均气温和无霜期)存在显著的相关关系。综上可知：热量差异的自然选择是导致短花针茅种群产生遗传分化的主要原因,而较强的基因流在其遗传分化中也起到了不可忽略的作用。2内蒙古短花针茅草原物种多样性研究区共统计种子植物31科,96属,161种,且集中分布在菊科(Compositae,29种)、豆科(Leguminosae,25种)、禾本科(Gramineae,23种)、百合科(Liliaceae,10种)等几个大科,区系的优势现象非常明显；该区属种比为班.68,较内蒙古自治区(1/3.33)及全国(1/8.73)均低,物种分化程度低；植物区系组成具有明显的温带性质,但与热带植物区系也存在一定的亲缘关系,具有过渡性；植物生活型特征表明本区多年生草本植物占绝对优势,表现出草原植物群落种类组成的特征,但由于该区土壤覆沙或沙质化明显,因此,灌木和半灌木种类也较多；植物水分生态类群以旱生为主,非旱生也占有很大比例,具有明显的过渡性。内蒙古短花针茅草原物种丰富度存在较大的空间变异,由西向东,随着经度增加物种丰富度呈现显著增多的经度格局,由南向北,随着纬度增加物种丰富度也呈现显著增多的纬度格局,物种丰富度随纬度增加而增多的纬度格局并不是纬度这一地理因子造成的,是在该特定研究区内经度和纬度的共线性造成的；年平均降水量是影响物种丰富度格局的主要气候因子,年平均温度及潜在蒸散量逐一次之,且在干旱及半干旱地区年平均降水量被作为生产力假说中的重要指标,因此,生产力假说是最适合揭示该区物种丰富度分布格局的现代气候假说；气候因子总共只解释了物种丰富度分布格局23.7%的变异,说明物种丰富度分布格局是多种因素(地史、现代气候、随机因素、人为干扰)综合作用的体现,不同区域及不同尺度下各种因素起的作用是不同的。既然生产力假说是最适合揭示该区物种丰富度分布格局的现代气候假说,于是从局域尺度及七个景观尺度(最小幅度为100×100 km,按照100 km连续增加,直到最大幅度为700×700 km)下探讨了生产力与物种丰富度关系的尺度依赖效应。发现局域尺度上生产力与物种丰富度呈单峰曲线关系,随着空间尺度的增大,两者间的正线性关系将变得更加普遍；生物因素是局域尺度生产力与物种丰富度呈单峰曲线关系最主要的原因,环境异质性(内蒙古草原主要是降水异质性)是生产力与物种丰富度在大尺度呈现正线性关系的主导因素；结合前人不同生态尺度下生产力与物种丰富度间关系的研究,本研究通过一系列地理尺度共同证实了生产力与物种丰富度间的正线性关系在内蒙古草原最为常见。3内蒙古短花针茅草原群落多样性运用双向指示种分析法(Two-way Indicator Species Analysis, TWINSPAN)在第四级水平上将短花针茅草原分为16个群丛,并运用除趋势典范对应分析排序方法分析了环境因子、空间因子、两者交互作用及其它因素对内蒙古短花针茅群落类型格局的影响：一方面,DCCA前两排序轴集中了大部分信息(75.3%),第一、二排序轴分别突出反映了群落类型格局在热量、水分梯度上的变化,并由此构建了内蒙古短花针茅草原生态系列图式,另一方面,环境因子对群落类型格局的解释能力为70.7%,其中26.5%为单纯环境因子引起,空间因子解释能力为55.6%,其中11.4%是独立于环境因子的,44.2%是环境因子和空间因子交互作用导致的,未能解释的部分达17.9%。综上可知,就本项研究所涉及的区域而言,环境因素(主要是热量和水分因素)是导致短花针茅草原群落类型分布格局的主导因素,且热量占主导地位。与此同时,选择赛汉、化德、准格尔3个典型样地,分析了局域尺度微地形对植被格局的影响及土壤效应。在群落结构方面,微地形通过地貌过程和起伏变化,外加风蚀、水蚀影响,严重改变了表层土(尤其是0-5 cm)的土壤特征,从而影响了建群种和优势种沿坡面的分布格局,进而导致缓丘上部坡面和下部坡面植被类型明显分异,且以群落复合体的形式出现,上部坡面发育的是本区气候顶级群落,下部坡面发育的为地形群落；在生态系统功能方面,微地形通过起伏作用导致了水分因子在空间的再分配,从而形导致上部坡面和下部坡面生产力的差异,且下部坡面生产力高于上部坡面,形成2个不同的功能区域；在物种多样性方面,微地形导致在极小的范围内形成了非常明显的生境异质性,提供了多样化的生存环境,为局域范围内生物多样性的形成与维持提供了一种重要机制。更多还原

【Abstract】 Biodiversity is a necessary prerequisite of ecosystem function and ecosystem services. It maintains both the sustainability of natural ecological systems and the well-being of human society. Besides providing material resources for the humanity directly, biodiversity has other important ecological, scientific, and aesthetic values. In recent years, unreasonable exploitation of natural resources by the society has accelerated habitat loss and species extinction. These adverse effects seriously damage ecosystem integrity and pose a threat to human survival and development. Therefore, biodiversity preservation and maintenance is the matter of urgent international concern.In this study we chose Stipa breviflora grassland as the research object and explored biodiversity patterns and their relationships with environmental factors at multiple scales. First, our research contributes to the understanding of ecosystem function and provides additional empirical evidence for theories developed in plant ecology and biodiversity. Second, our findings can provide the needed scientific basis and theoretical support for rational utilization of grasslands and restoration of damaged grassland ecosystems. Main results from the study are outlined below.1. Genetic diversity of S. breviflora grassland in Inner MongoliaGenetic diversity of S. breviflora populations and its relationship with climatic variables were studied using Geographic Information Systems (GIS) and the Random Amplified Polymorphism DNA analysis (RAPD). The RAPD produced a total of 308 bands with twenty-eight arbitrary decamer oligonucleotides. Among those,151 (or 49.03%) were polymorphic to the populations, and 45 (or 14.61%) were unique to specific populations. The genetic diversity of S. breviflora was high, but lower than that of the other two common species in the area-S. grandis and S. krylovii. Eight different geographical populations were analyzed by 3 different methods-the Hierarchical cluster analysis, the Principal Component Analysis (PCA), and the Unweighted Pair-Group Method with Arithmetic mean (UPGMA), which resulted in 2 groups of populations-warm-temperate and temperate. Mantel test showed a significantly positive correlation between genetic distance and geographical distance. Both detrended canonical correspondence analysis (DCCA) and Pearson correlation analysis showed that correlations between genetic differentiation and temperature were strong in the area. In particular, we found significant correlations of genetic differentiation with accumulated temperature≥10°, accumulated temperature≥0°, mean temperature of the coldest and the hottest months, annual mean temperature, and the number of frost-free days. We therefore conclude that temperature variations play an important role in the genetic differentiations of the investigated S. breviflora populations. Genetic flow was found to be and important process in genetic differentiation.2. Species diversity of S. breviflora grassland in Inner MongoliaThe studied populations of S. breviflora contained a total of 161 species belonging to 31 families and 96 genera of Spermatophytes. Species found belong to several families: Compositae (29), Leguminosae (25), Gramineae (23), Liliaceae (10). Hence, the floristic diversity is high. The ratio of genera to species of studied populations was 1/1.68, which is smaller than that of the entire Inner Mongolia (1/3.33) or China (1/8.73). This result suggests that the level of species differentiation is low. We found that vegetation composition is mainly characterized as being representative of the temperate zone, although certain elements of the tropical flora were also found, leading us to the conclusion about the transitional character of the local flora. Statistical analyses of life form occurrences showed that perennial herbs dominated the steppe communities. Besides, shrubs and semi-shrubs were also common life forms. They mainly occupied sandy soils that covered many areas in this region. While xerophytes generally dominated plant communities, non-xerophytes accounted for a larger proportion of species found. We found that different ecological types of water regime controlled the distribution of plant communities.Spatial distribution of S. breviflora grassland communities in Inner Mongolia clearly followed longitudinal and latitudinal gradients:species richness increased significantly with longitude increasing (west-east gradient) and latitude increasing (south-north gradient). We found that species richness increase along the latitudinal south-north gradient is mainly due to the collinearity between environmental factors that change along the latitudinal and longitudinal gradients in the study area. Average annual precipitation is the major climatic factor that controls species richness patterns followed by annual average temperature and potential evapotranspiration. Moreover, the average annual precipitation is the main predictor variable for primary productivity in arid and semi-arid regions. We hypothesized that primary productivity should be explained largely by modern climate patterns that, at the same time, may help us reveal distribution patterns of species richness in the area. Climate factors, however, explained only 23.7% of variation in spatial distribution of species richness suggesting that richness patterns are influenced by a variety of factors including historical legacies, modern climate, human disturbances, and other random factors. These groups of factors play different roles in different parts of our study area and at different analysis scales.We collected data on species diversity (richness) and productivity (peak above-ground biomass) of the S. breviflora association in Inner Mongolia grassland to examine spatial scale dependency and possible underlying mechanisms responsible for relationships found. One local and seven different landscape scales (the first level starts at a 100 x 100 km area, which is increased consecutively by 100 km at the next level resulting in the 700 x 700 km area at the highest level) were considered. Unimodal relationship dominated the local scale, but it varied depending on the position along successional gradients. Positive linear relationship was common at larger spatial scales. Biotic processes were the most likely primary factor underlying local scale unimodal relationships, but environmental heterogeneity, mainly precipitation patterns, was the main determinant of relationships found at larger spatial scales. While earlier research demonstrated positive linear species richness-productivity relationships across a number of ecological scales in the Inner Mongolia steppe, our study specifically tested a spectrum of geographical scales to confirm scale-dependency of this relationship.3. Community diversity of S. breviflora grassland in Inner MongoliaThe community level analysis of the S. breviflora grassland produced a classification with 16 distinct groups evident at the fourth level of division using the two-way indicator species analysis (TWINSPAN) algorithm. We also investigated the effects of environmental and spatial factors, as well as their interaction, on the structure of S. breviflora communities by using detrended canonical correspondence analysis (DCCA). Our results showed that the first two DCCA axes, which corresponded to gradients in temperature and precipitation, respectively, explained most of the variation in community structure (75.3%). Based on these results different S. breviflora communities were arranged into an ecological series.70.7% of the total variance in S. breviflora community structure was explained by all environmental factors and 55.6% by all spatial factors. When these factors were examined separately, only 29.5% and 11.4% of the total variance was explained by the two groups of factors, respectively.44.2% was simultaneously explained by the two groups, while 17.9% was explained by other undetermined factors. According to these, we concluded that environmental factors (precipitation and temperature) play an important role in community differentiations.We chose 3 typical S. breviflora grassland sites (Saihantala, Huade, and Zhunger) to analyze the influence of micro-landforms and soil on vegetation patterns. Local scale species distribution patterns, i.e. species composition and dominant species distribution, were affected by micro-landforms along the slope gradient. On the other hand, vegetation associations represented by community complexes were clearly differentiated between the upper slope and the lower slope due to different types of micro-landforms of the two localities. Climatic climax community grew in dominance toward the upper slope, while terrain community developed in the lower slope locations. Such patterns can be explained by differences in soil physical properties at the top soil horizons (especially the 0-5 cm layer). Community productivity is largely controlled by soil moisture. It is sufficiently higher in the more moisture-rich lower slope locations. We found that micro-landforms also determine species diversity by forming significant habitat heterogeneity within a very limited spatial area. It provides an important mechanism for the formation and maintenance of biological diversity at local scales.更多还原