【作者】 张璞进；

【导师】 杨劼；

【作者基本信息】 内蒙古大学 ， 生态学， 2011， 博士

【摘要】 干旱和半干旱生态系统是一类非常重要的生态系统类型,它覆盖着世界陆地面积的1/3,储存着>30%的全球有机碳含量,但该生态系统较为脆弱,对气候变化和人类活动较为敏感,极易发生退化和破坏。水分是干旱和半干旱区域的限制性因子,对这里植物的生存和生产、生态系统的结构和生产力、植被动态起着决定性的作用。鄂尔多斯高原是我国干旱、半干旱区一个相对独立的自然单元,也是一个十分特殊和敏感的生态过渡带。藏锦鸡儿(Caragana tibetica)群落在该区是分布在草原和荒漠过渡带上的重要群落类型,也是非常重要的牧草场。本文通过分析鄂尔多斯高原藏锦鸡儿的群落特征、种群特征、生物学特征、以及藏锦鸡儿的沙堆效应,探讨藏锦鸡儿对干旱环境的适应特征,研究结果显示：1、藏锦鸡儿群落特征表现为：(1)其分布面积约为3684平方公里,可划分出15个群丛。(2)藏锦鸡儿的盖度约为11%,密度为42株每100平方米；草本层的Simpson和Shannon-Wiener多样性指数在7.3左右。(3)藏锦鸡儿群落包含种子植物88种,隶属于26科,58个属；含属、种最多的科是禾本科(Gramineae),其次为菊科(Compositae)和豆科(Leguminosae);含种最多的属是蒿属(Artemisia),其次为针茅属(Stipa);其中包含强旱生植物7种、典型旱生植物52种。2、通过分析代表性群落-藏锦鸡儿-无芒隐子草+短花针茅群落可知,藏锦鸡儿群落结构较为稳定。(1)垂直结构表现为：地上部分,优势层片藏锦鸡儿的高度在25 cm左右,丛生禾草无芒隐子草(Cleistogenes songorica)和短花针茅(Stipa breviflora)共建亚优势层片的高度在5-10 cm左右；地下部分,藏锦鸡儿根系分布在2 m左右,为双层根系类型,并发育一定不定根,小根和细根集中分布在20-60 cm和140-170 cm的土层中,草本层的根系集中分布在0-30 cm的土层。(2)水平结构表现为：在10 m×10 m的范围内,藏锦鸡儿为随机分布,狭叶锦鸡儿(Caragana stenophylla)、阿氏旋花(Convolvulus ammannii)、燥原荠(Ptilotrichum canescens)为聚集分布,短花针茅、无芒隐子草、单叶黄芪(Astragalus efoliolatus)、冷蒿(Artemisia frigida)随着取样范围的增加先呈聚集分布而后为随机分布。(3)藏锦鸡儿与其它多年生植物问没有相关关系,不存在种问竞争。(4)藏锦鸡儿引起了群落内土壤全氮、有机碳、土壤水分的空间异质性分布,但这对群落内其它多年生植物的分布格局没有影响。藏锦鸡儿富集的土壤养分并不被其它多年生植物所利用。2、藏锦鸡儿种群分布格局随着降水量的递减发生了变化。随着降水量的减少,藏锦鸡儿种群中存活藏锦鸡儿和成熟藏锦鸡儿在一定范围内的均匀分布格局被随机分布格局所取代。3、藏锦鸡儿形态特征为近半椭圆形的垫状特征,平均灌幅为57 cm×44 cm,灌丛高为22 cm；藏锦鸡儿的根和茎都存在劈裂现象。4、藏锦鸡儿沙堆效应体现固沙效应和沃岛效应,固沙效应表现为：藏锦鸡儿群落每平方米固定0.031 m3的风沙；藏锦鸡儿聚集的主要是细沙粒,占沙堆土壤机械组成的73%。沃岛效应表现为：藏锦鸡儿沙堆内的土壤平均有机质和全磷含量均高于沙堆外的。在沙堆内,土壤有机质和全磷含量随着土层深度的增加呈先增加后减小的趋势,在地面以上的20 cm处达到最大；土壤水分呈递增趋势。藏锦鸡儿对干旱环境表现出较强的适应能力,灌丛沙堆的形成促进了藏锦鸡儿的生长和发育。藏锦鸡儿群落虽然有相对较高的稳定性,但是鉴于现在藏锦鸡儿普遍退化较严重和藏锦鸡儿显著的生态功能,对藏锦鸡儿群落应合理利用,在夏秋季节可作为放牧草场,冬春季应加强保护。通过本研究我们更加系统的认识了干旱环境中植物与环境之间的相互关系,对干旱区的生态恢复及资源的可持续利用具有深远的意义。更多还原

【Abstract】 Arid and semiarid ecosystems are very important ecosystem types. They cover one third of land area in the world, produce more than 35% of global land net primary production and possess an excess of 30% of global organic carbon reserves. However, these ecosystems are more vulnerable and susceptible to degradation under climate changes and human activities. Water is a limited factor in these regions, and plays a crucial role in terms of plant survival and production, the structure and productivity of ecosystem and dynamics of vegetation. Ordos plateau is a relatively independent natural unit in arid and semiarid areas of China, and also a highly unique and susceptible ecotone. Caragana tibetica community is an important community type in the ecotones between steppe and desert of this region, and acts as a crucial pasture. In this study, we analyzed characteristics of C. tibetica in terms of community, population and biology, and also analyzed the effects of the nebkhas it induced to explore its adaptive characters to the arid environment. Our results were shown as follows:1. Caragana tibetica community belonged to the vegetation type of steppe desert. (1) Caragana tibetica community covered an area of about 3684 km2, and could be separated into 15 association. (2) The coverage of C. tibetica was about 11% and there were about 42 C. tibetica individuals per unit 100 m2; the Simpson and Shannon-Wiener diversity indices of herbs were both about 7.3. (3) There were 88 seed plant species in the C. tibetica community, which belonged to 26 family and 58 genera. Among these plants, family Gramineae contained the largest number of genus and species, and then followed by the family Compositae. The genus Artemisia had the largest number of species and the genus Stipa took the second place. In addition, there were 7 strong xeric species and 52 typical xeric species in C. tibetica community.2. Caragana tibetica community showed a stable structure. (1) The vertical structure was shown that:for the aboveground parts of the community, the height of dominant synusia was about 25 cm, and that of sub-dominant synusia consisting of bunchgrasses Cleistogenes songorica and Stipa breviflora ranged from 5 to 10 cm; for the belowground parts of the community, C. tibetica had bimodal root activity profile and most roots concentrated in the 0-200 cm soil layers with a certain amount of adventitious roots growing. The small roots and fine roots separately concentrated in 20-60 cm and 140-170 cm soil layers. The root system of herbs mainly distributed in 0-30 cm soil layer. (2) The horizontal structure was shown that:at the spatial scale of 10 m×10 m, C. tibetica individuals showed random pattern, while Caragana stenophylla, Convolvulus ammannii and Ptilotrichum canescens showed aggregation patterns. With the spatial scales increasing, Stipa breviflora, Cleistogenes songorica, Astragalus efoliolatus and Artemisia frigida firstly showed aggregation patterns and then exhibited random patterns. (3) Caragana tibetica did not show associations with other perennial species, and no interspecies competition was found among them. (4) Caragana tibetica caused the spatial heterogenous distributions of soil total nitrogen, soil organic carbon and soil moisture, which however did not influence the distribution patterns of other perennial species in the community. Therefore, soil nutrients accumulated by C. tibetica could not be used by other perennial plants.3. The distribution patterns of C. tibetica populations varied with the decrease of the precipitation. With the precipitation decreasing, the uniform distribution patterns of both the live and mature C. tibetica individuals at a certain scale were replaced by the random patterns.4. Morphologically, C. tibetica showed dwarf and near hemi-oval shape, and its average canopy was 57 cm in length and 44 cm in width. Both the root and stem of C. tibetica had the ability of split.5. Caragana tibetica nebkhas showed the sand-fixing and fertile island effects. (1) In C. tibetica community, the amount of sand trapped by C. tibetica per unit area was 0.0313 m3m-2. Caragana tibetica primarily accumulated fine sand, which accounted for 74% of the soil in the nebkhas. (2) The contents of soil organic matter and total phosphorus and soil moisture inside nebkhas were higher than those outside the nebkhhas. Inside the nebkhas, contents of soil organic matter and total phosphorus first increased and then decreased with increasing soil depth with the maximum value occurring in the layer of 20 cm, but soil moisture increased steadily.In a word, C. tibetica showed strong abilities to adapt arid environment, and the formation of nebkhas facilitated its growth and development. Yet, despite of the stability of C. tibetica community, more attentions should be paid on its rational utilization in view of current serious destruction and significant ecological functions of the species. In summer and autumn its community could be used as pasture while in winter and spring the protective measures should be considered to take. Our study provided more systematical understandings of the relationship between arid environment and plant, which will have profound significance for ecological restoration and sustainable utilization of resources.更多还原