【作者】 赵凌平；

【导师】 程积民；

【作者基本信息】 西北农林科技大学 ， 草业科学， 2008， 硕士

【摘要】 黄土高原植被破坏严重,是我国生态环境脆弱地区。不合理的利用导致了严重的水土流失。如何改善这一地区的生态环境是当前该区生态环境建设的主要任务。本研究以黄土高原典型草原区云雾山草地为研究区域,以封禁26年草地和放牧地为研究对象,采用野外调查和室内试验相结合的研究方法,研究封禁和放牧过程对植被特征变化和土壤种子库特征变化的影响,揭示典型草原退化和恢复过程中的草地植被和种子库的生态学效应。这可为退化植被如何快速恢复提供科学依据,同时对指导黄土高原其周边地区植被恢复具有重要借鉴意义。研究主要结果如下:1云雾山草原自然保护区地上植被的优势种和次优势种为:本氏针茅、大针茅、厚穗冰草、铁杆蒿、百里香、阿尔泰狗娃花和香薷,它们有着较高的重要值。地上植被生活型以多年生草本植物的比例最高,一年生草本次之,灌木比例较低。封禁和放牧措施显著改变了地上植被群落的结构:封禁措施显著提高了地上植被的物种数量、覆盖度、高度、生物量和多样性;小叶锦鸡儿的重要值在封禁样地较高,而铁杆蒿、狼毒、厚穗冰草、星毛委陵菜、白颖苔草和冷蒿这几种植物在放牧样地的重要值比封禁样地的高。2云雾山草原自然保护区土壤种子库特征的主要结论为:土壤种子库中共统计到37种物种,隶属于16科,其中禾本科、菊科、唇形科、豆科和毛茛科的植物占优势;从春季到秋季,种子库中豆科、禾本科、堇菜科所占比例呈下降趋势,唇形科和菊科所占比例明显提高;种子库的密度得到显著提高;种子库中种子数量在垂直分布上呈现出由表层土壤向深层逐层减少的变化规律;在水平分布上的变化规律为:封禁>放牧;阴坡>阳坡;下坡>中坡>上坡;封禁地土壤种子库中的Margalef丰富度和Shannon-Wienner指数都高于放牧地,Pielou均匀性指数低于放牧地。从春季到秋季,封禁地和放牧地土壤种子库的Margalef丰富度、Shannon-Wienner指数、Pielou均匀性指数都呈下降趋势。3百里香、异叶青兰和直径点地梅是云雾山自然保护区土壤种子库中的泛化种,生态位最宽,均达到3.0以上。物种均匀利用资源种类的程度在一定程度上决定了物种的生态位幅度。在同一资源空间中,种对间生态位宽度与生态位重叠并非成正相关关系。同一科属之间的生态位重叠系数均较高,表明在一定程度上生态位可以反映种群间亲缘关系的远近。4云雾山草原自然保护区,封禁措施、0~20cm土壤含水量、坡向和坡位为土壤种子库物种分布的主要影响因子,影响次序为:坡向>封禁措施=土壤含水量>坡位。5云雾山草原自然保护区,地上植被与土壤种子库相似性较低,且封禁草地的土壤种子库与地上植被的相似性高于放牧地。更多还原

【Abstract】 The vegetation of Loess Plateau has been destroyed seriously. And the area is one of most fragile ecosystems in China. Severe desertification on the Loess Plateau as a result of improper land utilization has caused critical soil erosion and water shortages. To prevent further soil erosion, it is very important to cover the bare land surface with natural vegetation. Restoring the ecological balance is the main task to improve the region environment. Field survey and laboratory experiment were conducted to study changes of characteristics of the vegetation and soil seed bank in the fencing and grazing grassland on the loess plateau in typical prairie, to open out ecological significance of the vegetation and soil seed bank in degenerating and restoring succession series, which also could be regarded as a scientific basis for the rapid restoration of natural vegetation, and possessed reference meaning for other areas to restore natural vegetation. Main results were as follow:1 Stipa bungeana, S. grandis, Aneurolepidium dasystaehys, Artemisa vestita, Thymus mongolicus, Heteropappus altaicus and Elsholtzia ciliate were dominant and hypo-dominant species in Yuwushan Reservation in terms of higher important value than other species. The proportion of life form of the vegetation was: Perennial herbaceous plant>Annual herbaceous plant>Shrub. Comparing with the grazing measure, fencing had changed community structure remarkably, and notablely improved the number of species, the coverage, the height, the biomass and the diversity. Caragana microphylla had high important value in fencing grassland. The important value of A. vestita, Euphorbia fischeriana, A.dasystaehys, Potentilla acaulis, Carex rigescens and A. frigida were higher in grazing grassland than the fencing grassland.2 The characteristics of soil seed bank in Yunwushan Reservation were that: 37 species, which belong to 11 families germinated in the plots. In the species of seed bank, Gramineae, Compositea, Labiatae, Leguminosae and Panunculaceae occupied dominant positions; From spring to autumn, the percent of Leguminosae, Gramineae and Violaceae decreased, however, the percent of Compositea and Labiatae increased greatly; densities of the soil seed banks increased significantly; On the vertical distribution, the number of seeds took on a decreasing trend with the depth of soil increasing; The level distribution of soil seed banks followed the order of fencing>grazing, lunar slope > solar slope and top >middle > bottom; The results of the study indicated that the Margalef and the Shannon-Wiener diversity indexes of the soil seed banks were higher in the enclosed grassland, and Pielou evenness indexes were higher in the grazed grassland. From spring to autumn, they all decreased.3 The niche breadth of T. mongolicus, Dracocephalum heterophyllum and Androsace umbellate in soil seed bank reached more than 3.0, and we could said they were generation species of soil seed bank in Yunwushan Reservation. To some extent, what a degree of evenness of resources used by species was to decide the niche breadth. In the same resources space, there was no positive correlation between niche breadth and niche overlap of a species counterpart. The niche overlap was higher in the same class, which showed that, to a certain degree, the niche reflected genetic relationship between species far or close.4 In Yunwushan Reservation,fencing measure, the soil water of 0~20cm depth, slope direction and slope level were dominant factors affecting species distribution. The influence order was: slope direction> fencing measure =the soil water of 0~20cm depth> slope level. 5 The species similarity of the vegetation and soil seed bank was low in Yunwushan Reservation. In fencing plot, the species similarity of the vegetation and soil seed bank was higher than in grazing plot.更多还原