【作者】 冯秀；

【导师】 仝川；

【作者基本信息】 内蒙古大学 ， 环境科学， 2007， 硕士

【摘要】 土壤种子库一直是植物生态学研究的一个重要领域，锡林郭勒草原在内蒙古高原草原中具有极大的代表性，对于锡林郭勒草原退化过程中以及长期围栏禁牧恢复后的土壤种子库特征的揭示具有重要的理论价值和实践意义。在锡林郭勒草原白音锡勒牧场选择退化系列，包括四连退化系列(轻度退化、中度退化、重度退化、极度退化等样地)和牧户干扰系列(包括根据距离牧户的距离的牧户1、牧户2、牧户样地3)；围栏禁牧系列(包括围栏禁牧23年、围栏禁牧10年、围栏外等样地)以及小叶锦鸡儿灌丛草原样地。为了揭示土壤总种子库和土壤种子库中可萌发种子萌发后且尚未得到新种子雨补充之前的土壤种子库状况和土壤种子库垂直分布特征，分别于2006年4月初和6月底分层取土样，采用萌发法鉴定土壤种子库组成和结构，并结合地上植被样方调查探讨了土壤种子库与地上植被的关系。研究结论如下：1．草原退化土壤种子库及地上植被特征四连退化系列的研究表明：4、6月取样土壤种子库的总物种数、多年生植物种数、土壤种子库中可萌发种子数均与退化程度呈负相关；土壤种子库中多年生植物密度所占比例与退化程度呈正相关；4月取样各样地土壤种子库密度在0.001水平上差异显著(F=33.749，P＜0.001，df.=15)，6月在0.05水平上差异显著(F=12.578，P＜0.05，df.=15)；羊草、克氏针茅、糙隐子草3种重要禾草在轻度退化、中度退化、中度退化样地中均有分布。中度退化样地地上植被密度最大，轻度退化样地生物量最大。重度退化样地地上植被密度和生物量均远小于轻度退化、中度退化样地。牧户干扰系列土壤种子库研究表明：土壤种子库的组成和大小特征随距牧户距离的增加，并没有明显的变化；4月取样各样地土壤种子库密度差异不显著(F=3.739，P=0.066，df.=11)，6月取样各样地土壤种子库密度在0.05水平上差异显著(F=10.096，P＜0.05，df.=11)；土壤种子库中多年生植物密度随着辐射距离的增加而增加。地上植被密度随距牧户距离的增加而降低，地上植被生物量则相反。2个退化系列各样地4月土壤种子库主要分布在0～3cm，6月主要分布在0～6cm。四连退化系列4、6月种子库密度随土壤深度的增加而减少。牧户干扰系列各样地4月种子库密度随土壤深度的增加而减少，6月没有一致的规律。2．退化草原长期围栏禁牧土壤种子库及地上植被特征4、6月2次取样，围栏外退化草原土壤种子库密度分别仅为围栏禁牧23年和10年的19.3％和18.0％、33.3％和34.5％，4月取样围栏禁牧23年、10年和围栏外样地土壤种子库密度差异显著(F=11.759，P＜0.001，df.=14)，6月三样地土壤种子库密度在0.05水平上差异显著(F=4.339，P＜0.05，df.=14)；多数植物土壤种子库主要分布在0～3cm层，各样地种子库密度随土壤深度的增加而减少；6月与4月相比，各样地土壤种子库密度明显减少，围栏禁牧23年样地6月土壤种子库密度仅为4月样地的52.6％，有将近一半可萌发种子已在春季萌发。围栏禁牧23年、10年样地植物种类明显增加，特别是一些中旱生杂类草，如防风(Saposhnikovia divaricata)和麻花头(Serratula centauroides)等；植被平均密度和物种数量随着围栏年限的增加而增加，长期围栏禁牧可明显恢复退化羊草+大针茅草原的物种组成和土壤种子库。退化系列和围栏禁牧系列上各样地一年生植物，包括黄蒿(Artemisiascoparia)、猪毛菜(Salsola collina)和2种藜(Chenopodium album、C.aristatum)的土壤种子库构成了样地土壤种子库密度的主要部分。3．灌丛化对土壤种子库的影响研究的初步结果显示小叶锦鸡儿灌丛下土壤种子库密度与灌丛的冠幅没有显著的相关性，但灌丛冠幅影响灌丛间与灌丛下土壤种子库大小关系。4．无论是4月还是6月，各系列地上植被与土壤种子库库在物种组成上的相似性处于不相似到中等相似水平。相对来说，围栏禁牧系列各样地地上植被与土壤种子库的相似性最高、退化系列次之、牧户干扰系列最小。4、6月各系列土壤种子库之间的相似性系数均大于植被与土壤种子库之间的相似性系数。说明土壤种子库比地上植被更为稳定。更多还原

【Abstract】 Soil seed bank is an important research area in plant ecology. The Xilingole steppe has great representation in the Mongolian Plateau grassland. It is important in theoretical value and practical significance to reveal the characteristics of the seed bank in grassland degradation process and the long-term grazing exclusion Four series were chosen in the study areas in the Baiyinxile Ranch of the Xiiingole steppe. The four series are as below: 1) the first series which includes light-degraded, moderate- degraded, heavy-degraded and extreme degraded sites; 2) the second series which includes degraded sites with different distances from herdsmen residential; 3) the third series including enclosed and over-grazed sites; 4)site with Caragana microphylla shrub. In order to reveal the total soil seed banks and soil seed bank which after seed germinated in spring and before new seed rain added to, and the vertical distribution of soil seed bank, soil samples were collected in early April and late June 2006. Soil seed banks composition and structure were identified using germination method. Furthermore, the relationship between soil seed bank and standing vegetation were discussed. Our results are described as follows:1. Characteristics of the soil seed bankand standing vegetation of degradation grassland.The results of the first series showed: The number of the total species and the perennial species and the density of soil seed banks in April and June are negative correlation with the degeneration degree. The variances of the density of soil seed banks between sites are significant both in April (F=33.749, P＜0.001, df. =15) andJune (F=12.578, P＜0.05, df. =15). Light-degraded, moderate-degraded and heavy- degraded sites all have leymus chinensis, Stipa krylovii and Cleistogenes squarrosa distribution. The density of standing vegetation is highest in moderate- degraded site. The dry biomass is highest in light-degraded site. They are both lowest in heavydegraded site.The results of the second series showed: The composition and size characteristics of soil seed bank have no significant changes as the distance from the herdsmen residential increased. The variances of the density of soil seed banks between sites are not signifacant in April (F=3.739, P=0.066, df. =11) but signifacant in June (F=10.096, P＜0.05, df. =11). The ratio of perennial density in the density Of soil seed banks is positive correlation with the distance from the herdsmen residential.Density of standing vegetation decreases with the distance from the herdsmen residential increased, but dry biomass of standing vegetation increases.The distribution of soil seed banks in the two series are mainly in the layer of 0～3cm in April and in 0～6cm in June, and the density of soil seed banks decrease with the depth of soil generally.2. Characteristics of the soil seed bank and standing vegetation of long-term grazing exclusion and over grazed grasslandIn April, the density of soil seed bank in over-grazed degradation site only accounted for 19.3% and 18.0% of the sites enclosed for 23 years and 10 years respectively, but 33.3% and 34.5% in June. The variances of the density of soil seed banks between sites are obvious in April (F=3.739, P=0.066, df.=11) and June (F =10.096, P＜0.05, df.=11).The soil seed banks of most species mainly distribute in the layer of 0～3cm, density of soil seed banks decrease with the depth of soil.The density of soil seed banks in sites in April were lower than they were in June obviously. For the site enclosed for 23 years, the density of soil seed bank in April accounts for 52.6% of that in June, half of seed germinate in the spring nearly. Plant species of standing vegetation increase significantly in the site enclosed for 23 years and the site enclosed for 10 years, especially some mesophytes forbs and grasses, such as Saposhnikovia divaricata and Serratula centauroides. Both density and dry biomass of standing vegetation increase with the years enclosing. Long-term grazing exclusion can restore the species composition and soil seed bank of degraded leyrnus chinensis+ Stipa grandis steppe.Annuals including Artemisia scoparia, Chenopodium album and C. aristatum constitute a major component of the soil seed bank.3. The impact of thicketization on soil seed bankThe study on effects of Caragana microphylla shrub on the soil seed banks showed that the density of soil seed banks has no obvious correlation with crown-width. But the relationship between the densities of soil seed banks among Caragana microphylla shrubs and under Caragana microphylla shrubs is impacted by crown-width.4. Generally, the similarity between soil seed banks and standing vegetation, are middle similary or not similar in all series both in April and in June. However, the similarity coefficients in the first series are highest, followed by that in the second series and that in the third are lowest. Meanwhile, it was observed that the similarity coefficients of soil seed banks in all sites between April and June are higher than those between soil seed banks and standing vegetation, indicating that the stability of soil seed banks is higher than standing vegetation.更多还原