【作者】 葛秀丽；

【导师】 王仁卿；

【作者基本信息】 山东大学 ， 环境科学， 2012， 博士

【摘要】 湿地是位于陆生生态系统和水生生态系统之间的过渡性地带,是生物多样性最丰富、单位生产力最高的生态系统之一,具有不可替代的生态功能,其重要性已经得到了广泛公认。但是由于湿地自身的脆弱性和人类活动的干扰,很多湿地遭受了严重的破坏,因而湿地的恢复和保护成为生态学研究的热点问题。农业利用是湿地退化的主要原因之一,为了遏制湿地退化态势,多个国家进行了湿地补偿、弃耕湿地恢复的实践,我国众多湖区都也在推行退耕还湿工程。大量退耕湿地亟需科学的指导和管理,因此迫切需要针对退耕湿地的特点开展生态恢复的理论和技术研究。植被恢复是湿地生态系统恢复的重要部分和前提条件,而种子库是湿地植被更新的潜在力量,是退化湿地自然恢复的基础。以往植被恢复工作主要以地上植被特征为依据,忽视了种子库在恢复中的作用。结合地上植被和种子库进行湿地植被恢复研究,可为退耕湿地植被恢复提供理论基础和技术支持。本研究首先结合文献资料和实地考察,通过对南四湖湿地植被历史、现状、物种区系组成、生活型谱、不同恢复方式下湿地典型群落的功能特征和关键影响因子的比较分析,对南四湖湿地植被特征进行了研究。然后对南四湖湖滨退耕湿地种子库特征及其影响因素进行了研究：应用种子萌发法测定了不同恢复方式的退耕湿地典型群落土壤种子库不同季节萌发特征；选择冬季种子库进行了水位控制萌发实验,分析了不同水淹对种子库萌发的影响机理,预测了水位急剧上升后依赖种子库萌发而形成的更新植被格局；以春季种子密度较高的芦苇群落和黑杨群落种子库为研究对象通过水位、光照控制条件下种子库萌发实验,进一步分析水位影响幼苗萌发的生态机理。随后在地上植被和种子库研究的基础上,从恢复方式、物种配置等方面提出南四湖湖滨退耕湿地恢复模式。最后,根据研究结果,对退耕湿地植被恢复工作和进一步的研究方向提出了建议。植被特征研究表明：南四湖湿地植被近几十年来受到人为干扰和水位波动的严重影响,植被分布面积萎缩、生境破碎、植被片段化、多样性降低并存在外来入侵的生态风险,迫切需要恢复和保护；南四湖湿地乡土植物区系成分和生活型谱均反应了该地区气候条件较寒冷潮湿、生境变动频繁；南四湖自然次生湿地群落具有更高的生物多样性,但是人工湿地可在较短时间内恢复植被大部分生态功能；水位和人为干扰是影响群落特征的关键因子。退耕湿地种子库特征研究表明,南四湖湖滨退耕湿地种子库初步检测到43种维管束植物,平均种子密度为2822粒/m2(0～12499粒/m2),群落类型和恢复方式对种子密度有极显著影响,并且群落类型和恢复方式对种子密度的影响有交互作用,季节和恢复方式对物种数的影响有交互作用,表现在：黑杨(Populus nigra)林群落全年和芦苇(Phragmites australis)群落冬季自然恢复方式的土壤种子库种子密度显著高于人工恢复方式；在冬季,芦苇群落自然恢复方式土壤种子库物种数显著高于人工恢复方式,黑杨群落在秋季和冬季自然恢复方式的土壤种子库物种数显著高于人工恢复；总体看,不同恢复方式对芦苇和黑杨群落的冬季土壤种子库物种数影响更明显。水位控制萌发实验结果显示水淹30cm处理下萌发的幼苗数最少,且在萌发第二个月水淹30cm处理下萌发的幼苗数显著高于其他处理,说明水淹对于种子萌发有抑制和延迟的作用。从物种水平来看,不同物种种子萌发对水淹的不同反映可通过物种对水淹的耐受能力种特异性解释；从群落水平来看,芦苇群落和黑杨群落种子库萌发更敏感；从恢复方式来看,自然恢复方式的退耕湿地比人工恢复方式的退耕湿地对水淹更为敏感,因此自然恢复的退耕湿地芦苇群落和黑杨群落种子库更容易受到水淹的影响。据此预测,当南四湖蓄水后,湖滨带退耕湿地的挺水植被和湿地森林将会有明显的格局变化,种子库中的一些水生植物可能自然恢复种群,未来群落中适应水淹的物种将更具有优势。另外,对种子库萌发时间动态的分析结果说明延长萌发实验时间能够检测到更多种子,减少实验误差。水位、光照控制萌发实验结果显示,高光浸渍处理下萌发种子密度和物种数显著高于另外两种处理,黑杨群落种子库在高光水淹30cm下萌发数量显著低于低光浸渍处理。结果表明,光照对于芦苇群落和黑杨群落种子库萌发有促进作用,黑杨群落种子库中的物种对水淹更敏感,水淹和光照的影响因种子库物种特性而异。植被恢复模式研究建立了湿地植被恢复物种评价指标体系,对南四湖湖滨典型群落中的重要物种进行了综合评价；根据群落种间关系分析结果和各物种在种子库中的更新潜力,建立了初步的物种配置模式,提出了湿地植物管理措施,可应用于南四湖湖滨退耕还湿规划和管理。综上所述,本研究通过对南四湖湖滨湿地植被和退耕湿地土壤种子库的研究得到了植被和种子库现状,并探讨了恢复方式、水位等植被和种子库的影响,作出了退耕湿地植被适宜人工辅助恢复、南四湖湿地挺水群落和湿地森林受水淹影响较大的结论,建立了南四湖湖滨退耕湿地植被恢复模式。更多还原

【Abstract】 Wetland which locates in the transitional zone between the aquatic and terrestrial ecosystems is one of the ecosystems with richest biodiversity, highest productivity and numerous irreplaceable ecological functions. Its importance has been recognized widely. Many wetlands had been destroyed seriously due to its internal frangibility and human disturbance in the past century. So the studies on wetland restoration and protection become the hot topic of ecology research. Agricultural utilization is one of the two main causes of wetland degradation. To prevent the degrading trend of wetland, some countries have carried out various programs, such as wetlands compensation and restoration of wetland converted from farmland. In China, the project of converting farmland to wetland is carried out in most of the lake regions. Vegetation restoration of these wetlands lacks the scientific guidance and is in urgent need of the research of ecological restoration on the theories and techniques aiming at the characters of wetlands converted from farmland.The vegetation restoration is one important and antecedent step for wetland ecosystem restoration. The technique of vegetation restoration includes the selection of restoration mode, the selection and combination of species, etc. Soil seed bank is a stock of regeneration potential of wetland vegetation and it is the basement of natural restoration for degraded wetland. Thus the compositive ecological research on the stand vegetation and the soil seed bank will offer the theoretical basement and technique support.In this paper, the characters of wetland vegetation in Nansi Lake was studied by comparing the history and the status of wetland vegetation and the functional characters of typical wetland communities restored by different ways, analyzing the characters of the flora and the life-form spectrum of native plants and the key influencing factors. Then, the characters and the main affecting factors of soil seed banks of wetland converting by farmland were studied:the seasonal dynamics of soil seed bank of typical communities from different wetlands were detected by seedling emergence method; a simulation experiment was conducted in lab which simulated three flooding conditions to understand the response of wetland soil seed bank to different hydrological regimes, the prediction of vegetation pattern after Nansi Lake was impounded as a reservoir for China’s South-to-North Water Transfer Project was made accordingly; then, a seed bank germination experiment controlling the water level and light conditions was conducted to reveal the ecological mechanism of effect of flooding on the seed germination. On the base of the research of vegetation and soil seed bank, the restoration pattern was suggested for wetland converted from farmland in lakeshore of Nansi Lake. At last, suggestions on vegetation restoration of wetland converted from farmland in lakeshore of Nansi Lake and the future study were proposed.Results of vegetation study showed that, in Nansi Lake area, the vegetation had been affected seriously by the human disturbances and water-level fluctuation in the past decades, so that it has the trend of area shrinking, habitat broken, and biodiversity declining, at the same time, it is under the threats of vegetation fragmentation and exotic species invasion. Accordingly, wetlands in Nansi Lake are in urgent need of restoration and protection. The flora and the life-form spectrum of native species implied that the local environment was wet and changed frequently; the communities in natural secondary wetland had higher plant biodiversity, while constructed wetland could restore the most wetland ecological functions in a shorter time in term of its coverage and biomass; water level and human disturbances were the key factors influencing the community characters.Studies on soil seed bank of wetland converted by farmland found that there were43vascular species detected in the soil seed banks of wetland converted from farmland in lakeshore of Nansi Lake and the mean germinable seed density was2822seed/m2(0～12499seed/m2); community type and restoration mode presented significant effects on the germinable seed density and there are significant interaction effects between the two factors, season and restoration mode present significant effect on the germinable species abundance and there were significant interaction effect between them, which were demonstrated in the following aspects:in natural restoration wetland converted from farmland, soil seed banks of Populus nigra Plantation Community in all one year and Phragmites australis community in winter had higher seed density than soil seed banks in constructed wetlands; in the two type wetlands, species abundance of the winter soil seed banks of P. australis community and the summer and winter soil seed banks of P. tomentosa Plantation Community showed the same rule; in a word, restoration mode has stronger impact on the winter soil seed banks of P. australis community and P. tomentosa plantation community.Results of water controlled germination experiment showed that the seedling number was the least under submerged30cm treatment in all the ten months, but the data in the second month is higher significantly than the other two treatments which indicate that the flooding might delay and suppress the seed germination. From the species perspective, the difference response of distrinct species seeds to flooding could be explained by the species-specific flooding tolerance; from the community perspective, the P. tomentosa plantation and the P. australis community are more sensitive to flooding than the other types; from restoration mode angle, the natural restoration wetland converted from farmland is more sensitive than the man-made restoration one which might be caused by the relatively high proportion of terrestrial plants in the natural restoration wetland in our research. Accordingly, the P. tomentosa plantation and the P. australis community in the natural restoration wetlands will be affected more easily by flooding. Thus, a prediction of vegetation pattern after Nansi Lake was impounded as a reservoir for China’s South-to-North Water Transfer Project was made:the pattern of the emergent aquatic vegetation and the wetland forest will change greatly, some aquatic species existing in the soil seed bank might build natural restoring populations; the species with high flooding tolerance will dominate in the future communities. Addtionally, the temporal dynamic of seed ermergence implied the prolonged experiment time could help to decrease the test error.Results of the water and light controlled germination experiment showed that under substrate-saturated with strong light treatment, the seedling density and species abundance both were higher significantly than those under the other two treatments indicating that light promoted the seed germination of soil seed bank from P. tomentosa plantation and the P. australis community; the seedlings from the P. tomentosa plantation seed bank under flooding30cm with strong light treatment was notable less than those under substrate-saturated with weak light treatment indicating the more sensitivity of species in the P. tomentosa plantation seed bank. In view of the above results, the effect extent of light is different with the species-specific characters of seed bank, the same to flooding. In the studies on the vegetation restoration pattern, an evaluation index system was established for selecting species to restore wetland vegetation, the important species in lakeshore of Nansi Lake wetland communities were evaluated, selected and combined by their interspecific relationship and their regeneration potential in soil seed banks. Accordingly, the primary species configuration pattern was built and the management measures for wetland vegetation were put up which could be used in the practice of "converting farmland to wetland" project.To sum up, by the studies on vegetation and soil seed banks, their characters were revealed, the influncing mechanisms of restoration mode, water depth and light to soil seed bank were discussed, so the main conclusions were made that the wetland converting from farmland is suitable to be restored by additional artificial help, the ermergent plant communities and the wetland forest could be affect heavily by flooding in lakeshore wetlands of Nansi Lake. Also the wetland vegetation restoration mode in Nansi Lake was suggested based on the study.更多还原