【作者】 刘瑞雪；

【导师】 陈龙清；

【作者基本信息】 华中农业大学 ， 园林植物与观赏园艺， 2013， 博士

【摘要】 水滨带是陆地生态系统与水生生态系统的过渡地带,是两大生态系统相互作用的桥梁和纽带。虽然水滨带在整个地球生态系统中只占很小比例,但是其在生态系统中发挥着重要的作用。水滨带植被具有保护水域生态安全、稳定堤岸和保持生境连通性等一系列重要的生态功能,是保护水质预防水体污染的最后一道生态屏障。由于各种因素的影响,世界范围内的水滨带植被都出现了严重退化的现象。丹江口水库(32。36’-33。48’N,110。59’-111。49’E)是我国南水北调中线工程的水源地。自1973年大坝建成,丹江口水库已运行了近40年。经过40年的自然演替,丹江口水库在最低水位140m和最高水位157m之间的区域,以及157m以上可能受到水淹影响的区域内形成了明显不同于陆生或水生植被的水滨带植被。2014年南水北调中线将开始运行,水库常水位会抬升到170m,现有的水滨带植被将被淹没,在更高的海拔区域上会形成新的水滨带。如何保护和恢复水滨带植被,使其充分发挥生态功能,对水源地的水质保护和南水北调中线工程的正常运行有着重要意义。探讨水滨带的植被特征及其与环境之间的关系对水滨带植被的保护和恢复有重要的理论和实践意义。本文以丹江口水库水滨带为研究对象,在植被生态学、恢复生态学、数量生态学及相关理论的指导下,在实地调查和室内实验的基础上,综合运用数量生态学和统计学的相关方法,分析丹江口水库水滨带的植被特征及其与环境的关系。研究结果表明：(1)丹江口水库水滨带维管植物共72科208属285种,其中蕨类植物3科3属3种,裸子植物2科3属4种,被子植物67科202属278种。从科的组成看,水库水滨带维管植物的组成表现出两个趋势,一方面物种向豆科(Leguminosae)、禾本科(Gramineae)和菊科(Compositae)这样的世界性大科集中,同时又向少种科和区域性单种科分散,反映出本区域维管植物大科少小科多的特点。从属的组成看,水滨带维管植物的优势属明显,同时区域性单种属数量多,说明水滨带生境条件复杂,高度异质性的环境为多种植物提供了生存条件。从植物区系类型组成上,以热带成分和温带成分为主,体现出丹江口水库处于亚热带向北温带过渡的区域。从生活型组成看,乔木35种,灌木49种,木质藤本7种,草本蕨类植物3种,一二年生草本植物73种,多年生草本植物118种。草本植物发达,是构建水滨带植物群落的主要建群种。(2)丹江口水库水滨带植被主要包括7种群落类型,分别是篇蓄群落、苘麻群落、细叶水芹群落、狗牙根群落、响叶杨群落、杜梨群落和侧柏群落。不同群落类型在物种组成、群落结构和生活型组成上差异较大。植物群落类型以草本植物群落为主,木本植物群落少数,反映水滨带恶劣的环境条件使植物群落结构逐渐趋于简单化。7种植物群落类型沿海拔和水淹影响梯度分布,不同群落类型之间有一定程度的重叠。植物群落在水滨带的分布呈现出植物群落从位于低海拔的一年生草本植物群落,到位于中海拔的多年生草本群落和灌丛群落,再过渡到位于高海拔的乔木群落。以草本植物群落为主,上部零星木本植物群落分布的空间格局形成了水滨带植被的总体外貌特征。(3)相对高程和水文因素是影响水滨带植被变化的主导因素,土壤属性也对水滨带植被变化产生一定影响,而地形因素如坡度和坡向对植被变化的影响较小。对单个环境因子对植被变化解释能力的分析表明,13个环境因子中年平均水淹时间对植被变化的影响最大,其次是相对高程、水淹频率、土壤有机质含量、土壤pH、土层厚度、土壤速效磷含量、土壤总氮含量、土壤速效氮含量、坡度、坡向、土壤总磷含量和土壤质地,解释能力依次降低。对地形、土壤和水文3类环境因素,土壤因素的植被变化解释能力大于地形因素,水文因素的解释能力最小。各类环境因素之间存在交互作用,地形、水文和土壤因素三者间的交互作用最大,其次是地形和水文因素、土壤和水位因素之间的交互作用,地形和土壤因素之间的交互作用最小。所收集的3类环境因素13个环境因子共解释了水滨带植被变化的21.99%,未解释部分为78.01%。(4)通过主成分分析和多元回归得到水滨带植物多样性与环境因素的回归模型,结果表明,与水滨带植物群落物种丰富度相关性较大的环境变量有坡向、土层厚度、坡度、相对高程和土壤速效氮含量；与水滨带植物群落物种多样性相关性较大的环境因子有土层厚度、坡向、土壤有机质含量、土壤速效氮含量和水淹频率。根据Pearson相关性检验,物种丰富度与相对高程、土壤质地、年平均水淹时间、坡向和土层厚度显著相关；物种多样性与土层厚度、土壤有机质含量、水淹频率和土壤速效氮含量显著相关。对单个环境因子对水滨带植物多样性的影响效应进行分析,其中物种丰富度与相对高程呈二次抛物线关系,与土壤质地呈三次抛物线关系,与年平均水淹时间呈三次抛物线关系,与土层厚度呈幂函数曲线关系；物种多样性与土层厚度呈幂函数曲线关系,与土壤有机质含量呈三次抛物线关系,与水淹频率呈指数曲线关系。(5)丹江口水库水滨带土壤种子库共有维管植物44种,隶属于20科38属。物种组成以草本植物为主,仅出现2种木本植物—白刺花(Sophora davidii)和假穸包叶(Discocleidion rufescens)。土壤种子库的平均密度为8950粒／m2,种予密度最大的是一年生草本植物。对不同水淹影响区域土壤种子库特征比较,发现水滨带土壤种子库的物种丰富度和利,了密度随着水淹影响程度的增强而增加。结果表明水淹影响造成的水滨带植被退化并不会严重影响其土壤种子库的储量,水滨带退化植被的恢复不受土壤种子库种子储量的限制。水滨带土壤种子库和地上植被在物种组成上存在显著差异,而且水淹影响对土壤种子库和地上植被之间的相似性有明显影响,中度淹没区土壤种子库和地上植被在物种组成上的差异最大,而永久淹没区土壤种子库和地上植被之间的差异最小。水滨带的土壤种子库与地上植被之间的相似性较低表明土壤种子库对于水滨带植被恢复的贡献有限,水滨带的植被恢复不能仅仅依靠土壤种子库。但水滨带的土壤种子库与地上植被之间有着非常密切的联系,证明了土壤种子库是水滨带植被恢复与重建的重要资源。通过对水滨带土壤种子库密度和环境关系的分析发现,与土壤种子库密度相关性较大的环境因子是地上植被盖度、土壤速效氮含量和土壤全磷含量。根据Pearson相关性检验,土壤种子库密度与土壤有机质含量、地上植被盖度、土壤速效氮含量、水淹干扰和土壤饱和含水量显著相关。水滨带土壤种子库密度与土壤饱和含水量呈线性增加趋势,与水淹影响因子呈指数曲线关系。更多还原

【Abstract】 Riparian zone is the transition area between aquatic and terrestrial ecosystems located along rivers, streams as well as lakes, and it is the critical zone for the interaction between aquatic and terrestrial ecosystems. Although riparian zone is a small portion of the global ecosystem, it plays an important role in ecological system. Riparian vegetation performs important ecological functions in protecting water ecological security, stabilizing the bank, maintaining habitats connectivity and enhancing local biological diversity, which is the last defense against water pollution. However, riparian vegetation has been degraded severely throughout the world because of various factors. Danjiangkou Reservoir (32°36’-33°48’N,110°59’-111°49’E), located in Central China, is the water source for the Middle-Route of the South-to-North Water Transfer Project. Danjiangkou Reservoir has operated for almost40years since the dam was completed in1973. Through the natural ecological succession of40years, the riparian vegetation of Danjiangkou Reservoir is present distinctive characteristics in the area between the lowest water level of140m and the highest water level of157m, and the area above the highest water level which may be affected by elevated water level or flooding occasionally, which is distinctive form terrestrial and aquatic vegetation. The water transfer project will operate in2014, the normal water level of Danjiangkou Reservoir will be up to170m. Most of the existing riparian vegetation will been submerged, and the new riparian zone will been shaped at the higher elevation. How to protect and restore the riparian vegetation and giving full play to its ecological functions is significant to the protection of water quality and the normal operation of the Middle-Route of the South-to-North Water Transfer Project. Exploring the characteristics of the riparian vegetation and its relation to environment factors has important significance for conservation and restoration of riparian vegetation. In this paper, the characteristics of the riparian vegetation and its relation to environmental factors were analyzed based on field investigation and laboratory experiment. The main results are as follows:(1) There were285species in the riparian zone of Danjiangkou Reservoir, which belonged to208genera and72families. Among them there were3species,3genera and3families of pteridophyte,4species,3genera and2families of gymnospermae,278species,202genera and67families of angiosperm. Species composition of the riparian vegetation displayed two obvious trends in families, on the one hand the big world families, such as Leguminosae, Gramineae and Compositae took large proportion, on the other hand small families and regional single-species families also owned a certain proportion. It indicated that the characteristic in species composition of this area is few large families and some small families. In addition, the dominant genera were evident. And small genera and regional single-species genera also owned a large proportion. This indicated that the environmental conditions of the riparian zone were complex, and high environmental heterogeneity provided habitats for most species. The floristic analysis showed that tropic and temperate types were dominant, this indicated that the climate feature of Danjiangkou Reservoir was the transition from North Temperate Zone to subtropical zone. There were35trees,49shrubs,7woody vines,3herbaceous pteridophytes,73annual or biennial herbs and118perennial herbs. Herb species were the dominant groups, which were the major constructive species of the riparian vegetation.(2) Seven plant community types were clearly identified in the riparian zone of Danjiangkou Reservoir. There were Polygonum aviculare community, Abutilon theophrasti community, Oenanthe dielsii var. stenophylla community, Cynodon dactylon community, Populus adenopoda community, Pyrus betulifolia community and Platycladus orientalis community. The riparian plant communities were dominated by herbaceous plant communities, with a small number of woody plant communities. It indicated that the severe environmental conditions of the riparian zone resulted in the simplification of vegetation structure. Seven plant community types distributed along the gradients of elevation and flooding influence, while there were some overlaps among different plant community types. Plant communities commonly displayed a distribution pattern with annual herbaceous species dominating the lower wet zones, perennial herbaceous species occupying the moderate elevation, larger shrubs appeared at the mid-up land, and trees occurring in the high zones where less prone to inundation. The total macroscopic feature of the riparian vegetation is herbaceous plant communities based with a few woody communities appearing at the upper land.(3) Height above water and hydrologic factors (flood duration and flood frequency) were significantly associated with the variation in species composition within the riparian vegetation. The soil property also had a strong influence on the characteristics of the riparian vegetation, while the topographic factor, slope and aspect, had a little influence on the riparian vegetation. There were respectively13environmental variables significantly explaining the variation of species composition, flood duration had the strongest explanatory power, followed by height above water, flood frequency, soil organic matter content, soil pH, soil thickness, soil available phosphorus content, soil total nitrogen content, soil available nitrogen content, slope, aspect, soil total phosphorus content and soil thickness, whose the explanatory power decreased successively. With regard to topographic, soil and hydrological factors, the explanatory power of soil factor was more than the explanatory power of topographic factor, and the explanatory power of hydrological factor was least. There were interactive effects among environmental factors, the interactive effect among topographic, soil and hydrological factors was largest, followed by the interactive effect between topographic and hydrological factors, the interactive effect between soil and hydrological factors. The interactive effect between topographic and soil factors was smallest. The collected environmental factors accounted for21.99%of the variation of the riparian vegetation, the unexplained portion accounted for78.01%.(4) Based on Principal Component Analysis and multiple regression, the regression models was obtained between plant diversity of the riparian vegetation and the environmental factors. The results indicated that there were greater correlation between the species richness and aspect, soil thickness, slope, height above water and soil available nitrogen content. And there were greater correlation between the species diversity and soil thickness, aspect, soil organic matter content, soil available nitrogen content and flood frequency. Based on Pearson correlation coefficient, the species richness correlated significantly with height above water, soil texture, flood duration, aspect and soil thickness, and to the significant correlate to the species diversity were soil thickness, soil organic matter content, flood frequency and soil available nitrogen content. Based on the analyses of the explanatory power of environmental variables respectively, the distribution discipline of species richness along the gradient of height above water was quadratic parabola, it along the gradient of soil texture was cubic parabola, it along the gradient of flood duration per year was cubic parabola, and it along the gradient of soil thickness was power function curve; The relationships between the species diversity and soil thickness was power function curve, the species diversity and soil organic matter content showed a cubic parabola relationship, and the distribution discipline of species diversity along the flood frequency was exponential curve.(5) There were44species in the soil seed bank of the riparian vegetation in Danjiangkou Reservoir, which belonged to38genera and20families. Herbs species were the dominant groups, and only two woody species appeared, Sophora davidii and Discocleidion rufescens. The average seed density of the soil seed bank was8950seeds/m2, and annual herbs had the greatest seed density. Comparing the quantitative characteristics of the soil seed banks from the different flood disturbance zone, it showed that the species richness and seed density of the soil seed bank were increased with the increase of flood disturbance. This result indicated that the vegetation degradation causing by flooding disturbance couldn’t have a significant impact on the seed density of the soil seed bank in the riparian zone, and the restoration of seriously disturbed riparian vegetation was not seed-limited. The soil seed bank and aboveground vegetation were obviously different in the riparian zone, and the flood disturbance had obvious significance to the similarity between the soil seed bank and aboveground vegetation. The discrepancy between the soil seed bank and aboveground vegetation was greatest at the moderate inundated zone, and smallest at the permanent inundated zone. Low similarity between the soil seed bank and the aboveground vegetation in riparian land indicated that the soil seed bank played a minor role in contributing to the regeneration of vegetation, and the managers could not just rely on soil seed bank for vegetation restoration. However, the soil seed bank was closely connected with the aboveground vegetation and was an important source for vegetation regeneration and restoration. The relationships between the soil seed bank and the environmental factors were analyzed. The seed density of the soil seed bank was mainly influenced by the cover of the above-ground vegetation, soil available nitrogen content and soil total phosphorus content. Based on Pearson correlation coefficient, the seed density of the soil seed bank correlated significantly with soil organic matter content, the cover of the aboveground vegetation, soil available nitrogen content, flood disturbance and saturated moisture content of soil. The seed density of the soil seed bank revealed a linear increasing trend along the increase of saturated moisture content of soil, and the seed density of the soil seed bank and flood disturbance showed an exponential curve relationship.更多还原