湖泊水动力对水生植物分布的直接影响研究与展望

水动力作为湖泊水生植物恢复的关键限制性因子,其对水生植物的影响机制是当前迫切需要关注的科学问题。从水动力作用下水生植物的分布、水生植物受力以及水生植物自身机械抗性3个方面系统梳理了当前的研究方法与结论。结果表明,水生植物在河流湖泊中的丰度、空间分布与水动力密切相关,各物种对水流胁迫表现出不同的响应;植物在水动力作用下的受力观测和研究主要依赖模拟试验,通过计算定量表征不同物理外型物种在水动力作用下的受力,明确了生物量和植物系数等影响受力的关键参数,为不同塑形物种受力的对比分析提供了研究方法;植物机械抗性主要基于测力装置观测,通过断裂应力、弯曲力等生物力学参数表征。在当前研究背景下,水生植物尤其是沉水植物在湖泊中的实际受力情况依然是研究难点,需要借助新的观测手段和研究方法来阐明植物在复杂的湖泊水动力环境下的实际受力特征。此外,还需要进一步开展水生植物在湖泊中的实际受力与植物自身机械抗性的耦合研究,这是开展水生植物响应湖泊水动力机理研究的关键。     

湖泊水动力对水生植物分布的直接影响研究与展望

水动力作为湖泊水生植物恢复的关键限制性因子,其对水生植物的影响机制是当前迫切需要关注的科学问题。从水动力作用下水生植物的分布、水生植物受力以及水生植物自身机械抗性3个方面系统梳理了当前的研究方法与结论。结果表明,水生植物在河流湖泊中的丰度、空间分布与水动力密切相关,各物种对水流胁迫表现出不同的响应;植物在水动力作用下的受力观测和研究主要依赖模拟试验,通过计算定量表征不同物理外型物种在水动力作用下的受力,明确了生物量和植物系数等影响受力的关键参数,为不同塑形物种受力的对比分析提供了研究方法;植物机械抗性主要基于测力装置观测,通过断裂应力、弯曲力等生物力学参数表征。在当前研究背景下,水生植物尤其是沉水植物在湖泊中的实际受力情况依然是研究难点,需要借助新的观测手段和研究方法来阐明植物在复杂的湖泊水动力环境下的实际受力特征。此外,还需要进一步开展水生植物在湖泊中的实际受力与植物自身机械抗性的耦合研究,这是开展水生植物响应湖泊水动力机理研究的关键。     

湖泊形态与水生植物多样性关系——以长江中下游湖群典型湖泊为例

通过野外调查、资料收集并结合GIS方法对长江中下游9个湖泊岸线形态演变和水生植物多样性现状及变化进行了研究。结果显示,近几十年来长江中下游一些湖泊岸线长度和计盒维数均显著降低;水生植物物种多样性总体呈下降趋势。相关性分析表明,湖泊岸线发育系数和湖泊计盒维数均与水生植物多样性呈显著相关;湖泊岸线形态特征显著影响沉水、漂浮植物物种多样性。本研究表明湖泊岸线形态对水生植物的生长及分布影响显著,保护湖泊岸线形态对维持水生植物多样性及湖泊生态系统功能具有重要作用。     

湖泊水生植物稳定碳同位素分馏机制与应用研究进展

水生植物是维持湖泊生态系统健康发展的重要基础与支撑。与陆地植物相比,水生植物稳定碳同位素(δ~(13)C)的分馏过程较复杂,为系统的了解水生植物δ~(13)C的分馏过程及其在湖泊现代生态系统和古环境研究中的应用,调研了国内外相关研究进展。总结已有研究表明,水生植物的δ~(13)C主要与其吸收利用的碳源和水体环境要素等密切相关,影响因素较复杂,而且目前在利用水生植物的δ~(13)C研究不同时间尺度上湖泊环境变化时所选用的载体存在差异。植物不同组分样品的选择对解释水生植物δ~(13)C与环境之间的关系至关重要。因此,以太湖典型水生植物为研究实例,探讨了水生植物不同组分稳定碳同位素的分布特征及其对环境因子的响应差异,结果显示水生植物不同组分的δ~(13)C存在一定的差异,而且对环境的响应也不同,未来在利用水生植物δ~(13)C研究湖泊环境变化时对于水生植物样品组分的选择应谨慎考虑。     

淡水湖泊生态系统中砷的赋存与转化行为研究进展

砷(As)是一种无处不在的元素,目前已有很多关于湖泊水体、沉积物、浮游生物、底栖动物、鱼类及水生植物中As的含量分布与赋存形态的研究报道.As在全球淡水湖泊中分布不均,区域差异性较大;湖泊沉积物中As含量水平对底栖动物的自然生境影响很大,甚至造成底栖物种生物区系的改变;水生植物普遍具有富集As的能力,一般表现为沉水植物＞浮水植物＞挺水植物;水生动物中As含量一般为底栖动物＞浮游动物＞鱼类.相对于海洋生态系统,目前对湖泊生态系统环境与生物质中砷的赋存形态及其转化的认识还很不足,今后应加强人类活动影响下我国重要湖泊As的迁移、富集与转化行为的研究.     

小兴凯湖的水生植被及其生态作用

本文论述了小兴凯湖水生植物的种类组成、植被类型、生物量及其在湖泊淤积和渔业中的作用。该湖属老年期湖泊,水生维管束植物共有25科56种,优势种为竹叶眼子菜、荇菜、芦、菰等。植被类型可划分为沉水植被、浮叶植被和挺水植被等三个亚型,包括12个主要植物群丛。全湖水生植物总生物量(湿重)为196380吨;以植物现存量计算,草食性鱼类的年生产力应为78.75吨。由于水生植物大量繁殖,为减缓湖泊的垫平作用,可适量放养草食性鱼类,控制住水生植物的过量繁殖;同时引种一些经济水生植物,压住水中杂草的生长。     

湖泊生态恢复的基本原理与实现

当前我国湖泊污染及富营养化问题非常严重。湖泊治理的一个有效途径就是恢复水生植物,通过草型湖泊生态系统的培植来达到控制富营养化和净化水质的目的。但是,迄今为止,只有在局部水域或滨岸地区获得成功,恢复的水生植物主要是挺水植物或漂浮植物。鲜有全湖性的水生植物恢复和生态修复成功的例子。原因是对湖泊生态系统退化及其修复的机理了解甚少。实际上,环境条件不同决定了生态系统类型的不同,只有通过环境条件的改变才能实现生态系统的转变。利用草型湖泊生态系统来净化水质,其实质是利用生态系统对环境条件的反馈机制。但是,这种反馈无法从根本上改变其环境条件,因此其作用是有限的,不宜过分夸大。以往许多湖泊生态修复的工作之所以鲜有成功的例子,原因就是过于注重水生植物种植本身,而忽视了水生植物生长所需的环境条件的分析和改善。实施以水生植物恢复为核心的生态修复需要一定的前提条件。就富营养化湖泊生态恢复而言,这些环境条件包括氮磷浓度不能太高,富含有机质的沉积物应该去除,风浪不能太大以免对水生植物造成机械损伤,水深不能太深以免影响水生植物光合作用,鱼类种群结构应以食肉性鱼为主等等。因此,在湖泊污染很重或者氮磷负荷很高的情况下,寻求以沉水植物为核心的湖泊生态恢复来改善水质是不切实际的。为此,提出湖泊治理应该遵循先控源截污、后生态恢复,即先改善基础环境,后实施生态恢复的战略路线。     

长江中下游浅水湖泊水生植被生态恢复种的筛选与应用研究

湖泊富营养化是全球性的生态学问题。长江中下游浅水湖泊群作为我国八大湖泊群之一, 近30年来水体富营养化以及生态系统功能退化极为严重, 亟待系统性修复。水生植物生态修复技术则是面向富营养化浅水湖泊生态治理的重要技术。然而, 选择合适的水生植物恢复种来保证恢复效果以及长期的生态安全与稳定性仍是目前恢复工程中的重要且薄弱环节。结合长江中下游湖泊中水生植物的生长、分布、繁殖、来源及污染耐受性等提出了以乡土物种操控为理念适合该区域湖泊的生态恢复先锋物种建议名录, 并依据所筛选的物种特性和淡水生态学相关理论, 提出不同的优化组合方案来指导长江中下游不同类型湖泊的水生植物生态恢复。     

长江中下游浅水湖泊水生植被生态修复种的筛选与应用研究

湖泊富营养化是全球性的生态学问题。长江中下游浅水湖泊群作为我国八大湖泊群之一,近30年来水体富营养化以及生态系统功能退化极为严重,亟待系统性修复。水生植物生态修复技术则是面向富营养化浅水湖泊生态治理的重要技术。然而,选择合适的水生植物恢复种来保证恢复效果以及长期的生态安全与稳定性仍是目前恢复工程中的重要且薄弱环节。结合长江中下游湖泊中水生植物的生长、分布、繁殖、来源及污染耐受性等提出了以乡土物种操控为理念适合该区域湖泊的生态恢复先锋物种建议名录,并依据所筛选的物种特性和淡水生态学相关理论,提出不同的优化组合方案来指导长江中下游不同类型湖泊的水生植物生态恢复。     

水生维管束植物在太湖生态系统中的作用

水生维管束植物(简称水生植物)是鱼类的饵料基础,它的种群数量变动对湖泊生态及水域环境的影响,都具有重要的作用。因此,在大中型湖泊中如何开发利用水生植物,是值得探讨的问题。作者近年来在太湖资源调查的基础上,对水生植物在太湖生态系统中的作用进行了初步研究。     

Predicting the hydraulic forces on submerged macrophytes from current velocity, biomass and morphology

Aquatic macrophytes are important in stabilising moderately eutrophic, shallow freshwater lakes in the clear-water state. The failure of macrophyte recovery in lakes with very soft, highly organic sediments that have been restored to clear water by biomanipulation (e.g. in the Norfolk Broads, UK) has suggested that the physical stability of the sediment may limit plant establishment. Hydraulic forces from water currents may be sufficient to break or remove plants. Our aim was to develop a simple model that could predict these forces from plant biomass, current velocity and plant form. We used an experimental flume to measure the hydraulic forces acting on shoots of 18 species of aquatic macrophyte of varying size and morphology. The hydraulic drag on the shoots was regressed on a theoretically derived predictor (shoot biomass × current velocity^1.5). Such linear regressions proved to be highly significant for most species. The slopes of these lines represent species-specific, hydraulic roughness factors that are analogous to classical drag coefficients. Shoot architecture parameters describing leaf and shoot shape had significant effects on the hydraulic roughness factor. Leaf width and shoot stiffness individually did not have a significant influence, but in combination with shoot shape they were significant. This hydraulic model was validated for a subset of species using measurements from an independent set of shoots. When measured and predicted hydraulic forces were compared, the fit was generally very good, except for two species with morphological variations. This simple model, together with the plant-specific factors, provides a basis for predicting the hydraulic forces acting on the root systems of macrophytes under field conditions. This information should allow prediction of the physical stability of individual plants, as an aid to shallow-lake management. Received: 11 March 1999 / Accepted: 18 January 2000     

湖湾效应对长江中游湖泊水生植物多样性的影响

在３ａ野外调查和定位研究的基础上,本文对长江中游地区水生植物物种多样性进行了初步研究。主要工作在１０个有代表性的湖泊进行,结果表明：湖泊水生植物多样性指数沿湖湾至中央敞水区由２．１６５５降至０．３６３３;植物种类和个体数自湖湾至湖心区急剧减少,植物群落生物量自湖湾至湖中央区也发生明显变化;水深梯度与植物种类分布密切相关,在保安湖０．５ｍ水深中有１９种植物,在２ｍ水深中仅有４种植物,绘出３个湖的种－     

Hydrodynamically mediated macrophyte silica dynamics

In most aquatic ecosystems, hydrodynamic conditions are a key abiotic factor determining species distributions and abundance of aquatic plants. Resisting stress and keeping an upright position often relies on investment in tissue reinforcement, which is costly to produce. Silica could provide a more economical alternative. Two laboratory experiments were conducted to measure the response of two submerged species, Egeria densa Planch. and Limnophila heterophylla (Roxb.) Benth., to dissolved silicic acid availability and exposure to hydrodynamic stress. The results were verified with a third species in a field study (Nuphar lutea (L.) Smith). Biogenic silica (BSi) concentration in both stems and leaves increases with increasing dissolved silica availability but also with the presence of hydrodynamic stress. We suggest that the inclusion of extra silica enables the plant to alternatively invest its energy in the production of lignin and cellulose. Although we found no significant effects of hydrodynamic stress on cellulose or lignin concentrations either in the laboratory or in the field, BSi was negatively correlated with cellulose concentration and positively correlated with lignin concentration in samples collected in the field study. This implies that the plant might perform with equal energy efficiency in both standing and running water environments. This could provide submerged species with a tool to respond to abiotic factors, to adapt to new ecological conditions and hence potentially colonise new environments.     

Phenotypic plasticity in response to mechanical stress: hydrodynamic performance and fitness of four aquatic plant species

Plastic responses of plants exposed to mechanical stress can lead to modified, performance-enhancing, morphologies, sometimes accompanied by costs to reproduction. The capacity to present short-term plastic responses to current stress, the resulting performance (expected lower mechanical forces), and the costs of such responses to reproduction were tested for four aquatic plant species. Two ramets of the same genet were submitted to running vs standing water treatment. Traits describing the morphology, hydrodynamic performance and reproduction (sexual and vegetative) were measured. For one species, plastic responses led to reduced hydrodynamic forces, without apparent costs to reproduction, indicating that the plastic response could be beneficial for plant maintenance in stressful habitats. For two species, plastic responses were not associated with variations in performance and reproduction, possibly because of the low hydrodynamic forces experienced, even for morphologies produced under standing conditions. For one species, plastic responses were associated with a sharp decrease in sexual reproduction, without variations in performance, revealing the negative impact of currents over a short time scale. Species maintenance is linked to the capacity of individuals to tolerate mechanical forces. The contrasting responses to currents may be a key element for predicting community dynamics.     

The influence of flood duration on the surface soil properties and grazing management of karst wetlands (turloughs) in Ireland

This study tested the hypothesis that lake augmentation with well water impacts the distribution and abundance of aquatic plants in lakes. Water chemistry was measured from 14 wells, 14 augmented lakes, and 14 lakes without augmentation. Nine in-lake aquatic macrophyte abundance and species distribution metrics were measured in all lakes. Net photosynthetic rate (NPR) of nine submersed species was also measured in well and lake water. Augmentation increased alkalinity in receiving lakes, but total phosphorus was significantly lower, which resulted in lower chlorophyll and greater Secchi depths. Although measured NPR was higher for all plants incubated in well water, only one (emergent species richness) in-lake aquatic macrophyte metric was different in lakes with and without augmentation. Lake augmentation significantly changed water chemistry of receiving waters, but effects on aquatic macrophytes were minimal, suggesting that other environmental factors are limiting the distribution and abundance of macrophytes in the study lakes. The lower phosphorus levels in augmented lakes were unexpected because phosphorus concentrations in well water were significantly greater than in lakes with or without augmentation. Precipitation of calcium phosphate likely accounts for the reduced phosphorus levels in augmented lakes.     

Effect of light stress from phytoplankton on the relationship between aquatic vegetation and the propagule bank in shallow lakes

1. The way light stress controls the recruitment of aquatic plants (phanerogams and charophytes) is a key process controlling plant biodiversity, although still poorly understood. Our aim was to investigate how light stress induced by phytoplankton, that is, independent from the aquatic plants themselves, determines the recruitment and establishment of plant species from the propagule bank. The hypotheses were that an increase in light stress (i) decreases abundance and species richness both of established aquatic plants and of propagules in the bank and (ii) decreases the recruitment success of plants from this bank. 2. These hypotheses were tested in 25 shallow lakes representing a light stress gradient, by sampling propagule banks before the recruitment phase and when the lakes are devoid of actively growing plants (i.e. at the end of winter), established vegetation at the beginning of the summer and phytoplankton biomass (chlorophyll a) during the recruitment and establishment phase. 3. The phytoplankton biomass was negatively correlated with the richness and abundance of established vegetation but was not correlated with the propagule bank (neither species richness nor propagule abundance). The similarity between the propagule bank and established vegetation decreased significantly with increasing phytoplankton biomass. 4. The contrast in species composition between the vegetation and the propagule bank at the highest light stress suggests poor recruitment from the propagule bank but prompts questions about its origin. It could result from dispersal of propagules from neighbouring systems. Propagules could also originate from a persistent propagule bank formerly produced in the lake, suggesting strong year‐to‐year variation in light stress and, as a consequence, in recruitment and reproductive success of plants.     

Same species,same habitat preferences? The distribution of aquatic plants is not explained by the same predictors in lakes and streams

1. Studying the geographical distribution of species can reveal conditions and processes that may drive species presence and abundance. Organism distribution has frequently been explained by climate, but the relative role of local environmental predictors is not fully understood. Moreover, in the freshwater realm, intrinsic differences existing between different categories of water bodies can lead to significant differences in species–environment relationships. Here, we tested the relative importance of broad-scale climate and local environmental predictors in explaining plant species distributions in freshwater lakes and streams.
2. We built species distribution models to investigate which predictors best explain aquatic plant distribution in two categories of water bodies. We used species inventories and records of three climate and eight local environmental predictors for 150 lakes and 150 streams in Finland.
3. We found that sets of predictors that explain the distribution of macrophyte species are unique depending on if species are in a lake or a stream. Overall, air temperature and ecosystem size were essential to predict aquatic plant species presence in both water body categories. Broad-scale climate predictors were always very important in explaining species distribution, while local environmental conditions such as water chemistry were of variable influence, depending on species and water body category.
4. These results are probably due to high spatial and temporal variability and range of water physico-chemical parameters, especially in streams. Nonetheless, despite a lower relative importance than climatic factors, local environmental predictors also strongly affected species distributions.
5. Our findings highlight that incorporating local environmental conditions to species distribution models in addition to climate predictors is necessary to improve predictions, particularly for distribution of stream flora. Considering the species-specific responses of aquatic plants to their environment, studying species individually with species distribution models represents a useful analysis.

     

长湖水生维管束植物群落研究

长湖位于湖北省荆州地区,面积133.2km~2是江汉湖群中较大的淡水湖。湖中分布有40种水生维管束植物、12个群丛,湖中植被呈不规则环带状分布,并可划分为湿生、挺水、浮叶和沉水四个植物带。水生植被生物量随水深的增加而减少。     

1998年特大洪水后鄱阳湖自然保护区主要湖泊水生植被的恢复

鄱阳湖自然保护区的湖泊是相对独立于鄱阳湖主体湖的一个区域,是国际重要湿地。1998年的特大洪水导致湖泊中水生植物的地上部分大量毁灭。通过1999年和2001年的植被调查,并与历史资料比较,探讨了特大洪水干扰后的植被恢复动态。结果表明,1999年湖泊水生植物的种类和生物量均低于干扰前的水平;2001年物种种类已经恢复,苦草(Vallisneria spp．)和黑藻(Hydrialla verticillata)的生物量已超过干扰前的水平,但其它物种的生物量仍较低,尚处于恢复的初始阶段。据此推断,物种问恢复速度的差异主要与物种的无性繁殖方式有关。鄱阳湖自然保护区湖泊的植被恢复不同于温带和其它亚热带的湖泊,不经历轮藻(Chara spp．)作为先锋优势种的阶段,苦草和黑藻可以作为先锋种首先在湖泊中恢复。这可能与鄱阳湖作为通江湖泊其水位频繁波动、轮藻不易定居有关。研究显示,洪水导致的水生植物生物量下降和物种数目减少只是短期现象,湖泊水生植物能在几年内恢复到干扰前的水平。     

激素对水生植物生理生态的影响及其应用

激素代谢是植物传导信号和调节生长发育的重要途径.陆地植物五大类激素在水生植物中也有分布,尽管近年来环境污染导致水生植物衰退的问题日益得到重视,但水生植物激素的研究和应用却远滞后于陆生植物.在总结了近年来激素类物质在水生植物中的研究成果,分别从激素的种类、激素的生理生态作用、激素生物合成的途径及作用的部位和机制、激素之间的相互作用.激素类物质在实验和实践上的应用等进行了全面阐述,指出了水生植物激素生理生态学研究的发展方向,从利用激素类物质诱导水生植物抗性的表达,提高抗逆性,恢复水生植被,以及研究和开发适于水生植物生产和管理的生长调节剂等方面,就水生植物激素的进一步研究和应用进行了探讨.