Lakes of south-western Uganda

The vegetation of Lake Bunyonyi, a high altitude lake in Kigezi, S.W. Uganda, is described. The lake had two distinct plant communities. In the shallow sheltered bays and inflows extensive floating swamps of Cyperus papyrus L. and Cladium janiaicen. se Cranz. existed. On the steep, exposed shores there was only a narrow band of vegetation, dominated by firmly rooted Phragmites australis (Cav.) Steud., usually with papyrus behind. Floating-leaved Potamogeton and Nymphaea sometimes occurred outside the emergent species, and submerged species, including Ceratophyllum demersum L. grew down to 8 m. The pattern of vegetation, and the contribution of floating islands to the distribution of plants in the lake is discussed. Susceptibility to fragmentation, and distribution by wind are thought to be major factors governing the pattern. Oxygen proflies measured at the fringe of swamps indicated that the swamps did not cause appreciable deoxygenation of the water.     

台湾植被分类方案

复杂的自然条件导致面积仅为36 000多平方公里的台湾兼有热带和寒温带的群落类型,堪称中国乃至世界植被之缩影.它的植被分类也是对中国乃至世界植被分类的补充.台湾植被分类采用的是外貌-区系原则,分类单位和系统自上而下是:植被型纲、植被型目、植被型、群团组、群团和群丛.高级单位(植被型纲、植被型目和植被型)以群落的生态外貌为依据;中、低级单位主要依据种类组成,兼顾优势种和标志种的指示意义.在中级单位中(群团组、群团),重视优势种的作用,在低级单位中(群丛)更重视特征种(或标志种)的意义.按此原则将台湾植被划分为5个植被型纲(森林、灌丛、草本植被、岩原植被、沼泽和水生植被),29个植被型目(寒温性针叶林,凉温性针叶林,暖温性针叶林,暖性针叶林、落叶阔叶林、常绿阔叶落叶阔叶混交林、常绿苔藓林、常绿硬叶林、常绿阔叶林、热带雨林、热带季雨林海岸林、暖性竹林、常绿针叶灌丛、革叶灌丛、落叶阔叶灌丛、常绿阔叶灌丛、刺肉灌丛、竹灌丛、草甸、疏灌草地、干热早生草地、岩屑堆稀疏群落、石隙植被、木本沼泽、草本沼泽、藓类沼泽、淡水水生植被和咸水水生植被),53个植被型.列举了各个植被型中的重要群团.     

台湾植被分类方案

复杂的自然条件导致面积仅为36000多平办公里的台湾兼有热带和寒温带的群落类型,堪称中国乃至世界植被之缩影。它的植被分类也是对中国乃至世界植被分类的补充。台湾植被分类采用的是外貌-区系原则,分类单位和系统自上而下是：植被型纲、植被型目、植被型、群团组、群团和群丛。高级单位(植被型纲、植被型目和植被型)以群落的生态外貌为依据;中、低级单位主要依据种类组成,兼顾优势种和标志种的指示意义。在中级单位中(群团组、群团),重视优势种的作用,在低级单位中(群丛)更重视特征种(或标志种)的意义。按此原则将台湾植被划分为5个植被型纲(森林、灌丛、草本植被、岩原植被、沼泽和水生植被),29个植被型目(寒温性针叶林,凉温性针叶林,暖温性针叶林,暖性针叶林、落叶阔叶林、常绿阔叶落叶阔叶混交林、常绿苔藓林、常绿硬叶林、常绿阔叶林、热带雨林、热带季雨林海岸林、暖性竹林、常绿针叶灌丛、革叶灌从、落叶阔叶灌丛、常绿阔叶灌丛、刺肉灌从、竹灌丛、草甸、疏灌草地、干热旱生草地、岩屑堆稀疏群落、石隙植被、木本沼泽、草本沼洋、藓类沼泽、淡水水生植被和成水水生植被),53个植被型。列举了各个植被型中的重要群团。     

干旱对湖北省长湖水生植物多样性的影响

将断面法和地理信息系统（GIS）与全球定位系统（GPS）技术相结合,通过比较湖北省长湖2000年（干旱年）与1999年（非干旱年）的水生植物多样性,探讨了干旱对淡水湖泊水生植物多样性的影响,主要结论如下：（1）干旱对长湖淡水湖泊水生植物物种多样性无影响,但可增加优势种数目（从12个至14个）。（2）干旱使长湖水生植物群丛数目从14个增加至18个,且能显著提高各群丛的Simpson与Shannon-Wiener物种多样性指数。（3）干旱显著提高了长湖水生植被覆盖率与各群丛的盖度,并使全湖水生植被平均单位面积生物量与各群从单位面积生物量显著升高。（4）在干旱年（2000年）,长湖挺水植被消失,但浮水植被面积与沉水植被面积显著扩大：分别从1999年的3.71％与41.32%上升至2000年的12.63%与53.84%（占湖泊总面积的百分比）。（5）干旱条件下淡水湖泊水生植物的生长发育明显加快：2000年7月菹草石芽萌发率、菹草幼株长度和野菱黄叶率显著高于1999年同期值。     

Macrophyte induced microchemical changes in the water column of a northern Boreal Lake

Water quality was compared between open water and vegetated regions of the littoral zone of a Boreal lake. Within region variation occurred in vegetated areas and was species dependent. In the water lily versus the open water stations, conductivity and concentrations of B, Ca, Fe, K, Mg, Mn, S and Sr were elevated in the water column while N concentrations were lower. Wild rice areas were characterized by lower S and higher conductivity and Ca and Fe concentrations than open water areas. Variations in water quality in the vegetated regions occurred as a result of chemical exchange with the sediment in the proximity of the vegetation. Elemental concentrations in the sediment appeared to vary as a result of root aeration and nutrient uptake by the plants. Open water stations had elevated sediment levels of N, P and Al while elevated levels of Na were present in both the open water and wild rice plots. Water lily stations exhibited higher pH levels and higher concentrations of Fe, Mn and Ca than the open water plots. Plant tissue analysis indicated that between species elemental variation existed as well. Water lily tissue had higher concentrations of N, P, Mn, Zn, Ca, K and Mg than that of wild rice. It was postulated that aquatic macrophytes can influence the redox level of sediments and thereby dramatically alter the overlying water column forming microchemical environments in stagnant regions of the littoral zone.     

Herbivores Enforce Sharp Boundaries Between Terrestrial and Aquatic Ecosystems

The transitions between ecosystems (ecotones) are often biodiversity hotspots, but we know little about the forces that shape them. Today, often sharp boundaries with low diversity are found between terrestrial and aquatic ecosystems. This has been attributed to environmental factors that hamper succession. However, ecosystem properties are often controlled by both bottom-up and top-down forces, but their relative importance in shaping riparian boundaries is not known. We hypothesize that (1) herbivores may enforce sharp transitions between terrestrial and aquatic ecosystems by inhibiting emergent vegetation expansion and reducing the width of the transition zone and (2) the vegetation expansion, diversity, and species turnover are related to abiotic factors in the absence of herbivores, but not in their presence. We tested these hypotheses in 50 paired grazed and ungrazed plots spread over ten wetlands, during two years. Excluding grazers increased vegetation expansion, cover, biomass, and species richness. In ungrazed plots, vegetation cover was negatively related to water depth, whereas plant species richness was negatively related to the vegetation N:P ratio. The presence of (mainly aquatic) herbivores overruled the effect of water depth on vegetation cover increase but did not interact with vegetation N:P ratio. Increased local extinction in the presence of herbivores explained the negative effect of herbivores on species richness, as local colonization rates were unaffected by grazing. We conclude that (aquatic) herbivores can strongly inhibit expansion of the riparian vegetation and reduce vegetation diversity over a range of environmental conditions. Consequently, herbivores enforce sharp boundaries between terrestrial and aquatic ecosystems.     

Delineation of vegetation shaded ox-bow lakes in Ganges flood plain,India

Floating vegetation cover over the ox-bow lake withstands against its sharp delineation. A good many spectral indices are successfully used for water body delineation. But how far these are applicable in vegetation-shaded ox-bow lakes is a research question. The study also aimed that if the existing indices are not satisfactory and how a new index could be endorsed for resolving the problem. The study additionally monitored the ox-bow lake and vegetation cover area from 1991 to 2021 based on Landsat satellite images.Normalized differences water index (NDWI), Modified NDWI (MNDWI), Re-modified NDWI (RmNDWI), and Normalized Difference Vegetation Index (NDVI) spectral indices were used for delineating ox-bow lakes and multiple accuracy test measures revealed that these are not highly satisfactory. Vegetation inclusive aggregated water index (ViAWI) was built by coupling mentioned spectral indices with the vegetation index and the ensemble map was found more accurate.Monitoring the ox-bow lake area clearly showed that these declined in the last 30 years irrespective of the historical drainage modification legacy of the major rivers to which the ox-bow lakes belonged. Aquatic vegetation cover within ox-bow lakes changed dynamically.The endorsed ViAWI would be a good approach for resolving wetland delineation shaded with floating vegetation and it could be used in other regional units worldwide. Quantitative information regarding ox-bow lake and vegetation cover within ox-bow lakes would be valuable data support for adopting ox-bow lake conservation and restoration planning.     

Recovery of plankton from hurricane impacts in a large shallow lake

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Fish communities in the perennial wetland of the Sudd, southern Sudan

SUMMARY. 1. Cyperus papyrus and Typha domingensis swamps were recognized as the major ecological zones in the perennial wetland of the Sudd.
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3. The highest diversity and abundance of tishes was obtained in the shallow Sudd lakes which revealed considerable uniformity in population structures. The most numerous species in gill-nets were Alestes dentex, Synodontis frontosus and S. schall , whereas Heterotis niloticus, Mormyrus cashive and Distichodus rostratus assumed importance in terms of biomass. Micralestes avutidens and cichlids were abundant among the small fishes inhabiting fringes of Eichhornia crussipes , and air-breathing species occurred beneath the vegetation mat.
4. Flowing-water habitats exhibited a similar but restricted fauna. Catches were dominated by Synodontis frontosus in open-water and by Micralestes acutidens and Chelaethiops bibie in the margins. The latter species was shown to have a clear preference for running water.
5. Peak catches in a representative river-lake could be interpreted as the arrival of fish for breeding or their migration through the lake for reproduction elsewhere. The capture of fry or juveniles of many species in fringing or marginal vegetation indicates that the permanent floodplain of the Sudd provides suitable spawning and rearing grounds.
6. Access to the extensive Typha zone was limited but from available evidence it was inferred that air-breathing fishes, notably Heterotis and Gymnarchus , may penetrate the swamps to reach areas remote from perennial transmission channels.     

Aquatic feeding by moose Alces alces in a Canadian lake

The aquatic feeding behaviour of moose, and the abundance, species, and chemical composition of aquatic plants, were studied in a small Canadian lake which attracted many animals. Feeding was much more common in June than later in the summer, and somewhat more common during the morning and evening than in (he afternoon. Individual adult moose appeared to use the lake intensively during 1- to 4-day visits. Compared to deciduous browse, the aquatic plants had high levels of sodium and iron, less fat, and similar levels of crude protein, crude fibre, sulphate and other minerals. In the preferred feeding areas, compared to other parts of the lake, plants were more abundant, had a different species composition, and were richer in iron and calcium. Recent flooding, a flow of water through the feeding areas, and a bicarbonate-rich tributary may all have contributed to the lake's attraction for moose.     

CHEMICAL AND PHYSICAL CHARACTERISTICS OF SHALLOW GROUND WATERS IN NORTHERN MICHIGAN BOGS,SWAMPS, AND FENS

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武汉月湖水生植被重建的实践与启示

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巢湖崩岸湖滨基质-水文-生物一体化修复

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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。     

Assessing the biomass and distribution of submerged aquatic vegetation using multibeam echo sounding in Lake Towada, Japan

Here we report on an advanced survey system that combines multibeam echo sounding with underwater photography, which was used to collect accurate data on the distribution and abundance of submerged aquatic vegetation (SAV) in Lake Towada. The use of this system enabled us to visualize the cover, height, and biomass of the SAV over the lake bottom, as well as to distinguish between different components of the SAV such as vascular and algal plants. The spatial distributions of these major components of the SAV varied as a function of the depth gradient. The vascular component was mostly represented by Potamogeton species, which accounted for around one-third of the standing mass of SAV, whilst more than half of the SAV was algal (charophytes). This abundance of charophytes may well be responsible for the high water quality and transparency of Lake Towada.     

Diatom community succession in the recent history of a eutrophic Yunnan Plateau lake, Lake Dianchi, in subtropical China

Fish introduction, eutrophication and disappearance of aquatic vegetation are important disturbances of aquatic ecosystems, especially in plateau lakes, which are generally considered to be very vulnerable. Fish were introduced to Lake Dianchi, a eutrophic plateau lake in southwest China, in the late 1950s and 1970s. After the introduction, invasive fish became the dominant species, and the total fish yield increased. Meanwhile, the trophic level of Lake Dianchi had a tendency to increase in the past decades because of the increases in human activities in the watershed area. In addition, the area of aquatic vegetation decreased from more than 90 to 1.8% of the lake area from the 1950s to 2000. This study investigated the effects of fish introduction, eutrophication and aquatic vegetation on the diatom community of Lake Dianchi by examining the changes of microfossil diatom assemblage and abundance. Results showed that the absolute abundance and diatom assemblages changed after fish were introduced. The endemic species, Cyclotella rohomboideo-elliptica, disappeared with the introduction of fish and increasing trophic levels after 1958. Fragilaria crotonensis entered into the lake with the introduction of fish and gradually thrived in the lake after 1958. Diatom species numbers also decreased gradually from 21 to 9 from the past to present. Epiphytic diatoms disappeared with the decrease of aquatic vegetation after 1985. Our study indicated that eutrophication was the most important process determining diatom abundance, and fish introduction was a secondary process determining diatom abundance, while aquatic vegetation had a more important role in structuring the diatom community in this eutrophic plateau lake.     

Spontaneous and assisted restoration of vegetation on the bottom of a former water reservoir,the Elwha River,Olympic National Park,WA, U.S.A.

Early seral vegetation was studied on a former lake bottom after the removal of the 64‐m‐tall Glines Canyon Dam on the Elwha River. In 2015, vegetation cover of all vascular plant species was determined in 63 plots located on sites that emerged in 2011–2012. The sites had been planted and/or seeded, or were permitted to revegetate spontaneously. The plots were further classified by substrate texture: coarse sediments on the valley bottom and fine ones on the valley slopes. Plots were located randomly along random transects perpendicular to the former lake shore that extended into coarse sediment terraces perched above the floodplain. Additionally, 32 plots were sampled in surrounding native forests near these transects. Data were analyzed by detrended correspondence analysis and by canonical correspondence analysis. Substrate texture, that is whether fine or coarse, appeared to explain most of the variability in vegetation. The distance to forest and successional age, that is time since the site had been drained, were also significant explanatory variables, while assisted restoration by planting and seeding appeared to be insignificant to date. Spontaneous succession on fine sediments led to a species composition approaching that of adjacent natural forests. Invasive species were much less abundant than expected. Spontaneous restoration of vegetation on fine sediments in drained lake bottoms can rapidly produce a desirable vegetation composition and structure. On coarse sediments, active restoration may be useful to accelerate the development of native vegetation communities.