Aquatic vegetation and hydrology of a braided river floodplain

The response of aquatic vegetation to the complex hydrology of a river floodplain was investigated on a stretch of former braided channels of the Rhône River near Lyon, France, which is fed by three different water inputs: underground water, surface flow from a small tributary and river overflow during spates. Water temperature, pH, conductivity, alkalinity, sulfate, nitrate, and phosphate content were measured monthly at seven sampling stations. Principal Component Analysis (PCA) of these data revealed two gradients: a gradient of spatial heterogeneity and a gradient of temporal fluctuations. A PCA of samples based on substrate grain size, flow velocity, channel width and depth, height and shade of bank vegetation suggested the division of the braided system into four zones. Along these former channels, the vegetation varies from communities with Potamogeton coloratus of nutrient-poor water, to meso-eutraphent communities with Callitriche platycarpa, Elodea canadensis, and Ranunculus trichophyllus. Correspondence Analysis (CA) of the floristic data revealed four zones. Regarding the habitat parameters investigated, one zone is assumed to be linked to the instability and the nutrient inputs of a former channel (running water from the tributary and flood disturbances), while another is linked to the stability and nutrient-poor conditions of the other former channel (supplied by underground water). The other two zones are considered as ecotones, each of them occurring in a former channel, upstream of the confluences. The location as well as the floristic and functional differences between these two ecotones are discussed.     

Shifts in macrophyte species composition as a result of eutrophication and pollution in Dutch transboundary streams over the past decades

The catchment areas of transboundary streams in the Netherlands have been subject to increasing agricultural and industrial activities over the past decades. To evaluate the effects of these activities on the aquatic vegetation, a study has been carried out in 28 Dutch transboundary lowland streams. Recent data on distribution of 58 aquatic plant species and their growth forms were compared with historical data and were correlated with abiotic variables. Most of these streams lost species that are characteristic for streams and are sensitive to turbidity, eutrophication and pollution (e.g. Potamogeton alpinus, P. polygonifolius, P. densus, Ranunculus peltatus ssp. heterophyllus, Callitriche stagnalis and Myriophyllum alterniflorum.) Species, not common in streams but tolerant to turbidity, eutrophication or pollution (e.g. Potamogeton trichoides, Elodea nuttallii) appeared in many streams or increased in abundance. There was also a shift in growth forms: submerged species decreased or were replaced by emergent/floating-leaved species. Correspondence analysis was carried out to study the relation between the observed changes and the abiotic characteristic of the streams. The magnitude of the shift in species composition was positively correlated with the PO₄ ^3- concentration and pH (which was highly correlated with Cd²⁺) of the water. This leads to the hypothesis that increased input of sewage, agricultural and industrial water causes a change in species composition and main growth forms of aquatic plant species in lowland streams.     

Recolonization of cleared riverine macrophyte patches: importance of the border effect

Abstract. Recolonization of two experimentally cleared 9 m²-patches by macrophytes in a former channel of the Rhône River, France, was investigated from May to July 1994. Two patterns of recolonization were recognized: (1) Groenlandia densa, Luronium natans and Potamogeton natans invaded the bare areas by propagation from the adjacent vegetation (border effect); (2) Potamogeton pusillus colonized the disturbed areas at random, apparently independently from the position of nearby clumps. An intermediate recolonization pattern was shown by Callitriche platycarpa, Elodea canadensis, Hippuris vulgaris, Ranunculus circinatus and Sparganium emersum. Species recolonization patterns and associated strategies were related to species traits, particularly vegetative and sexual reproduction.     

鄂东花马潮水生高等植物研究——Ⅱ.水生植被

花马湖位于湖北省鄂州市境内,面积约27.5km~2。湖中分布有水生高等植物82种2变种。花马湖水生植被可分为15个群丛,其中菱群丛、竹叶眼子菜群丛、金鱼藻+狐尾藻+菹草+苦草群丛较为重要。湖中水生植波呈不规则的环带状分布,并可划分为湿生、挺水、浮叶和沉水4个植被带,各带均有相应的群丛分布。     

A Study of Pollen Morphology of Some Aquatic Vascular Plants in Honghu Lake,Hubei

This paper deals with the pollen morphology of 22 species of the aquatic plants belonging to 18 genera and 13 families. 11 species of them are first time reported: Potarnogeton maackianus Benn; P. malaianus Miq., MyriophyUurn spicatum L., Zizania latifolia Turcz., Sagittaria sagittifolia L. var. longilaba Turcz., Polygonum hydropiper L., Ranunculus sceleratus L., Cardamine lyrata Bunge, Cyperus difforrnis L., Eleocharis pellucida Presl and Scirpus rnucronatus Diels. All pollen grains were observed under light microscope (LM) but 12 species among them were also examined under scanning electronic microscope(SEM). The environmental conditions and community structure of aquatic vegetation in the lake are briefly discussed.     

东北地区湿地野生种子植物区系

据统计,东北地区湿地野生种子植物已知有693种、42变种、12变型,隶属于72科、257属,以草本植物为主。含物种比较丰富的科有莎草科、菊科、禾本科、蓼科、毛茛科及玄参科,含种数比较多的属包括薹草属(Carex)、蓼属(Polygonum)、柳属(Salix)、毛茛属(Ranunculus)、藨草属(Scirpus)、眼子菜属(Potamogeton)等。该区湿地种子植物种的地理成分包含24个分布区类型和25个亚型,以温带性质成分为主体,并包含了少量的热带性质成分。与其他地区相比,东北湿地种子植物含有寒带性质成分128种,占18.47%。地理联系广泛,尤其与西伯利亚和北极植物区系联系最密切。     

Gut bacterial assemblages of freshwater macroinvertebrate functional feeding groups

The use of remote sensing for monitoring of submerged aquatic vegetation (SAV) in fluvial environments has been limited by the spatial and spectral resolution of available image data. The absorption of light in water also complicates the use of common image analysis methods. This paper presents the results of a study that uses very high-resolution image data, collected with a Near Infrared sensitive DSLR camera, to map the distribution of SAV species for three sites along the Desselse Nete, a lowland river in Flanders, Belgium. Plant species, including Ranunculus peltatus, Callitriche obtusangula, Potamogeton natans L., Sparganium emersum R. and Potamogeton crispus L., were classified from the data using object-based image analysis and expert knowledge. A classification rule set based on a combination of both spectral and structural image variation (e.g. texture and shape) was developed for images from two sites. A comparison of the classifications with manually delineated ground truth maps resulted for both sites in 61% overall accuracy. Application of the rule set to a third validation image resulted in 53% overall accuracy. These consistent results not only show promise for species-level mapping in such biodiverse environments but also prompt a discussion on assessment of classification accuracy.     

江苏省湖泊水生植被的研究

 江苏为全国多湖泊的省份之一,水生植被十分繁茂。影响湖泊水生植被生长、分布的环境因素是多方面的,湖水深度与透明度的影响最为明显。江苏湖泊水生植被的组成植物隶属30科,48属,共62种,可区分为挺水、浮叶、漂浮及沉水四类生活型植物。它们的分布有一定的规律,在沿湖岸浅水处,形成挺水植物带,向湖心方向随着湖水变深,而为浮叶植物带、沉水植物带。漂浮植物因流动性大,通常不形成独立的植物带。各植物带内分别形成相应的植物群落,在两个植物带叠接处则形成混交的群落。江苏湖泊水生植被共有16个主要群落类型。本文对湖泊水生植被的经济用途作了较详细的讨论。     

三江并流地区干旱河谷植物物种多样性海拔梯度格局比较

在滇西北三江并流地区典型干旱河谷段, 在怒江、澜沧江和金沙江的东、西坡共设置了6条海拔梯度样带, 通过标准样地的植物群落调查, 分析各条样带植物的物种丰富度、物种更替率的海拔梯度格局, 并比较了地理和植被变量对分布格局的解释。干旱河谷植被带位于海拔3,000 m以下, 以灌丛和灌草丛为主, 其在各河谷的分布上限自西向东依次升高。植物物种丰富度的分布主要与海拔、流域、经纬度和植被带有关, 沿纬度和海拔梯度升高而显著增加的格局主要表现在草本层和灌木层, 灌木物种丰富度还呈现自西向东显著增加的趋势。怒江的灌木和草本种物种丰富度显著高于金沙江和澜沧江, 三条江的乔木种丰富度差异则不显著。森林带的样方草本物种丰富度显著低于灌草丛带样方, 并且还拥有后者没有的乔木种。不同样带的植物物种更替速率呈现了不一致的海拔梯度格局, 但均在样带海拔下部的灌草丛群落与海拔上部森林群落之间的交错带出现峰值。森林-灌草丛植被交错带在怒江样带处于海拔1,900-2,100 m处, 在澜沧江河谷位于海拔2,300-2,400 m, 在金沙江河谷位于海拔2,700-2,900 m。所有海拔样带的森林段或灌草丛段相对于同一样带不同植被段之间的物种更替程度为最小, 不仅小于同一流域不同样带相同植被段之间物种更替率的均值, 更小于所有样带相同植被段之间的更替率均值。在三条河流6条海拔样带的12个植被带段之间的物种更替变化中, 空间隔离因素可以解释34.2%, 而植被类型差异仅能解释不到0.5%。本研究结果显示了环境差异对不同植被类型物种丰富度的首要影响, 和各河流之间的空间隔离对植物群落构建和物种构成的主要作用。     

镜泊湖水生植被

镜泊湖位于黑龙江省宁安县境内,海拔350米,面积约300平方公里,最大水深约60米,是我国最大的堰塞湖。水生植物主要生于南部和西部的河流、沟涧的入湖处及港湾、湖叉等地段。因底质、水深、透明度等环境不同、植物种类和覆盖度有明显差异。我们根据植物的不同生活型和优势种,划分为下列3个类型和12个群落。挺水植物7个群落:水蒿,芦苇,菰,泽泻+慈菇,大基荸荠,拂子茅+荻,湿苔草+大穗苔草;浮水植物3个群落:两栖蓼,菱,荇菜;沉水植物2个群落:眼子菜,杉叶藻。       

Similarity between seed banks and above‐ground vegetation along a salinity gradient

Abstract. Zonation of above‐ground vegetation often occurs in salt marshes along salinity and moisture gradients. The above‐ground vegetation and seed bank in four physiognomically different vegetation zones in a salt marsh were compared to determine their level of similarity using percent similarity as a distance measure. 10‐m transects were established along a salinity gradient through four different vegetation zones; a Salicornia zone, a Salicornia‐Atriplex zone, an Atriplex zone and an Atriplex‐Hordeum zone. A UPGMA cluster analysis demonstrated that the above‐ground vegetation was not usually highly correlated with the seed bank composition of zonal communities. Since seeds of these annual salt marsh species occurred in all zones, the levels of salt stress may be the main factor determining which species were found in the above‐ground vegetation.     

The macrophytic vegetation of Loch Urigill and other lochs of the Ullapool area

Summary

From the 15 lochs examined at altitudes between 9 and 267 m in western Sutherland and Wester Ross, a few areas of tall fen (with Hippuris, Sparganium erectum, Osmunda etc.) survive to indicate its potential distribution. Predominant grazed fen comprises patches of short Juncus articulatus and Carex nigra. Reedswamp is scarce, being dominated by Eleocharis palustris, Carex lasiocarpa and Schoenoplectus lacustris and, rarely, by Phragmites and Sparganium erectum. Floating-leaved vegetation was only encountered twice. Submerged vegetation to water depths of at least 1 m consists in the main of sparse Lobelia-Littorella with Juncus bulbosus, typical of the prevailing stony shores in every loch. Extensive Isoetes lacustris meadows may occur beyond that, with Potamogeton praelongus or P. perfoliatus stands in waters of alkalinities over 0·45 m-equiv 1^-1, reaching depths of 3 m in Loch Urigill. Loch Urigill is unusual in having dominant Isoetes at a water alkalinity of 0·76 m-equiv 1^-1 along with abundant Anabaena species and some Potamogeton filiformis.     

Distribution of submerged macrophytes in the Camargue in relation to environmental factors

Abstract. The species composition of stands of submerged macrophytes was studied in relation to the main environmental factors in oligohaline wetlands of the Camargue, southern France. Correlations were sought between the environmental factors and the abundance of the different species using canonical analysis. 24 species of submerged macrophytes, including 10 species of Charophyta, were recorded in the 60 sites studied. The hydrological regime and the salinity appeared to be the main factors controlling the abundance of the different species. This is related to the management of the marshes in the Camargue, which is carried out using these two controlling factors, particularly the hydrological regime, and also includes the destruction of emergent vegetation, mechanically or by grazing. The bivariate ecological amplitude of the individual species was calculated from field data along the gradients of flooding duration and conductivity of the water. My-riophyllum spicatum, Potamogetón pectinatus and Ruppia cirrhosa dominate permanent marshes along the conductivity gradient. In temporary marshes, all having a low conductivity, Zannichellia pedunculata, Ranunculus baudotii, Chara áspera and Callitriche truncata dominate.     

Seed and tuber banks of aquatic macrophytes in the Askö area, northern Baltic proper

Sediment samples from 5 stations in the northern Baltic proper, 6.5 o/oo S, were collected in April 1987 and the emergence of seedlings was recorded over 120 days in a greenhouse at 20°C. Total seedling densities varied from 0 to 3328 m^-2: and of seven species, Zannichellia palustris and Chara spp. were the most abundant among seedlings and sporelings, respectively. Several common macrophytes in the area were rare as seedlings and no seedlings were recorded for the most abundant angiosperms, Potamogeton pectinatus, Potamogeton perfoliatus and Ranunculus baudotii. Except for the few annual species, reproduction by seeds contributed little to the dynamics of the vegetation in the area and no correlation was found between vegetation composition and the seed bank. For perennial species the winter survival of vegetative propagules is the most important factor for vegetation dynamics.     

Plant community distribution along water table and grazing gradients in montane meadows of the Sierra Nevada Range (California, USA)

This study aimed to identify dominant plant communities across five wet and mesic meadows in the Sierra Nevada Range (California, USA) and examine the impacts of environmental and grazing gradients on plant community distribution and diversity. Species composition and environmental conditions were recorded in 100 plots over two years. Classification and ordination analyses were used to classify plant communities and identify relationships between community types and both environmental and grazing gradients. We identified the following six plant community types: Carex jonesii, Carex leporinella, Carex nebrascensis, Carex utriculata, Eleocharis pauciflora, and Veratrum californicum. We found strong connections between plant communities and water table variables, with low water table (r ²?=?0.56) and mean water table (r ²?=?0.30) significantly correlated with Axis 1 while high water table (r ²?=?0.29) and elevation were correlated with Axis 3 (r ²?=?0.49). We found significant differences among community types for all three water table variables and for elevation. We found no correlation between grazing and community type classification, but there was a significant difference in grazing levels among community types. The plant communities and relationships to water table found in this work may aid managers in understanding present conditions and identifying future changes in meadow ecosystems.     

青藏高原四县水生植物群落调查

青海省玛多县,达日县,甘肃省久治县和四川省阿坝县地处黄河上游,是高原水生植物分布的重要地区之一。此区有水生植物群落９个,它们是篦齿眼子菜群落,钝叶菹草群落,帕米尔眼子菜群落,圆叶碱毛茛群落,草群落,黄花水毛茛群落,看麦娘群落,曲轴黑三棱群落和西伯利亚蓼群落。     

土壤盐分对高寒草甸主要植物生态位的影响

采用Levins生态宽度指数和Cowell生态位相似性公式,计算了巴音布鲁克高寒草甸主要物种在4个盐分梯度上土壤水分、有机质、速效钾3个资源维的生态位宽度及生态位相似性.结果表明：在3个资源维上,随着土壤盐分含量的增加,主要建群种细果苔草的平均生态位由0.4433降至0.1740,伴生种鹅绒委陵菜的平均生态位由0.1263升至0.2215,说明耐盐性较差的物种生态位宽度逐渐减小,耐盐性较好的物种逐渐增大,可能成为重要的演替种.随土壤盐分含量的增加,耐盐性较差物种间的生态位相似性逐渐升高, 而耐盐性较好的物种则逐渐降低.细果苔草和线叶嵩草的生态位相似比例由0.701升至0.842, 而鹅绒委陵菜和山地蒲公英的生态位相似比例由1降至0.708.物种的生物学特性是物种对土壤盐分响应不同的主要原因.     

雅鲁藏布江河岸植物物种丰富度分布格局及其环境解释

沿环境梯度物种多样性的分布格局及其环境影响因子的研究是生态学研究的重点内容之一。雅鲁藏布江是我国海拔最高的大河, 目前还没有针对其流域的河岸植物群落物种丰富度分布格局的系统研究。作者沿海拔梯度从雅鲁藏布江上游源头区至下游共设置了15个海拔样带, 在每个海拔样带随机取6个5 m×5 m样方, 共对90个样方的河岸植物群落物种组成和植被类型进行了调查, 共记录到238种维管束植物。DCA排序结果表明物种组成变化主要受海拔和经度控制。CCA排序区分出5种大的植被类型, 即高寒草甸或高寒草原、高山草原、两种亚高山灌丛草原和林缘灌丛植被。各植被类型的分布和变化主要受海拔和经度影响。雅鲁藏布江河岸植物物种丰富度沿海拔和经度梯度呈浅“U”形分布格局, 物种丰富度与年均降水量和植被盖度成显著正相关。     

武汉东湖水生植物群落演替的研究

 本文根据1992～1993年调查结果并结合前人研究资料,讨论了东湖水生植物群落30多年来的动态变化及其与富营养化和渔业养殖等因素的关系,提出了东湖水生植物群落的演替系列是从微齿眼子菜阶段→微齿眼子菜+大茨藻+金鱼藻+狐尾藻阶段→微齿眼子菜消失阶段→大茨藻阶段→大茨藻+狐尾藻+苦草阶段。同时,还从物种生理生态、补偿和再生能力、生活史及生殖对策、种间关系等方面探讨了水生植物群落演替的物种替代机制及其演替模式,为湖泊水生植被恢复、人工调控和优化提供理论依据。