Dynamik der Schilfröhrichte am Bodensee unter dem Einfluss von Wasserstandsvariationen

On the basis of different sets of aerial photos the dynamics of the reed bed areas of Lake Constance were investigated in relation to the dynamics of the water levels. The objectives of the study were to quantify the changes of reed areas due to different flood events in the last decades and their recovery in the time periods between these events. The results should given information of the relevance of water level variations on reed bed dynamics and the regeneration times of reed beds after extreme disturbance events.Following the extreme flood at Lake Constance in 1999 the reed belts of Lake Constance lost approximately 30 ha (24%) of the lakeside reed beds. The loss is comparable to the situation in the late 1960s, when approximately 40 ha died back due to the extreme flood in 1965 and the high spring water levels in the subsequent years. In the time period between the extreme floods of 1965 and 1999, the reed areas expanded to nearly 85% of the area before 1965. The expansion rates increased with increasing distance to the flood event of 1965. Especially in periods with series of years of low spring water level the expansion rates were high.The damage degrees of the reed areas in the years 2000 and 2002 showed a clear relation to the elevation (i.e. average water level) of the stands. The damage degree increased with decreasing elevation. Furthermore the regeneration process of severely damaged stands was related to the elevation level of the stands. Whereas stands at high elevation regenerate fast, those at low elevation died off completely in the years after the extreme flood. This supports the hypothesis that the water level flutuations play a major role in the reed dynamics of Lake Constance.As a consequence of the climate change an increase in the frequency of high spring water levels is expected. Thus, it seems unlikely that reed stands will ever expand again to the same area as before 1965.     

Geschichte und Ursachen des Röhrichtrückgangs am Ammersee (Deutschland)

The development of aquatic reed stands at Lake Ammersee was documented by using vertical airborne photographs which were taken during four partial and five complete flights beginning in 1944. A dramatic decline of reed, especially of those parts which stood in deep water, was demonstrated. Between the years 1963 and 1969 60% and until 1992 another 30% of the Phragmitetum disappeared. Only at the east bank did the lake reed beds slightly expand.The examination of possible factors affecting the development of reed at Lake Ammersee lead to the following scenario: Until 1940 reed stands at Lake Ammersee spread and covered large aquatic areas. Only the east bank of the lake, where the influence of wind and waves was high, and banks near towns and recreation areas remained uncovered. Since the regulation of the River Ammer between 1920 and 1938 flood occurrence increased enormously. The flood disaster of the year 1965 coincided with the period of the highest rate of reed decline. The peak of eutrophication in the lake was reached in 1975. Huge carpets of green algae caused further retreat of reeds.At the present time recovery is not possible because of the negative influence of human recreation and of reed consuming waterfowl. Interestingly enough an expansion of reed has been observed at the east bank of Lake Ammersee at places were there was no Phragmites previously.     

Effects of flooding on the amino acid and carbohydrate patterns of Phragmites australis

Changes in the contents and composition of dissolved amino acids and carbohydrates were monitored in different Phragmites australis stands in Germany. Four different reed clones planted in 1997 in a degraded fen area in NE-Germany were compared with respect to the seasonal development in the total amount of amino acids and sugars in the basal culm internodes. The individual Phragmites clones showed significant differences in the absolute content of both parameters indicating an influence of the genotype. Flooding affected the ratio of amino acids to carbohydrates within the reed clones. Plants grown in flooded parts of the fen area revealed a significantly higher total amino acid content together with a lower total content of carbohydrates.Furthermore, the effects of extreme flooding on the content and composition of amino acids and carbohydrates in the basal culm internodes of Phragmites australis were studied in nine reed stands with different degrees of damage on Lake Constance. Shoots from extremely damaged reed stands were characterised by a significant decrease in the total content of carbohydrates, an increase in the total content of amino acids and an increase in the share of γ-aminobutyric acid. These changes in the content and composition of carbohydrates and amino acids were discussed with respect to their value as stress indicators, such as for oxygen deprivation which causes a hypoxic metabolic state in Phragmites australis stands.     

Characteristics of reeds on Lake Peipsi and the floristic consequences of their expansion

The reeds of Lake Peipsi (surface area 3555 km², mean depth 7.1 m, max. depth 15.3 m, not-regulated) have increased through the last 30 years. The most significant increase has taken place in the larger formerly mesotrophic northern part where the mean air-dry biomass of reed shoots has increased from 20 g m⁻² in 1970 through 789 g m⁻² in 1989 to 1563 g m⁻² in 2002. The data of 34 transects for 2001–2002 along the Estonian coast and aerophotos made in 2001 showed that in places reeds reach a water depth of 1 m (mean 0.64 m) and a width of more than 200 m (mean 89.5 m). Their area of 9.3 km² accounts for about 0.6% of the Estonian territory of the lake. The longer and thicker shoots grew in the lakeward and intermediate zones of reeds. Near villages the shoots were weaker and their biomass lower. Phosphorus content of shoots, being higher near settlements, was generally low; in some cases content of phosphorus was ≤0.001%. The monotonous reed belt occupies the growth area of shallow-water submergent and shorter emergent species and favours the accumulation of organic sediments. The frequency of several species demanding light and sandy bottom has decreased, as well has the overall diversity of the macrovegetation. The main reasons for expansion of the reed could be eutrophication, combined with low-water periods, and the decline of cattle breeding in the shore areas. Some suppressed species have reappeared on stretches cleaned from reeds.     

Susceptibility of lakeside phragmites reeds to environmental stresses: Examples from Lake Constance-Untersee (SW-Germany)

The lakeside border of Phragmites reeds is under the control of many environmental factors, among which the flooding height and the degree of mechanical load by waves and washes are the most prominent. Examples from Lake Constance-Untersee show that the reed front retreats under enhanced stresses. Models are presented that describe the susceptibility of lakeside reeds to mechanical damage and to flooding events. A monitoring programme which ran from 1984/85 to 1992/93 showed a slow lakeward progression of the reeds in a decade of abnormally low water conditions.     

Stickstoff- und Kohlenhydratspeicherung in Rhizomen von Phragmites australis (Cav.) Trin. ex Steudel an unterschiedlichen aquatischen Standorten oberbayerischer Seen

Nitrogen and carbohydrate utilization in Phragmites australis rhizomes was investigated under natural conditions at 10 sites in 5 lakes in Upper Bavaria over a period of two years. Nitrate and ammonium of surface and interstitial water was determined. The results indicate that conditions of habitat and environment, such as climate and fluctuation of water level, lead to different adaptations of reed. These parameters had an effect on the storage of nitrogen and carbohydrate. The reed stands exposed to high water level during spring and summer have a high carbohydrate content in the rhizomes. A positive correlation was shown between the aboveground biomass and the content of storaged carbohydrates during the vegetation period. No relationship could be demonstrated between the nitrogen availability of the habitats and the type of storage of carbohydrates and nitrogen. The nitrogen content in the rhizomes can be used as an indicator of the ability of reed stands to produce new secondary shoots after shoot loss. The differently established reed genotypes are not able to compensate short-term environmental changes, such as growing leisure problems and higher shoot loss by the increasing appearance of waterfowl, from their reserve storage.     

Seasonal insect emergence from three different temperate lakes

Knowing the aquatic resources, such as emerging insects, that are entering terrestrial systems is important for food web and conservation studies, especially when water availability or quality is limited. Even though studies concerning benthic macroinvertebrates are numerous, insect emergence from lakes is less studied.To understand if water parameters (e.g., water temperature, oxygen concentration etc) determine insect emergence and the possible seasonal differences, we collected emergent insects from three different lakes in South Germany, during three seasons. We searched for common patterns of insect emergence at the three lakes. Moreover, the relative contribution of insects of aquatic origin to aerial flying arthropods was assessed, with collecting aerial flying arthropods at the shore.Chironomidae constituted the highest number of emerged insects in all lakes, however different patterns of emergence occurred in each lake (unimodal vs. bimodal) with different season-dependent times for the emergence peaks (spring, summer, beginning of autumn). Aquatic insects constituted a considerable proportion (at least 17%) of the aerial flying arthropods at the shore. The variation in insect emergence was explained by water temperature, however not by other water parameters or the nutrient values. Seasonal and spatial differences in insect emergence, should be considered when investigating aquatic-terrestrial interactions and designing conservation plans. A total biomass of up to 1.8 g m⁻² of emerging insects from the littoral zone of Lake Constance can enter the terrestrial system in a year. We also provide length-dry weight relationships for emerged (adult) Chironomidae. These equations are useful to estimate the dry insect biomass from length data and currently such data lack for adult aquatic insects.     

苏北溱湖芦苇和芦苇+香蒲群落中植物对湿地土壤N、P的固持效果

湿地土壤是湿地生态系统固持氮(N)、磷(P)的重要库,水生高等植物在湿地土壤固持N、P过程中起到了非常重要的作用.本研究采用室外取样与室内实验结合的方法,对溱湖湿地两种主要湿地类型(芦苇(Phragmites australis)群落和芦苇+香蒲(Typha latifolia)群落)影响湿地土壤N、P固持过程的规律展开研究.分析了芦苇、香蒲各器官生物量和总氮(TN)、总磷(TP)含量及储量对于土壤各土层TN和TP含量的影响.结果显示:(1)溱湖湿地对于水体TN和TP有一定的削减作用,且对TN的削减作用更大;(2)芦苇可以增强湿地土壤(30 cm以下的土层)富集N的效率,并且芦苇+香蒲群落中土壤固N效率更高,芦苇植株内TN和TP储量都是根茎叶穗,而香蒲则是根穗茎叶;(3)芦苇和香蒲茎、叶器官的TN和TP含量在夏季均显著高于其他几个季节,尤其是芦苇茎的TN含量在夏季高出其他几个季节70%~84%,而TP含量甚至高出其他几个季节81%~92%;(4)芦苇、香蒲对于P贫瘠的响应机制不同,导致芦苇会消耗土壤P,而香蒲的介入可以抵消这一消耗过程.因此,芦苇+香蒲的植物配置模式可以提高湿地土壤固持N、P的综合效率.     

Early succession of the macroinvertebrate community in a shallow lake: Response to changes in the habitat condition

In the present study the initial succession of the aquatic macroinvertebrate communities of a newly created shallow lake in a wetland area was monitored during 15 months. Three different types of macroinvertebrate samples (multihabitat, associated to the Phragmites australis stands and associated to the sediment) were collected monthly from May 2004 to July 2005. Additional samples were collected in the reed stand in 2007, when the reed belt had become much taller and thicker. Colonization of the lake was fast, and the colonization sequence was mainly related to the dispersal abilities of the taxa. Habitat-specific changes in the assemblage's structure and composition were registered. The communities associated to the sediment showed a decrease in overall biomass, density and species richness along time. The density of the gastropod Physella acuta and the chironomid species Dicrotendipes pallidicornis, Polypedilum nubifer and Tanytarsus horni decreased significantly, after Chara stands declined; while the chironomid Chironomus riparius became dominant. The epiphytic macroinvertebrate communities associated with the reed stands followed a seasonal pattern, with a warm-period community dominated by the chironomid species Ablabesmyia monilis and Psectrocladius sordidellus-group, and a cold-period community dominated by the chironomid species Cricotopus ornatus and D. pallidicornis.     

Calcite patchiness in Lake Constance as viewed by LANDSAT-TM

Calcite precipitation is a phenomenon occuring in most hardwater lakes world-wide. On May 5th, 1990, a whiting in Lake Constance was observed by LANDSAT for the first time. Physical, chemical and biological ground data sets prove that the observed structures are caused by calcite precipitation. This satellite observation provides information about the patchiness of calcite crystals suspended in the surface water of the lake western basin.     

Carbohydrate and nutrient content in rhizomes of Phragmites australis from different habitats of Lake FertÕ/Neusiedlersee

Changes in the soluble sugar, starch, total non-structural carbohydrate (TNC) and nutrient (N, P, K) concentration in the reed rhizome were investigated in different reed habitat types in Lake Fertõ/Neusiedlersee during the vegetation period in 1993 to 94. Three die-back and four vigorous reed stands were monitored.For biomass estimations rhizomes were collected twice, in early summer and in autumn. They were calculated to be 1.9 to 2.7 kg/m² at die-back and 3.1 to 6.1 kg/m² at vigorous sites.The carbohydrate and nutrient concentrations of the reed rhizomes were high at the beginning of the vegetation period; they reached their minima in May–June, which was followed by a gradual increase until the end of the vegetation period. From autumn to spring the concentrations decreased, e.g. TNC concentration by 15 to 40% at vigorous, 50 to 70% at die-back sites.In both years the lowest carbohydrate concentrations were recorded at the end of May, a month before the inflorescence developed (vigorous sites: 50–70 mg TNC/g, die-back sites: 70–120 mg TNC/g). In that period the standing stock of the TNC in the rhizome did not separate the sites clearly, and the smallest carbohydrate standing stock was measured at a vigorous site with a high water cover.At the beginning of summer and in autumn the soluble sugar, TNC and N concentration values were higher at the die-back than at the vigorous sites but the standing stock was higher at the vigorous sites. In autumn the TNC standing stock of the rhizomes was between 780 and 1200 g/m² at vigorous, between 380 and 690 g/m² at die-back sites. This is especially important for the reactions and resistance of die-back reed stands to unfavourable conditions.     

武汉东湖受控生态系统中水生植被恢复结构优化及水质动态

于１９９３－１９９５４上对武汉东湖的布和网围受控生态系统中的植被恢复,结构优化及水质进行了初步研究。结果表明;在受控生态系统中,水生维管束植物生物量明显增加,控制养殖规模是恢复水生植被的前提,自然恢复的水生植被,结构较简单,通过选种优良植物,可优化植被结构,加速植被恢复进程;恢复水生植被时,应以沉水植物为主体。生长良好的水生维管束能使水中Ｎ,Ｐ浓度明显降低,浮游植物生物量减小;莲,芦苇,苦草,狐尾     

吉兰泰盐湖典型地物波谱反射率特征及其遥感解译标志

１９９７年８－９月期间,预外调查了吉兰泰盐湖及其外围的２５个典型地物,并对其实地进行了１０个通道的光谱反射率测试。根据吉兰泰盐湖地物地学特征,可将所测得的２筱典型地物分为５类：植被、基岩、水体、化学沉积物和松散沉积物,通过对５类典型地物波谱反射率特征及其影响因素的研究,并依据彩红外航空图象和ＴＭ标准假彩色的成象原理,建立了吉兰泰盐湖遥感解译标志。     

Bruthabitatmodellierung für den Drosselrohrsänger (Acrocephalus arundinaceus L.) als Bestandteil eines integrativen Managementsystems für Seeufer

Within the context of the European legislative (e.g. Water Framework Directive, Natura 2000 network) monitoring and assessment of wetland areas are of great significance. This research points out the relevance of spatially explicit habitat models as an essential part of a decision support system for lake shore management. The Great Reed Warbler (Acrocephalus arundinaceus L.) was selected as a key species of aquatic reed structures. Many results of investigation about breeding behaviour of this German Red List species are available. The factors of selecting a breeding range were modelled in a Geographic Information System (GIS) using indices that quantify the corresponding spatial characteristics of patches in the ecosystem (e.g. shape complexity or distance to other vegetation structures). A habitat suitability map was created for a nature conservation area at Lake Constance, Germany. The observed breeding places in the investigation area showed a great coincidence with the modelled habitat ranges. This modelling approach of integrating spatial indicators is an important basis to provide automated monitoring systems based on remote sensing methods.     

Low genetic variation in perch (Perca fluviatilis L.) from three major European drainage systems in Switzerland

Previous genetic studies on perch (Perca fluviatilis L.) in northern and southern regions of Europe have shown low heterozygosity. No such investigation has been conducted in the central part of Europe. The genetic variability ofP. fluviatilis in four Swiss lakes (Lake Constance, Lake Zürich, Lake Geneva and Lake Maggiore) was investigated. These four lakes belong to three different drainage systems (Rhine, Rhone and Po) without connections. A total of 136 fish were analysed electrophoretically. Only one locus (SOD ^*) was highly polymorphic in Lake Constance among the 27 loci studied. The expected heterozygosities for each population and for the total population were higher than in the previous studies but low (H _S= 0.38–2.7%;H _T=1.22%) and Nei's genetic distances were small (0.000–0.003). However, the jack-knifed mean of the Wright'sF _STwas calculated as 0.142, which indicates modest genetic differentiation among the perch populations in Switzerland, due to the differentiated population in Lake Constance.     

Bildung bromhaltiger Desinfektionsnebenprodukte nach Chlorung von Bodenseewasser in Abhängigkeit von Aufbereitungsschritten und der Bromidkonzentration

Formation of Brominated Disinfection By-products after Chlorination of Water from Lake Constance Depending on Treatment Steps and Bromide Concentration The formation of halogenated disinfection by-products (DNP) (trihalomethanes (THM), haloacetic acids (HES), haloacetonitriles (HAN), haloketones (HKE) and chloropicrin (TCNM)) was studied after chlorination (0.5 mg/L) of raw water and drinking water from Lake Constance. The objectives of this study were to investigate the effect of bromide ion on the distribution of DNP-species resulting from chlorination and to draw up a bromide mass-balance. The treatment of water from Lake Constance with ozone decreased the formation of DNP about 35% and of total organic halogens (AOX) about 45%. This decline in DNP-formation is mainly due to the formation of chloroform, dichloro- and trichloroacetic acid. Though there is only a small amount of bromide (6.2 μg/L) in water from Lake Constance, about 32% of THM, 16% of HES, and 30% of HAN contained bromine after chlorination of treated water. The addition of bromide ion (up to 1 mg/L) shifted the DNP-composition to more brominated species. The distribution of the DNP-species depends on the initial molar bromide-to-chlorine ratio. A mathematic model showed the same pattern of DNP-species depending on the initial molar bromide-to-chlorine ratio that was observed experimentally in microstrained raw water and drinking water from Lake Constance. After chlorination of microstrained raw water, 27% of the bromide were incorporated in known DNP, 34% in unknown substances, and about 39% of bromide were not converted to organic bromine. After chlorination of treated water, only 16% of the bromide were incorporated in unknown substances, whereas 34% were found in known DNP. About 50% were found as bromide again. After addition of bromide (up to 25 μg/L) to ozonated and treated water from Lake Constance, between 60 and 72% of the bromide that had reacted after chlorination were found in analyzed low-molecular DNP.     

Water level changes in Lake Constance and their relationship to changes in macrophyte settlement in the outflows of Lake Constance Upper and Lower Lake

Since 2008, water level differences between Upper and Lower Lake Constance have increased after they decreased significantly in the 20th century. Questioning the causes leads to the hypothesis that the significant changes in the submerged macrophyte vegetation due to eutrophication and subsequent oligotrophication have played an essential role over the past decades. To clarify whether macrophyte vegetation is the cause of the changed water levels, the spatial distribution of Swiss pondweed Potamogeton helveticus (syn. Stuckenia helvetica) and the other submerged macrophytes was mapped in 2017. Swiss pondweed, in particular plays a key role as a perennial plant type in flow channels. Shoot densities and lengths of this species were recorded by diving. The investigations were supplemented by hydrodynamic modeling of the effects of macrophyte flow resistance on lake water level relationships.The results show that P. helveticus has indeed increased significantly over the past decade. The species colonizes the bottom of flow channels in the Seerhein up to 6 m deep with up to 1000 shoots per square meter and a length of up to 5 m, whereas in the previous decades it only occurred at the edges of flow channels as small stands with shoot lengths of less than 1 m. In the shallow water zones outside the flow channels, stoneworts in particular have spread in the Seerhein over the past decade. The hydrodynamic modeling supports the hypothesis that aquatic plants are the cause of the changed lake water level conditions and illustrate the related changes in the flow velocity field.     

Detection of local site effects through the estimation of building damages

After the Umbria Marche seismic sequence of September–October 1997, an extensive microzoning study was conducted, from October 1997 to May 1998, to detect the zones where the ground motion was amplified because of local geological and geomorphological settings. The goal of the investigation was to return amplification coefficients to local authorities for the post-seismic reconstruction and repairing of pre-existing buildings, by examining the seismic behaviour of the most damaged 60 villages. The analysis consisted in the application of well known computer codes and the results were arranged as reference table, used to assign the amplification coefficients to the rest of damaged localities.The present study has the aim of evaluating the accuracy of that methodology, following a completely different approach. The actual damages, detected by an aerial photo interpretation, are compared to the theoretical damages estimated through empirical curves, obtained from the analysis of recent Italian earthquakes. This approach was reliable enough to calibrate the results of the microzoning study and appropriate when an immediate assessment of the damage is required, to assign funds and estimate the amplification zones, that need to be investigated in finer detail.     

岱海生物群落结构的演变及其对渔业发展的影响

岱海水生生物种类贫乏,生物量低,渔产力不高,优化岱海水体生物群落组成,引种耐低温、耐盐碱的水生植和藻类,改善水体环境调整鱼类种群结构是渔业发展的重要措施。     

Bestimmungsschlüssel für Bodenseefische

Difficulties and misunderstandings in the classification of the fish species of Lake Constance, especially of Cyprinidae and Coregoninae, induced us to work out a determination key. When basing a classification only on the number of gill rakers it was impossible to determine the Coregoninae. Further characteristics, even ones influenced by external factors, have been used, because these were combined contemporaneously with different genetic behaviour. The distribution of the Lake Constance Coregoninae on the 5 or 6 species recognized today has been corrected.