不同生态型芦苇种群对盐胁迫的生长和光合特性

土壤盐渍化是影响我国土壤利用效率的主要因素之一,芦苇是改良土壤盐渍化的良好实验材料,但芦苇有着多种的生态型,比较各生态型芦苇的耐盐差异成为亟待解决的问题。通过设置淡水(0.00%)与加盐(质量浓度2.00%)处理控制实验,测量芦苇的生长指标和光合指标,比较河口型芦苇与内陆型芦苇耐盐性,寻找合适生态型的芦苇作为改良土壤盐渍化的生物材料。在实验中,与淡水条件相比,加盐(2.00%)处理条件下,河口型芦苇和内陆型芦苇的株高(height)、蒸腾速率(E)均显著性下降,但是两种生态型的芦苇的水分利用效率(WUE)明显提高;河口型的芦苇相对生长速率(RGR)和气孔导度(Gs)都明显高于内陆型芦苇。在淡水环境中,河口型芦苇的相对生长速率(RGR)和净光合速率(A)都显著性地高于内陆型芦苇。结果表明两种生态型的芦苇在进化过程中存在一定程度上的分化,盐胁迫会抑制两种芦苇的生长,两种生态型芦苇的相对生长速率和气孔导度在盐胁迫下出现明显地差异,表明两种生态型的芦苇对盐度的响应机制有所差异。相比于内陆型芦苇,河口型芦苇有着更强的耐盐性,内陆型及河口型芦苇的表型性状差异主要是由于其原生境的差异所决定的。     

Effects of cutting Phragmites australis along an inundation gradient, with implications for managing reed encroachment in a South African estuarine lake system

Substantive encroachment of Phragmites australis (common reed) occurred since the 1970s in the Wilderness estuarine lakes, a National Park and Ramsar site. Cutting of reeds in late summer as a means of controlling reed encroachment was investigated under three different inundation regimes, termed ‘wet zone’ (permanently inundated), ‘moist zone’ (infrequently inundated) and ‘dry zone’ (rarely inundated). The effects of a single annual cut were furthermore compared to those of two successive annual cuts. Without cutting, wet zones had thinner and shorter, but more abundant reeds than drier zones. Cutting in dry and moist zones resulted after one year in more, but shorter and thinner reeds, whereas in wet zones reeds were almost eliminated. After two years, reeds in wet zones had not recovered from the first annual cut. In moist and dry zones, a second annual cut did not result in amplified detrimental effects on reeds. Throughout the experiment, moisture zone was the factor with the largest effect, cutting had the second largest impact, and inter-annual variation was relatively unimportant. We have demonstrated that cutting alone has minimal long-term effect on above-ground reed biomass, whereas reed growth and survivorship can be strongly suppressed through cutting in late-summer in conjunction with inundation with moderately saline water (5.0–7.5 g kg⁻¹). Cut reeds must remain completely inundated for at least a four-week period, or else emerging shoots should be re-cut below the water level. Cut material should be removed from the treatment site. Whenever possible, cutting and inundation should be undertaken to coincide with periods when salinity levels of surface waters are higher. It is foreseen that reed management in the Wilderness Lakes would have positive effects on other biota by countering progression towards single species domination of wetland plant communities and reinstating exposed sandbanks which are extensively utilised by resident and migratory waterbirds.     

Impact of winter reed harvesting and burning on the nutrient economy of reed beds

The fringing reeds (Phragmites australis (Cav.) Trin. ex Steud., Poaceae) at Lake Constance-Untersee were mown or burnt in winter thereby drastically reducing the addition of decomposable organic matter to the sediment. The purpose of this study was to test whether or not this management significantly decreased the contents of organic matter and nutrients in the surface sediment layer and if the oxygen conditions in the withinreed water body improved. Hypotheses were tested by monitoring 6 treated reed beds and 3 reference fields over a period of up to 4 years. The sediment/water system of reed beds was found to be well buffered against the removal of the current year's crop of dead Phragmites straw, because only slight, and mostly insignificant, differences between treated and untreated reeds were detected. Hence, the benefit of winter reed harvesting to reduce nutrient overloading of the reed-belts and the die-back of reeds remains dubious.     

Claviceps arundinis identification and its role in the die-back syndrome of Phragmites australis populations in central Italy

Common reed Phragmites australis (Cav.) Trin. ex Steud. is one of the most widely distributed angiosperms with important ecological functions. In recent decades, it has been affected by a severe decline known as reed die-back syndrome (RDBS), the causal factors of which are still under investigation. Among the biotic factors that influence the dynamic of the reed population, the role of microorganisms is still poorly understood. During surveys carried out on P. australis populations in Central Italy, Claviceps-like sclerotia were detected: is Claviceps infection related to P. australis sexual reproduction and seed production? Could Claviceps infection be involved in the RDBS? These are the questions that we address. We characterized the sclerotia at the morphological, molecular, and chemical level and we demonstrated that they belong to Claviceps arundinis Pa?outová &; M. Kola?ík. To our knowledge, this is the first report of C. arundinis on P. australis in Italy. Furthermore, the association of C. arundinis with RDBS was evaluated considering a set of macromorphological traits generally related to RDBS, such as P. australis clumping habit, culm height and diameter. No correlation was seen between the occurrence of C. arundinis and the declining status of reed populations.     

Changes inPhragmites australis in south-eastern Australia: A habitat assessment

The status of common reed (Phragmites australis) in south-eastern Australia was assessed by considering its physical habitat.Phragmites habitats were categorized into three types — wetland, riverine and estuarine and all three showed negative change (loss, degradation) since European settlement. However, there were also instances of positive (new, re-establishment) changes. Integrating these negative and positive changes at the catchment scale for the Murrumbidgee River, suggests a re-distribution ofPhragmites is occurring, and this may be true for other rivers managed for irrigation. Agriculture appears to be the principal cause ofPhragmites australis losses in eastern Australia. There is no evidence to date of reed decline in Australia like that in parts of Europe, nor of expansion as in the coastal wetlands of the United States of America. The habitat approach used here was qualitative but this was necessary due to the lack of historical data onPhragmites and to the limited number of case studies. However, quantitative studies are needed, in order to understand how river health and aquatic biodiversity are being affected.     

Assessment of aquatic and terrestrial reed (Phragmites australis) stands

A survey of recent publications shows that research on Phragmites australishas oftenapplied character because of the considerableecological and economic significance of the species.The main applications are water treatment, agriculture(food production or weed control) and natureconservation. In Europe, most research on natural reedstands has been motivated by reed die-back and effortstowards protection or restoration. Reed progressionand reed control have been the main concerns in otherparts of the world, and reed progression has alsoreceived increasing attention in Europe. While reeddie-back generally affects aquatic stands, progressioncan occur at both terrestrial and aquatic sites, andit can be desired (e.g. lake shore restoration)or unwanted (e.g. in species-rich fens ormarshes). Therefore, reed stands need to be assessedindividually to decide on management aims andappropriate methods. The varying status of Phragmites australisformed the background of the`European Reed Conference' held in Zürich/Switzerlandin October 1998. The seven contributions published inthis special issue are introduced with particularreference to differences between aquatic andterrestrial reed stands and to approaches used in theirassessment.     

Management Impacts on Stand Structure of Lakeshore Phragmites Reeds

Many lakeside Phragmites australis reeds are frequently harvested or burnt in winter for several purposes like extraction of raw material, natural preservation or facilitation of professional fishing or fish breeding. The question is, whether these practices support a sustainable development of the reeds. Data from a long term monitoring program at Lake Constance (Germany) demonstrate that culm morphology, stand structure and aboveground peak biomass are strongly influenced by the treatment. Winter harvested and burnt reeds exhibited higher culm densities (+76% of the untreated controls), and a higher peak biomass (+13%). The mean culm height was reduced by −13%. The percentage of insect infested shoots was 8.8% of the total shoot population, compared with 20.1% of the untreated controls. Consecutive harvesting treatments intensified these effects. In the first two years after the treatment had stopped the reed stands showed an ‘overshoot’ biomass production, and a strong trend towards the features of the untreated controls. The possible mechanisms (mechanical damage, frost kill of the growth tips and breaking of the apical dominance) are discussed. It is concluded that winter harvesting and burning treatments make the reeds more susceptible against some environmental hazards, and should therefore applied with precaution on the basis of a close examination of risks and benefits.     

Factors affecting willow leaf beetles (Phratora vulgatissima) when selecting overwintering sites

Abstract

• 1 Leaf beetles are major pests in willow plantations used as short‐rotation coppice for biomass production. The beetles overwinter mainly outside the plantations. An understanding of the factors affecting adult leaf beetles seeking overwintering sites may provide information that could be valuable when developing methods to control the beetles.
• 2 We conducted a field experiment in a willow plantation with a high abundance of the leaf beetle, Phratora vulgatissima. We positioned overwintering constructions (OWCs) made out of bundles of reed (Phragmites australis) outside the plantation.
• 3 Leaf beetles preferred (i) to fly towards silhouettes; (ii) OWCs positioned 1.5 m above the ground compared with ones 0.5 m above the ground; (iii) OWCs orientated vertically compared with OWCs orientated horizontally; and (iv) reeds of a diameter of approximately 5 mm.
• 4 Leaf beetle size was not correlated with reed diameter.
• 5 It is concluded that the leaf beetle P. vulgatissima selects an overwintering site based on factors at both larger and smaller scales. The possibilities for using OWCs made of reed bundles as tools to monitor and control are discussed.

     

Effects of lead contamination on the clonal propagative ability of Phragmites australis (common reed) grown in wet and dry environments

Clonal propagation is important for the survival and maintenance of the common reed Phragmites australis. Pot culture experiments were conducted to investigate the effects of lead (Pb) concentration (0, 500, 1500, 3000, 4500 mg·kg^?1) and water stress on the clonal reproductive ability of this species. The Pb concentration found in plant organs, in decreasing order, was roots >shoots >rhizomes. There was a negative relationship between the growth of clonal propagative modules (excluding axillary shoot buds) and Pb concentrations, which caused a decrease in biomass, rhizome growth and number of axillary and apical rhizome buds. Daughter axillary shoots exhibited a tolerance strategy, with no significant change in their number; the axillary and apical rhizome buds, daughter apical rhizome shoots and rhizomes exhibited compensatory growth during the late stage of Pb (excluding 4500 mg·kg^?1) treatment in a wet environment. Pb applications above 500 mg·kg^?1 reduced these parameters significantly in the drought treatment, except for the number of axillary shoot buds, which did not change. Our results indicate that clonal propagative resistance to Pb contamination can occur via tolerance strategies, compensatory growth and a Pb allocation strategy, enabling these reeds to maintain population stability in wet environments. However, clonal modular growth and reproductive ability were inhibited significantly by the interaction between drought and Pb, which would cause a decline in P. australis populations in a dry environment. Lead concentrations of 4500 and 500 mg·kg^?1 in soils might meet or exceed the Pb tolerance threshold of clonally propagated reeds in wet and dry environments, respectively.     

Sulphide utilization and injuries in hypoxic roots and rhizomes of common reed (Phragmites australis)

The presented investigations have been carried out in order to estimate toxic sulphide levels and to examine detoxification capabilities in roots and rhizomes of the common reed (Phragmites australis). Underground organs of common reed are sensitive towards sulphide above 1 mM applied exogenously under hypoxia. However, certain tolerance may be achieved by sulphide detoxification. Accumulated sulphide is partially used for the synthesis of non-toxic thiols, mainly glutathione. But the detoxification capacity of the underground organs is limited. Maximum concentrations of thiols are about 60 nmol/g^?1 fw in roots and 300 nmol/g^?1 fw in rhizomes. Energy metabolism is considerably affected by low sulphide concentrations of 1 mM for 4 days, and immediately disturbed by increased concentrations up to 6 mM sulphide. Adenylate energy charge, total adenylates, posthypoxic respiration, and fermentation capacity decrease significantly. Roots are more sensitive than rhizomes.     

Genetics,novel weapons and rhizospheric microcosmal signaling in the invasion of Phragmites australis

Chemical communication and perception strategies between plants are highly sophisticated but are only partly understood. Among the different interactions, the suppressive interaction of a class of chemicals released by one plant through root exudates against the neighbouring plants (allelopathy) have been implicated in the invasiveness of many exotic weedy species. Phragmites australis (common reed) is one of the dominant colonizers of the North American wetland marshes and exhibits invasive behavior by virtually replacing the entire native vegetation in its niche. Recently, by adopting a systematic bioassay driven approach we elucidated the role of root derived allelopathy as one of the important mechanisms by which P. australis exerts its invasive behavior. Additionally, our recent preliminary data indicates the involvement of rhizobacterial signaling in the invasive success of P. australis. A better understanding of biochemical weaponry used by P. australis will aid scientists and technologists in addressing the impact of root secretions in invasiveness of weedy species and thus promote a more informed environmental stewardship.Key words: Phragmites australis, roots, phytotoxicity, reactive oxygen species, microtubules, microcosm     

敦煌阳关湿地芦苇叶性状对土壤水分的响应

为了了解干旱区湿地不同水分梯度下芦苇叶性状的构建模式及对不同水分环境的适应策略差异性,以敦煌阳关渥洼池湿地植物芦苇(Phragmites australis)为研究对象,分析不同水分梯度下芦苇叶性状对土壤水分的响应。结果表明:(1)低水分梯度下的叶厚度(LT)和叶片磷含量(LPC)显著高于中、高水分梯度(P0.05),高水分梯度下的叶碳含量(LCC)也显著高于中、低水分梯度(P0.05)。(2)芦苇叶性状之间的关系也因水分的变化而有所不同。就整体而言,叶片碳含量与叶干物质含量(LDMC)极显著正相关(P0.01);叶厚度与叶片磷含量极显著正相关(P0.01),比叶面积(SLA)与叶氮含量(LNC)极显著正相关(P0.01)、与叶碳氮比(C/N)极显著负相关(P0.01)。(3)在水分作为限制因素的条件下,叶片碳含量与比叶面积对水分的响应最为突出。土壤含水量与叶厚度、叶碳含量和叶片磷含量均显著负相关(P0.05)。芦苇在低水分环境下采取高收入低投入的积极型生存策略,高水分下则采取低获取高消耗的保守型生存策略,说明了芦苇在适应异质生境的自我调节机制。     

Dynamics of common reed (Phragmites australisTrin.) in Swiss fens with different management

Dynamics of common reed (Phragmites australisTrin.) in Central Europe have so far mostly beeninvestigated in connection with studies on reed`die-back' along lake shores. However, there hasrecently been increasing concern about reed expansionat terrestrial sites, such as fens and wet grasslands.In this paper we report on the results of fourseparate studies which monitored reed dynamics inSwiss fens with various mowing regimes over a periodof 4 to 15 years. The first study compared unmownplots with plots mown in winter in a triennialrotation; the second one included unmown plots, plotsmown in summer, and plots mown in winter; the thirdone compared plots mown in June and September withplots only mown in September; the fourth studyinvestigated only plots mown in September. Shootnumber and shoot size were recorded in permanentquadrats. In all studies the performance of P.australisfluctuated without trend or tended todecrease during the period investigated. Thedecreasing tendency concerned shoot size rather thanshoot number, and within a given study it was strongerfor plots with initially taller shoots. The variousmowing regimes did hardly influence these changes.Mowing in winter every three years reduced shoot sizein the year after mowing, but not on the long term.Mowing every year in late summer reduced the shootsize compared with unmown plots on the short term, butthis effect almost disappeared on the long term, aftermowing had become biennial. Mowing in June (inaddition to in September) caused no noticeableeffects. We conclude that other factors (e.g. weatherconditions, competition, or population processes) aremore important than management in determining theabundance of P. australisin the fen communitiesinvestigated here, although long-term effects ofmowing in summer still need more investigation. As apractical consequence it is suggested that at siteswhich are not strongly dominated by P.australis, as most of those investigated here,reducing the performance of this species should notconstitute a major target of nature conservationmanagement, nor can its dynamics be used as anindicator for management success before underlyingcauses are better understood.     

Freshwater wetlands: fertile grounds for the invasive Phragmites australis in a climate change context

Climate change will likely affect flooding regimes, which have a large influence on the functioning of freshwater riparian wetlands. Low water levels predicted for several fluvial systems make wetlands especially vulnerable to the spread of invaders, such as the common reed (Phragmites australis), one of the most invasive species in North America. We developed a model to map the distribution of potential germination grounds of the common reed in freshwater wetlands of the St. Lawrence River (Québec, Canada) under current climate conditions and used this model to predict their future distribution under two climate change scenarios simulated for 2050. We gathered historical and recent (remote sensing) data on the distribution of common reed stands for model calibration and validation purposes, then determined the parameters controlling the species establishment by seed. A two‐dimensional model and the identified parameters were used to simulate the current (2010) and future (2050) distribution of germination grounds. Common reed stands are not widespread along the St. Lawrence River (212 ha), but our model suggests that current climate conditions are already conducive to considerable further expansion (>16,000 ha). Climate change may also exacerbate the expansion, particularly if river water levels drop, which will expose large bare areas propitious to seed germination. This phenomenon may be particularly important in one sector of the river, where existing common reed stands could increase their areas by a factor of 100, potentially creating the most extensive reedbed complex in North America. After colonizing salt and brackishwater marshes, the common reed could considerably expand into the freshwater marshes of North America which cover several million hectares. The effects of common reed expansion on biodiversity are difficult to predict, but likely to be highly deleterious given the competitiveness of the invader and the biological richness of freshwater wetlands.     

基于野外调查和同质种植园实验的芦苇植物功能性状变异研究

研究表型可塑性和遗传变异在植物表型分化中的相对作用,有助于预测全球环境变化下的植物群落组成和生态系统功能的变化。芦苇（Phragmites australis）是全球性广布的草本植物,种内变异丰富,在我国西北和东部均存在多个分化稳定的生态型,但中国芦苇在更大尺度上的表型研究还非常匮乏。将位于黄河上游的宁夏平原和黄河下游的黄河三角洲作为研究区域,通过野外调查和同质种植园实验对芦苇自然种群的植物功能性状变异进行观测。结果表明,无论在野外还是同质种植园,黄河三角洲芦苇的基径、叶长和叶宽均显著大于宁夏平原芦苇,说明两个地区的芦苇种群之间存在着受遗传决定的表型分化,这可能与两个地区间的降水等气候差异有关。在野外,宁夏芦苇的株高和叶厚显著大于黄河三角洲芦苇,但在同质园中差异消失或相反,说明株高、叶厚受环境影响较大,表型可塑性也是芦苇适应环境变化的重要机制。在同质种植园中,宁夏平原芦苇的叶片氮磷含量较低,但株数却显著多于黄河三角洲芦苇,反映了不同地区芦苇之间存在不同的适应策略,宁夏平原芦苇更偏向于高扩散率的杂草策略,而黄河三角洲芦苇更偏向于竞争策略。此外,宁夏平原芦苇的株高、叶长两个性状以及基径-比叶面积相关性在野外和同质园两个环境中存在一致性,表明了性状变异和权衡策略的遗传稳定性。综上,位于黄河上下游的芦苇种群间存在着适应性分化,这是表型可塑性和遗传变异共同作用的结果,不同来源芦苇对全球变化下的多重环境因子的响应还需要进一步研究。     

Seeds contribute strongly to the spread of the invasive genotype of the common reed (<Emphasis Type="Italic">Phragmites australis</Emphasis>)

The introduced subspecies of the common reed (Phragmites australis (Cav.) Trin. ex Steud. subsp. australis; Poaceae) is considered one of the most invasive plants in North American wetlands. Given its relatively low seed set and its tremendous capacity to spread via stolons or rhizomes, it has generally been thought that the spread of vegetative diaspores was responsible for the establishment of new populations. To test this hypothesis, we sampled a single plant from each of 345 visually-distinct common reed stands located along the shores of Lake St. François (southern Quebec, Canada). With a set of six nuclear microsatellite markers, we distinguished 134 different genotypes. The number of individuals sharing the same genotype ranged from one to 16, and averaged 2.1. Most genotypes were encountered only once. We examined the spatial distribution of the most frequent genotypes and found little evidence of clusters along the lakeshore. These data contradict the hypothesis that a common reed invasion is initiated by the introduction of vegetative diaspores from a few clones. Rather, they clearly support the alternative hypothesis that seeds were the primary diaspores responsible for the establishment of common reed populations.     

Why do reed beds decline and fail to re‐establish? A case study of Dutch peat lakes

相似文献   

Genetic and epigenetic changes during the invasion of a cosmopolitan species (Phragmites australis)

While many introduced invasive species can increase genetic diversity through multiple introductions and/or hybridization to colonize successfully in new environments, others with low genetic diversity have to persist by alternative mechanisms such as epigenetic variation. Given that Phragmites australis is a cosmopolitan reed growing in a wide range of habitats and its invasion history, especially in North America, has been relatively well studied, it provides an ideal system for studying the role and relationship of genetic and epigenetic variation in biological invasions. We used amplified fragment length polymorphism (AFLP) and methylation‐sensitive (MS) AFLP methods to evaluate genetic and epigenetic diversity and structure in groups of the common reed across its range in the world. Evidence from analysis of molecular variance (AMOVA) based on AFLP and MS‐AFLP data supported the previous conclusion that the invasive introduced populations of P. australis in North America were from European and Mediterranean regions. In the Gulf Coast region, the introduced group harbored a high level of genetic variation relative to originating group from its native location, and it showed epigenetic diversity equal to that of the native group, if not higher, while the introduced group held lower genetic diversity than the native. In the Great Lakes region, the native group displayed very low genetic and epigenetic variation, and the introduced one showed slightly lower genetic and epigenetic diversity than the original one. Unexpectedly, AMOVA and principal component analysis did not demonstrate any epigenetic convergence between native and introduced groups before genetic convergence. Our results suggested that intertwined changes in genetic and epigenetic variation were involved in the invasion success in North America. Although our study did not provide strong evidence proving the importance of epigenetic variation prior to genetic, it implied the similar role of stable epigenetic diversity to genetic diversity in the adaptation of P. australis to local environment.     

Physiological consequences of mowing and burning of Phragmites australisstands for rhizome ventilation and amino acid metabolism

Mowing and burning of Phragmitesaustralis-stands have been recommended in the recentliterature as management tools for both protection andcontrol, and both favourable and detrimental effectsof these treatments were actually observed. This studyaims to clarify this apparent contradiction using anew physiological approach. Reed stands in thebiosphere reserves of Trebon (Czech Republic) and theDanube Delta (Romania) were investigated usingparameters of convective ventilation and amino acidpatterns. Flooded mown reed and unflooded burned reedwas compared to unmanaged control stands withcomparable hydrology and trophic level. Managementtook place in winter. The elimination of old culmsthrough mowing resulted in a lower ventilationefficiency due to a high counterpressure of rhizomes.The corresponding gas flow rates were reduced to 38%of the value in control stands, indicating a stronglyimpaired oxygen supply to basal and below-ground plantparts after mowing. Concomitantly, significantlyincreased levels of alanine and gamma-aminobutyricacid in basal culm internodes of shoots were measuredas signs of a metabolic shift due to hypoxic stress.Conversely, shoot loss by burning (without flooding)did not diminish ventilation efficiency and gas flowrate, i.e. oxygen supply to buried organs wasunaffected. Correspondingly, the level ofhypoxia-indicating amino acids (alanine,gamma-aminobutyric acid) did not indicate more severeoxygen deficiency in basal and below-ground plantparts of burned reed. It is concluded that the impactof mowing and burning on P. australisstronglydepends on the water level and on whether or notflooding occurs after the treatment. The mechanismresponsible for detrimental effects is probablyimpaired convective ventilation followed by hypoxia inbasal plant parts. This aspect should be taken intoaccount when mowing or burning in winter are used asmanagement tools for wetlands.     

Flooding events and rising water temperatures increase the significance of the reed pathogen <Emphasis Type="Italic">Pythium phragmitis</Emphasis> as a contributing factor in the decline of <Emphasis Type="Italic">Phragmites australis</Emphasis>

Pythium species are economically significant soilborne plant pathogens with worldwide distribution, causing seedling damping-off or root rot diseases. Pythium phragmitis is a newly described pathogen of common reed (Phragmites australis), widespread in the reed-belt of Lake Constance, Germany. It is highly aggressive towards reed leaves and seedlings, but obviously does not affect roots. In the context of ‘reed decline’ phenomena, P. phragmitis infection of reed inundated during flooding events may be of particular significance. We could show that flooding itself is not necessarily detrimental for reed plants. In the presence of the pathogen, however, most submerged leaves and plants were killed within several weeks. Clipped plants did not show regrowth in the Pythium infested treatments. Significant losses in assimilating leaf area of reeds could, thus, be the result of Pythium infection rather than of flooding alone. Therefore, we suggest that the combination of extended flooding and the presence of P. phragmitis might considerably contribute to ‘reed decline’ at Lake Constance. In parallel, we could show that pathogenicity and spread of this species are considerably favoured by rising temperatures. Since an increase in average water temperature has been found for Lake Constance, we propose that P. phragmitis could be an important factor in the dieback of reed stands likely to be promoted by predicted climate change phenomena.