Lakeshore Vegetation Research Articles

Peatland restoration pathways to mitigate greenhouse gas emissions and retain peat carbon

Peatlands play a crucial role in the global carbon (C) cycle, making their restoration a key strategy for mitigating greenhouse gas (GHG) emissions and retaining C. This study analyses the most common restoration pathways employed in boreal and temperate peatlands, potentially applicable in tropical peat swamp forests. Our analysis focuses on the GHG emissions and C retention potential of the restoration measures. To assess the C stock change in restored (rewetted) peatlands and afforested peatlands with continuous drainage, we adopt a conceptual approach that considers short-term C capture (GHG exchange between the atmosphere and the peatland ecosystem) and long-term C sequestration in peat. The primary criterion of our conceptual model is the capacity of restoration measures to capture C and reduce GHG emissions. Our findings indicate that carbon dioxide (CO2) is the most influential part of long-term climate impact of restored peatlands, whereas moderate methane (CH4) emissions and low N2O fluxes are relatively unimportant. However, lateral losses of dissolved and particulate C in water can account up to a half of the total C stock change. Among the restored peatland types, Sphagnum paludiculture showed the highest CO2 capture, followed by shallow lakes and reed/grass paludiculture. Shallow lakeshore vegetation in restored peatlands can reduce CO2 emissions and sequester C but still emit CH4, particularly during the first 20 years after restoration. Our conceptual modelling approach reveals that over a 300-year period, under stable climate conditions, drained bog forests can lose up to 50% of initial C content. In managed (regularly harvested) and continuously drained peatland forests, C accumulation in biomass and litter input does not compensate C losses from peat. In contrast, rewetted unmanaged peatland forests are turning into a persistent C sink. The modelling results emphasized the importance of long-term C balance analysis which considers soil C accumulation, moving beyond the short-term C cycling between vegetation and the atmosphere.

Identifying the critical lakeshore zone to optimize landscape factors for improved lake water quality in a semi-arid region of Northeastern China

The degradation of water quality and decline in purification capacity of lakeshore zones due to anthropogenic activities and climate change is a growing concern in China. The identification of the critical width of the lakeshore zone remains a challenge due to natural geographic features and pollutant types, that is why a general identification approach has yet to be developed. To facilitate the planning of lakeshore restoration plans, it becomes necessary to conduct studies focusing on the development of relationships between water quality and landscape factors within the lakeshore zone in different regions. In this study, spatio-temporal patterns of water quality of 49 lakes in Western Jilin Province, China, were determined through field monitoring from 2015 to 2019. Multivariate statistical methods were applied to quantitatively identify the relationships between lakes water quality and landscape factors within lakeshore zones of different widths. The results indicated that nitrogen (N) contributed more to eutrophication, while fluoride concentrations were found to be abnormally high. Furthermore, the width of the lakeshore zone was found to have a significant impact on water quality, with a critical width of 150 m having the greatest effect. Cropland and saline land explained almost 50% of the water quality variability throughout different seasons. The results also revealed that dual control of N and phosphorus (P) will be required to prevent eutrophication in the study area. Agricultural activities and severe soil salinization were identified as the main causes of diffuse pollution. The establishment of a width threshold identification framework for lakeshore zones is not only of great significance for development of scientific and acceptable restoration plans for lakeshore vegetation filters in ecologically vulnerable areas of western Jilin, but should also provide an effective and user-friendly tool for implementing diffuse pollution control.

Lakeshore vegetation: More resilient towards human recreation than we think?

AbstractLakes and their shoreline vegetation are rich in biodiversity and provide multiple functions and habitats for fauna and flora. Humans are attracted by the scenic beauty of these ecosystems and the possibilities for recreational activities they offer. However, the use of lakes for recreational activities can lead to disturbance of vegetation, threatening the integrity and functionality of shoreline areas. Recent literature reviews revealed that impacts of the seemingly harmless activities bathing and lingering on the shore on lakeshore vegetation are poorly understood. In this study, we analysed the effects of shoreline use connected with bathing on the structure, composition and diversity of lakeshore vegetation. Vegetation relevés were recorded in 10 bathing and 10 adjacent control sites in the nature park ‘Dahme‐Heideseen’ (Brandenburg, Germany). In addition visitor counts were performed. The species composition and the cover of herbaceous and shrub vegetation differed between bathing and control sites, but all sites had a high percentage of plant species not typical for the community. The vegetation parameters did not correlate with visitor counts. The results indicate that the present visitor intensity in the nature park does not impact the vegetation severely.

Responses of lakeshore herbaceous plant guilds to altered water level fluctuations in Yangtze floodplain lakes, China

River–lake disconnection has led to alterations in natural water level fluctuations (WLFs) in lakes along the middle and lower reaches of the Yangtze River to various extents. To predict the effects of altered WLFs on lakeshore vegetation, lakeshore herbaceous plant guilds (LPGs) in six Yangtze floodplain lakes were classified in this study. The lakeshore herbaceous plant distribution pattern, main influencing factors, and responses of different LPGs to altered WLFs were analyzed. A total of 130 plant species were identified from the six lakes. With the increase in the amplitude of WLFs, the total species number in the six lakes showed a hump–shaped trend, whereas the lakeshore herbaceous plant coverage showed a positive correlation. The Qili Lake with the largest WLFs had the lowest species number and highest plant coverage. The species numbers, average biomass, and coverage of lakeshore herbaceous plants in all the six lakes were obviously higher in spring than in autumn. The lakeshore herbaceous plants in the six lakes were classified into eight guilds. Small differences in pH, organic matter, total nitrogen, and total phosphorus were detected in the substrate among the eight LPGs, but obvious differences in soil moisture content and duration and depth of submergence were observed. The canonical correspondence analysis showed that the main environmental factors affecting the distribution of different LPGs in the six lakes in spring and autumn were the amplitude of WLFs and duration of submergence. The regression analyses showed that the biomass of perennial mesophyte with erect stem guild and perennial hygrophyte with well–developed rhizome guild responded sensitively to alterations in the amplitude of WLFs and duration of submergence, and the guilds could be considered as indicator groups at a regional scale. Morphological parameters such as plant height, stem diameter, leaf thickness, and specific leaf area of the eight LPGs showed no significant linear relationships with the increase in WLFs. The use of these parameters in the evaluations of alterations in WLFs needs to be further analyzed.

Controls of precipitation and vegetation variability on the NE Tibetan Plateau during the late Pliocene warmth (~3.5–3.0 Ma)

To better understand precipitation variability in a warmer-than-present world with elevated atmospheric CO2 concentrations, this study presents high-resolution palynological and element geochemical analyses of a late Pliocene drill core (3.5–3.0 Ma) from the today hyperarid Qaidam Basin on the north-eastern Tibetan Plateau. Quantitative rainfall estimates based on modern pollen-climate transfer functions indicate a 10-fold higher annual rainfall during the mid-Piacenzian Warm Period (mPWP; 3.264–3.025 Ma) than today, with values of 300–400 mm/a. Throughout the late Pliocene, the Qaidam Basin was covered with a temperate semi-desert shrubland. Varying percentages of the local lakeshore vegetation and long-distance arboreal pollen, as well as fluctuations in carbonate-silicate geochemistry, indicate a highly variable rainfall. Our study suggests that precipitation in the northern Qaidam Basin was primarily controlled by an East Asian Monsoon system (EAMS) that was located further north than today. Spectral analysis of the Artemisia/Chenopodiaceae (A/C) pollen ratio indicates an orbitally controlled cyclicity with a strong link between moisture availability and insolation forcing. A decline in precipitation before the end of the mPWP at ca. 3.15 Ma is likely to be linked to cooling in the North Atlantic and initial Northern Hemisphere ice-sheet build-up. Our study identifies NH insolation and ice-sheet advances as major controls of the late Pliocene variability and strength of the EAMS in semi-arid NW-China.

Analysis of pollen across the surface sediments of Lake Imbradas, Lithuania

AbstractIn conventional pollen analysis, usually one sediment core per basin is analyzed to reconstruct past environmental conditions. This approach does not consider spatial heterogeneity of pollen assemblages, and assumes that one analyzed location is representative of the whole basin. To improve the spatial resolution of fossil pollen studies, further knowledge of the factors influencing variations in pollen assemblages throughout a basin is needed. We examined the spatial heterogeneity of pollen assemblages from 45 lacustrine surface samples from a lake with relatively simple hydrology and compared this dense network of surface pollen samples with the Lithuanian State Forest Service arboreal vegetation database. Calculations of pollen productivity at different locations across the lake revealed variations in the behavior of a pollen-vegetation relationship model in different parts of the basin. Our findings suggest that the model underestimated pollen contributions from the lakeshore vegetation. We demonstrate that detailed investigations of surface pollen as a step prior to fossil pollen investigations can provide useful insights, including understanding the influence of sedimentation rate on modelling results and spatial variations in pollen composition, thus providing guidance for site selection for fossil pollen studies.

Late Oligocene leaf and pollen flora of Southwestern Siberia: taxonomy, biogeography and palaeoenvironments

ABSTRACT Late Oligocene leaf assemblages from four sites in Southwestern Siberia (Kurgan, Tyumen, Omsk oblasts) are described. Twenty-three leaf taxa and 3 reproductive structures represent local vegetation of a lake (Salvinia, Typha, Phragmites, Nelumbo, Hemitrapa, Liquidambar, Pterocarya, Alnus, Populus, Salix, Nyssa). Additionally, 57 spore and pollen taxa were recorded from one site (Shish River). Gymnosperms dominate the assemblage with ~30% Pinaceae and ~25% taxodiaceous (papillate) Cupressaceae pollen. Ferns and peat mosses (Sphagnaceae) comprised ~6%. Angiosperms were dominated by Fagaceae, Betulaceae, Juglandaceae and Ulmus and comprised a few exotic elements (Liquidambar, Eucommia, Nyssa, Symplocos); scarce herbaceous plants reflect lakeshore vegetation. The flora of the Turgay type comprised old elements (Nelumbo protospeciosa, Liquidambar europaea, taxodiaceous/papillate Cupressaceae, Quercus sect. Protobalanus) and taxa present in Siberia/Kazakhstan during the Paleogene with later arrivals in Europe (Ulmus pyramidalis, Quercus pseudocastanea, Alnus julianiformis, Byttneriophyllum tiliifolium). A few taxa were endemic in the late Oligocene of western Siberia (Trapa praeconocarpa, Platycrater iljinskajae sp. nov.). Combined macrofossil and palynological evidence places the Shish River site flora into the late Oligocene Zhuravka (Turtas) Formation. Floras of similar composition from western Eurasia are commonly middle Miocene or younger in age highlighting the dynamic spatiotemporal evolution of temperate Eurasian floras during the Cenozoic.

Hydrological and soil physiochemical variables determine the rhizospheric microbiota in subtropical lakeshore areas.

BackgroundDue to intensive sluice construction and other human disturbances, lakeshore vegetation has been destroyed and ecosystems greatly changed. Rhizospheric microbiota constitute a key part of a functioning rhizosphere ecosystem. Maintaining rhizosphere microbial diversity is a central, critical issue for sustaining these rhizospheric microbiota functions and associated ecosystem services. However, the community composition and abiotic factors influencing rhizospheric microbiota in lakeshore remain largely understudied.MethodsThe spatiotemporal composition of lakeshore rhizospheric microbiota and the factors shaping them were seasonally investigated in three subtropical floodplain lakes (Lake Chaohu, Lake Wuchang, and Lake Dahuchi) along the Yangtze River in China through 16S rRNA amplicon high-throughput sequencing.ResultsOur results showed that four archaeal and 21 bacterial phyla (97.04 ± 0.25% of total sequences) dominated the rhizospheric microbiota communities of three lakeshore areas. Moreover, we uncovered significant differences among rhizospheric microbiota among the lakes, seasons, and average submerged depths. The Acidobacteria, Actinobacteria, Bacteroidetes, Bathyarchaeota, Gemmatimonadetes, and Proteobacteria differed significantly among the three lakes, with more than half of these dominant phyla showing significant changes in abundance between seasons, while the DHVEG-6, Ignavibacteriae, Nitrospirae, Spirochaetes, and Zixibacteria varied considerably across the average submerged depths (n = 58 sites in total). Canonical correspondence analyses revealed that the fluctuation range of water level and pH were the most important factors influencing the microbial communities and their dominant microbiota, followed by total nitrogen, moisture, and total phosphorus in soil. These results suggest a suite of hydrological and soil physiochemical variables together governed the differential structuring of rhizospheric microbiota composition among different lakes, seasons, and sampling sites. This work thus provides valuable ecological information to better manage rhizospheric microbiota and protect the vegetation of subtropical lakeshore areas.

Assessment of the status of lake afdera in the danakil depression; afar, Ethiopia

Lake Afdera is a supper saturated saline Lake located in the Danakil Depression, lying below a sea level with the lowest point at –120m. It is a major source of salt extraction in Ethiopia, where the Lake water is pumped to saltpans for solar evaporation. This study was conducted to generate basic information on the impacts of salt mining on the Lake ecology and its biotic resources as well as the surrounding hot springs. Purposive sampling method with semi-structured questionnaire, and focus group discussions were used to generate data. Results indicated that excessive water pumping, pollution, deforestation of lakeshore vegetation and climate change are the most important threats to the Lake and its biodiversity. Majority of the respondents are aware of the negative impact of salt extraction on the Lake and its biodiversity. Because of the absence of lack of awareness and alternative sources of livelihood, however, they still are comfortable to continue business as usual. The absence of active roles of the government and NGOs engaged in the areas of conservation and sustainable use of biodiversity has contributed for over-exploitation and misuse of the resources in the area. Therefore, conducting regular awareness raising and environmental education activities, adoption of restrictive use of resources as well as creating alternative livelihoods and selected nature reserves at carefully selected Lakeshores are of paramount importance to save the Lake and its biodiversity before its eventual demise.

Inundated shore vegetation as habitat for cichlids breeding in a lake subjected to extreme water level fluctuations

Climate change and human overexploitation of freshwaters jointly lead to extreme fluctuations in lake water levels. The latter induces changes in the structure and availability of littoral habitats, thereby affecting fish that reproduce in the littoral zone. Recent increased water level fluctuations in Lake Kinneret, Israel, provided an opportunity to evaluate the impacts of those fluctuations on reproduction of fishes that spawn in the littoral zone. We assessed the use of inundated shore vegetation for reproduction by the common native cichlids, Sarotherodon galilaeus and Oreochromis aureus, in a series of field surveys of reproduction activity in littoral areas with and without inundated vegetation. The cichlids spawned in spring and early summer, when water levels are at their annual maximum and part of the shore vegetation is inundated. Spawning was always in water <2 m depth. Lagoon habitats constituted nesting “hotspots,” with nest densities 3-fold higher than open-shore sites. At open-shore sites, significantly higher nest densities were found in areas with inundated vegetation than in plant-free areas. Juvenile cichlids were significantly more abundant in littoral zone habitats with inundated vegetation. These findings highlight the important role of inundated vegetation, particularly at low lake levels when lagoon habitats are dry. We recommend maintaining water levels that support the existence of lagoons and vegetated littoral habitats. When development of lakeshore vegetation is massive, we recommend selectively removing part of the vegetation to form narrow vegetation-free corridors. In addition, wherever possible the vegetation should be removed to form lagoon-type habitats. Our insights and recommendations are probably applicable to similar situations of seasonal destabilization of lake water levels elsewhere.

Evaluating Sentinel-2 for Lakeshore Habitat Mapping Based on Airborne Hyperspectral Data.

Monitoring of lakeshore ecosystems requires fine-scale information to account for the high biodiversity typically encountered in the land-water ecotone. Sentinel-2 is a satellite with high spatial and spectral resolution and improved revisiting frequency and is expected to have significant potential for habitat mapping and classification of complex lakeshore ecosystems. In this context, investigations of the capabilities of Sentinel-2 in regard to the spatial and spectral dimensions are needed to assess its potential and the quality of the expected output. This study presents the first simulation of the high spatial resolution (i.e., 10 m and 20 m) bands of Sentinel-2 for lakeshore mapping, based on the satellite’s Spectral Response Function and hyperspectral airborne data collected over Lake Balaton, Hungary in August 2010. A comparison of supervised classifications of the simulated products is presented and the information loss from spectral aggregation and spatial upscaling in the context of lakeshore vegetation classification is discussed. We conclude that Sentinel-2 imagery has a strong potential for monitoring fine-scale habitats, such as reed beds.

Impact of marine inundation after a period of drought on the lakeshore vegetation of Lake St Lucia, South Africa: resilience of estuarine vegetation

The shore of Lake St Lucia in the vicinity of Catalina Bay, in the southern part of the lake, receives freshwater input as surface and groundwater seepage from the adjacent elevated coastal plain. Vegetation, water quality and landform were recorded on the lakeshore and on the dry lakebed near one of these seepage zones. This was done along a gradient perpendicular to the lakeshore and along the lakeshore away from the fluvial source of freshwater input. A number of plant communities were found along a gradient of water salinity from the shoreline (fresh water) towards the centre of the lake, and also away from the fluvial input of water (increasingly saline). Species richness decreased with increasing salinity. The first study was conducted in 2006 after a prolonged drought associated with low lake levels and closure of the mouth, and repeated again in 2010 three years after breaching of the estuarine mouth by a tropical cyclone at sea, which caused inundation of the partly dry lakebed with sea water. The vegetation of the lakeshore after these major disturbances was remarkably similar in the two time periods, suggesting rapid recovery near freshwater seepage zones, following an influx of sea water.

Use of inundated lakeshore vegetation by Cichlids for reproduction in Lake Kinneret (Israel)

Use of inundated lakeshore vegetation by Cichlids for reproduction in Lake Kinneret (Israel)

Effects of water level fluctuations on lakeshore vegetation of three subtropical floodplain lakes, China

Vegetation communities in floodplain lakes are adapted to natural water regimes. Construction of sluices or dams between rivers and their floodplain lakes will inevitably lead to great changes in plant communities. In order to evaluate the effects of water level fluctuations (WLFs) on lakeshore vegetation in floodplain lakes of the Yangtze River, a field investigation was conducted in two river-disconnected lakes (Wuchang Lake and Shengjin Lake) and one river-connected lake (Shimen Lake). The results showed that plant species richness was highest in the disconnected Shengjin Lake with intermediate amplitude of WLFs, and lowest in the connected Shimen Lake. Species composition differed among the three lakes and the two disconnected lakes with more similar WLFs exhibiting the greatest similarity. Six plant communities were classified using TWINSPAN. Multivariate analyses showed that the amplitude of WLFs was the most important factor in determining the distribution of lakeshore plants, followed by relative elevation and duration of submergence. Our results provide an eco-hydrological basis for plant restoration in the Yangtze floodplain lakes. We suggest that fluctuating amplitude should be increased in lakes with small WLFs, and small habitats with various hydrological regimes should be created in lakes with large WLFs.

Using ice‐scars as indicators of exposure to physical lakeshore disturbances, Corvette Lake, northern Québec, Canada

ABSTRACTThe hypothesis tested in this study is that ice‐scars recorded by lakeshore tree stands can be used as an integrative proxy indicator of the overall hydrodynamic disturbance regimes affecting northern lakeshores. A 2‐km‐long shore segment was divided into 21 sections according to shore orientation and slope. An ice‐scar chronology and a wave exposure index value were obtained for each shore section. A significant relationship was found between ice‐scar chronology and wave exposure index, which indicates that the mechanical action and physical force of ice activity mainly depend on the same environmental factors determining exposure to wave action (i.e. fetch, wind direction and velocity, and shore slope). The spatial and temporal variability of ice‐scar chronology features also corresponded to the distribution of geomorphological features associated with ice activity along the shoreline. Analysis of the hydrological signal associated with these ice‐scar chronology features indicated that an increase in ice‐push frequency observed in the 1930s can be associated to an increase in wave action related to more frequent spring floods maintaining high lake levels during the ice‐free period. This study demonstrates that ice‐scars have strong potential as proxy indicators of shore exposure and provide a temporal frame to reconstruct the history of lakeshore disturbance regimes at a local scale. Together, ice‐scars and wave exposure index provide essential information to interpret the evolution of lakeshore vegetation mosaics in time and space. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Lakeshore Vegetation Effects on Avian and Anuran Populations

Riparian zones are hotspots of wildlife diversity and also particularly attractive for housing development. Landscaping associated with homes contributes to a wide range of lakeshore vegetation structures. Based on calling surveys in Northern Wisconsin, we investigated effects of lakeshore vegetation structure on bird diversity and frog abundance at three spatial scales: parcel (30 m of shoreline), whole-shore (340 m of shoreline) and whole-lake scales. For parcel and whole-shore scales, we selected sites paired by lake: 10 sites with an intact understory vegetation layer and 10 sites with a cleared understory. Green frog (Rana clamitans) abundances were somewhat related to presence of forest understory at the parcel scale. More clearly, we found higher avian species richness at sites with intact understory vegetation than those without, and increasing richness with canopy coverage. Aerial insect abundances, which were also higher at sites with an intact understory, may help explain bird distributions. Our results suggest that riparian understory landscaping at the scale of individual parcels can alter local bird communities.

Health Hazard Assessment for Native Americans Exposed to the Herbicide Fluridone via the Ingestion of Tules at Clear Lake, California, USA

ABSTRACT This study addresses concerns expressed by Native Americans regarding exposure via the consumption of aquatic vegetation to the herbicide fluridone (active ingredient) used by the California Department of Food and Agriculture (CDFA) Hydrilla Eradication Program in Clear Lake, California. In 2005, the Department monitored lakeshore vegetation, water, and sediment at four locations, before and after seasonal applications of fluridone. Subchronic and chronic exposures were evaluated, and hazard quotients calculated for a worst-case exposure (WCE) scenario. Ingestion rates and other exposure factors were developed in public meetings with tribal members. Environmental sampling found fluridone present at extremely low levels in tule vegetation, water, and sediment. Exposures were four times greater in subchronic timeframes than chronic timeframes; however, hazards were less due to the 25-fold larger reference dose (RfD) used for subchronic calculations: RfD(subchronic) = 2.0 mg/kg-day, RfD(chronic) = 0.08 mg/kg-day. Conservative, child, total daily ingestion (TDI) doses were calculated to be 8.3 × 10−5 mg/kg-day (subchronic) and 2.1 × 10−5 mg/kg-day (chronic). Hazard quotients (HQ) for subchronic and chronic exposures were on the order of 10−5 and 10−4, respectively, indicating that at current application regimes, there is little to no hazard of adverse effects from fluridone exposure via ingesting Clear Lake tules.

Paleoenvironments and taphonomy of a Triassic lacustrine system (Los Rastros Formation, central-western Argentina)

The Triassic Ischigualasto-Villa Union Basin is an extensional basin located in central-western Argentina. It includes the Los Rastros Formation, a lacustrine-deltaic sequence comprising several coarsening-upward cycles of black shale, siltstone, and sandstone. We performed a taphonomic analysis of the floral and faunal fossils of the Los Rastros succession and have defined five plant taphofacies, four invertebrate taphofacies, and four vertebrate taphofacies. Our taphonomic model characterizes four subenvironments within the lacustrine-deltaic environment of Los Rastros Formation. These include 1) offshore lacustrine, 2) prodelta, 3) deltaic mouth bar, and 4) deltaic plain subenvironment. Our analysis of fossil assemblages allows us to reconstruct the structure of the original ecosystem. The lake margins were vegetated with small ginkgophytes, corystosperms, and sphenophytes. River margins were characterized by riparian thickets of sphenophytes, while the proximal floodplains supported closed woodlands of corystosperms, cycadophytes, and pteridophytes. More distal floodplains were covered with open conifer forests. The invertebrate fauna included insects (Blattoptera, Hemiptera, Coleoptera) associated with lakeshore vegetation and conchostracans that inhabited both the lake shoreline and smaller ponds in the floodplains. Fish and temnospondyl amphibians probably inhabited the delta plain and incoming fluvial systems. The activity of nonmammalian therapsids, crurotarsal archosaurs, and putative dinosaurs is recorded by trackway surfaces in the lake shoreline subenvironment.

DNA sequences identify invasive alien Cardamine at Lake Constance

The shores of Lake Constance in southwest Germany inhabit an endemic and highly endangered lake-shore community. In spring 2004, a so far unknown Cardamine (Brassicaceae) was detected at the lake-shores. In the subsequent years, this taxon has spread rapidly, 95 locations have been recorded until spring 2007. We tested the utility of DNA sequences to distinguish between two alternative hypotheses regarding the appearance of this new invasive taxon: a local formation via hybridization between native species versus an introduction of a non-native taxon. The relative DNA contents was analysed as an additional independent character. DNA sequences provided substantial evidence that the unknown Cardamine taxon, recently discovered at Lake Constance in southwest Germany, is a non-native species introduced from abroad. Sequences of the internal transcribed spacer of the large subunits of nuclear ribosomal DNA and two noncoding regions of chloroplast DNA (trnL intron, trnL/F spacer) were distant from sequences of all native Cardamine species providing evidence against a hybridization hypothesis. In contrast, DNA sequences of the unknown Cardamine were identical to one accession of Cardamine flexuosa auct. non With. (Asian C. flexuosa) from Japan. The introduction history of Asian C. flexuosa at Lake Constance and the potential threat to the native lake-shore vegetation is discussed. Our study highlights the potential of DNA sequences to identify invasive genotypes and source regions.

EVALUATION OF URGENT MEASURES PROTECTING LAKESHORE VEGETATION IN LAKE KASUMIGAURA IN TERMS OF LAKESHORE STABILIZATION

Urgent measures protecting lakeshore vegetation have been carried out at eleven locations in Lake Kasumigaura since 2000. In these measures, beach nourishment was carried out to create a stable growth zone of lakeshore vegetation along the lakeshore, using wooden offshore breakwaters, submerged breakwaters and artificial berm produced by stones. Aerial photographs were compared to investigate the stabilization effect of the ground by these structures as well as the analysis of bottom sounding data. It was found that in the past restoration method of lakeshore vegetation, the consideration regarding dynamic changes of lakeshore due to wave action was insufficient. To create a stable lakeshore ground, wave action and beach changes at each location must be deeply considered.