Klaus Schmieder

European lake shores in danger — concepts for a sustainable development

In Europe, when small (> 0.01 km2) lakes are considered, approximately 500,000 natural lakes occur. This considerable number points to the fact that lakeshore habitats and ecosystems are of significant importance to the total biodiversity of European landscapes, not only because of their expanse, but also because they are ecotones between land and water, which attract many kinds of wildlife, economical, cultural and recreational uses and human settlement. These very considerable stretches of shore are not currently registered, mapped or evaluated anywhere. Apart from providing habitat, the littoral biocoenosis performs a string of additional functions in the ecosystem, of which several are also of great importance to people, such as self purification, buffer zone, erosion protection and recreation scenery. In particular, the recreational function provides a main economic base for many lake areas and even whole countries in Europe. However, human interests have resulted in lake shore deterioration, such that many European lakes are now bare natural shores or retain only relics of them. Apart from the loss of the ecological functions, this also leads to a substantial loss of economic benefits. This precipitates the need for a responsible management, which can be done only on the base of a sound assessment method and a continuous monitoring of the status of lake shore areas. On a European scale, the European Water Framework Directive (WFD, 2000/60/EC) and the Habitat Directive (92/43/EEC) provide the frame for the assessment and monitoring of the status of littoral habitats of lakes. The WFD focuses on entire surface water bodies, including their associated wetlands under influence of their natural water-level fluctuations. However, the provided set of quality elements has to be adapted for an approach specific to lake shores. Apart from quality elements indicating the natural spatial pre-requisites, biocoenotic diversity and integrity, and ecosystem function and dynamics, also quality elements representing the human pressure of land use and the social and economic value of the lake shore zone should be included in an integrated lakeshore assessment and monitoring concept. However, the application of such an integrated quality assessment scheme requires an integrated administrative counterpart, just as the WFD requires for water management aspects on a catchment scale. Only by overcoming the splitting of competence among a variety of authorities and planning corporations can an integrated approach to sustainable shore development be translated into action.

Littoral zone — GIS of Lake Constance: a useful tool in lake monitoring and autecological studies with submersed macrophytes

Abstract In 1993, the submersed vegetation of the whole littoral zone of Lake Constance was mapped by boat on the basis of aerial photographs. The survey was the third of its kind after 1967 and 1978, including a period of fast eutrophication in the 1960s and 1970s (mainly caused by increasing phosphate concentrations) and a subsequent period of decreasing trophy, due to the international efforts of the countries and states in the catchment area in eliminating phosphate from waste water. The change in distribution of most aquatic macrophytes shows a high relation to the changes in trophic status of the lake. The oligotraphentic species Chara contraria Kutzing decreased in the 1960s and 1970s and increased in the 1980s and 1990s, the eutraphentic species Zannichellia palustris L., a very rare species before the 1970s, increased to one of the most dominant species until the late 1970s, but decreased in the 1980s and was rarely found in 1993. The use of GIS for data storage and analyses enabled to plot geographically referenced maps of single species distribution areas, to analyse changes of distribution area of species based on data from the whole littoral zone of the lake and to calculate summarising indices like a macrophyte index of nutrient load in the littoral zone. GIS-based analyses of whole lake above ground biomass and depth niches of selected species for the mappings of 1978 and 1993 show, that the difference in aboveground biomass of Potamogeton pectinatus L. is small, but distribution area and depth distribution are wider, whereas density of stands is lower in 1993. Potamogeton perfoliatus L. in 1993 has a higher aboveground biomass, a wider distribution area and depth distribution and a deeper depth optimum than in 1978

Auswirkungen des Extremhochwassers 1999 auf die Flächendynamik und Bestandsstruktur der Uferröhrichte des Bodensees

Abstract In consequence of the extreme flood at Lake Constance in 1999 the reed belts showed a severe loss in vitality so that a permanent damage could be expected. The monitoring project presented here focuses the documentation of the damage following the disturbance event, the identification of co-factors, and is designed to find out significant stressors that may impede the recovery of the reeds. The monitoring is based on CIR aerial photo interpretation, quantitative GIS-analyses and field data. The design of the study implies the definition of five degrees of damage using the interpretation of CIR aerial photo series from July 2000. The aquatic reed beds were digitised and areal sums were calculated. These data were compared with the corresponding data from 1999 and 1993. Stand structural and biomass attributes were investigated in 50 randomly distributed permanent plots covering all site types and damage degrees. The results showed a loss of about 24 hectares of aquatic reeds at Lake Constance Untersee alone. The stands which had survived showed a great patchiness in terms of culm density, shoot population composition, culm architecture, and aboveground biomass production. Severely damaged stands were mainly composed of secondary shoots, whereas primary and insect infested shoots dominated in less damaged stands. One co-factor which explained the patchiness was the vertical position of the stand, i.e. the probability of being severely damaged increased with increasing distance below mean water level. The monitoring programme will be continued till 2003.

Dynamik der Schilfröhrichte am Bodensee unter dem Einfluss von Wasserstandsvariationen

Abstract 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.

High-resolution satellite remote sensing of littoral vegetation of Lake Sevan (Armenia) as a basis for monitoring and assessment

Physics-based remote sensing in littoral environments for ecological monitoring and assessment is a challenging task that depends on adequate atmospheric conditions during data acquisition, sensor capabilities and correction of signal disturbances associated with water surface and water column. Airborne hyper-spectral scanners offer higher potential than satellite sensors for wetland monitoring and assessment. However, application in remote areas is often limited by national restrictions, time and high costs compared to satellite data. In this study, we tested the potential of the commercial, high-resolution multi-spectral satellite QuickBird for monitoring littoral zones of Lake Sevan (Armenia). We present a classification procedure that uses a physics-based image processing system (MIP) and GIS tools for calculating spatial metrics. We focused on classification of littoral sediment coverage over three consecutive years (2006–2008) to document changes in vegetation structure associated with a rise in water levels. We describe a spectral unmixing algorithm for basic classification and a supervised algorithm for mapping vegetation types. Atmospheric aerosol retrieval, lake-specific parameterisation and validation of classifications were supported by underwater spectral measurements in the respective seasons. Results revealed accurate classification of submersed aquatic vegetation and sediment structures in the littoral zone, documenting spatial vegetation dynamics induced by water level fluctuations and inter-annual variations in phytoplankton blooms. The data prove the cost-effective applicability of satellite remote-sensing approaches for high-resolution mapping in space and time of lake littoral zones playing a major role in lake ecosystem functioning. Such approaches could be used for monitoring wetlands anywhere in the world.

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

Abstract 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.

Lakeside reed border characteristics at Lake Constance (Untersee): A comparison between 1981–1983 and 1994

Eutrophication and the associated proliferation offilamentous algae were often considered importantcauses of reed die-back that occurred in the sixtiesand seventies at Lake Constance. According to thishypothesis the reduction in lake water nutrientconcentrations during the eighties and nineties shouldhave reduced the abundance of filamentous algae andwhich should have reduced the supposed mechanicalimpact of filamentous algae on the lakeside reedstands. To examine whether this had actually occurred,the condition of the lakeside reed border at LakeConstance (Untersee) was surveyed in 1994 and resultswere compared to those of similar surveys carried outin the years 1981–83. The extent of mechanical damageto reed stalks, the amount of macrophyte wash and thedegree of shoreline erosion were assessed forshoreline segments of 25 m along a total shorelinelength of 65 km. The results showed that mechanicaldamage to reed stalks was generally higher in 1994than in 1981–83, while macrophyte wash and shorelineerosion were generally less severe. The decreasedamount of macrophyte wash was associated with a changein macrophyte species composition from a dominance offloating filamentous algae to a dominance of rootedPotamogetonaceaeand fragile Characeae,and therefore probably was due to the lower nutrientconcentrations of the lake. The opposite trends foundfor mechanical damage to reed stands and the amount ofmacrophyte wash between 1981–83 and 1994, as well asthe absence of relation between the two variables in1994, suggested that macrophyte wash had only a minoreffect on the condition of lakeside reed stands atLake Constance. Highly damaged reed stands and erodedcliffs were often located at wind exposed sites orclose to highly frequented shipping routes in 1994,suggesting that mechanical stress from waves wasresponsible for the damage. Due to the lakewardprogression of reed stands during the early nineties,reed stalks were, on average, located in deeper waterin 1994 than in 1981–83. This might have strengthenedthe mechanical stress from wave action even more andhave caused the higher frequency of mechanical damageto reed stalks. Other causes of damage such asmacrophyte wash, roosts of birds or bird swarmsprobably played a minor and only local role.

Accuracy assessment of supervised classification of submersed macrophytes: the case of the Gavaraget region of Lake Sevan, Armenia

The necessity of assessing the accuracy of spatial data derived from remote sensing methods and used in geographic information system (GIS) analyses has been regarded as a critical component of many projects. In this article, supervised classified QuickBird satellite imageries of submersed macrophytes of the Gavaraget region of Lake Sevan (Armenia) during 2006–2008 are validated in a GIS environment. The results of this assessment are represented by error matrices presenting the overall accuracy, the user and producer accuracies in each category, as well as the kappa coefficients. The assessments were done at three levels: the vegetation types, the growth (vertical) type, and the species levels. At the vegetation level, an overall accuracy of more than 86% was achieved in 2006 and 2007, while that in 2008 was about 72%. Substantial agreements were achieved between the classified remote sensing data and the reference (groundtruth) data for both 2006 and 2007. Only a fair agreement was attained in 2008. The kappa coefficients ranged from 0.39 to 0.89. At the growth type level, only the 2006 classification attained a substantial agreement, with an overall accuracy of 80%. The 2007 and 2008 classifications had above average and average overall accuracies of 72 and 64%, respectively. The kappa coefficient had a lowest value of 0.35 and a highest value of 0.70 at the growth type level. At the species level, Chara spp. or Zannichellia palustris and Potamogeton pectinatus had high user accuracies of more than 90% and a high overall accuracy of 82% in 2006. High user accuracies (>80%) occurred for P. pectinatus (for 2007 and 2008) and No Vegetation (for 2007). The remaining species, however, had low user and producer accuracies of less than 64%. The kappa coefficients ranged between 0.36 and 0.73 at the species level.

Retrieval of water constituents from multiple earth observation sensors in lakes, rivers and coastal zones

Earth observation sensors collect valuable data of aquatic systems, which are further used for the retrieval of concentrations of water constituents such as suspended matter and phytoplankton. Different sensors deliver data with various spatial and temporal resolution ranging from 1 day to approximately a month in time and from 1km to 3m in space, high spatial resolution being connected with low temporal resolution and vice versa. In order to have detailed information on both spatial distribution of water constituents and their temporal variability, that is especially important for small aquatic objects like rivers and lakes, it is necessary to combine the data from several sensors. This creates certain problems as also spectral and radiometric resolutions of the sensors can be different. The use of the modular image processing system MIP for the integration of data from different sensor is advantageous as it ensures standardized product outputs for a variety of satellite sensors such as MERIS, MODIS, SPOT, IKONOS, RapidEye. The processing chain of this system is automatically adapted to the sensor parameters as well as to the region specific inherent optical properties (SIOP) of the water basin. Various worldwide applications and time series for lakes, rivers and coastal areas are demonstrated and discussed.

Bioenergy Crop Identification at Field Scale Using VHR Airborne CIR Imagery

Abstract The present study is aimed at developing a methodology to extract maize, a predominant energy crop, and efficiently map its spatial distribution in a Natura 2000 region of northern Germany.Following a GEOBIA approach, segmentation was performed on two hierarchical levels. Level 1 consisted of field boundaries,and level 2 represented variations within level 1. Decision rules were developed for level 2 based on spectral information, vegetation indices, standard deviations and knowledge of crop phenology. For this purpose, first, level 2 image objects were classified. Subsequently classification was shifted to level 1.Maize covered 10.6 percent of total study area. The presented methodology gives the advanced user the flexibility to integrate expert knowledge in the classifier. In addition, the implementation time of decision rules was very fast and helped to produce results with high accuracy.