Vergleichende analyse des standortfaktors licht in einem dynamisierten abschnitt der donauaue bei ingolstadt

Monitoring of ecosystem traits is an important element of ecological restoration. Thus, it is crucial not only to assess vegetation data but also direct ecological factors such as light. The project "Restora-tion of the Danube Floodplain between Neuburg and Ingolstadt" (Bavaria) was initiated to restore the typical flooding regime and groundwater fluctuations of a near-natural floodplain forest. One monitor-ing scheme is focusing on vegetation change along transects perpendicular to a new bypass river since 2007. Here the ecological factor light was estimated using the "Wörlein scale". The overall aim of the work was to test the reliability of this method in comparison with digital hemispherical photography which is known to deliver quantitative data. The specific questions were (1) whether or not estimates based on the Wörlein scale are correlated with results of digital hemispherical photography, and (2) if Ellenberg indicator values would represent a useful alternative to the direct measurement or estimation of the ecological factor light in a floodplain environment. A number of specifically designed devices were employed to produce the hemispherical photo-graphs under difficult conditions in the floodplain forest. Data processing was done with the programs "SideLook" for thresholding, and "Gap Light Analyzer" for modeling. Inferential statistical analyses were carried out to check the reliability of the Wörlein scale and Ellenberg indicator values. The results revealed considerable differences among the three methods. The results based on the Wörlein scale were closely related to the photographic measurements, although the resolution under low light conditions was rather poor. Ellenberg indicator values were only weakly correlated with the measured values across a wide range of the dataset, both with logarithmic and pure cover abundance correction. We conclude that digital hemispherical photography is a relatively quick and flexible method for measuring light as ecological factor. The Wörlein scale also seems to be robust and reliable, although the logarithmic quality of light estimates due to the Weber-Fechner law has to be taken into account. Ellenberg indicator values are not recommended for describing the light climate in a floodplain forest.