Bachelor Thesis

Auswirkungen des Spätfrostereignis im Mai 2011 auf Grünlandbestände unterschied-licher Diversität im Raum Bayreuth – eine Analyse auf Basis räumlich hochauflösender Satellitendaten.

Lukas Wiesner (01/2013-08/2013)

Support: Jürgen Kreyling, Carl Beierkuhnlein

In May 2011 a late spring frost backlashed vegetation in the region of Bayreuth. With ongoing climate change the impacts of this type of extreme events will increase due to warmer spring temperatures and faster phenological development. This study aims to investigate the impact of a late spring frost on different types of grassland vegetation in the region of Bayreuth, with calibrated high spatial resolution remote sensing data (RapidEye). Therefore several data sources were involved to illustrate the influence of various parameters on changes of the NDVI between flypast before and after the time of the late spring frost. In addition to field mapping data of grassland, to show the effects of different classes of diversity, a digital elevation model (DGM25) and night-time temperature information (MODIS) were used. Results showed significant differences in trends of the NDVI with high regional distinctions. Furthermore it has been demonstrated that especially altitudes between 400m and 475m were affected. Surprisingly MODIS-data showed that regions with lower temperatures during the whole event (3rd to 5th May) had a more positive trend than others with a lower total frost exposition. The results showed significant differences between classes of diversity as well but with smaller importance than other parameters. Less diverse biotope types had a higher decline and a larger variance of NDVI-development before and after the frost event than grassland with higher number of species. The observed decline of NDVI suggests damages of grassland vegetation caused by the late spring frost event. Due to the lack of field data from the grasslands during the event and adequate fundamental research it was finally not possible to prove whether the observed differences in the development of the NDVI were caused by damage by the late spring frost event or naturally recurrent seasonal changes. Nevertheless it was possible to understand mostly variance of development pattern. Referring to high importance of spatial distribution further research is needed to identify additional parameters, like phenology or small-scaled minimum temperatures at night.