Prescribed burning as potential regeneration technique in temperate reed ecosystems - a pilot study at Lake Neusiedl, Austria

Abstract

The reed belt of Lake Neusiedl, with an area of 181 km², covers more than half of the total lake area (ca. 320 km²) and is part of the Natura 2000 and Ramsar Conservation site of lake Neusiedl. It is the second biggest contiguous reed ecosystem in Europe after the Danube delta. The ageing of the reed belt and subsequently growth of the reed mats represents an obstacle for numerous bird species worth protecting such as the Great Reed Warbler and Reed Buntings in the National Park Lake Neusiedl because many are specialized and dependent on the presence of younger reed plants (Phragmites australis). Traditional regeneration measures, most notably mowing, are becoming decreasingly suitable as a management tool due to warmer temperatures and subsequently insufficient freezing in winter. Therefore, prescribed burning of old reed stands, which is currently prohibited by Austrian law, is being considered as a regeneration measure as a way to maintain invaluable habitats for bird species. For this reason, a pilot study was carried out in January 2024 in the reed belt of Lake Neusiedl near Jois (province of Burgenland, Austria) in order to gain insights on consequences of controlled burning of old reed mats. The burning was conducted in winter to minimize harm of wildlife. Our research includes pre- and post-fire laboratory analyses of biomass and carbon content from standing vegetation, litter (matted reed), and the underlying partially decomposed organic soil layer. Furthermore, the fire behavior and intensity, as well as moisture contents during and after the fire were monitored. To support the area-wide mapping UAV-LiDAR and RGB flights were undertaken. The results can provide valuable insights into the closely linked balances between nature conservation and carbon stocks that arise in the management of reed-dominated ecosystems through burning. The mean fire temperature was slightly above 700°C and peaked at 1034°C. A total area of 15.6 ha was affected, on which the standing dead reed was lost completely, and the reed mats were reduced by 31.2% on average. A total of 54.5 tC were released from the study area. The layer of matted reed, which is to be affected by the fire, should have a maximum moisture content of 30% to ensure biomass removal. A significant reduction of the matted reed horizon thickness was achieved, which will help Phragmites australis regrowth and young-stock-specialized bird repopulation. The fire also left unburned patches of intact old stock behind, which could provide habitats for bird species specialized in old reed stock. Our results indicate that prescribed fire can be a suitable management tool at the reed belt of lake Neusiedl for the purpose of reed regeneration and habitat restoration.