Beyond flood protection to prevent severe damage, the restored floodplain grassland in Austria provides ecosystem services in terms of carbon balance. Net ecosystem exchange (NEE), gross primary productivity (GPP), and ecosystem respiration (Reco) were quantified by the eddy covariance (EC) method before, during and after a severe flooding event. Our results show that the carbon balance is heavily influenced by water level in the study site. The diurnal variations influenced by various degree from the flood are analysed, showing the average daily GPP of the floodplain grassland in Marchegg dropping from 1.048 g C m-2 day-1 before the flood, down to 0.470 g C m-2 day-1 during the flood. The study demonstrates that the restored floodplain grassland in Marchegg functions as a robust CO2 sink with a cumulative NEE of 38.8 g carbon per m2 over the three-month study period, despite temporary disruptions caused by flooding events. The findings emphasise the considerable potential of floodplain grassland restoration for carbon storage and climate change mitigation, with the new data from the EC station offering valuable insights for future restoration projects. Finally, this supports the adoption of the new EU Nature Restoration Law and the need for restoring wetlands, floodplains and rivers to secure water availability and biodiversity in these unique ecosystems. NBS and more specifically as Soil and Water Bioengineering (SWBE) are methods with ecological advantages and a huge potential for sustainable recreation of nearnatural ecosystems. It is of crucial importance to prove these beneficial effects, and to quantify them transparently in terms of quality assurance and use of resources in a sustainable and eco-friendly way.

Understanding the impacts of diurnal freeze-thaw cycles (DFTCs) on soil microorganisms and greenhouse gas emissions is crucial for assessing soil carbon and nitrogen cycles in the alpine ecosystems. However, relevant studies in the permafrost regions in the Qinghai-Tibet Plateau (QTP) are still lacking. In this study, we used high-throughput pyrosequencing and static chamber-gas chromatogram to study the changes in topsoil bacteria and fluxes of greenhouse gases, including carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), during autumn DFTCs in the permafrost regions of the Shule River headwaters on the western part of Qilian Mountains, northeast margin of the QTP. The results showed that the bacterial communities contained a total of 35 phyla, 88 classes, 128 orders, 153 families, 176 genera, and 113 species. The dominant phyla were Proteobacteria, Acidobacteria, Actinobacteria, Chloroflexi, and Gemmatimonadetes. Two DFTCs led to a trend of increasing bacterial diversity and significant changes in the relative abundance of 17 known bacteria at the family, genus, and species levels. These were predominantly influenced by soil temperature, water content, and salinity. In addition, CO2 flux significantly increased while CH4 flux distinctly decreased, and N2O flux tended to increase after two DFTCs, with soil bacteria being the primary affecting variable. This study can provide a scientific insight into the impact of climate change on biogeochemical cycles of the QTP.

Rising air temperatures and changes in precipitation patterns in boreal ecosystems are changing the fire occurrence regimes (intervals, severity, intensity, etc.). The main impacts of fires are reported to be changes in soil physical and chemical characteristics, vegetation stress, degradation of permafrost, and increased depth of the active layer. Changes in these characteristics influence the dynamics of carbon dioxide (CO2) and methane (CH4) fluxes. We have studied the changes in CO2 and CH4 fluxes from the soil in boreal forest areas in central Siberia underlain by continuous permafrost and the possible impacts of the aforementioned environmental factors on the emissions of these greenhouse gases. We have used a fire chronosequence of areas, with the last fire occurring 1, 23, 56, and more than 100 years ago. The soils in our study acted as a source of CO2. Emissions of CO2 were lowest at the most recently burned area and increased with forest age throughout the fire chronosequence. The CO2 flux was influenced by the pH of the top 5 cm of the soil, the biomass of the birch (Betula) and alder (Duschelcia) trees, and by the biomass of vascular plants in the ground vegetation. Soils were found to be a CH4 sink in all our study areas. The uptake of CH4 was highest in the most recently burned area (forest fire one year ago) and the lowest in the area burned 56 years ago, but the difference between fire chronosequence areas was not significant. According to the linear mixed effect model, none of the tested factors explained the CH4 flux. The results confirm that the impact of a forest fire on CO2 flux is long-lasting in Siberian boreal forests, continuing for more than 50 years, but the impact of forest fire on CH4 flux is minimal.