Although conservation of percolation mires is very important for the European biodiversity, our understanding of their functioning is still insufficient, as most of the studied sites are to some extent degraded. We present a study on the relationship between vegetation patterns, hydrochemical gradients and water level fluctuations carried out in the Rospuda valley (NE Poland), which was recently discovered for science as a uniquely preserved fully functioning percolation mire. Vegetation composition, mire water chemistry and water level dynamics were studied along five transects perpendicular to the valley. Eight major vegetation types were identified: brown moss-small and slender sedge fens, Sphagnum-small sedge fens, brown moss-tall sedge fens, tall sedge-reed fens, pinebirch fen woodlands and shrublands, spruce fen woodlands, inundated alder woodlands, alder spring fen woodlands. The seasonal dynamics of water table was revealed as the major factor explaining vegetation patterns. The studied chemical parameters were relatively homogeneous in the whole mire-there is a rather uniform type of mineral-rich nutrient-poor subsurface water all across the fen.

We explored the background of differences in long-term stability between two parts in an undisturbed mire system (Rospuda fen, NE Poland). We re-constructed the Holocene history of the mire and compared it with current vegetation, water level dynamics, water chemistry and nutrient availability in two basins: A, where the mire terrestrialised a deep gyttja-filled lake, and B, where peatland developed directly on fluvial sands. The current vegetation of sedgemoss fens was described in 10 relevés from each basin, groundwater was sampled from piezometers and analysed for major ions, while its relative water level was recorded during three years. N and P content was measured in above ground vascular plant samples collected within the relevés. Fens in basin A were stable in the past, whereas fens in basin B switched between open and wooded or reed-dominated phases. In basin B, where trees are more abundant, we found higher water fluctuations, occurrence of river floods and a higher N:P ratio than in basin A. Our interpretation follows that the subsurface geology of fen basin may govern mire stability by determining its hydrological-buffering capacity, which may affect N:P ratios. Our results suggest that Plimited fens are more vulnerable for changes in water level.

The aim of this study is to evaluate the effectiveness of the identification of Natura 2000 wetland habitats (Alkaline fens—code 7230, and Transition mires and quaking bogs—code 7140) depending on various remotely sensed (RS) data acquired from an airborne platform. Both remote sensing data and botanical reference data were gathered for mentioned habitats in the Lower (LB) and Upper Biebrza (UB) River Valley and the Janowskie Forest (JF) in different seasonal stages. Several different classification scenarios were tested, and the ones that gave the best results for analyzed habitats were indicated in each campaign. In the final stage, a recommended term of data acquisition, as well as a list of remote sensing products, which allowed us to achieve the highest accuracy mapping for these two types of wetland habitats, were presented. Designed classification scenarios integrated different hyperspectral products such as Minimum Noise Fraction (MNF) bands, spectral indices and products derived from Airborne Laser Scanning (ALS) data representing topography (developed in SAGA), or statistical products (developed in OPALS—Orientation and Processing of Airborne Laser Scanning). The image classifications were performed using a Random Forest (RF) algorithm and a multi-classification approach. As part of the research, the correlation analysis of the developed remote sensing products was carried out, and the Recursive Feature Elimination with Cross-Validation (RFE-CV) analysis was performed to select the most important RS sub-products and thus increase the efficiency and accuracy of developing the final habitat distribution maps. The classification results showed that alkaline fens are better identified in summer (mean F1-SCORE equals 0.950 in the UB area, and 0.935 in the LB area), transition mires and quaking bogs that evolved on/or in the vicinity of alkaline fens in summer and autumn (mean F1-SCORE equals 0.931 in summer, and 0.923 in autumn in the UB area), and transition mires and quaking bogs that evolved on dystrophic lakes in spring and summer (mean F1-SCORE equals 0.953 in spring, and 0.948 in summer in the JF area). The study also points out that the classification accuracy of both wetland habitats is highly improved when combining selected hyperspectral products (MNF bands, spectral indices) with ALS topographical and statistical products. This article demonstrates that information provided by the synergetic use of data from different sensors can be used in mapping and monitoring both Natura 2000 wetland habitats for its future functional assessment and/or protection activities planning with high accuracy.

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