Forest management, site characteristics and climate change affect multiple biotic threats in riparian forests

Forest managers’ perspectives on environmental changes in the biosphere reserve Mura-Drava-Danube

“…Most respondents expected an increase of biotic and abiotic damage, of non-native species, and of tree dieback in future. This matches the estimation that non-native species belong to the most pertinent threats to the environment (e.g., Simberloff, 2005;de Groot et al, 2022).…”

“…The respondents in our study estimated that the conditions of forests are deteriorating, especially after observing changes themselves. 10.3389/ffgc.2023.1160166 This corresponds to ecological studies in the area (de Groot et al, 2022;Sallmannshofer et al, 2021a;Tadić et al, 2022). Nearly 80% of the survey respondents expected further changes, which was significantly correlated with having observed past changes.…”

River distance, stand basal area, and climatic conditions are the main drivers influencing lying deadwood in riparian forests

“…The number of sample sites per country was proportional to the area of TBR in the respective country. GIS orthophoto and river edge analysis in QGIS (v. 2.18.16) from Bing satellite images was used to randomly determine 47 forest transects (Austria: 7, Slovenia: 6, Hungary: 11, Croatia: 13, Serbia:10) with their axes orthogonal to the respective river, with a minimum width of 20 m and a minimum length of 300 m (de Groot et al 2022). If the criteria were not met, transects were re-located up-or down-stream to the closest position meeting the defined criteria.…”

“…Additionally, extended transects were planned in each of the five countries in order to allow sampling in forests more distant to the rivers. Therefore, eleven of the largest forest complexes extending beyond TBR borders were selected and transects extended for an additional 300 m into these forests to include potential historic riparian forests that may have been cut off from streams over time (de Groot et al 2022). Sample plots were set up every 75 m along all transects, resulting in 322 sample plots covering a gradient of forest communities which were summarized into softwood, transition and hardwood forests.…”

“…Stressed trees are hosts for non-native tree pest species enabling their spread and establishment, especially those that are becoming invasive and pose major challenges due to their unpredictability (Lapin et al 2021). Consequently, almost all tree species in the TBR and in central as well as south-eastern European riparian forests are currently threatened by various pests, diseases or invasive plants (de Groot et al 2022). The proportion of ash species (Fraxinus excelsior and Fraxinus angustifolia) has declined in recent decades due ash dieback (Hymenoscyphus fraxineus), oak species are facing a complex of factors causing oak decline, and alder species are harmed by Phytophthora alni, Armillaria sp.…”