Riparian hardwood forests of Quercus robur, Ulmus spp and Fraxinus spp that are present along major rivers are valuable communities protected by the EU Habitat Directive and recommended for monitoring. Part of the reason for that is relative rarity on the scale of Europe as a whole, and also in Poland. This in turn reflects the way in which fertile habitats were, in their majority, deforested long ago, drained and changed into grasslands or arable land. Additionally, the greater part of these habitats have lost their specific features, as a result of river engineering and – primarily – the construction of the river embankments that have acted to limit flooding and alluvial processes, in that way also initiating change in the composition of both soils and plant communities. Specifically, this article presents selected results of the research project: Riparian hardwood forest services in the middle Vistula river valley. One of the main objectives thereof was to assess the condition of forest ecosystems from which flooding has now been absent for at least 50 years, as well as to prepare guidelines for actions necessary to maintain or restore their diversity, and proper ecological and biological functions. Our research questions therefore revolved around components of riparian hardwood forest ecosystems have been most changed … and why? The research was conducted in six riparian hardwood forests (to date unmonitored) located in the valley of the middle Vistula (in Mazowieckie voivodship). Relevant work was carried out using the standard monitoring guidelines – as primarily based on an assessment of vegetation composition and structure together with water conditions. However, in the work in question, these were augmented by additional analyses allowing for detailed characterisations of soil, the topoclimate, and the species diversity achieved by selected groups of invertebrate (Hymenoptera: Apidae: Bombus and Haplotaxida: Lumbricidae). The communities selected represent multi-functional, species-rich forests. Extensive use of the studied riparian mixed forests ensures that deadwood resources are quite considerable. Moreover, the studied forests exert a strong impact when it comes to mitigation of climate locally. The observed soil types indicate fertile and biologically-active habitats, as well as to soil development largely determined by the height of the groundwater table causing the gleyic process in the lower parts of profiles. However, in some forest patches it is possible to note transformations related to habitat drying, with significant canopy gaps and disturbances of topsoil and the undergrowth. There was a great abundance of invasive alien plant species (mainly Impatiens parviflora) in the undergrowth. Moisture conditions have an impact on the occasional occurrence of Lumbricidae associated with wet and flooded areas. In turn, the domination by Bombus of open-habitat species indicates a transformation of forest structure, and the patchy nature of riparian forests located in a rural landscape. The obtained results demonstrate that protective actions should focus on ensuring adequate soil-moisture conditions, and on restoring the natural structure of vegetation with a view to invasions of alien species being hampered. Another important issue is the proper use of land adjacent to forest patches, as fallows prove to be invaded quickly by the kenophytes preferring abandoned and disturbed places.

Riparian forests with oaks, ashes and elms, now highly fragmented and rare in Europe, are considered hotspots for ecosystem services. However, their capacity to provide pollination seems to be quite low, although reports from in-situ research supporting this view are scarce. Our goal was therefore to thoroughly assess their pollination potential based on multifaceted field measurements. For this, we selected six test sites with well-developed riparian hardwood forests, located in the agricultural landscape along the middle Vistula River in Poland. We used seven indicators relating to habitat suitability (nesting sites and floral resources) and pollinator abundance (bumblebees and other Apoidea) and propose a threshold value (AdjMax) based on value distribution and Hampel’s test to indicate the level of pollination potential for this type of riparian forest. The obtained AdjMax for bumblebee density was 500 ind. ha⁻¹, for Apoidea abundance—0.42 ind. day⁻¹, while for nectar resources—200 kg ha⁻¹. We demonstrate that the investigated small patches of the riparian hardwood forest have a higher pollination potential than reported earlier for riparian and other broadleaved temperate forests, but the indicators were inconsistent. As forest islands in the agricultural landscape, riparian hardwood forests play an important role in maintaining the diversity and abundance of wild pollinators, especially in early spring when there is still no food base available elsewhere.

Polish forests differ in their potential to provide ecosystem services (ES), but it is unclear how and to what extent. We assessed the potential of 35 forest habitat types to provide 17 key ES and showed that the montane mesic broadleaved forest has a high potential to provide the largest number of key forest services (14 out of 17), which gives it the status of a multi-service hotspot. The highest overall potential was found in the forests of mountain regions, slightly lower in the postglacial northern regions, and the lowest in the central lowland regions.