Pollination Potential of Riparian Hardwood Forests—A Multifaceted Field-Based Assessment in the Vistula Valley, Poland

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

Early response of understory vegetation to the mass dieback of Norway spruce in the European lowland temperate forest

Spruce-dominated forests are commonly exposed to disturbances associated with mass occurrences of bark beetles. The dieback of trees triggers many physical and chemical processes in the ecosystem resulting in rapid changes in the vegetation of the lower forest layers. We aimed to determine the response of non-tree understory vegetation to the mass dieback of Norway spruce (Picea abies) in the first years after the disturbance caused by the European spruce bark beetle (Ips typographus) outbreak. Our study area was the Białowieża Biosphere Reserve covering the Polish part of the emblematic Białowieża Forest, in total 597 ​km2. The main data source comprised 3,900 phytosociological relevés (combined spring and summer campaigns) collected from 1,300 systematically distributed forest sites in 2016–2018 – the peak years of the bark beetle outbreak. We found that the understory responded immediately to mass spruce dieback, with the most pronounced changes observed in the year of the disturbance and the subsequent year. Shade-tolerant forest species declined in the initial years following the mass spruce dieback, while hemicryptophytes, therophytes, light-demanding species associated with non-forest semi-natural communities, as well as water-demanding forest species, expanded. Oxalis acetosella, the most common understory species in the Białowieża Forest, showed a distinct fluctuation pattern, with strong short-term expansion right after spruce dieback, followed by a gradual decline over the next 3–4 years to a cover level 5 percentage points lower than before the disturbance. Thus, our study revealed that mass spruce dieback selectively affects individual herb species, and their responses can be directional and non-directional (fluctuation). Furthermore, we demonstrated that the mass dieback of spruce temporarily increases plant species diversity (α-diversity)

Wpływ przesiedleń po II wojnie światowej na długookresową dynamikę krajobrazu w polskich Karpatach

Armed conflicts and major political changes can result in the forced displacement of thousands of people and may have substantial effects on the environment. However, it is difficult to predict and mitigate long-term consequences of such displacements, especially when they trigger abrupt land-use changes that result in a regime shift of the land-use system. Our main goal was to determine the effects of post-WWII forced displacements on long-term landscape dynamics in the Polish Carpathians. After World War II, 630,000 Ukrainians were forcibly displaced from southeastern Poland, leading to permanent depopulation of mountain borderlands. We conducted a village-level analysis of forest area change across the Polish Carpathians (1685 villages/cadastral communities), and a detailed analyses of landscape change and land-cover trajectories in two highly depopulated test sites. Our source data were pre-war (1850s-1860s and 1930s) and post-war (1970s and 2010s) census data and topographic maps. We found a substantial forest area increase after displacements, far outpacing the widely reported forest increase due to the collapse of socialism in early 1990s, and a striking landscape simplification. Astonishingly, almost two thirds of the post-war (1930s-1970s) forest area increase in the entire Polish Carpathians (115,000 ha out of 181,000 ha) was due to the forced displacements. The land-use regimes shifted from being agriculturally-dominated to being forest-dominated, and approached a stable alternative state. As a result, a once densely populated rural region has become one of the largest ‘wilderness’ areas in Central Europe, with vast areas void of human settlements and resurgent wildlife populations. This highlights that forced displacements, which are common during and after armed conflicts, can have substantial and long-lasting effects on land use