Monitoring of stable isotopes in throughfall (delta 18O, delta 2H) and meteorological parameters is a valuable tool for researching forest hydrology, particularly during extreme events like droughts and floods. This study presents the first systematic analysis of air temperature and precipitation changes over the past 65 years in two Slovenian lowland forests: Murska & scaron;uma and Krakovski gozd, in combination with isotopic composition research of throughfall. The observed rising air temperatures and altered precipitation patterns are reflected in the isotopic composition of throughfall. Over the last 65 years, air temperature has increased by approximately 2.5 degrees C. Although total annual precipitation amounts have remained relatively stable, in the last 35 years there is a notable decrease in precipitation in growing season and an increase during the dormant season, influenced by air masses of Mediterranean origin. Extreme drought in 2022 and flood in 2023 are confirmed by the Standardized Precipitation Index and isotopic variations in throughfall due to fractionation processes. Annual variability appears as seasonal changes, with sine-curve amplitudes of 3.71 parts per thousand in Krakovski gozd and 3.61 parts per thousand in Murska & scaron;uma. Together with the Local Meteoric Water Lines, these patterns support estimates of groundwater mean residence time and the origin of water used by trees.
In addition to being influenced by global drivers, forest herb-layer communities are also shaped by various local factors, such as topography, stand characteristics and soil properties. The responses of ground vegetation were studied in the ravine forests of a Natura 2000 site in eastern Slovenia. A high species richness of 218 plant species was observed in the herb layer, including some woody species. On average, 52.8 different plant species were recorded per plot. Species richness was significantly associated with topographic and forest stand factors, rather than soil characteristics. It was positively associated with altitude and the amount of deadwood and negatively associated with tree height. However, the main predictors for the species composition of the ground vegetation were tree layer cover and soil pH. Among the studied ravine forests, Tilia-dominated stands are characterised by the highest species diversity and the lowest herb-layer cover, indicating a composition of less competitive, site-specific species inhabiting sites with high resource heterogeneity and diverse microhabitats. To preserve the high level of biodiversity of heterogeneous ravine forests and to maintain their favourable conservation status, it is crucial to sustain the natural state of forest soils and stands by implementing appropriate management measures. Such measures may include close-to-nature forest management, which is already being implemented in the studied ravine forests.
The finite resource of fertile soil can take thousands of years to develop. Non-degradable toxic metals (heavy metals), pose a significant health risk due to their persistence in the environment. Soil washing with EDTA (ethylenediaminetetraacetic acid) has been shown to remove toxic metals (Pb, Zn, Cd), but this process can also have a significant impact on soil microbial diversity. In this study, we investigated, using molecular methods (18S rRNA amplicon sequencing), the development of the arbuscular mycorrhizal (AM) fungal communities in the roots of Lolium perenne after a soil remediation treatment with EDTA. Plants were grown on two soil types (calcareous and acidic), in remediated and control (unremediated, polluted) soils, and with or without the addition of a local environmental inoculant (grassland soil and roots). The addition of the inoculant increased the richness and evenness of AM fungi, and reduced the compositional dissimilarity of communities between remediated and unremediated soils. Disturbance from the remediation process and inoculation, lead to a shift in the identity of dominant taxa reflecting different traits among the AM fungi. This suggested two main mechanisms behind community development in remediated soils, i.e. priority effects and competitive exclusion among dominant taxa. These findings emphasise the importance of nature-based solutions (indigenous environmental inoculants) and AM fungi for sustainable soil management practices. This is particularly important for restoring soil biodiversity in sites that have been exposed to multiple disturbances, which may include contaminated sites and soil remediation, as well as conventional agricultural systems, and urban soils.
Interpopulation variation was investigated using seed samples originating from twenty-six European beech (Fagus sylvatica L.) populations across the Balkan Peninsula, a part of the species' distribution range characterized by high ecological heterogeneity in key climatic factors, such as temperature (5.8-10.6 degrees C), precipitation (648-1632 mm), and elevation (185-1410 m a.s.l.). The statistical significance of intrapopulation differences was confirmed by analysis of variance (ANOVA) for all seed traits analyzed: seed weight (g), length (mm), width (mm), thickness (mm), eccentricity and flatness indices, and germination capacity (%). Multivariate principal component analysis (PCA) was applied to examine seed traits in relation to environmental variables of the maternal site, such as mean temperature and precipitation in September and October (the seed maturation period), revealing distinct patterns of relationships among the variables studied. Seed traits were significantly positively correlated with mean temperatures of the maternal site in September and October, indicating that temperature during the seed-filling period affects seed mass. Germination capacity was associated with precipitation during the same period, though the correlation coefficient was not statistically significant; a shorter vector length in the PC biplot suggests a weaker contribution to population separation. Elevation of the site of origin showed a significant negative correlation with temperature, precipitation, and seed traits. Agglomerative hierarchical clustering analysis identified three distinct population clusters. Higher temperature and precipitation values did not necessarily result in higher seed trait values or higher germination percentages. The population with the highest seed mass exhibited the lowest germination capacity (32%) during seed maturation under the lowest precipitation. Conversely, the population characterized by the lowest seed mass showed a higher germination rate of 68% in environments with high precipitation. These results provide valuable insights into the reproductive ecology of European beech, suggesting that other factors beyond those analyzed here may have a more substantial influence on seed germination. The variation in seed traits across habitats that are either drier and hotter or colder and wetter, along the elevation gradient of the studied populations, paves the way for future research and breeding efforts to enhance the species' survival and reproductive success amid anticipated climate change scenarios.
Wild bees (Hymenoptera: Anthophila) and hoverflies (Diptera: Syrphidae), the two major groups of insect pollinators, are undergoing alarming declines worldwide, including Europe. The lack of accessible and verified spatial and temporal occurrence records currently challenges efforts to understand and mitigate this decline. Here, we compiled datasets from diverse sources, including taxonomists, national experts, public repositories, museum collections, published literature, verified open-access platforms, and aggregated datasets from previous European projects. The collected data were standardised, cleaned and validated by taxonomists and national experts. This collective effort resulted in two databases comprising more than 4.34 million and 1.04 million records for wild bees and hoverflies, respectively. The databases cover 97% of the European bee fauna (2,083 species out of 2,138 recorded in Europe) and 97% of the European hoverfly fauna (886 species out of 913 recorded in Europe). These standardised databases constitute essential resources for future assessments of status and trends, habitat associations, and other research and conservation initiatives to protect and understand wild pollinators on the European continent.
