The distylous plant Primula veris has long served as a model species for studying heterostyly, that is the occurrence of multiple floral morphs within a population to ensure outcrossing. Habitat loss, reduced plant population sizes, and climate change have raised concerns about the impact of these factors on morph ratios and the related consequences on fitness of heterostylous species. We studied the deviation of floral morphs of P. veris from isoplethy (i.e. equal frequency) in response to plant population size, landscape context and climatic factors, based on a pan-European citizen science campaign involving observations from 28 countries. In addition, we examined the relative frequency of morphs to determine whether landscape and climatic factors disrupt morph frequencies or whether a specific morph has an advantage over the other. Theory predicts equal frequencies of short-styled S-morphs and long-styled L-morphs in populations at equilibrium. However, data from >3000 populations showed a substantial morph deviation from isoplethy and a significant excess of S-morphs (9% higher compared to L-morphs). Deviation of morph frequency from equilibrium was substantially stronger in smaller populations and was not affected by morph identity. Higher summer precipitation and land use intensity were associated with an increased prevalence of S-morphs. Five populations containing individuals exhibiting short homostyle phenotypes (with the style and anthers in low positions) were found. Genotyping of the individuals at CYP734A50 gene of the S locus, which determines the length of the style and the position of anthers of P. veris, revealed no mutations in this region. Our results based on an unprecedented geographic sampling suggest that changes in land use and climate may be responsible for non-equilibrium morph frequencies. This large-scale citizen science initiative sets foundations for future studies to clarify whether the unexpected excess of S-morphs is due to partial intra-morph compatibility, disruption of heterostyly or survival advantage of S-morphs. Synthesis. Human-induced environmental change may affect biodiversity indirectly through altering reproductive traits, which can also lead to reduced fitness and genetic diversity. Further research should consider the possible role of pollinators in mediating the ecological and evolutionary consequences of recent landscape and climatic shifts on plant reproductive traits.

Large solitary trees (LSTs) represent important wood volumes and carbon stocks outside forests. However, quantification remains difficult as most allometric relationships have been developed using trees in forests. Here, we explore the volumetric assessment of aboveground woody biomass of LSTs outside forests and compare them to forest trees. Using terrestrial laser scanning, we captured detailed 3D point clouds of 215 solitary trees for three widely distributed species, i.e. Quercus robur, Tilia sp. & Fraxinus excelsior, across nine cities in temperate Europe. Leaf-off lidar point clouds were processed using a quantitative structure model (QSM) to estimate the aboveground volumes and develop new species-specific allometric volume equations for solitary trees. Our findings show that the woody volumes of LSTs estimated by QSMs are, on average, 83 % higher than those predicted by species-specific allometric equations tailored to forest trees of similar height and diameter at breast height. To validate this discrepancy, we applied the same laser scanning and modeling methods to both LSTs and forest trees. Regression analysis confirmed that LSTs have significantly greater woody volumes than forest trees. However, this difference diminishes with increasing height, resulting in converging volumes in the tallest height class. Our results highlight the substantial carbon storage and wood volume potential of LSTs in both urban and rural areas, and underpin the urgent need for dedicated allometric volume equations tailored specifically to large solitary trees.

Habitat fragmentation increases the proportion of forest borders in the landscape and many forest borders lose their structural complexity due to modern forestry practices. However, remnants of structurally complex deciduous forests can remain as ecotones between plantations and agricultural fields. In this study we used terrestrial laser scanning to measure structural complexity of different forest borders, measured microclimate, and surveyed bats and macro-moths to understand how these taxa are affected. Our aim is to disentangle the main drivers, direct or indirect, that influence bat and moth assemblages. We studied 79 forest borders, and surrounding landscapes and compared them with adjacent agricultural fields and coniferous plantations. Overall, we found less bat activity and lower macro-moth diversity in simple compared to complex borders. Using structural equation modelling, we show the contrasting responses of forest-specialist bats and moths to structural complexity; with bats responding positively and moths negatively. We found similar divergent results in relation to understorey openness; with increasing forest-specialist bat activity but a lower diversity of forest-specialist moths in more open borders. Understorey vegetation also appears to regulate microclimate with more open borders being warmer and less humid. This has a potential knock-on effect for bats as they favoured borders that were warmer and more humid. Surrounding land-cover was more important than structural complexity for generalist species; with increasing generalist bat activity due to a higher proportion of local deciduous forest cover and increasing generalist moth diversity in landscapes with more forest borders. Overall, these complex relationships between forest structure, microclimate and landscape factors, coupled with divergent responses of both taxa highlight their diverse ecological needs. Therefore, we highlight the importance of managing forest borders to retain complexity and connectivity within multifunctional landscapes.

Soils are the largest terrestrial carbon (C) pool on the planet, and targeted grassland management has the potential to increase grassland C sequestration. Appropriate land management strategies, such as organic matter addition, can increase soil C stocks and improve grasslands' resilience to drought by improving soil water retention and infiltration. However, soil carbon dynamics are closely tied to vegetation responses to management and climatic changes, which affect roots and shoots differently. This study presents findings from a 3-year field experiment on two Swedish grasslands that assessed the impact of compost amendment and experimental drought on plant biomass and soil C to a depth of 45 cm. Aboveground biomass and soil C content (% C) increased compared with untreated controls in compost-amended plots; however, because bulk density decreased, there was no significant effect on soil C stocks. Experimental drought did not significantly reduce plant biomass compared to control plots, but it stunted the increase in aboveground biomass in compost-treated plots and led to changes in root traits. These results highlight the complexity of ecosystem C dynamics and the importance of considering multiple biotic and abiotic factors across spatial scales when developing land management strategies to enhance C sequestration.

Anthropogenic biodiversity decline threatens the functioning of ecosystems and the many benefits they provide to humanity. As well as causing species losses in directly affected locations, human influence might also reduce biodiversity in relatively unmodified vegetation if far-reaching anthropogenic effects trigger local extinctions and hinder recolonization. Here we show that local plant diversity is globally negatively related to the level of anthropogenic activity in the surrounding region. Impoverishment of natural vegetation was evident only when we considered community completeness: the proportion of all suitable species in the region that are present at a site. To estimate community completeness, we compared the number of recorded species with the dark diversity—ecologically suitable species that are absent from a site but present in the surrounding region2. In the sampled regions with a minimal human footprint index, an average of 35% of suitable plant species were present locally, compared with less than 20% in highly affected regions. Besides having the potential to uncover overlooked threats to biodiversity, dark diversity also provides guidance for nature conservation. Species in the dark diversity remain regionally present, and their local populations might be restored through measures that improve connectivity between natural vegetation fragments and reduce threats to population persistence.

Large solitary trees are keystone features for biodiversity in many urban and rural landscapes around the world. Yet, because of their isolation, they do not benefit from the buffering effect of neighbouring trees as in forests. As they are more exposed, solitary trees are more vulnerable to the impacts of climate change, such as extreme droughts, heat waves, and wind gusts. Research on microclimates below solitary trees is scarce and a more detailed understanding is needed to better understand and predict the future impacts of climate change on their associated biodiversity and ecosystem services. Here we quantified air temperatures and vapour pressure deficits below the crown of >200 trees along rural-to-urban gradients for three tree species (oak, ash, and lime) across nine European cities. We recorded microclimate measurements every 30 min for 10 months and analysed the effects of the surrounding built-up area and how different tree species influence microclimatic conditions. The microclimate below trees in more urban areas was overall warmer and drier than below rural trees, whereby 10 % more built-up area caused average summer air temperatures to increase by 0.1 °C and average vapour pressure deficits by 0.02 kPa. Oak and lime were able to dampen the temporal fluctuations of air temperature and vapour pressure deficit more than ash and were able to mitigate maximum summer temperatures 0.55 °C more than ash. Our research thus underpins that solitary trees shape their own species-specific microclimate. We advocate for integrated tree planning to preserve and provide space for solitary trees, and by adopting solitary trees as key components of urban and rural green infrastructures, we can improve microclimatic conditions and enhance biodiversity, ultimately creating more sustainable and liveable landscapes.

The boreal forest, one of the world's largest terrestrial biomes, is currently experiencing rapid climate-driven changes. This review synthesizes the limited research available on climate-change impacts on boreal plant-pollinator systems, revealing several knowledge gaps and shedding light on the vulnerabilities of boreal ecosystems. Using four complementary Web of Science searches, we found 5198 articles, of which only 11 were relevant. Our findings reveal that research on boreal plant-pollinator interactions is limited to date, as is our understanding of the insect fauna and pollination systems in the boreal region. Existing research often focuses on conspicuous plants, neglecting many other ecologically significant species. In addition, current studies often lack detailed data on pollinator species, which restricts our capacity to assess the vulnerability of specific plant-pollinator interactions to climate change. For example, most articles use plant reproductive success as a proxy for pollinator effectiveness without considering pollinator identity. This approach successfully assesses overall plant fitness, but overlooks changes to pollinator communities, such as those resulting from thermophilization, that may be relevant to projecting climate-change impacts. Moreover, pollinator taxon seems to affect the responses of plant reproduction to warming, with fly-pollinated plants appearing to be more resilient to temperature changes than bee-pollinated plants. Future research should prioritize foundational plant species and key pollinators, including flies, which are crucial to boreal pollination ecology. Understanding species-specific responses to warming is equally important for identifying which species and interactions may be most vulnerable to climate change. Studies should also examine the role of forest microclimates, as they may buffer boreal regions during broader climatic shifts, helping to mitigate the impacts of warming on these ecosystems. Addressing these gaps is essential for predicting climate impacts on boreal biodiversity and for informing conservation strategies that support biodiversity and benefit human communities reliant on boreal ecosystem services.

Context: Agriculture-driven land-use changes over the past decades have not only reduced the amount of habitat for species but also influenced the genetic exchange among the remaining fragmented populations. Many recent studies have found a delayed response in population genetic diversity and differentiation of species in fragmented habitats to past landscape disturbances, a so-called time lag. However, the specific role of species’ individual reproductive traits and the population genetic measures used remain poorly understood. Objectives: We examined the impact of past and current agricultural landscape composition in temperate Europe on the population genetic structure of three long-lived, slow-colonizing forest herb species – Anemone nemorosa, Oxalis acetosella and Polygonatum multiflorum, which vary in their reproductive traits. Methods: We considered four time points in history (mid-1900s, 1985, 2000 and 2017) to identify the potentially different length of time that is needed by each species to respond to landscape change. We also explored the impact of using different genetic measures in quantifying the time lags. Results: Our findings show that despite substantial landscape alterations about 70 years ago, the mid-1900s landscape composition was not reflected in the current genetic diversity and differentiation of the three species. This indicates a possible unexpected quick genetic adjustment of these species. Nevertheless, by combining the signals of multiple genetic measures, we found that O. acetosella, which reaches sexual maturity earlier than the other two species and is self-compatible, showed signs of faster genetic adjustment to these landscape changes. In contrast, A. nemorosa and P. multiflorum, which take longer to reach sexual maturity, might exhibit longer time lags that were beyond this study’s time frame. Conclusions: This study underscores the importance of considering the species’ reproductive traits and especially the role of temporal scales of different genetic measures when investigating the impact of landscape history on current population genetic structures.

1. Agricultural intensification, afforestation and land abandonment are major drivers of biodiversity loss in semi-natural grasslands across Europe. Reversing these losses requires the reinstatement of plant–animal interactions such as pollination. Here we assessed the differences in species composition and patterns of plant-pollinator interactions in ancient and restored grasslands and how these patterns are influenced by landscape connectivity, across three European regions (Belgium, Germany and Sweden).
2. We evaluated the differences in pollinator community assemblage, abundance and interaction network structure between 24 ancient and restored grasslands. We then assessed the effect of surrounding landscape functional connectivity (i.e. green infrastructure, GI) on these variables and tested possible consequences on the reproduction of two model plants, Lotus corniculatus and Salvia pratensis.
3. Neither pollinator richness nor species composition differed between ancient and restored grasslands. A high turnover of interactions across grasslands was detected but was mainly due to replacement of pollinator and plant species. The impact of grassland restoration was consistent across various pollinator functional groups, whereas the surrounding GI had differential effects. Notably, bees, butterflies, beetles, and dipterans (excluding hoverflies) exhibited the most significant responses to GI variations. Interestingly, networks in restored grasslands were more specialised (i.e. less functionally redundant) than in ancient ones and also showed a higher number of insect visits to habitat-generalist plant species. Landscape connectivity had a similar effect, with habitat-specialist plant species receiving fewer visits at higher GI values.
4. Fruit set in S. pratensis and L. corniculatus was unaffected by grassland type or GI. However, the fruit set in the specialist S. pratensis increased with the number of pollinator visits, indicating a positive correlation between pollinator activity and reproductive success in this particular species.
5. Synthesis and applications. Our findings provide evidence of the necessity to enhance ecosystem functions while avoiding biotic homogenisation. Restoration programs should aim at increasing landscape connectivity which influences plant communities, pollinator assemblages and their interaction patterns. To avoid generalist species taking over from specialists in restored grasslands, we suggest reinforcing the presence of specialist species in the latter, for instance by means of introductions, as well as increasing the connectivity to source populations.

In recent years, restoration on former grassland sites has been widely encouraged globally, aiming to address the historical loss of 90% of ancient species-rich grasslands, and to mitigate the associated threat to grassland biodiversity. The objective of our study was to investigate on a small-scale how plant species spontaneously colonize restored grasslands. We inventoried 275 permanent plots twice (in 2019 and 2021) in a restored grassland, following the removal of a conifer plantation. Species richness and vegetation cover in surveyed plots were dependent on grazing activity and distance to adjacent grassland. Plant species associated with forest habitats declined, while the occurrence of generalist species together with a few grassland specialists generally increased. However, not all grassland specialists gained occurrence and the colonization pattern was not consistent over time, possibly due to the lack of continuous seed arrival and low livestock activity and hence lack of disturbance. These results suggest that successful colonization of plant species benefits from links to species-rich sites adjacent to the restoration target, with spatial dispersal and improved conditions for species establishment being key to species occurrence. Both dispersal and establishment potential are likely facilitated through the presence of grazing livestock with access to both species-rich grasslands and restoration targets. However, the shift towards a more typical grassland community takes place gradually, with vulnerable populations of early colonizing grassland species prone to local extinction in short-term. As a result, continued functional connectivity provided by grazing animals is necessary to improve the diversity of the restored site and ensure the establishment of grassland specialists and to maintain the plant community composition.