Biotic predictors complement models of bat and bird responses to climate and tree diversity in European forests.

Bats and birds are key providers of ecosystem services in forests. How climate and habitat jointly shape their communities is well studied, but whether biotic predictors from other trophic levels may improve bird and bat diversity models is less known, especially across large bioclimatic gradients. Here, we achieved multi-taxa surveys in 209 mature forests replicated in six European countries from Spain to Finland, to investigate the importance of biotic predictors (i.e. the abundance or activity of defoliating insects, spiders, earthworms and wild ungulates) for bat and bird taxonomic and functional diversity. We found that nine out of 12 bird and bat diversity metrics were best explained when biotic factors were added to models including climate and habitat variables, with a mean gain in explained variance of 38% for birds and 15% for bats. Tree functional diversity was the most important habitat predictor for birds, while bats responded more to understorey structure. The best biotic predictors for birds were spider abundance and defoliating insect activity, while only bat functional evenness responded positively to insect herbivory. Accounting for potential biotic interactions between bats, birds and other taxa of lower trophic levels will help to understand how environmental changes along large biogeographical gradients affect higher-level predator diversity in forest ecosystems.

Continental mapping of forest ecosystem functions reveals a high but unrealised potential for forest multifunctionality.

Humans require multiple services from ecosystems, but it is largely unknown whether trade-offs between ecosystem functions prevent the realisation of high ecosystem multifunctionality across spatial scales. Here, we combined a comprehensive dataset (28 ecosystem functions measured on 209 forest plots) with a forest inventory dataset (105,316 plots) to extrapolate and map relationships between various ecosystem multifunctionality measures across Europe. These multifunctionality measures reflected different management objectives, related to timber production, climate regulation and biodiversity conservation/recreation. We found that trade-offs among them were rare across Europe, at both local and continental scales. This suggests a high potential for 'win-win' forest management strategies, where overall multifunctionality is maximised. However, across sites, multifunctionality was on average 45.8-49.8% below maximum levels and not necessarily highest in protected areas. Therefore, using one of the most comprehensive assessments so far, our study suggests a high but largely unrealised potential for management to promote multifunctional forests.

Environmental drivers of Ixodes ricinus abundance in forest fragments of rural European landscapes.

BACKGROUND: The castor bean tick (Ixodes ricinus) transmits infectious diseases such as Lyme borreliosis, which constitutes an important ecosystem disservice. Despite many local studies, a comprehensive understanding of the key drivers of tick abundance at the continental scale is still lacking. We analyze a large set of environmental factors as potential drivers of I. ricinus abundance. Our multi-scale study was carried out in deciduous forest fragments dispersed within two contrasting rural landscapes of eight regions, along a macroclimatic gradient stretching from southern France to central Sweden and Estonia. We surveyed the abundance of I. ricinus, plant community composition, forest structure and soil properties and compiled data on landscape structure, macroclimate and habitat properties. We used linear mixed models to analyze patterns and derived the relative importance of the significant drivers. RESULTS: Many drivers had, on their own, either a moderate or small explanatory value for the abundance of I. ricinus, but combined they explained a substantial part of variation. This emphasizes the complex ecology of I. ricinus and the relevance of environmental factors for tick abundance. Macroclimate only explained a small fraction of variation, while properties of macro- and microhabitat, which buffer macroclimate, had a considerable impact on tick abundance. The amount of forest and the composition of the surrounding rural landscape were additionally important drivers of tick abundance. Functional (dispersules) and structural (density of tree and shrub layers) properties of the habitat patch played an important role. Various diversity metrics had only a small relative importance. Ontogenetic tick stages showed pronounced differences in their response. The abundance of nymphs and adults is explained by the preceding stage with a positive relationship, indicating a cumulative effect of drivers. CONCLUSIONS: Our findings suggest that the ecosystem disservices of tick-borne diseases, via the abundance of ticks, strongly depends on habitat properties and thus on how humans manage ecosystems from the scale of the microhabitat to the landscape. This study stresses the need to further evaluate the interaction between climate change and ecosystem management on I. ricinus abundance.

Impact of patch age and size on forest soil characteristics in European agricultural landscapes.

Many landscapes worldwide are characterized by the presence of a mosaic of forest patches with contrasting age and size embedded in a matrix of agricultural land. However, our understanding of the effects of these key forest patch features on the soil nutrient status (in terms of nitrogen, carbon, and phosphorus) and soil pH is still limited due to a lack of large-scale data. To address this research gap, we analyzed 830 soil samples from nearly 200 forest patches varying in age (recent versus ancient forests) and size (small versus larger patches) along a 2500-km latitudinal gradient across Europe. We also considered environmental covariates at multiple scales to increase the generality of our research, including variation in macroclimate, nitrogen deposition rates, forest cover in a buffer zone, basal area and soil type. Multiple linear mixed-effects models were performed to test the combined effects of patch features and environmental covariates on soil nutrients and pH. Recent patches had higher total soil phosphorus concentrations and stocks in the mineral soil layer, along with a lower nitrogen to phosphorus ratio within that layer. Small patches generally had a higher mineral soil pH. Mineral soil nitrogen stocks were lower in forest patches with older age and larger size, as a result of a significant interactive effect. Additionally, environmental covariates had significant effects on soil nutrients, including carbon, nitrogen, phosphorus, and their stoichiometry, depending on the specific covariates. In some cases, the effect of patch age on mineral soil phosphorus stocks was greater than that of environmental covariates. Our findings underpin the important roles of forest patch age and size for the forest soil nutrient status. Long-term studies assessing edge effects and soil development in post-agricultural forests are needed, especially in a context of changing land use and climate.

Inventory of the terrestrial isopods in Belgium (2011-2020).

This data paper describes a recent and spatially complete inventory of the terrestrial isopods of Belgium between 2011 and 2020. During these 10 years every 10 × 10 km² cell of the Universal Transverse Mercator (UTM) grid in Belgium (373 grid cells) was visited in search for terrestrial isopods. Inventories covered different habitat types in every grid cell such as forest, wetlands or stream sides, and urban areas. Most of the dataset records were obtained by hand-collection methods such as turning stones and dead wood, or by sieving litter and through casual observations. These inventories were carried out by specialists from Spinicornis, the Belgian Terrestrial Isopod Group. Their data is complemented with pitfall trap data from scientific projects and verified citizen science data collected via waarnemingen.be and observations.be from the same time period. This resulted in 19,406 dataset records of 35 terrestrial isopod species. All dataset records are georeferenced using the centroid of their respective 5 × 5 km² UTM grid cell. The dataset is published as open data and available through the Global Biodiversity Information Facility (GBIF). Direct link to the dataset: https://doi.org/10.15468/mw9c66.

Land use and soil characteristics affect soil organisms differently from above-ground assemblages.

BACKGROUND: Land-use is a major driver of changes in biodiversity worldwide, but studies have overwhelmingly focused on above-ground taxa: the effects on soil biodiversity are less well known, despite the importance of soil organisms in ecosystem functioning. We modelled data from a global biodiversity database to compare how the abundance of soil-dwelling and above-ground organisms responded to land use and soil properties. RESULTS: We found that land use affects overall abundance differently in soil and above-ground assemblages. The abundance of soil organisms was markedly lower in cropland and plantation habitats than in primary vegetation and pasture. Soil properties influenced the abundance of soil biota in ways that differed among land uses, suggesting they shape both abundance and its response to land use. CONCLUSIONS: Our results caution against assuming models or indicators derived from above-ground data can apply to soil assemblages and highlight the potential value of incorporating soil properties into biodiversity models.

Promoting biodiversity values of small forest patches in agricultural landscapes: Ecological drivers and social demand.

Small forest patches embedded in agricultural (and peri-urban) landscapes in Western Europe play a key role for biodiversity conservation with a recognized capacity of delivering a wide suite of ecosystem services. Measures aimed to preserve these patches should be both socially desirable and ecologically effective. This study presents a joint ecologic and economic assessment conducted on small forest patches in Flanders (Belgium) and Picardie (N France). In each study region, two contrasted types of agricultural landscapes were selected. Open field (OF) and Bocage (B) landscapes are distinguished by the intensity of their usage and higher connectivity in the B landscapes. The social demand for enhancing biodiversity and forest structure diversity as well as for increasing the forest area at the expenses of agricultural land is estimated through an economic valuation survey. These results are compared with the outcomes of an ecological survey where the influence of structural features of the forest patches on the associated herbaceous diversity is assessed. The ecological and economic surveys show contrasting results; increasing tree species richness is ecologically more important for herbaceous diversity in the patch, but both tree species richness and herbaceous diversity obtain insignificant willingness to pay estimates. Furthermore, although respondents prefer the proposed changes to take place in the region where they live, we find out that social preferences and ecological effectiveness do differ between landscapes that represent different intensities of land use. Dwellers where the landscape is perceived as more "degraded" attach more value to diversity enhancement, suggesting a prioritization of initiatives in these area. In contrast, the ecological analyses show that prioritizing the protection and enhancement of the relatively better-off areas is more ecologically effective. Our study calls for a balance between ecological effectiveness and welfare benefits, suggesting that cost effectiveness studies should consider these approaches jointly.

Habitat properties are key drivers of Borrelia burgdorferi (s.l.) prevalence in Ixodes ricinus populations of deciduous forest fragments.

BACKGROUND: The tick Ixodes ricinus has considerable impact on the health of humans and other terrestrial animals because it transmits several tick-borne pathogens (TBPs) such as B. burgdorferi (sensu lato), which causes Lyme borreliosis (LB). Small forest patches of agricultural landscapes provide many ecosystem services and also the disservice of LB risk. Biotic interactions and environmental filtering shape tick host communities distinctively between specific regions of Europe, which makes evaluating the dilution effect hypothesis and its influence across various scales challenging. Latitude, macroclimate, landscape and habitat properties drive both hosts and ticks and are comparable metrics across Europe. Therefore, we instead assess these environmental drivers as indicators and determine their respective roles for the prevalence of B. burgdorferi in I. ricinus. METHODS: We sampled I. ricinus and measured environmental properties of macroclimate, landscape and habitat quality of forest patches in agricultural landscapes along a European macroclimatic gradient. We used linear mixed models to determine significant drivers and their relative importance for nymphal and adult B. burgdorferi prevalence. We suggest a new prevalence index, which is pool-size independent. RESULTS: During summer months, our prevalence index varied between 0 and 0.4 per forest patch, indicating a low to moderate disservice. Habitat properties exerted a fourfold larger influence on B. burgdorferi prevalence than macroclimate and landscape properties combined. Increasingly available ecotone habitat of focal forest patches diluted and edge density at landscape scale amplified B. burgdorferi prevalence. Indicators of habitat attractiveness for tick hosts (food resources and shelter) were the most important predictors within habitat patches. More diverse and abundant macro- and microhabitat had a diluting effect, as it presumably diversifies the niches for tick-hosts and decreases the probability of contact between ticks and their hosts and hence the transmission likelihood. CONCLUSIONS: Diluting effects of more diverse habitat patches would pose another reason to maintain or restore high biodiversity in forest patches of rural landscapes. We suggest classifying habitat patches by their regulating services as dilution and amplification habitat, which predominantly either decrease or increase B. burgdorferi prevalence at local and landscape scale and hence LB risk. Particular emphasis on promoting LB-diluting properties should be put on the management of those habitats that are frequently used by humans. In the light of these findings, climate change may be of little concern for LB risk at local scales, but this should be evaluated further.