Contrasting impacts of cultivated exotics on the functional diversity of domestic gardens in three regions with different aridity

Cultivated exotic plants are often introduced for their aesthetic value and today comprise a substantial fraction of the flora of urban domestic gardens. Yet, their relative contribution to the functional diversity of domestic gardens and how it changes across different climate zones is insufficiently understood. Here, we investigated whether the effects of cultivated exotics on functional diversity of three plant traits related to plant aesthetics (that is, plant showiness, plant height, and leaf area) varied in suburban domestic gardens in three regions (Minnesota, USA; Alt Empordà, Spain; and central South Africa) that differ in aridity. For each garden, we calculated the mean and variance of each plant trait considering all co-occurring species and also splitting them into co-occurring cultivated exotics and natives. Our results revealed that mean plant showiness increased linearly with the proportion of cultivated exotics both across and within studied regions. Moreover, co-occurring cultivated exotics were, on average, showier than natives in all regions, but differences in their trait variances were context-dependent. The interaction between cultivated exotics and aridity explained variation in mean plant height and leaf area better than either predictor alone, with the effect of cultivated exotics being stronger in more arid regions. Accordingly, co-occurring cultivated exotics were taller and had larger leaves than natives in warmer and drier regions, while the opposite was true in cooler and wetter regions. Our study highlights the need to consider the combined effects of exotic species and climate in future studies of urban ecology

A global database for metacommunity ecology, integrating species, traits, environment and space

The use of functional information in the form of species traits plays an important role in explaining biodiversity patterns and responses to environmental changes. Although relationships between species composition, their traits, and the environment have been extensively studied on a case-by-case basis, results are variable, and it remains unclear how generalizable these relationships are across ecosystems, taxa and spatial scales. To address this gap, we collated 80 datasets from trait-based studies into a global database for metaCommunity Ecology: Species, Traits, Environment and Space; “CESTES”. Each dataset includes four matrices: species community abundances or presences/absences across multiple sites, species trait information, environmental variables and spatial coordinates of the sampling sites. The CESTES database is a live database: it will be maintained and expanded in the future as new datasets become available. By its harmonized structure, and the diversity of ecosystem types, taxonomic groups, and spatial scales it covers, the CESTES database provides an important opportunity for synthetic trait-based research in community ecology

Coupling a landscape-based approach and graph theory to maximize multispecific connectivity in bird communities

International audienceEnvironmental policies have highlighted the importance of preserving ecological networks to limit the fragmentation of natural habitats and biodiversity loss. A crucial issue for landscape managers is how to reconcile conservation measures that benefit all species and the maintenance of human activities. This study aimed to promote landscape multifunctionality, i.e., improving connectivity for several species without significantly modifying human activities. The objectives were to identify the most strategic natural landscape types to prioritize for preservation and to propose landscape management actions in highly anthropized areas that would benefit a majority of species. The analysis combined landscape types and bird species observation data to model landscape suitability for six species profiles defined by their affinity for wetlands, agricultural areas, urban areas and three types of forested landscapes. By graph modelling, we analysed the functional connectivity of the ecological networks of these species profiles. The results revealed that only ten landscape types out of 72 were core habitats for three species profiles simultaneously. These were primarily forested landscape types — either strict or associated with open areas (wasteland, forest clearing). Conversely, some anthropogenic landscapes dominated by built areas and sometimes shared with agriculture were completely unfavourable for all species profiles. The graph modelling analysis showed that the transformation of some landscape types could potentially improve connectivity for four species profiles presenting different ecological requirements. This coupling approach thus provided guidance to propose some landscape management actions that benefit the majority of species while preserving land uses

Disentangling spatial and environmental effects: Flexible methods for community ecology and macroecology

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Effects of Climate Change on Hydrological Indicators of Subsurface Drainage for a Representative French Drainage Site

International audienceThe aim of this study is to evaluate from a hydrological perspective and in the context of climate change the future of subsurface drainage of the La Jaillière site (western France), which is representative of the pedology of the majority of French subsurface drainage. We used a uniquely large and comprehensive range of 17 hydrological indicators (HIs), describing the temporal dynamics of drainage season, soil saturation, drained water balance and flood events. The HI values are calculated from simulated discharges provided by a subsurface drainage model, the SIDRA-RU model, fed by 12 climate projections from 1975 to 2100 (CMIP5 Euro-Cordex project), with three climate change scenarios: Representative Concentration Pathways (RCP) 2.6, RCP4.5 and RCP8.5. We first verified that the HIs simulated using climate projections in the SIDRA-RU model over the historical period were not critically biased compared to the HIs obtained from the reference climatic reanalysis (SAFRAN). Second, we analysed and compared the HI evolution over different periods and under different scenarios. Our results showed that the number of significant changes in HI values increased under climate change by 2100, depending on the RCP: 2 HIs out of the 17 changed under RCP2.6; 6 HIs under RCP4.5; 10 HIs under RCP8.5. The intensity of drainage peak flows linked to flood events and the annual maximal discharge changed significantly under all RCPs. The temporality of the drainage season was substantially affected according to how pessimistic the RCP was. The worst changes were observed under RCP8.5, which exacerbated extreme events: The wet period was shorter while the dry period was longer by about 67%; the drought index increased by 100%; the summer drained water balance decreased by 9%. On the contrary, in winter, the duration of the wet period decreased while maintaining the same drained water balance, thus inducing stronger flood events leading to an earlier saturation of the drainage networks. The sustainability of the drainage system design at La Jaillière is therefore threatened, with the risk of fulfilling its function less effectively by 2100, exposing current crops to more important runoff and affecting water quality by increasing the leaching of agrochemical inputs

Combiner une approche paysage-centrée et la théorie des graphes pour évaluer la connectivité multi-spécifique

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Level-dependence of the relationships between amphibian biodiversity and environment in pond systems within an intensive agricultural landscape

International audienceWetlands, especially ponds, and their associated amphibian biodiversity are threatened by agricultural intensification. To improve conservation planning of these ecosystems, we need to understand at which scales biodiversity responds to human-induced disturbances. This study aims to assess the level-dependence of environment-amphibian biodiversity relationships in 150 ponds in an intensive agricultural landscape in Seine-et-Marne (France). Amphibian diversity surveys, site characteristic measurements and landscape descriptions are analysed. The hierarchy of the effects of local and regional variables on species richness, regional heterogeneity of species composition and species occurrences is investigated at three spatial levels: pond level, 1-, and 4-km(2) level. Species richness is negatively influenced at all levels by the fish presence. Water quality and pond density, which emphasize level-dependent effects, significantly increase species richness at the local and regional levels, respectively. With few exceptions, species occurrence analysis shows similar patterns, confirming, locally, the importance of fish avoidance, and, regionally, the need for increasing pond density. Environmental variables have no effect on the regional heterogeneity of species composition, questioning the potential existence of dispersal processes at scales above 1 km(2). This study highlights the relevance of a pond-group-centred approach compared to a pond-centred approach with regard to pond conservation in agricultural landscapes

Impacts of agricultural intensification on bird communities: New insights from a multi-level and multi-facet approach of biodiversity

International audienceFollowing the multiplicity of studies dealing with the effects of agricultural intensification on birddiversity, one of the lessons drawn is that these effects depend on both the taxonomic group, thecomponent of diversity, the aspect of intensification, and the spatial scale. This often leads todisparate results among studies suggesting that the investigation of agriculture-biodiversityrelationships suffers from scale-dependence, information redundancy, non-linearity problems, andthus, unpredictability.Here, we propose a multi-scale and multi-facet approach to clarify the impacts of agriculturalintensification on biodiversity and possible mitigating actions. Our study is based on bird and agriculturalpractice surveys of 199 agriculturalfields in three agricultural regions of France. Using landscapecharacteristics and agricultural practice variables, we disentangled four main gradients of agriculturalintensification on our study sites: landscape opening (farmland expansion), landscape homogenization(decrease in crop and land cover diversity), chemical intensification (fertilizer, insecticide, and fungicide),and tillage vs. herbicide.We tested whether and how these gradients interacted with each other atfield, farm and regionallevels in shaping taxonomic diversity (alpha, gamma and beta diversity) and ecological responses of birdcommunities (relative proportion of specialist vs. generalist species, trophic categories).Landscape homogenisation and opening affected the taxonomic and ecological responses of birds atfield and farm levels, but not at the regional level, highlighting the scale-dependence of agriculture–biodiversity relationships. Atfield and farm levels, landscape opening had a positive effect on betadiversity, and community specialization by enabling the existence of farmland specialists, whileheterogeneous landscapes promoted generalists.Chemical intensification had negative impacts, especially at the farm level and on almost all facets ofdiversity. However, some bird species seemed to tolerate higher levels of both chemical and tillageintensification.Some important interaction effects between landscape and agricultural practices, which are oftendisregarded, were also revealed, such that landscape homogenization in interaction with tillagereduction was correlated with higher specialization.Thefield level appeared mostly relevant for explaining community variations by habitat and resourceavailability. Meanwhile at the coarsest scale, i.e., the Small Agricultural Region, only some possibledispersal limitations were likely to occur. Finally, our results highlight the farm level (intermediatescale) as a relevant unit for management and agricultural policies, since the community responded toboth landscape and agricultural practices intensification at this level. In particular, we emphasize thenecessity to conserve both heterogeneous and homogeneous agricultural landscapes under extensivepractices; the former promotes taxonomic diversity, when the latter favors specialized farmlandbiodiversity