The Influence of Low Intensities of Light Pollution on Bat Communities in a Semi-Natural Context

International audienceAnthropogenic light pollution is an increasingly significant issue worldwide. Over the past century, the use of artificial lighting has increased in association with human activity. Artificial lights are suspected to have substantial effects on the ecology of many species, e.g., by producing discontinuities in the territories of nocturnal animals. We analyzed the potential influence of the intensity and type of artificial light on bat activity in a semi-natural landscape in France. We used a species approach, followed by a trait-based approach, to light sensitivity. We also investigated whether the effect of light could be related to foraging traits. We performed acoustic surveys at sites located along a gradient of light intensities to assess the activity of 15 species of bats. We identified 2 functional response groups of species: one group that was light-tolerant and one group that was light-intolerant. Among the species in the latter group that appear to be disadvantaged by lighting conditions, many are rare and threatened in Europe, whereas the species from the former group are better able to thrive in disturbed habitats such as lighted areas and may actually benefit from artificial lighting. Finally, several methods of controlling light pollution are suggested for the conservation of bat communities. Recommendations for light management and the creation of dim-light corridors are proposed; these strategies may play an important role in protecting against the impact of light pollution on nocturnal animals

A decision support tool to reuse fine dam sediments as fertile constructed soils

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Potential use of dam sediment for soil construction in urban greening: Agronomic fertility and soil structuration

International audienceSediments are natural materials coming mainly from watershed soils and rocks erosion. They are composed of elementary mineral and organic particles. Each year in France, several hundred thousand cubic meters of sediments are dredged from EDF hydraulic power installations to ensure their correct operation, and returned to the river to respect the sedimentary continuity. In some cases, sediments may not be returned to water.In order to find a way to reuse the dredged sediments and to preserve natural soil resources, a research program to use sediments, and particularly fine sediments (< 2 mm) as fertile constructed soils in urban green spaces has been developed. Soils built from sediments could be at the same time a way to restore soils functions and ecosystem services in urban areas and a way to prevent natural soil resource destruction andscarcity. Then the potential fertility of such sediments, and particularly their ability to form aggregates is studied.The objective of the present study is to assess the agronomic fertility of dam sediments located in different geological environments by (i) following the early pedogenesis of constructed soil from sediment mixed or not with exogenous organic material and (ii) understanding the involved aggregation dynamics, leading to soil structuration.Four sediments contrasted in texture (from sandy loam to silty loam), mineral composition and initial organic matter content (from 29.1 to 224.3 g kg-1) were studied and compared to an agricultural loam soil used as control. The sediments were dredged from hydropower plant reservoirs, air-dried and sieved with a 40 mm screen to eliminate the coarse organic debris and stones.An in situ experiment started in July 2015 where the four sediments and the control soil were put into 50 individual 350-L containers, sown with ray grass (Lolium perenne) and placed under natural conditions over a 3-yr period. The sediments and the control soil were used alone or mixed with 40% v/v of a green waste compost. The hydraulic properties (water content and soil matric potential) of the substrates were continuously monitored using dataloggers. Moreover, after 6 (April 2016), 12 (October 2016) and 18 (April 2017) months, we measured the evolution of substrates chemical properties (pH, CEC, OM content, nutrients contents), biological properties (C-mineralization potential, microbial C biomass, plant biomassproduction) and physical properties (aggregate stability, bulk density, hydraulic conductivity at saturation (Ks), porosity, available water). The aggregate stability was assessed according to Le Bissonnais (1996) to distinguish three breakdown mechanisms: slaking, mechanical breakdown and microcracking and calculate the mean weight diameter (MWD (mm)) index.Studied sediments presented good initial agronomic properties that allowed plant growth. After 12 months we observed contrasted cumulated plant biomass production, depending on the sediment and on the compost addition, from 522 g DM m-2 to 1637 g DM m-2. These results are mainly explained by the different physical properties of the constructed soils and more precisely by the low aggregate stability (MWD Fourvel G.- 121 - under 1 mm whereas a stable aggregate MWD is above 2 mm) of certain sediments leading to slaking crusts and poor hydrodynamic behavior. The addition of compost in sediment changed the soil structure organization by slightly increasing the soil total porosity by 2.5 % to 13 % v/v, increasing the macroporosity (34 % v/v on average) and decreasing the microporosity (10 % v/v on average).From a chemical point of view, the addition of compost leads to a lower aerial biomass production than for pure sediments after 12 months (from 17% to 89%). These results can be mainly explained by the low nitrogen content of the mixed sediment-compost soil after 6 months (from 2.34 to 16.9 mg N kg-1) and after 12 months (from 0.2 to 11.16 mg N kg-1), leading to nitrogen organization by the microbial communities to the detriment of plant nutrition. Nevertheless, the development of roots is important for all the modalities, which suggests a plant growth potential for next months.In conclusion, the four studied sediments have contrasted aggregation and plant biomass production capacities but all of them showed a potential use for urban greening of high interest. Results on sediment aggregation showed that some sediments are already mature with strong aggregates that resist to external aggressions and that other sediments with lower maturity should be improved with treatment, such as high organic matter content material addition.In situ experiment gave interesting results about aggregation dynamics but the main factors favoring sediment structuration (addition of a high organic matter content material, wetting-drying cycles and microbial community dynamics) need to be investigated during a controlled conditions experiment to understand more accurately the aggregation processes in such constructed soils. In parallel, the remaining 18 months of the in situ experiments should confirm over time physical properties improvement or conservation and they will allow to assess the impact of the structuration on the hydrodynamic behavior of constructed soils (soil water retention and aeration, and soil water drainage)

A decision support tool to reuse fine dam sediments as fertile constructed soils

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Potential use of dam sediment for soil construction in urban greening: agronomic fertility and environmental harmlessness

International audienceThere is today a growing demand to develop green spaces in city, as they provide a support for biodiversity and can contribute to ecological connectivity with surroundings. Greening urban areas requires large amounts of arable soil that is a non-renewable resource. The purpose of our study is todetermine whether river dam sediments can be used as alternative materials to preserve soil resource in urban greening. Indeed, sediments are natural materials coming mainly from soils erosion available in large volumes. Sediments are composed of elementary mineral and organic particles. Each year in France, several hundred thousand cubic meters of sediments are dredged from EDF hydraulic power installations to ensure their correct operation, and returned to the river to respect the sedimentary continuity. In some cases, sediments may not be returned to water. Then, ways of valorization are sought. Most often they do not contain anthropic contaminants, in relation with their origin, far fromhuman activities (Brochier et al., 2016), but in some cases, they could contain traces of heavy metalscoming from the natural geochemical backgrounds

Fertility of Technosols constructed with dam sediments for urban greening and land reclamation

International audienceFine sediment accumulates upstream of hydroelectric dams. To ensure that dams can operate properly, part of the sediment has to be dredged and land managed. In parallel, using topsoil from agricultural parcels for urban greening or land restoration is currently controversial because arable surface areas are decreasing. An alternative idea for protecting these natural resources consists in reusing fine dredged sediment to construct multifunctional soils. This agronomic use is only possible if sediment can provide acceptable physical and chemical properties for plant growth

Capacité d'un sédiment à se substituer à la terre végétale en construction de sol

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Potentiel d’utilisation de sédiments fins de barrage pour la construction de sols urbains végétalisés : fertilité agronomique et premières étapes de pédogenèse

International audienceLes sédiments sont des matériaux naturels provenant principalement de l’érosion des roches et des sols. Chaque année en France, plusieurs centaines de milliers de mètres cubes de sédiments sont extraits des retenues hydroélectriques d’EDF dont une partie doit être gérée à terre et est considérée comme un déchet. Dans le but de trouver des voies de valorisation robustes de ces sédiments, tout en préservant la ressource « sol naturel », un projet de valorisation des sédiments fins en construction de sol urbain végétalisé a été mis en place. Ses objectifs sont (1) d’évaluer la fertilité agronomique de sédiments provenant de quatre retenues hydroélectriques localisées dans des environnements différents (géographie, géologie, bassin versant) et (2) de suivre les premières étapes de l’évolution pédologique de ces sols construits à partir de sédiments seuls ou en mélange avec de la matière organique exogène. Quatre sédiments limoneux à sablo-limoneux et avec des teneurs en matière organique différentes sont comparés avec l’horizon supérieur d’un sol agricole limono-sableux, classiquement utilisé en tant que terre végétale pour l’aménagement d’espaces verts urbains (sol témoin). Les sédiments et le sol témoin sont étudiés seuls ou en mélange avec 40% v/v de compost de déchets verts pour mimer des horizons supérieurs fertiles. Chaque substrat a été placé dans des bacs lysimétriques individuels d’une capacité de 350 L en juillet 2015, semés avec du Ray Grass anglais (Lolium perenne) et placés en conditions naturelles pour une période de trois ans. Un dispositif de sondes permet de mesurer en temps réel certaines propriétés hydriques des sols (teneur en eau, potentiel matriciel) et la température des substrats. Six mois après la mise en place, nous avons suivi l’évolution des propriétés physiques des sols (stabilité des agrégats, densité apparente, conductivité hydraulique à saturation, porosité), des propriétés chimiques (pH, capacité d’échange cationique, teneur en matière organique, teneurs en majeurs et oligoéléments) et des propriétés biologiques (potentiel de minéralisation, biomasse microbienne, biomasse végétale aérienne et racinaire). Les caractéristiques agronomiques initiales des sédiments sont variables selon l’origine des sédiments et semblent être en adéquation avec la fonction de support de végétation attendue. D’un point de vue physique, l’apport de compost diminue la densité apparente de 0,09 à 0,32 g cm-3 selon le sédiment (densité apparente initiale des sédiments allant de 0,50 à 1,44 g cm-3). L’apport de compost pénalise à court terme la production de biomasse végétale aérienne de certains sédiments. Les hypothèses avancées pour expliquer ces résultats seront discutés lors de l’exposé. Les démontages semestriels du site expérimental permettront de vérifier l’évolution des propriétés agronomiques des sédiments, de comprendre leurs processus de structuration et de décrire leur comportement hydrodynamique sur le plus long terme

Influence of light intensity on the activity of each bat species.

<p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0103042#pone.0103042-Dietz1" target="_blank">[3]</a> Dietz C., Helversen O. von, Nill D.(2009) L'encyclopédie des chauves-souris d'Europe et d'Afrique du Nord: Biologie, caractéristiques, protection. Delachaux et Niestlé, Paris. 400 p.</p><p>Influence of light intensity on the activity of each bat species.</p

Influence of light type on the activity of each bat species.

<p>Because the type of light is a categorical variable, the given estimate is the average estimate of bat activity for each type (white or orange) compared with the absence of light. Thus, the p-value provides information about the significance of the difference between an absence of light <i>vs.</i> the artificial light type (white or orange). Back-transformed estimate effects represent the average estimate of bat activity for each color type on the original scale.</p><p>Influence of light type on the activity of each bat species.</p