Biotic soil-plant interaction processes explain most of hysteretic soil CO2 efux response to temperature in cross-factorial mesocosm experiment

Ecosystem carbon fux partitioning is strongly infuenced by poorly constrained soil CO2 efux (Fsoil). Simple model applications (Arrhenius and Q10) do not account for observed diel hysteresis between Fsoil and soil temperature. How this hysteresis emerges and how it will respond to variation in vegetation or soil moisture remains unknown. We used an ecosystem-level experimental system to independently control potential abiotic and biotic drivers of the Fsoil-T hysteresis. We hypothesized a principally biological cause for the hysteresis. Alternatively, Fsoil hysteresis is primarily driven by thermal convection through the soil profle. We conducted experiments under normal, fuctuating diurnal soil temperatures and under conditions where we held soil temperature near constant. We found (i) signifcant and nearly equal amplitudes of hysteresis regardless of soil temperature regime, and (ii) the amplitude of hysteresis was most closely tied to baseline rates of Fsoil, which were mostly driven by photosynthetic rates. Together, these fndings suggest a more biologically-driven mechanism associated with photosynthate transport in yielding the observed patterns of soil CO2 efux being out of sync with soil temperature. These fndings should be considered on future partitioning models of ecosystem respiration.French governmentFrench National Research Agency (ANR) ANR-10-IDEX-0001-02 PSL ANR-11-INBS-0001ENSUniversity of Arizona (UofA)Philecology Foundation (Fort Worth, Texas, USA)Thomas R. Brown Family FoundationRegion Ile-de-France I-05-098/R 2011-11017735European Union (EU)National Science Foundation (NSF) 1417101 1331408European Union (EU) 625988UofA Office of Global InitiativesOffice of the Vice President of Research at the UofAUMI iGLOBES program at the Uof

Green roofs and ecosystem services : enhancing multifunctionality through soil-plant interactions and plant diversity

Les toitures végétalisées sont des écosystèmes urbains et construits en essor constant en France et dans le monde. Elles sont associées à plusieurs services écosystémiques tels que la limitation du ruissellement des eaux de pluie vers les canalisations, la réduction des effets d'îlots de chaleur urbains ou l'augmentation de la biodiversité en ville. L'amélioration de la quantité et de la qualité des services écosystémiques attendus nécessite de comprendre l'influence des interactions entre les composantes de la toiture végétalisée, à savoir la composition du sol, sa profondeur et la communauté végétale, sur les multiples fonctions écosystémiques associées. Pourtant, ces interactions n'ont jamais été étudiées dans le contexte des toitures végétalisées. A l'aide d'expérimentations en milieu contrôlé puis en conditions réelles sur une toiture parisienne, nous avons cherché à comprendre comment les interactions entre les composantes des toitures végétalisées influencent des fonctions majeures liées aux cycles biogéochimiques du carbone, de l'azote et de l'eau, ainsi qu'à la pollinisation. Nous avons mis en évidence une influence majeure des interactions entre type de sol, profondeur du sol, espèces de plantes et diversité végétale sur (1) le niveau de réalisation des fonctions écosystémiques ainsi que (2) les interactions entre ces fonctions. Nous avons montré que le choix des composantes d'une toiture pouvait conduire à des compromis entre services écosystémiques. Nous proposons des pistes de conception et de gestion pour obtenir des toitures végétalisées multifonctionnelles.Green roofs are urban constructed ecosystems, associated with multiple ecosystem services, such as urban heat island and stormwater runoff mitigation or support for biodiversity. Enhancing the quality and quantity of expected ecosystem services requires to understand how interactions between substrate composition, substrate depth and plant community affect multiple ecosystem functions. However, such interactions have never been studied on green roofs. Using experimental approaches under controlled and real conditions on a Parisian rooftop, we focused on the influence of soil-plant interactions on key ecosystem functions related to carbon, nitrogen and water cycles as well as pollination. We highlighted that interactions between substrate type, substrate depth, plant species and plant diversity affect (1) the level of ecosystem functions and (2) interactions between functions. We found that the choice of green roof components could lead to trade-offs between ecosystem services. We propose general guidelines for the conception and management of multifunctional green roofs

Toitures végétalisées et services écosystémiques : favoriser la multifonctionnalité via les interactions sols-plantes et la diversité végétale

Green roofs are urban constructed ecosystems, associated with multiple ecosystem services, such as urban heat island and stormwater runoff mitigation or support for biodiversity. Enhancing the quality and quantity of expected ecosystem services requires to understand how interactions between substrate composition, substrate depth and plant community affect multiple ecosystem functions. However, such interactions have never been studied on green roofs. Using experimental approaches under controlled and real conditions on a Parisian rooftop, we focused on the influence of soil-plant interactions on key ecosystem functions related to carbon, nitrogen and water cycles as well as pollination. We highlighted that interactions between substrate type, substrate depth, plant species and plant diversity affect (1) the level of ecosystem functions and (2) interactions between functions. We found that the choice of green roof components could lead to trade-offs between ecosystem services. We propose general guidelines for the conception and management of multifunctional green roofs.Les toitures végétalisées sont des écosystèmes urbains et construits en essor constant en France et dans le monde. Elles sont associées à plusieurs services écosystémiques tels que la limitation du ruissellement des eaux de pluie vers les canalisations, la réduction des effets d'îlots de chaleur urbains ou l'augmentation de la biodiversité en ville. L'amélioration de la quantité et de la qualité des services écosystémiques attendus nécessite de comprendre l'influence des interactions entre les composantes de la toiture végétalisée, à savoir la composition du sol, sa profondeur et la communauté végétale, sur les multiples fonctions écosystémiques associées. Pourtant, ces interactions n'ont jamais été étudiées dans le contexte des toitures végétalisées. A l'aide d'expérimentations en milieu contrôlé puis en conditions réelles sur une toiture parisienne, nous avons cherché à comprendre comment les interactions entre les composantes des toitures végétalisées influencent des fonctions majeures liées aux cycles biogéochimiques du carbone, de l'azote et de l'eau, ainsi qu'à la pollinisation. Nous avons mis en évidence une influence majeure des interactions entre type de sol, profondeur du sol, espèces de plantes et diversité végétale sur (1) le niveau de réalisation des fonctions écosystémiques ainsi que (2) les interactions entre ces fonctions. Nous avons montré que le choix des composantes d'une toiture pouvait conduire à des compromis entre services écosystémiques. Nous proposons des pistes de conception et de gestion pour obtenir des toitures végétalisées multifonctionnelles

Multifunctionality is affected by interactions between green roof plant species, substrate depth, and substrate type

Summary Green roofs provide ecosystem services through evapotranspiration and nutrient cycling that depend, among others, on plant species, substrate type, and substrate depth. However, no study has assessed thoroughly how interactions between these factors alter ecosystem functions and multifunctionality of green roofs. We simulated some green roof conditions in a pot experiment. We planted 20 plant species from 10 genera and five families (Asteraceae, Caryophyllaceae, Crassulaceae, Fabaceae, and Poaceae) on two substrate types (natural vs. artificial) and two substrate depths (10 cm vs. 30 cm). As indicators of major ecosystem functions, we measured aboveground and belowground biomasses, foliar nitrogen and carbon content, foliar transpiration, substrate water retention, and dissolved organic carbon and nitrates in leachates. Interactions between substrate type and depth strongly affected ecosystem functions. Biomass production was increased in the artificial substrate and deeper substrates, as was water retention in most cases. In contrast, dissolved organic carbon leaching was higher in the artificial substrates. Except for the Fabaceae species, nitrate leaching was reduced in deep, natural soils. The highest transpiration rates were associated with natural soils. All functions were modulated by plant families or species. Plant effects differed according to the observed function and the type and depth of the substrate. Fabaceae species grown on natural soils had the most noticeable patterns, allowing high biomass production and high water retention but also high nitrate leaching from deep pots. No single combination of factors enhanced simultaneously all studied ecosystem functions, highlighting that soil-plant interactions induce trade-offs between ecosystem functions. Substrate type and depth interactions are major drivers for green roof multifunctionality. K E Y W O R D S ecosystem services, evapotranspiration, nitrogen and carbon cycles, soil-plant interactions, trade-offs, urban ecology, water retention 2358 | DUSZA et Al

Service de pollinisation et urbanisation: un projet expérimental dans Paris intra-muros: L'exemple de la Cité Internationale Universitaire de Paris

International audienc

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Hal.24-25: ilus. ; 28 c

Urban ecology, stakeholders and the future of ecology

International audienceThe world human population is more and more urban and cities have a strong impact on the biosphere. This explains the development of urban ecology. In this context, the goal of our work is fourfold: to describe the diversity of scientific questions in urban ecology, show how these questions are organized, to assess how these questions can be built in close interactions with stakeholders, to better understand the role urban ecology can play within ecological sciences. A workshop with scientists from all relevant fields (from ecology to sociology) and stakeholders was organized by the Foundation for Research on Biodiversity (FRB). Three types of scientific issues were outlined about (1) the biodiversity of organisms living in urban areas, (2) the functioning of urban organisms and ecosystems, (3) interactions between human societies and urban ecological systems. For all types of issues we outlined it was possible to distinguish both fundamental and applied scientific questions. This allowed building a unique research agenda encompassing all possible types of scientific issues in urban ecology. As all types of ecological and evolutionary questions can be asked in urban areas, urban ecology will likely be more and more influential in the development of ecology. Taken together, the future of towns, their biodiversity and the life of city dwellers is at stake. Increasing the space for ecosystems and biodiversity within towns is more and more viewed as crucial for the well-being of town dwellers. Depending on research and the way its results are taken into account, very different towns could emerge. Urban areas can be viewed as a test and a laboratory for the future of the interactions between human and ecological systems