Smart sustainable cities of the new millennium : towards design for nature

Urban environments consist of a mosaic of natural fragments, planned and unintentional habitats hosting both introduced and spontaneous species. The latter group exploits abandoned and degraded urban niches which, in the case of plants, forms what is called the Third Landscape. In the Anthropocene, cities, open spaces and buildings must be planned and designed considering not only human needs but also those of other living organisms. The scientific approach of habitat sharing is defined as Reconciliation Ecology, whilst the action of implementing the ecosystem services and functioning of such anthropogenic habitats is called Urban Rehabilitation. However, urban development still represents the main cause of biodiversity loss worldwide. Yet, the approach of planners and landscape architects highly diverges from that of ecologists and scientists on how to perceive, define and design urban green and blue infrastructure. For instance, designers focus on the positive impact that Nature (generally associated with indoor and outdoor greeneries) has on human well-being, often neglecting ecosystems’ health. Instead, considering the negative impact of any form of development and to achieve the No Net Loss Aichi’s objectives, conservationists apply mitigation hierarchy policies to avoid or reduce the impact and to offset biodiversity. The rationale of this review paper is to set the fundamentals for a multidisciplinary design framework tackling the issue of biodiversity loss in the urban environment by design for Nature. The method focuses on the building/city/landscape scales and is enabled by emerging digital technologies, i.e. Geographic Information Systems, Building Information Modelling, ecological simulation and computational design

For a better representation of African grass biomes in vegetation models : inputs from grass physiognomic traits, leaf area index and phytoliths

Les biomes herbacés africains intertropicaux devraient faire face, dans un proche futur, à des changements drastiques. Les modèles dynamiques de végétation (DGVM) ont des difficultés à simuler les limites actuelles de ces biomes, notamment parce qu’ils ne prennent pas en compte la diversité des couverts herbacés en C4. Il est donc nécessaire de caractériser cette diversité floristique et physionomique afin qu’elle puisse être facilement prise en compte dans les DGVMs, et que les comparaisons modèle/données (phytolithes) soient possibles.Dans cet objectif, les traits physionomiques des graminées en C4 dominantes au Sénégal et en Afrique du Sud ont été répertoriés. Quatre groupes physionomiques ont été statistiquement discriminés. Ils varient avec la distribution spatiale des biomes et les précipitations régionales. Deux groupes sont fortement corrélés à l’indice de surface foliaire (LAI) et à la biomasse herbacée. Au Sénégal ces deux groupes sont bien différenciés par l’indice phytolithique Iph qui est un proxy des couverts herbacés intertropicaux. En Afrique du Sud, les phytolithes n’ont pas permis de tracer l’ensemble de la transition savane/steppe. Ces deux groupes physionomiques remplissent les critères nécessaires à la caractérisation de types fonctionnels de plantes (PFT). L’intégration de ces PFTs dans le modèle LPJ-GUESS améliore la simulation des biomes herbacés actuels et permet de proposer des simulations pour l’horizon 2100. Ces simulations montrent que l’augmentation de la durée de la saison sèche et de la concentration en CO2 atmosphérique devraient favoriser l’expansion simultanée des steppes et des savanes fermées aux dépens des savanes ouvertes.Intertropical african herbaceous biomes are expected to face drastic changes in a near future. However Dynamic Global Vegetation Models (DGVMs) simulate their modern boundaries with poor accuracy, especially at the regional scale. DGVMs fail to consider the diversity of their C4 grass cover. Efforts are thus needed to characterize this floristic and physiognomic diversity in a way that can be used for enhancing DGVMs simulations, and enabling model/data (phytoliths) comparisons. For that purpose, physiognomic traits of dominant C4 grass species settled in Senegal and South Africa were listed. Four grass physiognomic groups were statistically identified. The abundance of four of them significantly varied with biome distributions and regional precipitation. Two grass physiognomic groups were additionally strongly correlated with leaf area index (LAI) and grass biomass. In Senegal, those two groups were also well traced by the Iph phytolith index which is a tropical grass cover proxy. In South Africa the limited set of phytolith data did not allow to observe the full savanna/steppe transition. The two physiognomic groups finally fulfilled the criteria required for creating Plant Functional Types (PFTs). Those new PFTs, parameterized in the LPJ-GUESS DGVM, enhanced the simulation of modern herbaceous biomes distribution in Senegal and South Africa. Simulations were additionally performed for the 2100 horizon. They evidence that the increase of both length of the dry season and atmospheric CO2 concentration should favor the simultaneous spread of steppes and closed savannas at the expense of open savannas

Grass Physiognomic Trait Variation in African Herbaceous Biomes

International audienceAfrican herbaceous biomes will likely face drastic changes in the near future, due to climate change and pressures from increasing human activities. However, these biomes have been simulated only by dynamic global vegetation models and failing to include the diversity of C 4 grasses has limited the accuracy of these models. Characterizing the floristic and physiognomic diversity of these herbaceous biomes would enhance the parameterization of C 4 grass plant functional types, thereby improving simulations. To this end, we used low-ermost and uppermost values of three grass physiognomic traits (culm height, leaf length, and leaf width) available in most floras to identify several grass physiognomic groups that form the grass cover in Senegal. We then checked the capacity of these groups to discriminate herbaceous biomes and mean annual precipitation domains. Specifically, we assessed whether these groups were sufficiently generic and robust to be applied to neighboring (Chad) and distant (South Africa) phytogeographic areas. The proportions of two phys-iognomic groups, defined by their lowermost limits, delineate steppe from savanna and forest biomes in Senegal, and nama-karoo, savanna, and grassland biomes in South Africa. Proportions of these two physiognomic groups additionally delineate the mean annual precipitation domains 600 mm in Senegal, Chad, and South Africa, as well as the 1000 mm domains in South Africa. These findings should help to identify and parameterize new C 4 grass plant functional types in vegetation models applied to West and South Africa

Enhanced Cooperative Interactions at the Nanoscale in Spin-CrossoverMaterials with a First-Order Phase Transition

International audienceWe analyzed the size effect on a first-order spin transition governed by elastic interactions. This study was performed in the framework of a nonextensive thermodynamic core-shell model. When decreasing the particle size, differences in surface energies between the two phases lead to the shrinking of the thermal hysteresis width, the lowering of the transition temperature, and the increase of residual fractions at low temperature, in good agreement with recent experimental observations on spin transition nanomaterials. On the other hand, a modification of the particle-matrix interface may allow for the existence of the hysteresis loop even at very low sizes. In addition, an unexpected reopening of the hysteresis, when the size decreases, is also possible due to the hardening of the nanoparticles at very small sizes, which we deduced from the size dependence of the Debye temperature of a series of coordination nanoparticles