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1. Pollinators are declining globally, with climate change implicated as an important driver. Climate change can induce phenological shifts and reduce floral resources for pollinators, but little is known about its effects on floral attractiveness and how this might cascade to affect pollinators, pollination functions and plant fitness. 2. We used an in situ long-term drought experiment to investigate multiple impacts of reduced precipitation in a natural Mediterranean shrubland, a habitat where climate change is predicted to increase the frequency and intensity of droughts. Focusing on three insect-pollinated plant species that provide abundant rewards and support a diversity of pollinators (Cistus albidus, Salvia rosmarinus and Thymus vulgaris), we investigated the effects of drought on a suite of floral traits including nectar production and floral scent. We also measured the impact of reduced rainfall on pollinator visits, fruit set and germination in S. rosmarinus and C. albidus. 3. Drought altered floral emissions of all three plant species qualitatively, and reduced nectar production in T. vulgaris only. Apis mellifera and Bombus gr. terrestris visited more flowers in control plots than drought plots, while small wild bees visited more flowers in drought plots than control plots. Pollinator species richness did not differ significantly between treatments. Fruit set and seed set in S. rosmarinus and C. albidus did not differ significantly between control and drought plots, but seeds from drought plots had slower germination for S. rosmarinus and marginally lower germination success in C. albidus. 4. Synthesis. Overall, we found limited but consistent impacts of a moderate experimental drought on floral phenotype, plant reproduction and pollinator visits. Increased aridity under climate change is predicted to be stronger than the level assessed in the present study. Drought impacts will likely be stronger and this could profoundly affect the structure and functioning of plant–pollinator networks in Mediterranean ecosystems.

International audience; Mangroves are ecosystems interfacing terrestrial and marine environments submitted to extreme abiotic factors (e.g. anoxia, flooding, salinity) producing stress on vegetation. Due to these stresses, we hypothesized that mangroves potentially emit biogenic volatile organic compound (BVOC), particularly isoprenoids as they are defense compounds. Despite mangroves cover only about 5% of the forest areas of the world, their emissions could impact air quality at the continental-ocean interface. As a result, it is important to fill the gap in the knowledge about BVOC emissions from the canopy of the major mangrove trees. The aim of this study was thus to screen isoprenoid emissions of the mangrove species. In this study, we sampled isoprenoid emissions of 14 species foliage among the 38 core species existing in the Indo-West Pacific (IWP) and the Atlantic Est Pacific (AEP) regions. Sampling was performed using a branch-bag dynamic enclosure system and analyzed with gas chromatography coupled to mass spectrometry. Our analysis showed that mangrove tree species are very low emitters suggesting that mangrove ecosystems would not strongly influence atmospheric chemistry and air quality.

Mangroves are highly productive and changing forests located in the intertidal zone of tropical regions. Leaf litter decomposition represents a substantial part of their carbon sink abilities. Little is known about the potential effect of climate change on this key process of ecosystem functioning. This study compared leaf litter microbial decay between fringe and riverine Avicennia germinans stands. A direct and reciprocal transplant experiment using litterbags was setup in French Guiana to test 3 hypotheses: (i) the activities and abundance of microbial decomposers are lowest in the fringe mangroves due to exposure to saline water and tidal immersion; (ii) for these reasons, litter decomposes faster in riverine stands; and (iii) according to the home-field advantage hypothesis, litter decomposes more rapidly in the environment from which it originates. Remaining litter masses, abundance of litter microbial community (phospholipid fatty acid signatures (PLFA)), and their functional capability (enzyme activities and Biolog) were assessed. Litter directly transplanted in riverine stands showed higher enzymatic activity (+ 77%), catabolic diversity (+ 10%), and microbial biomass (+ 60%) than litter transplanted directly in fringe stands. In contrast, both riverine and fringe derived litter showed faster decay at the fringe (14% mass loss) than riverine site (4% mass loss) between 30 and 45 days. Here, environmental conditions associated with different distances from the sea such as salinity and inundation regimes, rather than microbial features are suggested as main factors affecting decomposition process. Expected sea level rise in the coastal Guianas may therefore modify the mangroves productivity in the coming decades.

Given the importance of terpenes and fuel moisture content (FMC) on flammability, this work aims at checking how these parameters affect leaf flammability of different native and Wildland-Urban Interfaces species (Pinus halepensis, Cupressus sempervirens, Cupressocyparis leylandii, and Hesperocyparis arizonica) across seasons in the French Mediterranean region. We found that the highest terpene diversity and content seasonally varied according to the species, with diterpene content being lower in spring for C. leylandii, while monoterpene and diterpene content being higher in summer and winter, respectively, for P. halepensis. Flammability and FMC varied according to the season but the pattern differed among species. A significant correlation between the latters was rarely observed and occurred in only one season, differing among species. The correlations between flammability and terpenes were mostly highlighted using single compounds, compared to subgroups, and they presented seasonal patterns varying among species. Checking the seasonal effect of groups of terpene compounds on flammability, there were seasonal differences in these groups according to the species and the variable tested. Mostly, these significant compounds were not the most concentrated. The best flammability drivers of each model, mostly diterpenes, except for P. halepensis whose flammability was mostly drove by mono- and sesquiterpenes, changed among seasons according to the flammability variable considered. When a best driver remained the same in different seasons, its effect on flammability could be opposite. In contrast, FMC was generally not a significant explanatory parameter of leaf flammability or did not improve the fit of models.

International audience; In flammability assessment, the terpene effect is usually studied using their total or subgroup content, missing, therefore, the information that could be provided by the molecules themselves. In this study, the specific role of terpenes on leaf flammability was sought comparing different levels of terpene identification—total, subgroup (i.e. mono-, sesqui-, and diterpene), and single compound—as well as their interactions with fuel moisture content (FMC) in four species common in Mediterranean Wildland–Urban Interfaces (Pinus halepensis, Cupressocyparis leylandii, Hesperocyparis arizonica, Cupressus sempervirens). Pinus halepensis was the most flammable species (low FMC and higher sesquiterpene content but low terpene diversity) while Cupressocyparis leylandii presented the highest terpene diversity and total terpene content (higher mono- and diterpene content). Flammability was differently affected according to the terpene identification level used in the models. The effects ranged from non-significant for most species studied, using subgroup or total terpene content, to mostly significant, using single compound content. Regarding the former, the lack of significant results could be due to opposite effects of different single compounds within a terpene subgroup. For the latter, terpene molecules driving flammability and their effects (positive or negative) differed among species. A cumulative effect with FMC was also highlighted in some cases but terpenes mostly remained the main flammability drivers regardless of the species. Using the refined terpene level in modelling allowed a better understanding of the compounds’ role on flammability, which is useful in the identification of plant traits linked to flammability.

International audience; Soil organisms play a major role on litter decomposition process and nutrient cycling in forest ecosystems. These organisms are extremely sensitive to environmental conditions such as soil temperature and moisture conditions which control their demographic parameters and activity. The ongoing climate change can therefore directly affect soil biota communities and the processes they drive. Besides, climate change can also indirectly affect soil biota by altering tree functional traits (e.g., N, Ca, Mg, water holding capacity) with cascading effects on the litter quality. The aim of this study was to determine the relative effects of increased drought and litter type on microbial biomass (bacteria and fungi) and mesofauna abundance (Collembola and Acari) in three experimental sites representative of the three main forests encountered in the northern part of the Mediterranean Basin (dominated by either Quercus pubescens, Quercus ilex or Pinus halepensis) where rainfall exclusion experiments were taking place. At each site, and in each precipitation treatment (natural and amplified drought plots), we collected and transplanted foliage litters (i.e., species × drought level). After two years, we reported a litter species effect: Q. pubescens litter presented consistently the higher abundance of all soil biota groups compared to Q. ilex and P. halepensis litters in each forest. Surprisingly, despite that the amplified drought treatment induced a modification of the litter quality, we did not reported an indirect reduced precipitation effect on soil biota parameters. While Oribatid Acari abundance decreased with amplified drought in all three forest types, the direct effects on the other soil biota groups were forest-dependent. In P. halepensis forest, amplified drought resulted in higher bacterial and fungal biomasses but lower Collembola abundance. In Q. ilex forest both Collembola and predatory Acari abundances decreased with amplified drought. In addition, the positive relationships between Collembola and Oribatida abundances and litter mass loss disappeared under amplified drought conditions in both Q. ilex and P. halepensis forests. These results suggest a key role played by Ca, Mg, specific leaf area (SLA) and water holding capacity (WHC) as drivers of soil biota parameters. Finally, the study highlights that within the same Mediterranean region, climate change could differently alter the soil organisms inhabiting the litter layer and their contributions to the decomposition process depending on the tree species and soil biota group considered.

International audience; Leaf litter, at the interface between the soil and the atmosphere, releases Biogenic Volatile Organic Compounds (BVOC) which play an important role both in global atmospheric chemistry and plant ecology. Litter is especially important in the Mediterranean region, where it is produced in high amounts and decomposes slowly. Only leaf litter emissions of two dominant species (Pinus halepensis and Eucalyptus spp.) present in the Mediterranean region have been studied so far. The aim of this study is to characterize (quantitatively and qualitatively) the BVOC emissions (C10–C15) from litter (freshly fallen and non-decomposed leaves) under laboratory conditions. Sixteen species frequently found in the Mediterranean region were considered, nine of which possess terpene storage structures. Results show a large diversity of BVOC (87 compounds detected, terpenes, alkanes, alkenes, aldehydes, ketones, benzenoids), with terpene emission being higher than non-terpenic emission in most of the cases. Species were classified within 3 categories: negligible emitters (e.g. Acer monspessulanum and Quercus ilex, < 0.10 μg.gDM−1.h−1), low emitters (Pinus pinea, Quercus pubescens, 0.1–1.0 μg.gDM−1.h−1) and moderate emitters (Thymus vulgaris, Cotinus coggygria and Pinus halepensis between 1.5 and 4.7 μg.gDM−1.h−1). Litter that possessed terpene storage structures and known to store high terpene concentration did not always release the highest terpene emission rates (e.g. Eucalyptus globulus, Rosmarinus officinalis). Species that do not possess such structures release only non terpenic emissions (e.g. alkanes, aldehydes). Estimation of the potential contribution of P. halepensis and Q. pubescens litter to O3 and secondary organic aerosol (SOA) formation in the atmosphere showed that P. halepensis has a larger potential impact on the global air quality than Q. pubescens. This study will contribute to build future BVOC emissions inventories on leaf litter for their further integration in atmospheric chemistry models.

International audience; 15 The ecological transition zones also known as ecotones are specific ecosystems but how global change 16 will affect their biodiversity and functioning is poorly understood. In the case of the areas at the 17 interface between riparian forest and salt meadows the biodiversity conservation remains a major 18 issue. The aim of this work was to evaluate the effects of a salty environment on Fraxinus angustifolia 19 a non-halophyte species. For this, the photochemistry of PSII was in situ explored during the summer 20 between 2007 and 2016. The predawn maximum quantum efficiency of PSII (Fv/Fm) was always 21 greater than 0.8 which indicates an absence of chronic photoinhibition induced by salinity. During 22 these years, the light kinetic of the actual quantum yield of PSII (Φ PSII) was studied. It appears that 23 this yield is generally higher in salty environments than in the riparian forest. Multivariate analysis, 24 showed that the dissipation regulated light energy faction (Φ NPQ), the photochemical quenching (qP) 25 and the Fd/Fs ratio constitute the main explanatory variables of Φ PSII changes. The subsequent two-26 way-ANCOVA carried out demonstrated that Φ NPQ was weaker in saline environments, suggesting a 27 better efficiency of photosystem collecting antennas. Meanwhile, the analysis of photosynthetic 28 pigments did not exhibited a salt effect except the significant accumulation of chlorophyll a in 2016. 29 In order to address the question of the salt-related toxicity, sodium ion contents in the leaves were 30 found to be identical in the two sites, suggesting the establishment of an energy-dependent mechanism 31 of salt exclusion/retention in roots. The growth rings of F.angustifolia in saline areas highly follows 32 the annual water deficit changes. Between 2007 and 2016, the biomass in the salt meadow was higher 33 with a peak in 2011 representing 60% of the biomass of control individuals. But, since 2011 a 34 J o u r n a l P r e-p r o o f 2 continuous decline of growth was recorded. Water conditions seem to constitute a limiting factor even 35 if the photosynthetic apparatus generates the excess metabolic energy necessary to cope with the saline 36 toxicity. This study thus highlighted the plasticity of the photochemistry of the PSII depending to the 37 environmental conditions of the salt meadows. It also shows the vulnerability of an ecotone through 38 the decline in the productivity of a glycophyte with climate change. This augurs for changes in the 39 composition of plant communities which is in favor of strict halophytes. 40

The capacity of a Quercus pubescens forest to resist recurrent drought was assessed on an in situ experimental platform through the measurement of a large set of traits (ecophysiological and metabolic) studied under natural drought (ND) and amplified drought induced by partial rain exclusion (AD). This study was performed during the 3rd and 4th years of AD, which correspond to conditions of moderate AD in 2014 and harsher AD in 2015, respectively. Although water potential (Ψ) and net photosynthesis (Pn) were noticeably reduced under AD in 2015 compared to ND, trees showed similar growth and no oxidative stress. The absence of oxidative damage could be due to a strong accumulation of α-tocopherol, suggesting that this compound is a major component of the Q. pubescens antioxidant system. Other antioxidants were rather stable under AD in 2014, but slight changes started to be observed in 2015 (carotenoids and isoprene) due to harsher conditions. Our results indicate that Q. pubescens could be able to cope with AD, for at least 4 years, likely due to its antioxidant system. However, growth decrease was observed during the 5th year (2016) of AD, suggesting that this resistance could be threatened over longer periods of recurrent drought.

International audience; Plant–plant chemical interactions in forests can have a strong impact on the biodiversity and dynamics of these ecosystems, particularly in Mediterranean forests where plants exhibit a high secondary metabolite diversity. Allelopathic interactions in Mediterranean ecosystems have been mostly studied in the first stages of ecosystem dynamics, shrublands and pine forests, but little is known about these interactions in mature oak forests. In this study, the allelopathic effect of three main woody species of downy oak forests (Quercus pubescens, Acer monspessu-lanum and Cotinus coggygria) on germination and growth of two herbaceous species (Festuca ovina and Linum per-enne) was tested through aqueous extracts obtained from different leaf phenological stages (green, senescent and litter). The germination velocity of the two target species was inhibited by the aqueous extracts of senescent leaves from all the woody species. The growth of F. ovina seedlings was affected by aqueous extracts of green leaves of all the woody species, while the growth of L. perenne was only affected by aqueous extracts of green leaves of A. monspessulanum. This shows that (i) allelochemicals released by leaf leachates of the dominant woody species could control the dynamic of the herbaceous species, and then their potential competition with trees and (ii) allelo-pathic effects of woody species are related to their phenological stage and seem consistent with the development stage of target species.

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SEDYVIN [ADD1_IRSTEA]Dynamiques spatiales d'anthropisation; International audience; Among plant characteristics promoting flammability, terpenes have received far less attention, especially regarding the vegetation surrounding housing. Here, mono-, sesqui-, and diterpenes were screened in live and dead leaves of ornamental species found in Wildland-Urban Interfaces (WUI) of southeastern France. Terpene content and composition were compared among species and between fuel types. Their influence on flammability was assessed through several variables and compared to that of leaf thickness and moisture content. Six of the 17 species examined contained terpenes. Terpene diversity and content differed among species but not between fuel types. Mono-, sesqui-, and diterpenes (especially the highly concentrated compounds) were involved to varying degrees in both leaf and litter flammability. Their effects could be the opposite according to the flammability variable and the fuel type considered. Leaf sesquiterpene content and litter total terpene content had the strongest influence on maximum temperature; the former also mainly drove leaf flaming duration. The other flammability variables were more strongly associated with either moisture content or leaf thickness. Our findings underlined the idea that fire management in WUI must also acknowledge the potential for ornamental species containing terpenes, such as P. halepensis, in affecting fire behaviour.

International audience; Plant litter decomposition is an essential process of ecosystem functioning, driven by a complex soil food web. The identity and density of the predators, as well as the quality and quantity of litter, could conjointly affect the strength of trophic interactions within a soil food web. Pine and oak are dominant tree species in temperate and Mediterranean forests and, although they exhibit distinct litter characteristics, no previous study attempted to decipher how these two litters can affect a litter-based multi-trophic system with varying predator density. Using a microcosm experiment, we aimed at understanding how different densities of a predatory Acari (Stratiolaelaps scimitus) and two Mediterranean litter species (Quercuspubescens and Pinus halepensis) may impact the demographic parameters of the predatory Acari, its Collembola prey (Folsomia candida) and the fungal biomass associated with litter. We did not observe any interactive effect of litter identity and predator density on both predator and prey demographic parameters. Survival and fecundity rates of the predator and its prey decreased at high predator density. However, demographic parameters of the predator and its prey were differentially affected by litter identity, with greater prey demographic parameters in Quercus litter and, in the opposite, greater predator demographic parameters in Pinus litter, probably due to differences in physical characteristics providing more or less refuge for the prey. We also observed a higher increase in fungal biomass in Pinus compared to Quercus litter, i.e. the litter with the fungivorous Collembola abundance reduced by the predatory Acari. Litter identity could thus strongly regulate these tri-trophic interactions (Fungi – fungivorous Collembola – predatory Acari) in forest ecosystems. Finally, the implications of our findings could be important as the distribution area of oak and pine forests may be altered in response to climate change with then potentially strong cascading effects on soil organisms and the processes they drive.

The capacity of a Quercus pubescens forest to resist recurrent drought was assessed on an in situ experimental platform through the measurement of a large set of traits (ecophysiological and metabolic) studied under natural drought (ND) and amplified drought (AD) induced by partial rain exclusion. This study was performed during the third and fourth years of AD, which correspond to conditions of moderate AD in 2014 and harsher AD in 2015, respectively. Although water potential (Ψ) and net photosynthesis (Pn) were noticeably reduced under AD in 2015 compared to ND, trees showed similar growth and no oxidative stress. The absence of oxidative damage could be due to a strong accumulation of α-tocopherol, suggesting that this compound is a major component of the Q. pubescens antioxidant system. Other antioxidants were rather stable under AD in 2014, but slight changes started to be observed in 2015 (carotenoids and isoprene) due to harsher conditions. Our results indicate that Q. pubescens could be able to cope with AD, for at least 4 years, likely due to its antioxidant system. However, growth decrease was observed during the fifth year (2016) of AD, suggesting that this resistance could be threatened over longer periods of recurrent drought.

Biogenic volatile organic compounds (BVOC) emitted by plants are a large source of carbon compounds released into the atmosphere where they are precursors of ozone and secondary organic aerosols. Being directly involved in air pollution and indirectly in climate change, it is very important to understand what factors drive the BVOC emissions in order to characterize the atmospheric composition through models. The main algorithms currently used to predict BVOC emissions are mainly light and/or temperature dependent. Additional factors such as seasonality and drought have been also found to influence isoprene emissions, especially in Mediterranean region which is characterized by its drought period in summer. These factors are increasingly included in models but only for the principal studied BVOC which is isoprene but there are still some discrepancies in estimations of emissions. In this study, the main BVOC (isoprene, methanol, acetone, acetaldehyde, formaldehyde and MACR+MVK+ISOPOOH), emitted by Quercus pubescens a tolerant drought Mediterranean species, were monitored with a PTR-ToF-MS over an entire seasonal cycle, under both natural and amplified drought which is expected with climate change. Amplified drought impacted all BVOC by reducing emissions in spring and summer and, in the contrary, by increasing emissions in autumn. Two types of dependence were found: light and temperature dependence (isoprene, MACR+MVK+ISOPOOH and acetaldehyde), and light and temperature dependence during the day and only temperature dependence during the night (methanol, acetone and formaldehyde). Moreover, a methanol burst in early morning and formaldehyde deposition/uptake were also punctually observed which were not assessed by model.

International audience; 1. Over a century of agricultural abandonment across the Mediterranean region has favoured the installation of the pioneer expansionist species Aleppo pine (Pinus halepensis Miller). This species synthesizes a wide range of secondary metabolites that are partially released during needle decomposition , and which can thus affect the 'brown food chain'. Litter decomposition is a key process connecting ecosystem structure and function, and involving microbial and faunal components. 2. The goal of this study was to determine the effect of chemical compounds from Aleppo pine needles on the litter decomposition process along a gradient of Mediterranean forest secondary succession. Using in situ litterbags, we compared the dynamics of decomposers, particularly the relative contributions of fungal and mesofauna biomass to litter mass loss (calculations based on the measured decomposer biomass, published fungal growth efficiency and mesofauna feeding rate), against the dynamics of secondary metabolites associated with decomposed needles in three successional stages (early, middle and late, i.e. pinewoods that were aged 10, 30 and over 60 years old). 3. Our first key finding was that fungi accounted for the largest portion of overall litter mass loss (60– 79%) and detritivorous mesofauna contributed to 8–12%. In the early stage of succession, fungal biomass after 6 months of decomposition was lower than in middle and late stages, and may be responsible for the delay in litter colonization by mesofauna. We linked this result to a clearly longer residence time for phenolic compounds in young pine forest, leading to an overall slowdown in the decomposition process. 4. Synthesis. Litter phenolic content emerged as a key functional trait for predicting litter decomposition , delaying the colonization of litter by decomposers in Mediterranean forest ecosystems. Another key finding is that the relative contributions of fungi and detritivores to needle mass loss were different between the successional stages. From the food-web perspective, the organic matter available for higher trophic levels thus remains unchanged beyond 30 years after pine colonization.

International audience; Prescribed burning (PB) is gaining popularity as a low-cost forest protection measure that efficiently reduces fuel build-up, but its effects on tree health and growth are poorly understood. Here, we evaluated the impact of PB on plant defenses in Mediterranean pine forests (Pinus halepensis andP. nigra ssp. laricio). These chemical defenses were estimated based on needle secondary metabolites (terpenes and phenolics including flavonoids) and discussed in terms of chlorophyll fluorescence and soil nutrients. Three treatments were applied: absence of burning (control plots); single burns (plots burned once); and repeated burns (plots burned twice). For single burns, we also explored changes over time. In P. laricio, PB tended to trigger only minor modifications consisting exclusively of shortlived increases (observed within 3 months after PB) in flavonoid index, possibly due to the leaf temperature increase during PB. In P. halepensis, PB had detrimental effects on physiological performance, consisting of (i) significant decreases in actual PSII efficiency (ΦPSII) in light-adapted conditions after repeated PB, and (ii) short-lived decreases in variable-to-maximum fluorescence ratio (Fv/Fm) after single PB, indicating that PB actually stressed P. halepensistrees. Repeated PB also promoted terpene-like metabolite production, which increased 2 to 3-fold compared to control trees. Correlations between terpene metabolites and soil chemistry were found. These results suggest thatPB impacts needle secondary metabolism both directly (via a temperature impact) and indirectly (via soil nutrients), and that these impacts vary according to species/site location, frequency and time elapsed since last fire. Our findings are discussed with regard to the use of PB as a forest management technique and its consequences on plant investment in chemical defenses.

Dans cet article nous présentons la numérisation de la carte de végétation de la France publiée par le CNRS en 64 feuilles entre 1947 et 1991. Les couvertures géographiques et les tables de données réalisées lors de ce travail ont été regroupées au sein de la Base de Données Géographique de la VÉGétation de la France (BDGveg_FR). Les couvertures principales représentent respectivement les séries de végétation, sous forme de scan géoréférencé, à 1/200 000 et la carte harmonisée de la végétation potentielle, sous format vectoriel, à 1/1 000 000. La carte harmonisée de la végétation potentielle est accompagnée d'une typologie hiérarchique nationale sur six niveaux synthétisée à partir des légendes des 64 feuilles. L'utilisation de la BDGveg_FR est illustrée par plusieurs exemples de caractérisation des facteurs de répartition de la végétation (altitude, géologie, sol et climat) par croisement avec d’autres sources de données géographiques (modèle numérique d'altitude, couvertures vectorielles à 1/1 000 000 des sols et du sous-sol). La BDGveg_FR est complémentaire des bases de données existantes sur la végétation de la France du fait de sa période de réalisation, de ses échelles cartographiques locales et nationales, de son exhaustivité de couverture et de ses informations sur les groupements végétaux. Cette base peut-être utilisée pour analyser l’impact des changements globaux (par exemple climat, pollution atmosphérique) sur les écosystèmes., In this paper we present the digitalisation of the map of the vegetation of France edited by the CNRS in 64 sheets between 1947 and 1991. The geographical covers and the databases built during this work are gathered in a geographical database called “Base de Données Géographique de la VÉGétation de la France” (BDGveg_FR). The main covers show respectively the vegetation succession stages, as a georeferenced scan, at 1/200,000, and the harmonised map of the potential vegetation, in a vector format, at 1/1,000,000. The harmonised map of the potential vegetation is linked with a national 6-level typology synthesised from the keys of the 64 sheets. Possible uses of the BDGveg_FR are shown with some examples on the determination of the factors of vegetation distribution (altitude, geology, soil and climate) by intersecting it with others sources of geographical data (digital elevation model, vector covers at 1/1,000,000 of soil and geology). The BDGveg_FR is actually complementary to the other databases on the vegetation of France presently available thanks to its period of time, its local and national scales, its exhaustive cover and its information on the plant associations. It can be used to assess the impact of global changes (e.g. climate, atmospheric pollution) on ecosystems.

International audience; We investigated the effect of sewage sludge compost spreading on plant growth and leaf terpene emissions and content of Quercus coccifera, Rosmarinus officinalis and Cistus albidus in a Mediterranean shrubland. Measurements were performed during 3 consecutive summers on 2 different plots treated in 2002 or 2007 with 50 or 100 tons of compost per hectare, corresponding to observations carried out 2 months to 7 years after spreading. A slight nutrient enrichment of soil and leaves (R. officinalis and C. albidus) was observed, especially for phosphorous. Terpene emissions were not affected by compost spreading, although they tended to increase on treated plots after 6 and 7 years for R. officinalis and C. albidus respectively. Terpene content was not affected by any compost treatment. Leaf and stem growth were significantly enhanced by compost spreading after 2 and/or 7 years in all species with little difference between doses. Total leaf biomass on the last growth units was increased by more than 50% in C. albidus and more than 90% in Q. coccifera. The results suggest that compost spreading in Meditteranean shrublands has no or little direct effect on leaf terpene emissions, but indirectly leads to their increase through leaf biomass enhancement. Simulation of terpene emissions at stand level revealed an increase of terpene fluxes ranging between 6 and 13%, depending on the plant species. Overall, compost spreading was assessed to result in an emission rate of 1.1 kg ha−1 y−1 for a typical Q. coccifera shrubland, but can reach 2.6 kg ha−1 y−1 for a typical R. officinalis shrubland.

International audience; Compost spreading in Mediterranean shrublands has no strong short-term effect on Q. coccifera monoterpene emissions at leaf level. a b s t r a c t Monoterpene emissions of Quercus coccifera L. were repeatedly measured during the two years following the spreading of a sewage sludge compost at rates of 50 Mg ha À1 and 100 Mg ha À1 , in a twelve-year-old post-fire Mediterranean shrubland. We also monitored the patterns of change in soil and leaf nutrient content, plant water potential, chlorophyll fluorescence, and plant growth. Compost spreading resulted in weak changes in leaf nutrient content and plant water status, and therefore no significant effect on monoterpene emissions at leaf scale, except during one summer sampling, probably related to advanced leaf maturity with the highest compost rate. However, compost increased plant growth, particularly the leaf biomass. The results suggest that compost spreading in Mediterranean shrublands has no strong short-term effect on Q. coccifera monoterpene emissions at leaf level, but may indirectly increase volatile organic compound fluxes at the stand scale, which may contribute to regional ozone pollution.

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SEDYVIN; The large amount of volatile organic compound (VOC) emitted by vegetation modifies air quality contributing to both tropospheric ozone and secondary organic aerosol production. A better understanding of the factors controlling VOC emissions by vegetation is mandatory in order to improve emission estimates derived from tropospheric chemistry models. Although the Mediterranean shrublands are particularly abundant and rich in emitting species, their emission potential is poorly known. Focusing on a VOC-emitting shrub species widespread in the Mediterranean area (Cistus monspeliensis L.), we measured and analysed its emissions of terpenes taking into account the age of individuals, the season of sampling and the soil type. Sampling was done under natural environmental conditions. Species of the genus Cistus are frequently reported to be storing species, although we found only one stored monoterpene and three sesquiterpenes in very low amount. Major emitted compounds were a-pinene and b-myrcene. Total terpene emissions were not influenced by plant age but emission of some individual terpenes was positively correlated with age. A strong seasonal effect was evidenced. A larger amount of terpenes was emitted during spring and summer than during fall and winter. Summer emission rates were nearly 70 times higher than winter emission rates. Total and individual terpene emissions were influenced by soil type; emissions on siliceous substrate were ca. seven times higher than those on calcareous substrate. In conclusion, it appears clearly that environmental factors such as soil nature and season should be taken into account in order to achieve improved modelling of terpene emissions by shrub species.

En dépit de nombreux travaux de cartographie de la végétation, il n'existait jusqu’en 2008 aucune carte numérique des formations végétales couvrant le territoire métropolitain français. Ces informations sont indispensables, entre autres, pour comprendre, évaluer et limiter l'impact des changements environnementaux globaux, notamment des dépôts de polluants atmosphériques, sur les milieux naturels et semi-naturels à l’échelle nationale. L'objectif du travail, présenté ici, a consisté à produire une carte numérique de la végétation de la France à 1/1 000 000 en se basant sur des informations cartographiques existantes, et notamment les cartes de la végétation à 1/200 000 produites par le CNRS à l’initiative de Henri Gaussen. La première étape a conduit à numériser les cartes du CNRS: (i) scannage, assemblage et géoréférencement des cartes et des cartons associés; (ii) digitalisation, assemblage et géoréférencement des cartons botaniques, représentant, au 1/1 250 000, la végétation considérée comme potentielle. Une légende hiérarchique, éditée à partir des légendes détaillées de toutes les cartes au 1/200 000, a été synthétisée à l’échelle du territoire national pour renseigner la couverture de la végétation potentielle ainsi produite. Dans un deuxième temps la couverture de la végétation potentielle a été croisée avec des bases de données nationales de relevés floristiques (bases EcoPlant de l’Engref, SOPHY du CNRS et relevés de L’Inventaire Forestier National). Ce croisement, en plus d’être une procédure de validation de la couverture, a permis de renseigner chacune des unités cartographiques de la végétation avec des informations édaphiques (pH, rapport carbone sur azote, taux de saturation en bases, niveau d’engorgement) et floristiques (liste d’espèces caractéristiques et alliances phytosociologiques principales). Dans une troisième étape, l’occupation végétale actuelle a été déduite à partir d’un croisement avec d'autres cartographies numériques nationales récentes (occupation du sol avec Corine Land Cover 2000). Ce nouveau produit numérique à l’échelle nationale a pour but l’élaboration d’une cartographie des écosystèmes et de leur sensibilité vis-à-vis des pollutions atmosphériques acides, azotées et métalliques (« charges critiques »). Il constitue un outil précieux pour la communauté des chercheurs et des enseignants et participe à la sauvegarde d’un patrimoine scientifique. En effet certaines cartes de végétation du CNRS n'étaient plus disponibles qu'en quelques exemplaires papiers.

Date du contrat: 14/12/2006; Within the international convention of Geneva on long distance transboundary air pollution, the negotiation for the reduction of pollutants emission is impactoriented. The general approach to quantify the sensitivity of ecosystems to air pollutants is based on the concept of critical loads. To enhance the assessment of critical loads for eutrophying nitrogen at the national scale, there is a need of a detailed vegetation map with information on plant species composition. Such a map would enable: - to take into account impacts of air pollutants, particularly nitrogen, on biodiversity, as suggested by the most recent xi works of the convention, - to enhance the description of the spatial modelling units used at the national scale for critical load modelling, - to better characterise throughfall atmospheric deposition and nitrogen export by the biomass. In September 2006, Anne Probst, in charge of the modelling and the mapping of critical loads for France, applied to the French environmental agency (Ademe) for funds in order to realise a digital geographic database of the vegetation of France (BDGveg). The purposes of this database are the mapping of the French vegetation units and the description of their species composition. The BDGveg was based mainly based on the digitising of the vegetationmap of the CNRS. Thismap is composed of the 64 paper maps produced by the French centre for scientific research (CNRS) between 1947 and 1991. The objective of the final report is to present: – the material and the methods used to produce the BDGveg, – the characteristics of the produced items, – the perspectives for future works. All the items planed in the application for funds have beenmade: – a coherent nation wide hierarchical legend based on the vegetation map of the CNRS and validated by experts; – a raster coverage representing the vegetation at the time of the survey (1/200 000) resulting from the scan of the paper maps; – a vector coverage representing the potential vegetation at 1/1 250 000; this coverage has been checked by comparison with floristic databases (IFN and EcoPlant-Sophy); – some methodological lookouts for the development of biodiversity-targeted critical load models. Additional items have been produced during the course of this project: – a database compiling the information on the authors of the vegetation map of the CNRS; – extra layers at raster (sol nutrient status, soil use, agriculture, rainfall, agricultural risks) and vector format (secondary tree species, distribution of Mediterranean species, drainage levels); – the first draft version of a coverage representing the vegetation at the year 2000 with themethodology to realise a final version. xii; Dans le cadre de la convention internationale de Genève sur la pollution atmosphérique transfrontalière à longue distance, les réductions des émissions de polluants sont négociées en prenant en considération les impacts générés par ces contaminants. Plus particulièrement, l’approche retenue pour quantifier la sensibilité des écosystèmes est basée sur le concept de charge critique. Pour améliorer la détermination des charges critiques en azote eutrophisant pour le territoire national, il est aujourd’hui nécessaire de disposer d’une carte numérique de la France indiquant précisément la composition de la couverture végétale. En effet, un tel document, qui fait actuellement défaut, permettra notamment : – d’intégrer l’effet des pollutions atmosphériques, notamment azotées, sur la biodiversité comme recommandé par les récents travaux de la convention de Genève ; – d’améliorer la définition des unités écosystémiques sur lesquelles est basée la modélisation spatiale des charges critiques ; – de mieux modéliser les dépôts de polluants atmosphériques sous couvert et l’exportation d’azote par la biomasse. En septembre 2006, une demande de financement, portée par Anne PROBST responsable de la modélisation et de la cartographie des charges critiques en France, a été déposée auprès de l’Ademe pour constituer une Base de Données Géographiques de la VÉGétation de la France (BDGveg). L’objet de cette base est la cartographie des unités de végétation présentes ainsi que la description de leur composition floristique. La réalisation de la BDGveg s’appuie principalement sur la numérisation des 64 feuilles éditées par le CNRS entre 1947 et 1991 et qui constitue la carte de végétation du CNRS. L’objectif de ce rapport final est de présenter l’ensemble des travaux réalisés depuis janvier 2006, date du démarrage du projet. Dans le détail, il expose : – les sources et les méthodologies employées pour réaliser la BDGveg, – les caractéristiques des délivrables produits, – les perspectives de travail et de valorisation. L’ensemble des délivrables planifiés dans la demande de financement ont été réalisés : – une typologie hiérarchique de la végétation de la France basée sur la carte de végétation du CNRS et validée par expertise ; – une couverture géographique matricielle de la végétation au moment de l’établissement de la carte de végétation du CNRS au 1/200 000 (scan des cartes de la végétation) ; – une couverture géographique vectorielle de la végétation potentielle de la France à 1/1 250 000 vérifiée à l’aide des bases de données floristiques EcoPlant- Sophy et IFN ; – des perspectives méthodologiques pour le développement des modèles de charges critiques en azote eutrophisant qui prennent en compte l’impact sur la biodiversité végétale. Par ailleurs, quelques délivrables supplémentaires ont également été produits dans le cadre de ce projet : – une base de données des auteurs et des réalisateurs de la carte de végétation du CNRS; – des couvertures géographiques secondaires matricielles (édaphologie, utilisation du sol, agriculture, pluviométrie, adversité agricole) et vectorielles (essences forestières secondaires, aire des espèces méditerranéennes, niveau de drainage) ; – une première version intermédiaire d’une couverture « Végétation—État 2000 » avec la mise au point d’une procédure de généralisation pour produire une couverture finalisée. L’ensemble des couvertures géographiques numériques, ainsi que la base de données « typologie », ont été regroupées dans la BDGveg.