Claire Damesin

• PhD HDR
• University of Paris-Saclay

A l’ère où il semble devenu évident pour beaucoup que l’humanité doive changer sa façon d’habiter la terre, des prédictions d’avenirs très distincts parcourent les réseaux et nos cerveaux. Dans une perspective immédiate de davantage de respect vis-à-vis de la nature, une question pragmatique peut s’ériger en chacun de nous : « que faire ? ». Dans u...

3 PRIORITÉS SCIENTIFIQUES À ABORDER D’ICI 2030 Accroître la réflexivité sur les pratiques de recherche dans les laboratoires dans une démarche collective, ce qui exige du temps et des espaces de délibération dédiés Utiliser les éthiques environnementales non pas au service de la résolution de conflits entre les humains et la nature, mais comme des...

• Key message The increase in climate variability is likely to generate an increased occurrence of both frost-induced and drought-induced damages on perennial plants. We examined how these stress factors can potentially interact and would subsequently affect the vulnerability to each other. Furthermore, we discussed how this vulnerability could be...

One factor that determines a tree’s resilience capacity to drought is its level of interaction with aggravating biotic factors, such as bark beetles, which in turn depends on whether insect populations are at an endemic or epidemic stage. In a Mediterranean natural forest ecosystem, we investigated the ecophysiological characteristics of trees whic...

Art-science topic. This outdoor painting exhibition of the artist Jaime Olivares (2019) was realized for the 400th anniversary of the botanical garden of Strasboug (France). It combines a taxonomic approach of the trees and their role in some powerful mythological destinies.

Tree ring synthesis is a key process in wood production; however, little is known of the origin and fate of the carbon involved. We used natural 13C abundance to investigate the carbon-use process for the ring development in a temperate deciduous (Quercus petraea (Matt.) Liebl.) and a Mediterranean evergreen (Quercus ilex L.) oak. The sapwood carbo...

Exhibition in Sofia-Arosita Gallery (March-April 2019)

Forest decline is reported in recent decades all over the world. However, developing a clear vision of the associated tree dysfunctioning is still a challenge for plant physiologists. In this study, our aim was to examine the seasonal carbon adjustments of beech trees in the case of a long-term drought-induced decline. We compared healthy and decli...

Mixotrophic orchids do not use photosynthates for perennial underground organs

Functional studies of tree decline have mainly focused on process inside the plant showing possible alterations of carbon transport, storage and hydraulic functions. However, the processes occurring at the plant-soil interface have been seldom investigated. Our objective is to examine carbon functional alterations in the belowground compartment in...

Climate reconstructions in temperate Europe have been widely based on oak species. However, other co-occurring species, largely distributed in Europe, may be used for recording climate variability. In this paper, we documented the inter-trees and inter-species variations over 1960-2007 of oxygen and carbon isotopic compositions in ring cellulose of...

We investigated the relationships between δ13C in short and long-lived C pools of Quercus ilex, a broadleaf evergreen tree, and eddy-covariance flux-derived δ13C input in the Puéchabon experimental site over the period 2003 to 2012. The C pools under concern were current and one-year leaf, acorn and spring and autumn wood.

Functional studies of tree decline have mainly focused on process inside the plant showing possible alterations of carbon transport, storage and hydraulic functions. However, the processes occurring at the plant-soil interface have been seldom investigated. Our objective is to examine carbon functional alterations in the belowground compartment in...

The origin of N which contributes to the synthesis of N reserves of in situ forest trees in autumn and to the growth of new organs the following spring is currently poorly documented. To characterize the metabolism of various possible N sources (plant N and soil N), six distinct 20-year-old sessile oaks were 15N labelled by spraying 15NH415NO3: (i)...

The origin of the N which contributes to the synthesis of N reserves of in situ forest trees in autumn, and to the growth of new organs the following spring, is currently poorly documented. To characterize the metabolism of various possible N sources (plant N and soil N), six distinct 20 year-old sessile oaks were 15N labelled by spraying 15NH415NO...

Keymessage Under non-extreme drought conditions, reduced stem growth is not associated with reserve or hydraulic impairment in beech suffering from long-term decline. Abstract Global change is expected to increase the frequency and the intensity of drought events in temperate ecosystems. In some regions, this might be associated with an increase i...

Understanding whether tree growth is limited by carbon gain (source limitation) or by the direct effect of environmental factors such as water deficit or temperature (sink limitation) is crucial for improving projections of the effects of climate change on forest productivity. We studied the relationships between tree basal area (BA) variations, ed...

The ongoing climate change is altering the precipitation patterns (abundance and frequency) of most parts of the world. The consequences of these changes on forests are already visible through frequent declines. A lot of them can be linked to the occurrence of long and/or repeated drought periods. Although forest decline could severely impact the n...

Some forest plants adapt to shade by mixotrophy, i.e., they obtain carbon both from photosynthesis and from their root mycorrhizal fungi. Fully achlorophyllous species using exclusively fungal carbon (the so-called mycoheterotrophic plants) have repeatedly evolved from such mixotrophic ancestors. However, adaptations for this evolutionary transitio...

Monitoring cambial phenology and intra-annual growth dynamics is a useful approach for characterizing the tree growth response to climate change. However, there have been few reports concerning intra-annual wood formation in lowland temperate forests with high time resolution, especially for the comparison between deciduous and coniferous species....

• Context The carbon isotope composition of the CO2 efflux (δ13CE) from ecosystem components is widely used to investigate carbon cycles and budgets at different ecosystem scales. δ13CE, was considered constant but is now known to vary along seasons. The seasonal variations have rarely been compared among different ecosystem components. • Aims We a...

In addition to global warming, the frequency and the intensity of droughts will probably increase in central and southern Europe. Resulting climate changes and soil water deficits could alter tree growth, according to sensitivity of each species. The aim of this study was to compare the growth response of three European species (Fagus sylvatica, Qu...

a b s t r a c t Soil microbial communities play an important role in soil carbon functioning, particularly in forest ecosys-tems. Their variation in response to climate change may affect soil carbon processes, highlighting the importance of understanding how environmental factors affect microbial communities. This study aimed to determine to what e...

• Phloem is the main pathway for transferring photosynthates belowground. In situ(13) C pulse labelling of trees 8-10 m tall was conducted in the field on 10 beech (Fagus sylvatica) trees, six sessile oak (Quercus petraea) trees and 10 maritime pine (Pinus pinaster) trees throughout the growing season. • Respired (13) CO(2) from trunks was tracked...

Soil and trunk respiration are the major sources of carbon from forest ecosystems to the atmosphere and they account for a large fraction of total ecosystem respiration. The amount of photosynthate allocated to respiration affects the growth of the tree and the potential for carbon sequestration of forest ecosystems. This study, aiming at understan...

Tree-ring δ(13) C is often interpreted in terms of intrinsic water-use efficiency (WUE) using a carbon isotope discrimination model established at the leaf level. We examined whether intra-ring δ(13) C could be used to assess variations in intrinsic WUE (W(g), the ratio of carbon assimilation and stomatal conductance to water) and variations in eco...

In the context of climate change, the amount of carbon allocated to soil, particularly fresh litter, is predicted to increase with terrestrial ecosystem productivity, and may alter soil carbon storage capacities. In this study we performed a 1-year litter-manipulation experiment to examine how soil CO2 efflux was altered by the amount of fresh litt...

Stable carbon isotopic composition (δ¹³C) in tree rings is a widely recognized tool for climate reconstruction, and several works suggest that seasonal information can be extracted from intra-ring δ¹³C variations. In this study, we explored the link between climate and intra-seasonal oak ring δ¹³C using a process-based modelling approach. The ISOCA...

The present study examines the impact of the C source (reserves vs current assimilates) on tree C isotope signals and stem growth, using experimental girdling to stop the supply of C from leaves to stem. Two-year-old sessile oaks (Quercus petraea) were girdled at three different phenological periods during the leafy period: during early wood growth...

• Nitrogen (N) is one of the most important resources for plants, generally enhancing leaf photosynthesis because a large part of it is allocated to Rubisco and thylakoïds. This is well known in leaves where photosynthesis (i.e. gas exchange, Rubisco activity, chlorophyll content) is positively correlated to leaf N content. • In order to test this...

The delta(13)C (carbon isotope composition) variations in respired CO(2), total organic matter, proteins, sucrose and starch have been measured during tuber sprouting of potato (Solanum tuberosum) in darkness. Measurements were carried out both on tubers and on their growing sprouts for 23 days after the start of sprout development. Sucrose was sli...

The Gourma site in Mali is one of the 3 instrumented meso-scale sites deployed in West- Africa as part of the African Monsoon Multidisciplinary Analysis (AMMA) project. Located both in the Sahelian zone sensu stricto, and in the Saharo-Sahelian transition zone, the Gourma meso-scale window is the northernmost site of the AMMA-CATCH observatory reac...

The uncertainties of ecosystem response to global climate changes illustrate the need to improve knowledge of ecosystem functioning, in particular to explain the carbon (C) stock and fluxes variations and the abiotic and biotic factors driving such variations. Trunk CO2 efflux (RT) is a major component of total CO2 forest ecosystem efflux, but in c...

In deciduous trees, the δ13C values of leaves are known to diverge during growth from those of woody organs. The main purpose of this study is to determine whether the divergence in δ13C between leaves and current-year twigs of Fagus sylvatica (L.) is influenced by changes (i) in the relative contents of organic matter fractions and (ii) in the δ13...

Trunk CO2 efflux is a major component of total CO2 forest ecosystem efflux but its determinism is still poorly understood. This CO2 flux could originate from different carbon sources (respiration of newly assimilates or reserves; xylem sap flow dissolved CO2). These potential CO2 sources of the ecosystem vary at a diurnal and seasonal time scale. T...

From June to December, we determined the effects of variations in biochemical composition on δ13C of tree rings of 2-year-old oaks (Quercus petraea (Matt.) Liebl.) growing under semi-natural conditions, and the dependence of these effects of water stress during the growth season. Percent abundance, carbon concentration and δ13C were measured in hol...

Disentangling the autotrophic and heterotrophic components of soil CO2 efflux is critical to understanding the role of soil system in terrestrial carbon (C) cycling. In this study, we combined a stable C-isotope natural abundance approach with the trenched plot method to determine if root exclusion significantly affected the isotopic composition (δ...

In woody species, the photosynthesis of stems, especially young branches, occurs by refixing part of the internal respiratory CO2. The present study aims to improve the physiological characterization of stem photosynthesis by examining enzymatic characteristics. During an entire growing season, three enzymatic activities that are linked to C3 and C...

The stable C isotope composition (delta13C) of CO2 respired by trunks was examined in a mature temperate deciduous oak forest (Quercus petraea). Month-to-month, day-to-day and diurnal, measurements were made to determine the range of variations at different temporal scales. Trunk growth and respiration rates were assessed. Phloem tissue was sampled...

The photosynthetic characteristics of current-year stems of six deciduous tree species, two evergreen tree species and ginkgo (Ginkgo biloba L.) were compared. Gas exchange, chlorophyll concentration, nitrogen concentration and maximum quantum yield of PSII were measured in stems in summer and winter. A light-induced decrease in stem CO2 efflux was...

Here, the kinetic properties and immunolocalization of phosphoenolpyruvate carboxylase (PEPC) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in young stems of Fagus sylvatica were investigated. The aim of the study was to test the hypothesis that there is a C4-like photosynthesis system in the stems of this C3 tree species. The activ...

Soil microbial communities play an important role in soil carbon functioning, particularly in forest ecosystems. Their variation in response to climate change may affect soil carbon processes, highlighting the importance of understanding how environmental factors affect microbial communities. This study aimed to determine to what extent an increase...

In situ13C/12C isotopic labelling was conducted in field-grown beech (Fagus sylvatica) twigs to study carbon respiration and allocation. This was achieved with a portable gas-exchange open system coupled to an external chamber. This method allowed us to subject leafy twigs to CO2 with a constant carbon isotope composition (δ13C of −51.2‰) in an ope...

Some green orchids obtain carbon (C) from their mycorrhizal fungi and photosynthesis. This mixotrophy may represent an evolutionary step towards mycoheterotrophic plants fully feeding on fungal C. Here, we report on nonphotosynthetic individuals (albinos) of the green Cephalanthera damasonium that likely represent another evolutionary step. Albino...

The (13)C natural abundance of CO(2) respired by plants has been used in the laboratory to examine the discrimination processes that occur during respiration. Currently, field measurements are being expanded to interpret the respiration delta(13)C signature measured at ecosystem and global levels. In this context, forests are particularly important...

Temperature and light responses of CO 2 efflux of Fagus sylvatica (beech) current-year stems were measured for 1 yr to estimate their annual carbon balance. • Gas exchanges were determined using infrared gas analysis. Seasonal patterns of a fluorescence parameter ((F v / F m) max), nitrogen and chlorophyll contents were also assessed in stems and l...

Temporal variations in the stable carbon isotope composi-tion (d d d d 13 C) of leaves and current-year stems were examined in beech trees over one year. The d d d d 13 C of both tissues were equal in the bud stage and started to diverge during growth, with values decreasing by 2·5 and 4·5‰ for stems and leaves, respectively. The dynamics of the d...

Stem respiration of adult beech (Fagus sylvatica L.) trees was measured in the field in eastern France at several levels in the crown and along the stem. Strong variations in respiration rates throughout the season and within the trees were mainly caused by gradients in stem temperature, growth rates and distribution of living cells. The higher res...

1. Changes of δ13C and its relation to leaf development, biochemical content and water stress were monitored over a 2 year period in two co-occurring Mediterranean oak species: the deciduous Quercus pubescens and the evergreen Quercus ilex. 2. The time course of leaf δ13C showed different patterns in the two species. Young Q. pubescens leaves had a...

Stem and branch respiration of 30‐yr‐old Fagus sylvatica trees was measured in a temperate forest for 1 yr to estimate the annual flux at the stand level. The seasonal response of respiration to air temperature was determined using infra‐red gas analysis (IRGA) systems. Annual respiration was derived from half‐hourly temperature recording and allom...

The results of an investigation carried through within the ‹Euroflux›-programme in eastern France assessing the carbon fluxes above the canopy of the forest are presented. The photosynthetic activity within the annual and daily cycles are discussed. The high variability of the carbon netbalance and the variation of the total respiration make furthe...

1. We present measurements of CO2 fluxes over 2 years above and within a young Beech stand in the east of France. This site is part of the Euroflux network set up to monitor fluxes over representative European forests. 2. The net ecosystem carbon (C) exchange was derived from continuous eddy flux measurements. Major components of the total flux (i....

The results of an investigation carried through within the ‹Euroflux›-programme in eastern France assessing the carbon fluxes above the canopy of the forest are presented. The photosynthetic activity within the annual and daily cycles are discussed. The high variability of the carbon netbalance and the variation of the total respiration make furthe...

This paper presents a mechanistically based C3 leaf CO2 assimilation model linked with an empirical stomatal model to simulate Quercus ilex leaf net photosynthesis and transpiration in oak-savannah ecosystems of southern Spain. The model estimates (time integration) daily and seasonal changes in carbon fixation, transpiration, and water use efficie...

Tree species can be split into two groups in terms of their leaf life-spans: evergreens and deciduous. Their distinct geographical distribution suggests that these two groups have functional characteristics adapted to specific environments. However, deciduous and evergreen trees co-exist in some regions, such as those with a Mediterranean climate....

Xylem sap-flux densities were monitored continuously using Granier-type sensors on five Quercus ilex four Arbutus unedo and one Quercus pubescens from June 1993 to October 1994. Half-hourly measurements of incoming solar radiation, air temperature and humidity, horizontal wind speed and precipitation were carried out at the top of a tower at a heig...

In this study, sun leaf carbon isotope composition (δ13C) of two co-occurring woody Mediterranean species (Quercus pubescens Willd., a deciduous oak, and Q. ilex L., an evergreen one) was investigated on four sites with different water availability. The total range of δ13C values was 4.4 and 3.1‰ for Q. pubescens and Q. ilex respectively. The intra...

Leaf gas exchange and growth were determined on cork-oak (Quercus suber L) seedlings which were grown from acorns for periods of up to 4 months in greenhouses at ambient (350 mu mol mol(-1)) and at elevated (700 mu mol mol(-1)) concentrations of carbon dioxide. In well-watered conditions, daily maximum photosynthesis (15 mu mol m(-2) s(-1)) and sto...

The main goal of this study was to analyze the depth-distribution of leaf mass per area (LMA) measured in ten canopies of Mediterranean evergreen oaks, five canopies of Quercus coccifera and five canopies of Q ilex, across soil water availability gradients in southern France, Spain and Portugal. There was a significant site effect on LMA with value...

The responses of photosystem II (PS II) to drought were analysed on two Mediterranean oak species, Quercus ilex and Q pubescens, using the chlorophyll fluorescence pulse-amplitude-modulation technique. The maximal PS II photochemical efficiency (F-v/F-m) of the evergreen Q ilex and the deciduous Q pubescens oaks was only affected when leaf predawn...

Quercus pubescens Willd. is a winter deciduous oak species which co-occurs in the Mediterranean area with an evergreen oak, Q. ilex. As the knowledge of Q. pubescens assimilation patterns is poorly documented, we monitored leaf physiological parameters throughout a growing season. In summer, drought was particularly severe, and some trees experienc...

In Mediterranean-Type Ecosystems (MTE), the photosynthetic apparatus of plants are exposed to long summer droughts and high or low temperatures. Evergreen oak species are dominant in landscapes of countries surrounding: the Mediterranean sea plus parts of California and constitute large shrublands and woodlands. Some hypotheses have been advanced t...