16 research outputs found
A study of karst hydrosystem recharge at the parcel scale, using modeling and correlation analysis - Low noise underground laboratory of Rustrel site
La caractĂ©risation des flux dâeaux qui rechargent rĂ©ellement les hydrosystĂšmes souterrains reste un frein Ă la comprĂ©hension du fonctionnement hydrogĂ©ologique des milieux souterrains. Lors dâĂ©vĂ©nements pluvieux, quelle part de lâeau est Ă©vapo-transpirĂ©e ? Quelle part est temporairement stockĂ©e dans le sol ? Ces incertitudes sont particuliĂšrement fortes dans le cas de la recharge des milieux hĂ©tĂ©rogĂšnes tel que le karst. En gĂ©nĂ©ral, les calculs de recharge des hydrosystĂšmes karstiques se basent sur une reprĂ©sentation simplifiĂ©e de lâĂ©vapotranspiration qui considĂšre seulement le climat et pas le fonctionnement de la vĂ©gĂ©tation. Dans cette Ă©tude, un modĂšle de vĂ©gĂ©tation permettant de simuler les transferts dâeaux entre le sol et lâatmosphĂšre en contexte forestier (le modĂšle CASTANEA), a Ă©tĂ© appliquĂ© Ă une parcelle de ChĂȘne vert. Lâinfiltration efficace (un indicateur de la recharge) estimĂ© avec CASTANEA a Ă©tĂ© comparĂ©e Ă celle estimĂ©e par des approches classiques ainsi quâĂ des sĂ©ries long terme de flux dâeaux souterraines (9 annĂ©es). Les rĂ©sultats de cette analyse rĂ©vĂšlent que lâinfiltration efficace modĂ©lisĂ©e Ă partir dâun modĂšle de vĂ©gĂ©tation comme CASTANEA est plus satisfaisante que les approches classiques ne tenant pas compte du fonctionnement de la vĂ©gĂ©tation. Ce travail ouvre des perspectives intĂ©ressantes pour mieux tenir compte du fonctionnement de la vĂ©gĂ©tation et de lâusage du sol sur la recharge des hydrosystĂšmes karstiques.Assessing the recharge of underground hydrosystems remains an obstacle to understand their hydrologeological functioning. During a rain event, which part of the rain is evapotranspired ? And how much is temporarily stored within the soil ? These questions are particularly relevant in heterogeneous media such as karst hydrosystems. Currently, the models used to compute recharge of karst hydrosystems, rely on simplistic formulations of evapotranspiration that do not account for vegetation functioning. In this study, we used the vegetation process based model CASTANEA, which is designed to compute water transfer between soil, plant and atmosphere. We computed effective infiltration (an index of recharge) with CASTANEA and with other classical approach (based on precipitation minus ETP), and for a welldocumented holm oak site in Provence. Our results provide evidences that effective infiltration computed with CASTANEA yield more satisfactory correlation with measured outflow than simulations based on the classical approach. Our results provide a promising way to improve the simulation of karst hydrosystem recharge
Bilan et perspectives des deux écoles techniques « notions et techniques en écologie » organisées par le Département EFPA
La crĂ©ation du DĂ©partement «Ăcologie des ForĂȘts, Prairies et milieux Aquatiques» a suscitĂ© de la part des personnels techniques concernĂ©s une volontĂ© dâintĂ©gration collective sous le concept fĂ©dĂ©rateur de lâĂ©cologie. Pour cela deux Ă©coles techniques ont Ă©tĂ© organisĂ©es sur des notions et mĂ©thodes dâĂ©cologie par un ComitĂ© de pilotage composĂ© de techniciens et de scientifiques. Lâobjectif visait Ă familiariser les techniciens aux concepts de lâĂ©cologie et Ă les aider Ă se situer dans les thĂ©matiques de recherche du DĂ©partement EFPA. Enfin, il sâagissait dâinstaurer une communautĂ© de pratique autour de lâĂ©cologie. Ces Ă©coles ont rassemblĂ© 79 personnes, en proposant visites sur le terrain et sĂ©ances en salle. Deux animations ont particuliĂšrement Ă©tĂ© apprĂ©ciĂ©es, lâune sous forme dâun jeu en prĂ©ambule, lâautre sous forme de prĂ©sentations par des binĂŽmes techniciens/chercheurs. Les participants sont plutĂŽt convaincus dâavoir progressĂ© sur les notions en Ă©cologie et ils ont la volontĂ© dâaller plus loin avec la crĂ©ation dâun RĂ©seau de Technicien en Ecologie (RTE), la mise en place dâune liste de diffusion et lâorganisation rĂ©guliĂšre de rencontres entre membres du rĂ©seau
The GenTree Dendroecological Collection, tree-ring and wood density data from seven tree species across Europe
The dataset presented here was collected by the GenTree project (EU-Horizon 2020), which aims to improve the use of forest genetic resources across Europe by better understanding how trees adapt to their local environment. This dataset of individual tree-core characteristics including ring-width series and whole-core wood density was collected for seven ecologically and economically important European tree species: silver birch (Betula pendula), European beech (Fagus sylvatica), Norway spruce (Picea abies), European black poplar (Populus nigra), maritime pine (Pinus pinaster), Scots pine (Pinus sylvestris), and sessile oak (Quercus petraea). Tree-ring width measurements were obtained from 3600 trees in 142 populations and whole-core wood density was measured for 3098 trees in 125 populations. This dataset covers most of the geographical and climatic range occupied by the selected species. The potential use of it will be highly valuable for assessing ecological and evolutionary responses to environmental conditions as well as for model development and parameterization, to predict adaptability under climate change scenarios
The response to climate and its variations of Silver Fir, Beech, Blacks, Scots and mountain Pine in the Mediterranean mountains during the 20th century
Temporal instability of climate signal in tree-ring width of the five dominant species (Pinus nigra ssp. nigra,
P. sylvestris, P. uncinata, Abies alba, Fagus sylvatica) growing under Mediterranean mountainous climate was
studied over the last century (1910-2004). To disentangle the treeâclimateâsite complex, the effects of both
soil water availability (dry, mesic and humid sites) and altitude (from 430 to 1690 m) were investigated on
the response patterns. Responses to climate were analysed using bootstrapped correlation coefficients from
17 ring-width chronologies built from 293 trees sampled in 64 stands in South-Eastern France. Temporal
analyses were performed considering fourthy-six 50-years intervals (from 1910-1959 to 1955-2004). May-June
drought was the primary limiting factor. For Pinus sylvestris, summer precipitation played also a key role.
Fagus sylvatica was the less responding species with no clear common pattern. Low soil water availability
led to an increasing correlation with precipitation in May for Pinus nigra and Abies alba. Precipitation from
May to August prevailed on the driest conditions for Pinus sylvestris. Correlation analyses suggested that
warm autumn or winter enhanced growth, except for Fagus sylvatica. For Pinus nigra, the importance of April
temperature increased with increasing altitude. Temporal analyses revealed a stability of sensitivity for the
highest contexts (Pinus uncinata and Fagus sylvatica). At lower altitudes, the correlation with minimum
temperature in April increased while temperature more often exceeded the threshold of 0°C over the last
decades. For precipitation, a decrease in the strength of correlation was observed without close relationships
with local xericity.LâinstabilitĂ© temporelle des relations entre les cernes et le climat a Ă©tĂ© Ă©tudiĂ©e sur cinq espĂšces (Pinus nigra,
Pinus sylvestris, Pinus uncinata, Abies alba, Fagus sylvatica) en contexte méditerranéen montagnard sur la
période 1910-2004. Les réponses au climat ont été étudiées à partir de 17 chronologies de référence construites
sur 293 arbres Ă©chantillonnĂ©s dans un rĂ©seau de 64 peuplements dans la rĂ©gion Provence-Alpes-CĂŽtedâAzur.
Pour chaque espĂšce, un gradient dâaltitude et de disponibilitĂ© potentielle en eau (site sec, mĂ©sophile
et humide) a été considéré. Un faible niveau de précipitations printaniÚres (mai et juin) est apparu comme
le facteur majeur dâexplication des variations interannuelles de croissance. Pour le Pin sylvestre, les prĂ©cipitations
dâĂ©tĂ© jouent Ă©galement un rĂŽle central. Le HĂȘtre est lâespĂšce la moins rĂ©active et sans aucun facteur
commun entre les peuplements. Pour toutes les espÚces, la liaison avec les précipitations tend à augmenter
des sites humides aux sites secs. La croissance du Pin noir dépend également fortement des conditions
automnales de lâannĂ©e prĂ©cĂ©dente (rĂŽle de la tempĂ©rature minimale de novembre) et, pour les sites dâaltitude,
de la tempĂ©rature minimale dâavril. Sur le long terme, le Pin Ă crochets et le HĂȘtre sont apparus comme
les deux espÚces les moins réactives, sans changement de comportement au cours du temps. Pour les trois
autres espÚces poussant aux altitudes plus basses (inférieures à 1 300 m), le changement le plus notable a
Ă©tĂ© une augmentation de la rĂ©ponse Ă la tempĂ©rature minimale dâavril en liaison avec le rĂ©chauffement
important observé pour ce mois
Ontogenetic trends in the morphological features of main stem annual shoots of Pinus pinaster (Pinaceae)
International audiencePhase change refers to the transition between juvenile and adult vegetative phases. The study of trees throughout their entire life span requires retrospective analyses and validates the use of a chronosequence by sequencing observations at different and successive stages. The main axis growth pattern of 62 maritime pines (Pinus pinaster) selected in a chronosequence of three stands consisting of 8-, 22-, and 48-yr-old trees was analyzed retrospectively. Comparison of measured features (length, number of axillary products, reproductive organs) at common ages from the three stands supported the validity of using these data to form a continuous chronosequence. Endogenous trends in tree development are revealed free from variability due to annual growth conditions. Two main phases of development corresponding respectively to the juvenile vegetative and adult reproductive stages were identified, and the transition between both occurred in 9-yr-old trees. The relevance of these two phases and more generally the notion of phase changes are discussed in light of observed trends in the values of studied growth and branching parameters that may either show gradual variations (such as length of annual shoot) or a distinctive expression in one or the other phase (such as presence of female cones)
Ătude de la recharge des hydrosystĂšmes karstiques Ă lâĂ©chelle de la parcelle : modĂ©lisation et analyse de corrĂ©lation - Site du Laboratoire souterrain Ă bas bruit de Rustrel
National audienceAssessing the recharge of underground hydrosystems remains an obstacle to understand their hydrologeological functioning. During a rain event, which part of the rain is evapotranspired ? And how much is temporarily stored within the soil ? These questions are particularly relevant in heterogeneous media such as karst hydrosystems. Currently, the models used to compute recharge of karst hydrosystems, rely on simplistic formulations of evapotranspiration that do not account for vegetation functioning. In this study, we used the vegetation process based model CASTANEA, which is designed to compute water transfer between soil, plant and atmosphere. We computed effective infiltration (an index of recharge) with CASTANEA and with other classical approach (based on precipitation minus ETP), and for a well documented holm oak site in Provence. Our results provide evidences that effective infiltration computed with CASTANEA yield more satisfactory correlation with measured outflow than simulations based on the classical approach. Our results provide a promising way to improve the simulation of karst hydrosystem recharge.La caractĂ©risation des flux dâeaux qui rechargent rĂ©ellement les hydrosystĂšmes souterrains reste un frein Ă la comprĂ©hension du fonctionnement hydrogĂ©ologique des milieux souterrains. Lors dâĂ©vĂ©nements pluvieux, quelle part de lâeau est Ă©vapo-transpirĂ©e ? Quelle part est temporairement stockĂ©e dans le sol ? Ces incertitudes sont particuliĂšrement fortes dans le cas de la recharge des milieux hĂ©tĂ©rogĂšnes tel que le karst. En gĂ©nĂ©ral, les calculs de recharge des hydrosystĂšmes karstiques se basent sur une reprĂ©sentation simplifiĂ©e de lâĂ©vapotranspiration qui considĂšre seulement le climat et pas le fonctionnement de la vĂ©gĂ©tation. Dans cette Ă©tude, un modĂšle de vĂ©gĂ©tation permettant de simuler les transferts dâeaux entre le sol et lâatmosphĂšre en contexte forestier (le modĂšle CASTANEA), a Ă©tĂ© appliquĂ© Ă une parcelle de ChĂȘne vert. Lâinfiltration efficace (un indicateur de la recharge) estimĂ© avec CASTANEA a Ă©tĂ© comparĂ©e Ă celle estimĂ©e par des approches classiques ainsi quâĂ des sĂ©ries long terme de flux dâeaux souterraines (9 annĂ©es). Les rĂ©sultats de cette analyse rĂ©vĂšlent que lâinfiltration efficace modĂ©lisĂ©e Ă partir dâun modĂšle de vĂ©gĂ©tation comme CASTANEA est plus satisfaisante que les approches classiques ne tenant pas compte du fonctionnement de la vĂ©gĂ©tation. Ce travail ouvre des perspectives intĂ©ressantes pour mieux tenir compte du fonctionnement de la vĂ©gĂ©tation et de lâusage du sol sur la recharge des hydrosystĂšmes karstiques