Fagus | EPFL Graph Search

Les hêtres (Fagus) forment un genre d'arbres feuillus, de la famille des Fagaceae. On compte une dizaine d'espèces de hêtres en Europe, en Asie et en Amérique. Son fruit est la faîne. Un peuplement de hêtres est une hêtraie. L'espèce la plus répandue en Europe est Fagus sylvatica. Étymologie Le latin fāgus a donné les termes fol, fou, fau, foutel pour désigner cet arbre en ancien français et dans les dialectes et les langues d'oïl. D'où fouailler « fouetter » et fouet, à l'origine « petit hêtre ». Le mot latin est issu de l'indo-européen *bhāgós qui a aussi donné la racine germanique *bōk- (anglais beech, allemand Buche) et le gaulois *bāgos, attesté dans la toponymie (cf. Bahais, Manche) et signifiant tous « hêtre ». On trouve, selon les régions, de nombreux termes dialectaux issus du latin fagus : faye, foyard, fau, faou, faon, fayard (mot francoprovençal), favinier, foutel, fouteau, etc. On discerne ces noms dans la toponymie des communes ou des lieux-dits te

Ecological response of tree saplings to simulated climate change along an elevational gradient (CLIMARBRE)

María Paula Sanginés De Cárcer

Switzerland will face higher temperature increases than the global average, which will have strong impacts on the mountain ecosystems. How tree species will respond to future climate change scenarios, and what mechanisms will they adopt, remains as a gap of knowledge in ecological research. Foresters will have to make short-term decisions and plan future managements under the great uncertainty of climate change and they demand answers to know if the current species will cope with the predicted climate change and to what extent the ecological goods and services will be affected (e.g. timber industry). The project CLIMARBRE was developed in order to ease and support their decision making by providing an advanced knowledge about the responses of beech and spruce regeneration to simulated climate change (specifically, warmer and drier conditions) in the wooded pastures of the Swiss Jura mountains. This project, which was built on the interface between fundamental research in forestry ecology and applied sciences, should attract the attention of foresters, managers of natural environments and of the general public. By using transplantation along an elevational gradient, in the Jura mountains, ârealisticâ climate conditions were created to specifically simulated three potential future climatic scenarios from the IPCC (from A1B to A2). This space for time approach enabled the assessment of saplingsâ responses to simulated climate change and their acclimation abilities. Saplings adapted to subalpine conditions at 1350 m were collected and transplanted towards lower altitudes exposing them to an average increase of 6.3áµC and a reduction in 30% of precipitation, at the lowest site throughout the study period. The main findings include i) a longer growing season due to induced-elevation warming (downward shift) could not fully account for the species-specific positive growth responses; (ii) the contrasting species growth responses were linked to different sensitivities to elevated vapor-pressure deficits; (iii) models could better account for the growth response to warming after incorporating extreme climatic events and their effects; iv) beech leaves showed an increase of xeromorphism through the increase of the cuticle thickness, vein network and smaller stomata, associated, to a higher leaf area v) which allowed it to grow in warmer conditions while coping with an increase of evaporative; vi) and finally, the linkage between responses at tree, leaf, tissue and soil level, through a multiple level approach, improved the mechanistic understanding of these species capacities to respond to simulated climate change.

EPFL2017

Warming may extend tree growing seasons and compensate for reduced carbon uptake during dry periods

Christoph Bachofen, Charlotte Grossiord, Eugénie Isabelle Mas, Yann Vitasse

Warming and drought alter plant phenology, photosynthesis and growth with important consequences for the global carbon cycle and the earth’s climate. Yet, few studies have attempted to tease apart their effects on tree phenology, particularly leaf senescence, and on source and sink activity. 2. We experimentally assessed the single and combined effects of warming and reduced soil moisture on the phenology (leaf-out and senescence date, growing season length) and aboveground sink (height and diameter growth, leaf area and Huber values) and source activity (net photosynthesis, photosynthetic efficiency, chlorophyll concentration and total carbon (C) uptake) of two tree species with distinct strategies to deal with drought: European beech and pubescent oak. 3. Warming advanced leaf-out, irrespective of soil moisture levels, particularly in oak and to a lower extent in beech, leading to a prolonged growing season in oak but not beech. No impacts of warming on senescence timing were found for both species. Reduced moisture had little impact on the phenology of both species. Warming-induced advances in phenology and higher photosynthetic efficiency increased the annual C uptake for oak and compensated for the reduced photosynthetic activity in the presence of reduced moisture. Conversely, for beech, source activity, including yearly C uptake, was lower in all treatments than the control, indicating no compensation of the C budget by phenological shifts. 4. Synthesis. Our results demonstrate that a warming-driven earlier activity and higher photosynthetic efficiency compensates for reduced photosynthesis during hot and dry periods, but only for pubescent oak, which is a rather drought tolerant species. Current predictions of warming-induced mitigation effects through extended C uptake seem incorrect for beech.

2022

Retention and hydrolysable fraction of atmospherically deposited nitrogen in two contrasting forest soils in Switzerland

Claire Guenat, Isabelle Morier Jaquet

Nitrogen (N) from atmospheric deposition has been shown to be mainly retained in the organic soil layers of temperate forest ecosystems, but the mechanisms and the physico-chemical fractions involved are still poorly defined. We performed a hot-acid hydrolysis on N-15-labelled soil samples collected 1 week, 3 months and 1 year following a single in situ application of either (NO3-)-N-15 or (NH4+)-N-15 in two montane forest ecosystems in Switzerland: Grandvillard (beech forest on a calcareous, well-drained soil, 650 m above sea level) and Alptal (spruce forest on hydromorphic soil, 1200 m above sea level). After (NH4+)-N-15 application, recovery rates in the soil were smaller in Alptal than in Grandvillard through a large rate of absorption by mosses. At both sites, the organic soil layers retained most of the tracers at all three sampling times between 1 week and 1 year. In Grandvillard, the hydrolysable fraction (hydrolysable N : total N) of N-15 was on average 79% and thus similar to the hydrolysable fraction of native N. This similarity is probably because of the rapid incorporation of N into organic molecules, followed by stabilization of the recalcitrant N pool through organo-mineral bonds with soil minerals. In Alptal, the N-15 hydrolysable fraction was greater than that of native N, particularly after (NH4+)-N-15 application (N-15, 84%; native N, 72%). At both sites, N-15 and the fraction of hydrolysable native N remained constant between 1 week and 1 year. This shows that both the recalcitrant and the hydrolysable pools are stable in the mid-to long-term. We present arguments indicating that biological recycling through microbes and plants contributes to the stability of the hydrolysable N fraction.

2010