Publication

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

Charlotte Grossiord, Christoph Bachofen, Eugénie Isabelle Mas, Margaux Clara Lou Didion-Gency
2022
Journal Articles

Résumé

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.

Source officielle

https://infoscience.epfl.ch/entities/publication/50b73a5c-402c-4751-b4b0-ce59bba4eebf

Charlotte Grossiord, Christoph Bachofen, Eugénie Isabelle Mas, Margaux Clara Lou Didion-Gency
2022
Journal Articles

Résumé

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.

Source officielle

https://infoscience.epfl.ch/entities/publication/50b73a5c-402c-4751-b4b0-ce59bba4eebf

Concepts associés (32)

Photosynthèse

vignette|La photosynthèse végétale consiste à réduire le dioxyde de carbone de l'atmosphère par l'eau absorbée par les racines à l'aide de l'énergie solaire captée par les feuilles avec libération d'oxygène afin de produire des glucides. vignette|Équation de la photosynthèse. vignette|La feuille est l’organe spécialisé dans la photosynthèse chez les spermatophytes. vignette|Vue composite montrant la distribution de l'activité photosynthétique à la surface de la Terre, le rouge foncé indiquant les zones les plus actives du phytoplancton des milieux aquatiques et le bleu-vert celles de la végétation sur la terre ferme.

Photosynthetic efficiency

The photosynthetic efficiency is the fraction of light energy converted into chemical energy during photosynthesis in green plants and algae. Photosynthesis can be described by the simplified chemical reaction 6 H2O + 6 CO2 + energy → C6H12O6 + 6 O2 where C6H12O6 is glucose (which is subsequently transformed into other sugars, starches, cellulose, lignin, and so forth). The value of the photosynthetic efficiency is dependent on how light energy is defined – it depends on whether we count only the light that is absorbed, and on what kind of light is used (see Photosynthetically active radiation).

Carbone du sol

Le carbone du sol est la matière terrestre solide stockée dans les sols au niveau mondial. Cette appellation comprend à la fois la matière organique du sol et l'ensemble du carbone inorganique constituant les minéraux carbonatés. Le carbone du sol est un puits de carbone par rapport au cycle mondial du carbone, jouant un rôle dans la biogéochimie, l'atténuation du changement climatique et dans la construction de modèles climatiques mondiaux. Le carbone du sol est présent sous deux formes : inorganique et organique.

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