Project

DNA; climate change ecology; biogeochemistry; 14C; soil organic carbon; plant soil interactions; 13C

Lead
Les dynamiques dans la végétation qui résultent des changements du climat et de l’utilisation de sol influencent fortement les processus écosystémiques suite aux diverses interactions entre les plantes et le sol. Ce projet de recherche est axé sur l’influence des mycorhizes sur le taux de renouvellement du carbone organique dans le sol des écosystèmes de montagne. L’émissions potentielle de gaz à effet de serre vers l’atmosphère, résultant des changements des communautés de plantes est microorganismes, y est estimée.
Lay summary
La photosynthèse des plants représente le plus grand puit pour le dioxyde de carbone atmosphérique (CO2). La respiration du sol, par contre, est la plus grande source de CO2. C’est pourquoi l’équilibre entre ces deux flux est essentielle à une concentration stable de ce gaz à effet serre dans notre atmosphère. Les écosystèmes de montagne peuvent accumuler beaucoup de carbone dans le sol cars les températures froides limitent la décomposition de la matière organique. Avec le réchauffement du climat cependant, la décomposition augmente et libère d’avantage des nutriments pour les plantes, ce qui favorise des espèces des plantes plus grandes. De tels changements dans la végétation représentent un défi particulier dans l’estimation des flux nets de carbone de l’écosystèmes exposé au changement climatique, en vue des multiples interactions entre plantes et sol. Les changements du climat et de l’utilisation de sol augmentent ainsi la productivité de la végétation, ainsi que l’expansion de la forêt, dans les régions montagneuses. Ce projet de recherche analyse si ces évolutions modifient la structure et le fonctionnement des communautés de microorganismes décomposant la matière organique et ainsi accélèrent le cycle du carbone. Les recherches se concentrent sur l’activité de mycorhizes caractéristiques qui s’associent en symbiose avec différents types de végétation. Le projet évalue divers processus écologiques, de l’échelle de la plante à celle de l’écosystème, en se basant sur des expériences mécanistiques en laboratoire, ainsi que sur des observations réalistes sur le terrain. Cette approche hiérarchique améliore notre compréhension du cycle terrestre de carbone, et informe les politiciens des stratégies adaptatives durables pour les écosystèmes de montagne exposé au changement climatique.

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Last update: 18.12.2017

Lead
Vegetation dynamics resulting from climate and land-use change are important drivers of ecosystem processes as a variety of plant-soil interactions take place. This research project focuses on the role of mycorrhizae in the turnover of soil organic carbon in mountain ecosystems. It estimates the potential release of greenhouse gases to the atmosphere resulting from changes in above and belowground communities.
Lay summary
Plant photosynthesis represents the largest sink for atmospheric carbon dioxide (CO2). Soil respiration, in contrast, is the largest source of CO2. The balance between these two fluxes is therefore essential for the stable concentration of this greenhouse gas in our atmosphere. Mountain ecosystems have a strong capacity for accumulation of carbon (C) in the soil, due to cold temperatures limiting decomposition rates of soil organic matter. With warmer climate, however, decomposition rates increase, releasing more nutrients for plant growth and promoting taller vegetation. Such vegetation shifts are a particular challenge to estimations of net ecosystem C fluxes under climate change, as a multitude of plant-soil feedbacks take place. This research project investigates whether increased plant productivity and forest expansion in mountain areas under climate and land-use change causes shifts in the community structure and function of decomposing microorganisms and thereby accelerate the soil C cycle. Focus is laid on the activity of characteristic mycorrhizae symbiotically associated with different vegetation types. The project evaluates diverse ecological processes from the plant to the ecosystem scale, based on mechanistic lab experiments and realistic field observations. This hierarchical approach improves our understanding of the terrestrial carbon cycle and inform policy makers on which adaptive strategies are sustainable for mountain ecosystems under climate change.

Direct link to Lay Summary

Last update: 18.12.2017

Active participation

Self-organised

Title	Year

Number	Title	Start	Funding scheme

Terrestrial ecosystems represent the largest sink for atmospheric carbon dioxide (CO2) and their sustained functioning is essential for the future concentrations of greenhouse gases. High latitude and altitude ecosystems have a strong capacity for capturing and storing carbon (C) in soils, due to cold temperatures limiting decomposition rates. As climate progressively warms, not only constraints on decomposition are relieved, but also plant productivity is stimulated, promoting high stature vegetation and the accumulation of aboveground biomass. Such vegetation shifts present a particular challenge to estimations of net ecosystem C fluxes under climate change, as a multitude of plant-soil feedbacks are involved. In this project proposal, I argue that increased plant productivity and forest expansion in mountain areas under climate and land-use change inadvertently bring about shifts in the decomposer community and thereby accelerate the C cycle. Promoted are symbiotic associations with ericoid and ectomycorrhizal fungi, which are extremely efficient in breaking down accumulated soil organic carbon (SOC) compared to arbuscular mycorrhizae and bacterial assemblages, associated with the dominant herbaceous vegetation. The heterotrophic activity of the decomposers is further stimulated by the exudation of fresh photosynthates by the woody plants, creating a positive feedback loop to the release of previously stored C into the atmosphere. In addition to the biotic interactions with soil microbial communities, woody vegetation exerts abiotic controls on its microclimate. Its high stature provides shade, but also acts as an effective trap for snow accumulation, thereby modifying soil temperature extremes and growing season length. This can further stimulate heterotrophic activity in the soil and thereby exert a positive feedback to climate change through the decomposition of SOC stocks. Despite the high relevance, we currently lack a holistic understanding of the impacts from such large-scale shifts in vegetation communities on SOC and know little in terms of controlling mechanisms in relevant plant-soil interactions.In this project, I propose to advance our understanding using a hierarchical approach, covering ecological processes from the plant to the ecosystem scale. Under controlled conditions, I will assess the role of mycorrhizal fungi with contrasting life strategies in the breakdown of SOC and the linkage of plant productivity and rhizosphere priming. I will follow natural treeline gradients of forest and heath encroachment into mountain grasslands in order to determine the role of plants as vectors of soil microbial communities and their primary function. I will put these findings into perspective by comparing the net effect of tree growth in mountain grasslands on SOC stocks and dynamics along an afforestation chronosequence.