ECOWAX

Evaluating the variability of ecosystem water vapour fluxes and spatiotemporal effects of extreme events

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 Obiettivo del progetto (Objective)

'Water vapour fluxes are a key variable in the biosphere-atmosphere exchange of water in terrestrial ecosystems and have strong interactions with the climate system. However, research on the effects of climate change has been largely focused on carbon cycling and therefore, many open questions remain, in particular with respect to the long-term variability of water vapour fluxes and to spatiotemporal patterns in ecosystem responses to extreme events. The project ECOWAX intends to close this knowledge gap and contribute to a better understanding of ecosystem water cycling, thus assisting in the development of mitigation options to secure water supply for human society in a changing climate. The overarching goals of ECOWAX are (1) to assess the intra- and interannual variability of ecosystem water vapour fluxes across biomes and climate, and (2) to evaluate spatiotemporal effects of extreme events on these fluxes. To achieve these goals, ECOWAX will combine water vapour fluxes measured in situ from a new synthesis dataset of the global measurement network FLUXNET with a novel biophysical process model (BESS – Breathing Earth System Simulator) to upscale ecosystem fluxes globally for spatiotemporal analysis. The research objectives of ECOWAX are (1) to investigate the range and magnitude of intra- and interannual variability of water vapour fluxes across biomes and climates using the FLUXNET synthesis dataset, (2) to improve the novel biophysical model BESS to overcome current limitations, (3) to upscale water vapour fluxes globally with the improved version of BESS and validate the model results with site data from FLUXNET, and (4) to assess the spatiotemporal variability of water vapour fluxes and the effects of extreme events on these fluxes in Europe during the last decade. The outgoing host for ECOWAX will be the lab of Prof. Dennis Baldocchi at the University of California, Berkeley (USA) and the return host will be Prof. Nina Buchmann at ETH Zurich (Switzerland).'

Introduzione (Teaser)

Water vapour fluxes are a key factor in the biosphere-atmosphere exchange of water in terrestrial ecosystems and have a major influence on the climate. However, research on the effects of climate change has traditionally centred on carbon cycling of ecosystems rather than the long-term variability of water fluxes and how these respond to extreme events.

Descrizione progetto (Article)

The http://www.gl.ethz.ch/research/projects/ECOWAX/index (ECOWAX) project is addressing the question of variability in water fluxes to gain a clearer understanding of ecosystem water cycling. It will investigate how ecosystem water vapour fluxes change in time and space.

Researchers will also study how these fluxes vary among climates and different biomes, which are biological communities characterised by the dominant form of plant life. In addition, researchers will investigate the effects of extreme events such as drought on these fluxes.

The project will combine in situ measurements of water vapour fluxes from the global network FLUXNET with the biophysical process model BESS (Breathing Earth System Simulator). Preliminary results show that the seasonal timing of drought plays a major role for the impact on ecosystem water and carbon fluxes. Drought effects are different during spring and summer and among ecosystem types, such as grasslands and forests.

Furthermore, warmer temperatures during spring will increase carbon uptake, but the earlier vegetation activity will also deplete water resources sooner. The result is a potential heating feedback during the summer months, which could increase the intensity of heat waves.

Tropical ecosystems were found to play the most important role in the global hydrological cycle. This is because they have the highest absolute rates of water vapour transport to the atmosphere and by converting the largest proportion of available energy into water vapour.

ECOWAX will increase the understanding of ecosystem water cycling, especially during extreme events such as large-scale drought. This information will help to develop mitigation strategies to secure water supply for human needs in the face of a changing climate.