Project

Back to overview

COS and below-canopy CO2 fluxes of two Swiss forests: understanding land-atmosphere ecosystem exchange (COCO)

Applicant Buchmann Nina
Number 197357
Funding scheme Project funding
Research institution Departement Umweltsystemwissenschaften ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Other disciplines of Environmental Sciences
Start/End 01.04.2021 - 31.03.2025
Approved amount 806'735.00
Show all

All Disciplines (2)

Discipline
Other disciplines of Environmental Sciences
Environmental Research

Keywords (10)

carbon dioxide CO2; below-canopy flux; climate change; forest ecosystem; climate extreme; carbonyl sulphide COS; eddy-covariance method; ecosystem functioning; soil respiration; land-atmosphere exchange

Lay Summary (German)

Lead
Das übergeordnete Ziel des Projekts COCO ist ein besseres Verständnis des Land-Atmosphären-CO2-Austauschs zweier Schweizer Wälder. Der Klimawandel hat in den letzten Jahrzehnten intensive Forschungen über das globale Kohlenstoff (C)-Budget ausgelöst, v.a. zu Senken und Quellen von C. Um jedoch zu "naturnahen" Lösungen zu gelangen, wie sie im Pariser Abkommen vorgeschlagen werden, bedarf es eines umfassenden Verständnisses der Folgen des Klimawandels auf die Funktionsweise der Wälder. Dies wiederum erfordert die Existenz und Verfügbarkeit langfristiger, qualitativ hochwertiger Daten über den Netto-Ökosystemaustausch (NEE), der sich in CO2-Aufnahme (GPP) und Atmungsverluste (Reco) unterteilen lässt.
Lay summary

Unsere Ziele sind daher, (1) die unabhängige Validierung von Schätzungen der Bruttoprimärproduktion mit Carbonylsulfid (COS)-Flüssen (WP1), (2) die Abschätzung der Ökosystematmung durch Messungen von Flüssen unterhalb der Baumkronen (WP2), (3) die Quantifizierung der Advektion (WP3) und (4) die Identifizierung langfristiger Trends und kurzfristiger Reaktionen der CO2-Flüsse auf Klimaextreme (WP4). COCO wird in einem gemäßigten Mischwald und einem subalpinen Fichtenwald durchgeführt, für die Flussdaten von mehr als 40 Jahren vorliegen. Einer der Standorte verfügt über die 8. längste Zeitreihe für CO2- und Wasserdampfflüsse weltweit.

COCO kann so hoch signifikante Erkenntnisse über den CO2-Austausch zwischen Land und Atmosphäre liefern, basierend auf umfassenden und einzigartigen Messungen und einem innovativen Ansatz. Das Projekt trägt zu unserem Verständnis der Funktionsweise von Ökosystemen bei, liefert aber auch bessere Schätzungen von GPP und Reco und verbessert so dynamische Kohlenstoffmodelle. Die Voraussetzungen von COCO an beiden Waldstandorten sind ideal, um Hypothesen über Klimaauswirkungen zu testen und die Anfälligkeit der Wälder für künftige Veränderungen zu beurteilen. Die Reaktionen der Waldökosysteme auf langsame Umweltveränderungen wie den Klimawandel können nur mit langen Zeitreihen erfolgen, die für beide Standorte zur Verfügung stehen.

Direct link to Lay Summary Last update: 30.09.2020

Responsible applicant and co-applicants

Employees

Associated projects

Number Title Start Funding scheme
173691 ICOS-CH Phase 2 01.07.2017 Research Infrastructure
200918 Assessment of formal, natural and social insurances: how to cope best with impacts of extreme events on grasslands for sustainable farming systems? 01.04.2022 Project funding
198227 ICOS-CH Phase 3 01.07.2021 Research Infrastructure
198094 Unravel the changing contributions of abiotic vs. biotic drivers of ecosystem gas exchange under weather extremes 01.04.2021 COST (European Cooperation in Science and Technology)
172433 Reconciling innovative farming practices and networks to enable sustainable development of smart Swiss farming systems 01.01.2018 NRP 73 Sustainable Economy

Abstract

The overarching goal of the proposed project COS and below-canopy CO2 fluxes of two Swiss forests: understanding land-atmosphere exchange (COCO) is to better understand land-atmosphere CO2 exchange of two Swiss forests. Climate change due to anthropogenic greenhouse gas emissions has spurred intensive research about the global carbon (C) budget, sinks and sources of C, particularly in forests, and their drivers over the last decades. However, achieving “nature-based” solutions, proposed in the Paris Agreement, needs a comprehensive understanding of consequences of climate change on forest functioning, both in response to long-term trends in temperature and precipitation as well as to short-term extreme climate events. This requires the existence and availability of long-term, high-quality data on ecosystem functions, such as net ecosystem exchange (NEE), which can be partitioned into ecosystem CO2 uptake (GPP) and respiratory losses (Reco), crucial to understand the mechanisms underlying forest responses and assess their potential for sustained C sequestration. Thus, detection of flux (un)certainty is crucial, and is best done by additional constraints, e.g. by below-canopy flux measurements as well as advection estimates. More importantly, carbonyl sulphide (COS) fluxes provide a truly independent constraint for GPP since foliar uptake reflects photosynthesis but back-fluxes are lacking for COS. Despite this unprecedented option to validate GPP estimates, COS flux measurements are still very scarce. Thus, our specific objectives are (1) to independently validate gross primary production estimates with COS fluxes (WP1), (2) to constrain ecosystem respiration estimates using below-canopy fluxes (WP2), (3) to quantify advection CO2 (WP3), and (4) to identify long-term trends and short-term responses of CO2 fluxes to climate extremes (WP4). COCO is carried out at a temperate mixed forest and a subalpine spruce forest, for which 40+ years of flux data are available. One of the sites has the 8th longest time series for CO2 and water vapour fluxes globally. In WP1, turbulent COS fluxes are measured at both sites. Assumptions about soil and litter COS fluxes are tested, and the leaf relative uptake is determined for different plant species. Thus, GPP can be validated, providing additional constraints on flux partitioning. In WP2, below-canopy CO2 fluxes are quantified using an independent set-up at 1.5 m height at each site, complemented by soil respiration measurements. This provides additional constraints on Reco, and horizontal advection. In WP3, advection is quantified using vertical and horizontal profiles of CO2 concentration, wind direction and wind speed measurements. This provides quantitative constraints on NEE and a potential correction option, in particular in combination with WP2. In WP4, the long time series of CO2 exchange fluxes are used to evaluate long-term trends of fluxes and C sequestration rates in response to changing climatic conditions on the one hand and to identify short-term responses to climate extremes on the other hand. 40+ years of data provide a great opportunity to assess vulnerability of two mountain forests. COCO provides highly significant insights on land-atmosphere CO2 exchange based on comprehensive und unique measurements and an innovative approach. It contributes to our understanding of ecosystem functioning but also provides better estimates of GPP and Reco, improving dynamic carbon models. COCO’s prerequisites at both forest sites are ideal to test hypotheses of climate impacts and assess forest vulnerabilities to future changes. Responses of forest ecosystems to slow environmental change such as climate change can only be done with long time series, available for both sites, and both forests have also experienced climate extremes over the last decades. The broader impact of COCO is two-fold: (1) informing adaptive forest management, and (2) providing insights into forest functioning to develop nature-based solutions to meet the Paris targets. Applying a comprehensive systems approach as proposed in COCO seems mandatory to address climate change, one of the grand challenges of humankind.
-