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

Context

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. 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 (R_eco), 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, advection estimates as well as carbonyl sulphide (COS) fluxes.

Project aims

Thus, our specific objectives are

1. to independently validate gross primary production estimates with COS fluxes,
2. to constrain ecosystem respiration estimates using below-canopy fluxes,
3. to quantify advection of CO₂, and
4. to identify long-term trends and short-term responses of CO₂ fluxes to climate extremes.

COCO is carried out at a temperate mixed forest (Lägeren) and a subalpine spruce forest (Davos), for which 40+ site-years of flux data are available. It will provide 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.