From half-hour to quarter century- Drivers of carbon fluxes across a northern ecosystem tower cluster

Conference: ‘AmeriFlux Annual Meeting 2021’

Abstract: Long-running eddy covariance towers help provide the statistically robust insights into how the carbon cycle operates over multiple time-scales, across multiple climate extremes, disturbances, and during longterm trends in atmospheric composition. Long-running eddy covariance towers operating as a cluster provide an even stronger case for evaluating how processes that impact the carbon cycle vary across ecosystem properties, within the same climate and biome. Here, we present a lab initiated project to harmonize and evaluate variation in net ecosystem exchange of carbon dioxide across the Chequamegon Ecosystem-Atmosphere Study (ChEAS) Ameriflux core site cluster in the upper Great Lakes region USA. The tower network includes two mature hardwood forests with differing management regimes (US-WCr and US-Syv), two fen wetlands with varying exposure and vegetation (US-Los and US-ALQ), and a very tall (400 m) landscape level tower (US-PFa) that has been in continuous operation for eddy covariance since 1996. Together, they provide over 70 site-years of observations that can be coupled to climate drivers and remotely-sensed vegetation function. Short-term seasonal to 4-year studies of additional tower clusters in wetlands, forests of differing successional stage, and the 19-tower CHEESEHEAD19 campaign provide additional context on spatial variation. One remarkable consistent finding is the strong role that water, whether in atmosphere (VPD), soil, stream, or water table plays in modulating carbon flux variation, despite a general overall lack of water-limitation in the biome.