Light, temperature and water: How the combined effects of drought control terrestrial carbon flux

Abstract:

As meteorological extremes intensify with a warming climate the resilience of land sink capacity remains an important question. The divergent or congruent response of ecosystem processes such as Gross Primary Production (GPP) and Respiration (R) hold important implications for atmospheric accumulation of CO₂, as the net difference, or Net-Ecosystem Exchange (NEE), is the signal observed within the atmosphere. The turn-of-the-century drought has recently been highlighted as a test-case for the effect of water availability (as measured through evaporative fraction) on the current carbon dioxide sink that constitutes the western U.S. Here we leverage eddy co-variance FLUXNET observational data and expand on previous analyses to include observed ecosystem carbon flux response to surface air temperature, downwelling short-wave flux and evaporative fraction, as all three co-occur during drought, but the severity and duration of water availability and surface air temperature can vary significantly. The result is a comparison to previous ecosystem response analyses and an extrapolation to the more recent 2012 drought.