Does dissolved oxygen in rainwater contribute to pulses of CO2 after dry spells?

Abstract:

An anomalously high rate of CO₂ flux immediately after the rewetting of dry soils accounts for a significant fraction of the annual CO₂ flux budget in Mediterranean climates. This phenomenon, known as the Birch effect, is often attributed to the lysing of microbes during the drought phase and subsequent rapid mineralization of the readily accessible microbial C pool during the initial wetting phase. Slaking of dry aggregates upon rapid wetting and release of previously physically-protected C is also a possible mechanism. We propose the short-lived high concentration of dissolved oxygen (DO) of infiltrating water is also a significant contributor to the pulses of CO₂ flux. After the depletion of the initial DO supply, the low solubility and diffusivity of O₂ in water become the limiting factors. In this presentation, we will share experimental evidence and mathematical models that support the hypothesis.