Carbon and Oxygen Gas Exchange in Woody Debris: The Process and Climate-Related Drivers

• Main Authors: Victor A. Mukhin, Daria K. Diyarova, Mikhail L. Gitarskiy, Dmitry G. Zamolodchikov
• Format: Article
• Language: English
• Published: MDPI AG 2021-08-01
• Series: Forests
• Subjects: boreal forest; woody debris; CO₂; O₂; gas exchange; temperature
• Online Access: https://www.mdpi.com/1999-4907/12/9/1156

The carbon-to-oxygen relationship and gas exchange balance, organic carbon to CO₂ conversion intensity and efficiency, and their relevance to climate parameters and wood decay fungi were investigated for birch woody debris (WD) in the Mid-Urals mixed pine and birch forests. It was shown that, within the range of temperatures from 10 to 40 °C and relative moisture (RM) of wood of 40% and 70%, aerobic gas exchange was observed in the WD, encompassing the physiologically entwined processes of CO₂ emission and O₂ uptake. Their volumetric ratio (0.9) confirmed that (1) the WD represents a globally significant CO₂ source and appropriate O₂ consumer and (2) the oxidative conversion of organic carbon is highly efficient in the WD, with an average ratio of CO₂ released to O₂ consumed equal to 90%. The balance of carbon-to-oxygen gas exchange and oxidizing conversion efficiency in the WD were not affected by either fungal species tested or by moisture or temperature. However, the intensity of gas exchange was unique for each wood decay fungi, and it could be treated as a climate-reliant parameter driven by temperature (<i>Q</i>₁₀ = 2.0–2.1) and moisture (the latter induced a corresponding trend and value changes in CO₂ emission and O₂ uptake). Depending on the direction and degree of the change in temperature and moisture, their combined effect on the intensity of gas exchange led to its strengthening or weakening; otherwise, it was stabilized. Aerobic respiration of wood decay Basidiomycetes is an essential prerequisite and the major biotic factor in the WD gas exchange, while moisture and temperature are its climatic controllers only.