Soil CO2 Effluxes in Post-fire and Undisturbed Pinus nigra Forests: A Soil Moisture Manipulation Study

Abstract

Climate change impacts are driving hydrological extremes and frequent occurrences of forest fires. Whether these impacts result in dramatic changes in the soil CO2 efflux (FCO2) remains poorly understood. This study seeks to understand the changes in the soil FCO2 in recently burned forest (post-fire) and an undisturbed black pine (Pinus nigra, Arnold) forest in Türkiye. A field experiment in a three-way factorial randomized complete block design experiment was established with four replications and three factors; shaded (west) and exposed (east), types of forest fires (surface, crown, and control) and soil moisture regimes (dry, wet, and control). A dynamic survey chamber soil respiration machinery (LI-8100A) was employed to measure simultaneously the soil Fco2, the soil temperature, and the soil moisture for a total duration of one-year. The soil FCO2 showed significant differences among treatments (p<0.0001), time (p<0.0001), and moisture regimes (p<0.0001), but not with the interaction effects between treatment and time (p = 0.0058), aspects (p = 0.95410), and types of forest fires (p = 0.0059). A dry soil in the crown fire site situated in the exposed aspect exhibited a significantly different and lowest soil FCO2 compared to other treatments. No statistically significant differences in the FCO2 in the wet soil were detected among treatments. The soil and air temperatures showed a strongly positive correlation (r = 0.78), suggesting that a near-surface air temperature provides a good approximation of the soil temperature. This piece of information is a vital input for the projection of future trajectory of soil CO2 emissions and conservation of C stocks in the forest fire and undisturbed forests.