Soil respiration and controls in warmer winter: A snow manipulation study in postfire and undisturbed black pine forests

Abstract

Climate change impacts drive warmer winters, reduced snowfall, and forest fires. In 2020, a wildfire scorched about 1508 hectares of black pine ( Arnold) forests in Türkiye. Whether the combined effects of lack of snow and forest fires significantly alter winter soil respiration (R) and soil temperature remains poorly understood. A field experiment was conducted in the postfire and undisturbed black pine forests during the winter to quantify R rates as affected by lack of snow and forest fire. We applied four treatments: snow-exclusion postfire (SEPF), snow postfire (SPF), snow-exclusion-undisturbed forest (SEUF), and snow undisturbed forest (SUF). The SEPF exhibited the significantly lowest mean R rates (0.71 μmol m s) compared to the SPF (1.02 μmol m s), SEUF (1.44 μmol m s), and SUF (1.48 μmol m s). The R also showed significant variations with time ( < .0001). However, treatments and time revealed no statistically significant interaction effects ( = .6801). Total winter R (January-March) ranged from 4.47 to 4.59 Mt CO ha in the undisturbed forest and 2.20 to 3.16 Mt CO ha in the postfire site. The R showed a significantly positive relationship ( < .0001) with the soil (0.59) and air (0.46) temperatures and a significantly negative relationship ( = .0017) with the soil moisture (-0.20) at the 5 cm depth. In contrast, the R indicated a negative but not statistically significant relationship ( = .0932) with the soil moisture (-0.16) at the 10 cm soil depth. The combined effects of lack of snow and forest fire significantly decreased R, thus conserving the soil's organic carbon stocks and reducing the CO contribution to the atmosphere. In contrast, a warmer winter significantly increased R rates in the undisturbed forest, suggesting an acceleration of soil organic carbon losses and providing positive feedback to climate change.