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 (Pinus nigra Arnold) forests in T & uuml;rkiye. Whether the combined effects of lack of snow and forest fires significantly alter winter soil respiration (R-s) 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-s 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-s rates (0.71 mu mol m(-2) s(-1)) compared to the SPF (1.02 mu mol m(-2) s(-1)), SEUF (1.44 mu mol m(-2) s(-1)), and SUF (1.48 mu mol m(-2) s(-1)). The R-s also showed significant variations with time (p < .0001). However, treatments and time revealed no statistically significant interaction effects (p = .6801). Total winter R-s (January-March) ranged from 4.47 to 4.59 Mt CO2 ha(-1) in the undisturbed forest and 2.20 to 3.16 Mt CO2 ha(-2) in the postfire site. The R-s showed a significantly positive relationship (p < .0001) with the soil (0.59) and air (0.46) temperatures and a significantly negative relationship (p = .0017) with the soil moisture (-0.20) at the 5 cm depth. In contrast, the R-s indicated a negative but not statistically significant relationship (p = .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-s, thus conserving the soil's organic carbon stocks and reducing the CO2 contribution to the atmosphere. In contrast, a warmer winter significantly increased R-s rates in the undisturbed forest, suggesting an acceleration of soil organic carbon losses and providing positive feedback to climate change.