Soil Respiration and Controls in Warmer Winter: A Snow Manipulation
Study in Postfire and Undisturbed Black Pine Forests
Abstract
Climate change impacts are driving forest fires worldwide and reducing
snowfall in temperate countries. Whether these impacts result in a
significant alteration of winter soil respiration (Rs) rates and
temperature in the postfire and the undisturbed black pine (Pinus nigra)
forests remain poorly understood. A field experiment was conducted in
the postfire and the undisturbed black pine forests during a winter
period in Türkiye to quantify Rs rates as affected by lack of snow and
snow cover. Four treatments were applied: snow-exclusion postfire
(SEPF), snow postfire (SPF), snow-exclusion undisturbed forest (SEUF),
and snow-undisturbed forest (SUF). The SEPF exhibited the significantly
lowest mean Rs rates (0.71 µmol m-2 s-1) compared to the SPF (1.02 µmol
m-2 s-1), SEUF (1.44 µmol m-2 s-1, and SUF (1.48 µmol m-2 s-1). The Rs
also showed significant variations with time (p <.0001).
However, treatments and time exhibited no statistically significant
interaction effects (p = 0.6801). Total amounts of winter Rs (January to
March) ranged from 4.92 to 5.07 Mt CO2 ha-1 in the undisturbed forest
and 2.53 to 3.51 Mt CO2 ha-2 in the postfire site. The Rs showed a
significantly positive relationship (p <.0001) with the soil
(0.59) and air (0.46) temperatures and a significantly negative
relationship (p = 0.0017) with the soil moisture (-0.20) at the 5 cm
depth. In contrast, the Rs showed a negative, but not statistically
significant relationship (p = 0.0932) with the soil moisture (-0.16) at
the 10 cm soil depth. The combined effects of lack of snow and forest
fire resulted in a significant decrease of Rs. In contrast, a warmer
winter significantly increased Rs rates in the undisturbed forest,
suggesting that a warmer winter could potentially accelerate soil
organic carbon losses in naturally growing undisturbed forest
ecosystems, thus, providing positive feed backs to climate change.