Effects of prolonged soil drought on CH 4 oxidation in a temperate spruce forest

Our objective was to determine potential impacts of changes in rainfall amount and distribution on soil CH 4 oxidation in a temperate forest ecosystem. We constructed a roof below the canopy of a 65‐year‐old Norway spruce forest ( Picea abies (L.) Karst.) and simulated two climate change scenarios: (1) an extensively prolonged summer drought of 172 days followed by a rewetting period of 19 days in 1993 and (2) a less intensive summer drought of 108 days followed by a rewetting period of 33 days in 1994. CH 4 oxidation, soil matric potential, and soil temperature were measured hourly to daily over a 2‐year period. The results showed that annual CH 4 oxidation in the drought experiment increased by 102% for the climate change scenario 1 and by 41% for the climate change scenario 2, compared to those of the ambient plot (1.33 kg CH 4 ha −1 in 1993 and 1.65 kg CH 4 ha −1 in 1994). We tested the relationships between CH 4 oxidation rates, water‐filled pore space (WFPS), soil matric potential, gas diffusivity, and soil temperature. Temporal variability in the CH 4 oxidation rates corresponded most closely to soil matric potential. Employing soil matric potential and soil temperature, we developed a nonlinear model for estimating CH 4 oxidation rates. Modeled results were in strong agreement with the measured CH 4 oxidation for the ambient ( r 2 = 0.80) and drought plots ( r 2 = 0.89) over two experimental years, suggesting that soil matric potential is a highly reliable parameter for modeling CH 4 oxidation rate.