Abstract
In boreal forests, fire is an important part of the ecosystem that greatly influences soil respiration, which in turn affects the carbon balance. Wildfire can have a significant effect on soil respiration and it depends on the fire severity and environmental factors (soil temperature and snow water equivalent) after fire disturbance. In this study, we quantified post-fire soil respiration during the non-growing season (from November to April) in a Larix gmelinii forest in Daxing'an Mountains of China. Soil respiration was measured in the snow-covered and snow-free conditions with varying degrees of natural burn severity forests. We found that soil respiration decreases as burn severity increases. The estimated annual C efflux also decreased with increased burn severity. Soil respiration during the non-growing season approximately accounted for 4%–5% of the annual C efflux in all site types. Soil temperature (at 5 cm depth) was the predominant determinant of non-growing season soil respiration change in this area. Soil temperature and snow water equivalent could explain 73%–79% of the soil respiration variability in winter snow-covering period (November to March). Mean spring freeze–thaw cycle (FTC) period (April) soil respiration contributed 63% of the non-growing season C efflux. Our finding is key for understanding and predicting the potential change in the response of boreal forest ecosystems to fire disturbance under future climate change.
Highlights
Soil respiration (Rs) is the second-largest carbon flux in most terrestrial ecosystems—the amount of CO2 released by soil respiration is more than ten times that released by global fossil fuel combustion [1, 2]
The mean non-growing season Rs in the Larix gmelinii forest was 0.29 ± 0.06 μmol CO2Ám-2Ás-1 (Table 3). This result was consistent with Wang et al [20], who found that the average winter Rs rate of seven forest ecosystems in northern China was 0.28 μmol CO2Ám-2Ás-1
Many studies have found that the Rs of forest ecosystems during the non-growing season ranged from 0.15 to 0.67 μmol CO2Ám-2Ás-1 [12, 13, 16, 68]
Summary
Soil respiration (Rs) is the second-largest carbon flux in most terrestrial ecosystems—the amount of CO2 released by soil respiration is more than ten times that released by global fossil fuel combustion [1, 2] It contributes 20%–40% of the CO2 input to the atmosphere [3]. Soil respiration is estimated to be 80–98 Pg CÁyr-1 [4]. Many studies focus on forest soil respiration during the growing season [5,6,7,8,9], and estimated the annual soil respiration by assuming the respiration flux near zero during the non-growing season [10].
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