Effects of fire disturbance on soil respiration in the non-growing season in a <i>Larix gmelinii</i> forest in the Daxing'an Mountains, China

<div><p>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 <i>Larix gmelinii</i> 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.</p></div

Snow-covering and snow-free soil respiration (Rs) in (a) control, (b) low burn severity, and (c) high burn severity treatments.

<p>Mean ± se is shown in the figures.</p

Soil respiration(CO₂·m^–2·s^–1) (Rs) and soil temperature (°C) (T) of snow-covering and snow-free conditions.

<p>Soil respiration(CO₂·m^–2·s^–1) (Rs) and soil temperature (°C) (T) of snow-covering and snow-free conditions.</p

Snow-covering and snow-free soil temperature (T) in (a) control, (b) low burn severity, and (c) high burn severity.

<p>Mean ± se is shown in the figures.</p

Vegetative composition of the experimental plots.

<p>Vegetative composition of the experimental plots.</p

Distribution of soil respiration (Rs) rings and snow-covering soil respiration rings within a site.

<p>Each circle represents one sampling point.</p

The parameters and statistics of soil respiration as the exponential function of soil temperature at growing season, non-growing season snow-covering, and non-growing season snow-free stand for different burn severities.

<p>Parameter values are reported as mean ± se.</p

Regression of soil respiration (Rs) and soil temperature (T) fitted models of (a) control, (b) low burn severity, and (c) high burn severity in the non-growing season.

<p>Regression of soil respiration (Rs) and soil temperature (T) fitted models of (a) control, (b) low burn severity, and (c) high burn severity in the non-growing season.</p

Regression models of soil respiration(CO₂·m⁻2·s^–1) (Rs), soil temperature (°C) (T), and SWE is snow water equivalent (mm); T × SWE is the interaction effect of T and SWE; and <i>α</i>, <i>β</i>, <i>ε</i>, and <i>ω</i> are regression coefficients.

<p>Regression models of soil respiration(CO₂·m⁻2·s^–1) (Rs), soil temperature (°C) (T), and SWE is snow water equivalent (mm); T × SWE is the interaction effect of T and SWE; and <i>α</i>, <i>β</i>, <i>ε</i>, and <i>ω</i> are regression coefficients.</p

Non-growing season and annual C efflux in three different fire severity (control, low, and high).

<p>Non-growing season and annual C efflux in three different fire severity (control, low, and high).</p