Changes in the non-growing season soil heterotrophic respiration rate are driven by environmental factors after fire in a cold temperate forest ecosystem

Abstract

& Key message During the non-growing season, environmental factors changed after fire, leading to significantly increased nongrowing season soil heterotrophic respiration (R h ) and potentially decreasing the amount of net C stored in cold temperate forest ecosystems of China. & Context Intensifying forest fire regimes are likely to influence future C budgets of forest ecosystems. However, the mechanism of fire disturbance on the components of non-growing season soil respiration rate (R s ) and its environmental factors are not fully understood, creating uncertainties for future C sink estimates under climate change scenarios. & Aims This study examined the effects of recent fire on non-growing season (November 2017 to April 2018) R s , its heterotrophic (R h ) and autotrophic (R a ) components, and Q 10 in a cold temperate forest in northeast China. & Methods Soil CO 2 effluxes (including R h and R a ) were measured using an Li-8100 portable automatic measuring system for soil C flux (Li-Cor, Inc.; Lincoln, NE, USA). Soil temperature and moisture were measured using a temperature probe (Licor p/n8100-201) and soil volumetric water content probe (ECH20 167 EC-5; p/n 8,100,202), respectively, at a depth of 5 cm; snowpack depth was measured with a ruler. & Results During the non-growing season, fire significantly increased the R h by approximately 47% in burned stands. The Q 10 of R h significantly increased from 2.39 in the unburned stands to 3.12 in the burned stands. An interaction between soil temperature and snowpack depth was the driving environmental factor controlling the non-growing season soil respiration and its components after fire disturbance. & Conclusion Fire is a potent factor on the components of the soil respiration and should not be ignored in forest ecosystem C cycling, especially during the non-growing season as it is vulnerable to micro-environmental variation. Long-term studies involving diverse ecosystems are required to better elucidate mechanisms that have been found during the non-growing season R s under an increasing trend of fire occurrence.

Soil respiration and controls in warmer winter: A snow manipulation study in postfire and undisturbed black pine forests

“…Furthermore, the lower R s rates in the postfire area compared with the undisturbed forest could also be partly explained by the destructive effects of wildfires on soil organic matter, aboveground vegetation, roots, and soil organisms. Although some authors observed increased R s rates in postfire areas during the growing season (e.g., Hu et al, 2021;Maljanen et al, 2006;Masyagina et al, 2016;Wang, Yao, et al, 2021) due to the release of nutrients (Ca, P, K, and Mg), except N, increased soil pH in the mineral soil layer due to ashes (Ernfors et al, 2010;Maljanen et al, 2006;Moilanen et al, 2012), improved litter quality (Stirling et al, 2019), and increased C/N ratio and electrical conductivity (EC) (Francos et al, 2019), the winter R s rates showed a different trend, probably due to the combined inhibitory effects of destructive effects of wildfires and freezing temperature on R s rates. Forest fires result in the destruction of the autotrophic and heterotrophic organisms in the active layer depths of the soil, alteration of the chemical and biological components (Masyagina et al, 2016), and reduction in the quantity of soluble C and microbial activities (Francos et al, 2019;Hobley et al, 2019).…”

“…However, reported observations on the effects of fire on R s rates are not consistent, with some authors reporting an increase in R s due to enhanced heterotrophic respiration rates (Hu et al, 2021;Wang, Chen, et al, 2021;Wang, Yao, et al, 2021) while others reporting a decrease due to suppressed microbial activities and reduced microbial biomass (Chen et al, 2019;Hu et al, 2023). Kong et al (2019) reported no R s changes regardless of fire intensity.…”

“…Depending on the fire intensity, soil heating brings about severe modifications in the physical and chemical properties of the soil and other residual matter and affects microbial activities and other soil‐borne organisms (Ahlgren, 1974 ; Masyagina et al., 2016 ), particularly in the top 10 cm depth (Cowan et al., 2016 ). However, reported observations on the effects of fire on R s rates are not consistent, with some authors reporting an increase in R s due to enhanced heterotrophic respiration rates (Hu et al., 2021 ; Wang, Chen, et al., 2021 ; Wang, Yao, et al., 2021 ) while others reporting a decrease due to suppressed microbial activities and reduced microbial biomass (Chen et al., 2019 ; Hu et al., 2023 ). Kong et al.…”