Changes of soil organic carbon after wildfire in a Boreal Forest, Northeast China

Authors: HAN, CHUN-LAN - Shenyang Agricultural University; SUN, ZHONG-XIU - Shenyang Agricultural University; SHAO, SHUAI - Shenyang Agricultural University; WANG, QIU-BING - Shenyang Agricultural University; Libohova, Zamir; Owens, Phillip

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/18/2021
Publication Date: 9/25/2021
Citation: Han, C., Sun, Z., Shao, S., Wang, Q., Libohova, Z., Owens, P.R. 2021. Changes of soil organic carbon after wildfire in a Boreal Forest, Northeast China. Agronomy Journal. 11(10):1925. https://doi.org/10.3390/agronomy11101925.
DOI: https://doi.org/10.3390/agronomy11101925

Interpretive Summary: Soil Organic Carbon stored in forest plays an important role on sequestering atmospheric CO2. However, forest fires can release significant amounts of CO2 during burning and reduce the ability of the forest ecosystems to store SOC in short and long terms. Dynamic and stable SOC were measured 3 months, 17 years and 25 years after a forest fire. Following the wildfire, soil structure degraded significantly. Also, both dynamic and stable SOC, even after 25 years, did not recover to the pre-fire levels. Changes in physical and biochemical characteristics of forest type, revegetation, and canopy after wildfire were responsible for the observed SOC differences and dynamics over time. The carbon sequestration capacity was greater under the post fire emerging forest of the same species compared to other forest types. The results indicate that overall the ability of soil to sequester carbon decreased after wildfire disturbances.

Technical Abstract: Boreal forests with high carbon sequestration capacity play a crucial role in mitigating global climate change. Addressing dynamic changes of soil organic carbon (SOC) after wildfire helps in understanding carbon cycling. The post-fire soil chronosequence after 3 months, 17 years, and 25 years within a Larix gmelinii forest was used to examine dynamic and stable SOC after wildfire at the decadal scale. Soils in genetic horizons were sampled and analyzed for dynamic and stable SOC, including water stable aggregates (WSA), organic carbon associated with WSA (WSA-SOC), organic carbon associated with soil heavy fractions (HF-SOC) and total organic carbon (T-SOC). The T-SOC and WSA-SOC content of the Ah horizon was the greatest in the control site. There was no significant difference for T-SOC between burned and unburned deep BC horizons. The T-SOC for the Ah and B horizons at the 17-year-old site was significantly lower compared to the other sites. T-SOC did not recover to the pre-fire levels (control site) in any of the burned areas. The lowest WSA was found in the A and B horizons of the 3-month-old site. The WSA at the 25-year-old site was higher compared to the 17-year-old site. WSA increased with time following fire, but the recovery rate differed among different sites. The lowest concentration of WSA-SOC for the A horizon occurred at the 17-year-old site, and no significant difference was observed between the B and BC horizons. The HF content for the A horizon was the greatest at the 3-month-old site. There was no significant difference of HF-SOC between the B and BC horizons in all sites. T-SOC and stable SOC (HF and WSA) increased over time in areas of species-dominance relay stands, while areas of self-replacement stands showed the opposite. The results indicate that overall the ability of soil to sequester carbon decreased after wildfire disturbances. Stable SOC accumulated more in areas where species-dominance relay succession occurred compared to the self-replacement stands.