The role of pyrogenic carbon addition after wildfires in the boreal forest of China: Impact on plant–soil–microbial ecological stoichiometry

Abstract

Pyrogenic carbon (PyC) is a common byproduct of wildfires in terrestrial systems; however, its role in fire-prone forest ecosystems, particularly cold boreal forests, remains unclear. Ecological stoichiometry is a valuable tool for studying interactions within plant–soil–microbial continuum systems, which could help us understand post-fire changes in boreal forest ecosystems. In this study, we manipulated different additions of PyC in a forest of Dahurian larch (Larix gmelinii) after a wildfire to investigate the effects of PyC on plant–soil–microbial ecological stoichiometry. We engineered PyC under controlled conditions to simulate that produced by wildfires. The experimental design included no PyC addition (C0), 0.5 kg m⁻² PyC addition (C1), 1.0 kg m⁻² PyC addition (C2), and no fire as a control (CK). One year after PyC manipulation, understory vegetation and soil samples (0–10 cm depth) were collected to investigate how PyC addition affects plant–soil–microbial carbon (C), nitrogen (N), and phosphorus (P) stoichiometry. Our results showed that PyC addition (C1, and C2) increased plant biomass, particularly in the green tissues (35–53 % higher than that in the CK and 59–80 % higher than that in the C0 treatment). The C2 treatment also increased the plant C and N contents but did not significantly affect plant P content. PyC addition led to an increase in soil microbial biomass N (MBN) and P (MBP), altered the microbial biomass C:N:P ratio (to 27:1:1), and disrupted the microbial dynamic balance, indicating a possible shift towards a bacterial-dominated community. In boreal forest soils, post-fire PyC manipulation elevated soil organic C (SOC) and total P (STP). As there were no changes in soil total N (STN), the addition of PyC also increased the soil C:N and C:P ratios. Our findings highlight the potential of PyC as a soil conditioner that enhances plant biomass and alters nutrient cycling in boreal forests. However, PyC effects are modulated by soil resource availability and the nutrient environment. Further studies are required to elucidate the mechanisms underlying these differential nutrient responses.