Variability in pyrogenic carbon properties generated by different burning temperatures and peatland plant litters: implication for identifying fire intensity and fuel types

Abstract

Pyrogenic carbon (PyC), generated by fire, acts as a stable carbon deposit in natural ecosystems and is widely used to reconstruct fire history. Fuel type and burning temperature are the two major factors that influence PyC properties and exert variable effects on soil carbon pools, especially for peatlands. However, whether analysis of PyC can identify these two factors remains unclear. To address this knowledge gap, we selected typical peatland plant litters of seven shrub and seven herb plants in the Great Khingan Mountains, China. The properties of PyC produced at 250°C (low-intensity burning) and 600°C (high-intensity burning) without oxygen were evaluated. The results showed that the effects of burning temperature and plant type on δ 13 C-PyC were not significant. The differences in the initial compositions of herbs and shrubs led to more aromatic and carboxylic compounds in shrub PyC than in herb PyC. A high burning temperature led to less labile components (e.g. aliphatic compounds and acids) and higher thermal stability of hightemperature PyC compared to that of low-temperature PyC. Our results also indicate that several typical PyC chemical composition indicators (e.g. Fourier-transform infrared spectroscopy 1515/1050 ratio and 1720/1050 ratio) can potentially identify PyC sources.

Fire and geodiversity

“…For example, an Alaskan fire in 2007 was estimated to have contributed to ~2 Tg of carbon, with 60% attributed to soil organic matter, an amount comparable with the average annual net sink for carbon in the Arctic tundra in the past 250 years (Mack et al 2011in Adams 2013. Such occurrences undermine both the economic value of these sites as carbon stores and as sequestration environments, as well as diminishing their intrinsic value (Belyea and Clymo 2001;Gao et al 2022).…”

“…A positive change to soils, pyrogenic carbon has a longer mean residence time compared to other forms and may persist in the environment for multiple centuries under favourable conditions (Abney et al 2017). Pyrogenic carbon is particularly important for peatlands as a relatively intractable form, and contributes to soil dynamics in other landscapes through carbon storage (Gao et al 2022). Nevertheless, pyrogenic carbon is highly erodible due to properties of hydrophobicity and low-density (compared with other carbon forms), as well as being concentrated in the upper soil horizons, where it can be lost in post-fire erosive processes (Cotrufo et al 2016).…”