Smouldering natural fires: comparison of burning dynamics in boreal peat and Mediterranean humus

Abstract

Smouldering of the forest subsurface can be responsible for a large fraction of the total fuel consumed during wildfires. Subsurface fires can take place in organic material stored in shallow forest layers such as duff or humus, and in deeper layers such as peat, landfills and coal seams. These fires play a major role in the global emission to the atmosphere, the destruction of carbon storage in the soil and the damage to the natural environment. Burning dynamics in two different ecosystems affected by smouldering wildfires are studied here; boreal peat and Mediterranean humus. A series of small-scale smouldering experiments have been conducted under laboratory conditions to study the ignition and the severity to the soil. The experimental set-up allowed the temperature and velocity of the fire front to be measured for different fuel moisture contents. The two fuels, peat and humus, were tested and the results are compared.

Experimental study of peat ignition upon exposure to radiant energy

“…After ignition of the pyrolysis products, there is a further increase in the peat surface temperature until the cessation of energy supply. After that, the surface temperature decreases rapidly, flaming combustion ceases due to the absence of a sufficient amount of pyrolysis products, and transition to smoldering at a temperature of about 790 K occurs, which is consistent with the results of [2,14,15].…”

Fire-Induced Changes in Soil and Implications on Soil Sorption Capacity and Remediation Methods

“…Fires have also been described as flaming fires which burn at higher temperatures and spread faster or smoldering fires which burn more slowly, have lower temperatures, and are usually flameless [23]. Smoldering fires destroy large amounts of biomass and cause severe damage to the soil ecosystems [24,25]. Ground fires typically burn by smoldering and can last for days to months with relatively low temperatures (500 • C to 700 • C) compared to flaming fires (1500 • C to 1800 • C) [25].…”

“…Smoldering fires destroy large amounts of biomass and cause severe damage to the soil ecosystems [24,25]. Ground fires typically burn by smoldering and can last for days to months with relatively low temperatures (500 • C to 700 • C) compared to flaming fires (1500 • C to 1800 • C) [25]. Fires likely to affect soils are ground fires and crawling or surface fires because of their proximity to the soil surface.…”

Drying Kinetics of Indonesian Peat

“…In such conditions, peat is highly flammable, and when burning smoldering combustion in the peat, biomass and low-rank coal piles can continue for a long time and be difficult to extinguish (Saleh et al, 2017). Peat fire events originate from peatland conditions that have become dry, with the highest moisture content that can burn is approximately 250% (dry base) (Rein et al, 2008) or 150% (Prat-Guitart et al, 2016). The drying process takes place in two stages, namely heating and drying, and occurs through the changes in temperature, relative humidity and air flow (Kosasih et al, 2016).…”