Wildfires have been increasing over the past few decades, and the forecast is alarming. South America, in particular, is projected to be one of the regions most severely affected by climate change. Wetlands are increasingly vulnerable to fires, and despite their internationally recognized importance, field studies on temperature development during wetland fires are rare. To address this knowledge gap, two experimental fires were conducted in herbaceous wetlands of the Paraná River, Argentina. Induced temperatures were measured through three temperature towers, each equipped with five K-type thermocouples placed at five fixed positions (aerial, soil surface and belowground). The main features of fuel and soil were also studied in the field. Aerial temperatures (at 130 and 40 cm) and soil surface temperatures (0 cm) were highly variable, both between and inside burn events, which could be linked to fuel characteristics and disturbances caused by the installation of the temperature towers. Belowground (at -3 and -5 cm), the temperature rise was small in both events, although the increase persisted for a long period. Although high temperatures were recorded at the soil surface for brief periods, their magnitude and duration were likely insufficient to impact biological or physical processes. The results of this study suggest that, under the environmental conditions observed, prescribed burning could be a viable management strategy for reducing excessive fuel loads and preventing large wildfires in fluvial wetlands. However, a more comprehensive dataset is required to support the planning and implementation of fire as a management tool in these ecosystems. Graphical Abstract Wetlands are internationally recognized as vital ecosystems. However, wildfires have been increasing in South American wetlands, where field studies remain limited. This study investigates temperature dynamics during two experimental burns (B1 and B2) conducted in herbaceous wetlands along the Paraná River, Argentina, the second-largest river in South America. Temperature was measured using three towers (T1–T3), each equipped with five K-type thermocouples positioned at fixed heights. Key fuel and soil characteristics were also assessed. The vegetation was heterogeneous. Tall grasslands (Echinochloa polystachya) were dominant at both B1 and B2, short grasslands (Leersia hexandra) were better represented in B2, and bushes (Solanum glaucophyllum) were most prevalent in B1. Fuel load and moisture content were higher in B1 (1902 g/m2, 64.3%) than in B2 (1191 g/m2, 53.2%). In B1, live biomass accounted for 68.8% of the total fuel, whereas in B2, it comprised 49.9%. Maximum temperatures were recorded at 40 cm aboveground. The upper 5–6 cm of the soil had a clay texture, with an average particle density of 1.98 g/cm3 and a bulk density of 0.78 g/cm3. Porosity ranged from 49 to 70%, influenced by the high clay content and an average organic matter content of 11%. At the soil surface, temperatures remained below 50 °C in B1, while in B2 they ranged from 100 °C to slightly above 200 °C. At depths of -3 cm and -5 cm, maximum temperatures remained below 33 °C. After reaching peak, aerial temperatures rapidly returned to their previous state. In contrast, from 0 cm to -5 cm, temperatures decreased very slowly and did not return to initial levels within the following hour. These results suggest that prescribed burns may be an effective tool for managing fuel loads and reducing wildfire risk in fluvial wetlands.

Beneath the Flames: Soil Heating Thresholds in Prescribed Wetland Burns

期刊论文
发表日期：

2025年10月6日

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Z. Y. Marchetti,
L. Rodríguez,
P. Menotti,
A. Carrasco,
E. Veizaga,
E. Massa,
B. Bilbao

摘要

Wildfires have been increasing over the past few decades, and the forecast is alarming. South America, in particular, is projected to be one of the regions most severely affected by climate change. Wetlands are increasingly vulnerable to fires, and despite their internationally recognized importance, field studies on temperature development during wetland fires are rare. To address this knowledge gap, two experimental fires were conducted in herbaceous wetlands of the Paraná River, Argentina. Induced temperatures were measured through three temperature towers, each equipped with five K-type thermocouples placed at five fixed positions (aerial, soil surface and belowground). The main features of fuel and soil were also studied in the field. Aerial temperatures (at 130 and 40 cm) and soil surface temperatures (0 cm) were highly variable, both between and inside burn events, which could be linked to fuel characteristics and disturbances caused by the installation of the temperature towers. Belowground (at -3 and -5 cm), the temperature rise was small in both events, although the increase persisted for a long period. Although high temperatures were recorded at the soil surface for brief periods, their magnitude and duration were likely insufficient to impact biological or physical processes. The results of this study suggest that, under the environmental conditions observed, prescribed burning could be a viable management strategy for reducing excessive fuel loads and preventing large wildfires in fluvial wetlands. However, a more comprehensive dataset is required to support the planning and implementation of fire as a management tool in these ecosystems.

Graphical Abstract

Wetlands are internationally recognized as vital ecosystems. However, wildfires have been increasing in South American wetlands, where field studies remain limited. This study investigates temperature dynamics during two experimental burns (B1 and B2) conducted in herbaceous wetlands along the Paraná River, Argentina, the second-largest river in South America. Temperature was measured using three towers (T1–T3), each equipped with five K-type thermocouples positioned at fixed heights. Key fuel and soil characteristics were also assessed. The vegetation was heterogeneous. Tall grasslands (Echinochloa polystachya) were dominant at both B1 and B2, short grasslands (Leersia hexandra) were better represented in B2, and bushes (Solanum glaucophyllum) were most prevalent in B1. Fuel load and moisture content were higher in B1 (1902 g/m², 64.3%) than in B2 (1191 g/m², 53.2%). In B1, live biomass accounted for 68.8% of the total fuel, whereas in B2, it comprised 49.9%. Maximum temperatures were recorded at 40 cm aboveground. The upper 5–6 cm of the soil had a clay texture, with an average particle density of 1.98 g/cm³ and a bulk density of 0.78 g/cm³. Porosity ranged from 49 to 70%, influenced by the high clay content and an average organic matter content of 11%. At the soil surface, temperatures remained below 50 °C in B1, while in B2 they ranged from 100 °C to slightly above 200 °C. At depths of -3 cm and -5 cm, maximum temperatures remained below 33 °C. After reaching peak, aerial temperatures rapidly returned to their previous state. In contrast, from 0 cm to -5 cm, temperatures decreased very slowly and did not return to initial levels within the following hour. These results suggest that prescribed burns may be an effective tool for managing fuel loads and reducing wildfire risk in fluvial wetlands.