Propagação do calor no solo: revisão sistemática e análise experimental

Abstract

Soil is an essential resource for ecological balance and may undergo physical, chemical, and biological changes due to heat incidence on its surface. Heat propagation in soil depends on factors such as moisture, compaction, soil composition, density, and the residence time of heat on the surface. Among the various processes that generate soil heat transfer, fire stands out as a natural phenomenon that has been present on Earth for millions of years. However, with climate change and land-use alterations, the frequency and intensity of wildfires have increased, becoming both an environmental and economic concern. Wildfires can be mitigated through prescribed burning, a management technique aimed at reducing fuel loads and contributing to biodiversity conservation. Studying heat propagation in soil is crucial to understanding the physical, chemical, and biological impacts of burning events. Therefore, this study aimed to analyze soil heat propagation through controlled laboratory simulations and to compare the results with evidence available in the academic literature. Simulations reproduced prescribed burning and wildfire conditions, measuring soil temperatures at the surface, 2 cm, and 5 cm depth. To ensure a relevant literature base for comparison, a systematic review was conducted using bibliometric analysis, the Methodi InOrdinatio, and content analysis. Results showed that although wildfires presented slower heating, they reached higher temperatures at all depths compared to prescribed burning. Heat fluxes (q) during prescribed burning were 76.23 W/m² (surface to 2 cm) and 1.03 W/m² (2 to 5 cm), while for wildfires values reached 146.69 W/m² and 1.80 W/m², respectively. The thermal diffusivity obtained was 0.0000029 m²/s. In the systematic review, out of 276 articles initially identified, 18 addressed laboratory simulations of fire effects on soil. Of these, 56% focused on physical properties, 56% on organic matter, 28% on chemical properties, and 17% on biological aspects. The most frequently applied temperatures were 175 °C for prescribed burning and 300 °C for wildfires. Only two studies evaluated temperature across different soil layers, and just one considered more than one depth. It is concluded that heat propagation during wildfire simulations is greater when compared to prescribed burning, suggesting that prescribed fire can be an effective wildfire prevention strategy with lower soil thermal impact. Furthermore, opportunities remain for new and more robust studies on heat propagation, such as investigating fire impacts at greater soil depths and identifying which parameters most influence heat transfer.