Abstract: In the Mediterranean region, wind-driven crown fires are becoming more frequent, leading to increased atmospheric pollutant emissions. This study explored how the distribution of pre-fire fuels across the crown, shrub and litter layers varies among different fuel types, and how these variations were linked with fuel consumption and fire severity for each layer to quantify and compare atmospheric pollutant emissions (CO₂, CO, CH₄ and PM_2.5) in pine (Pinus halepensis) and oak (Quercus suber) forests. Our analysis was carried out in the Jonquera wildfire in Northeast Spain, which burned 10,264 ha. Pre-fire fuel loading among fuel types in pine and oak forests showed different vertical distributions despite, having similar fire-type patterns. Pine forests had a higher percentage of crown and shrub fuel loading for all fuel. In contrast, oak forests had more litter than pine forest. Fuel types characterized by large trees and low densities had the lowest fire severity in both forest types. Pine forests were more resistant to the effects of surface fires than oak forests due to their taller trees, which allowed them to withstand high-intensity surface fires with less tree damage. However, these fires have resulted in higher surface fuel consumption in pine forests. Fuel types with more vertical and horizontal continuity experienced higher fire severity and fuel consumption (72–85% of high severity). Fire severity rather than species or fuel type was the primary factor influencing pollutant emissions. Emissions of CO₂ and CH₄ were higher in pine than in oak forests especially at lower severities, while at intermediate and higher severity oak forests emitted more CO and PM_2.5. Although remote sensing technologies are useful for fuel loading and wildfire severity assessments, field data are essential for accurately quantifying fuel consumption across fuel types and layers.

Key words: Fuel loading, Fuel consumption, Forest structure, Pinus halepensis, Quercus suber, Pyrogenic emissions