Wildfire and black carbon in Andalusian Mediterranean forest

Abstract

The recent history of wildfires in forested and natural areas from Andalusia, Spain is studied in terms of black carbon (BC) and soot production. An estimation of the potential BC emissions in Andalusia Autonomous Community, Spain is presented. The main forms of refractory carbon present in selected soils affected by wildfires are described as studied by pyrolytic (Py-CG/MS) and spectroscopic (13C NMR) techniques. It is estimated that up to 31221.8 tonnes of refractory materials can be formed by forest fires in Andalusia every year. Among the Andalusian provinces, those in the coastal area (Malaga, Almeria, Huelva, Cadiz & Granada) show the higher potential for BC production in the range of 7.52-3.36 kg ha-1 year-1, whereas BC production figures are lower in the Guadalquivir Valley provinces (Seville, Jaen & Cordoba) with a BC potential production in the range of 1.94-0.72 kg ha-1 year-1. Using direct pyrolysis, most of the pyrolysis products present in undisturbed natural soils (sugars, furans, lipids, peptidic derivatives, etc) vanishes and charred "non pyrolyzable" refractory carbonous materials dominate the pryrograms of the forest soils affected by fire. This dominant presence of condensed carbon in the soil organic carbon pool after a forest fire is again apparent when studying the CPMAS 13C NMR spectra. A neat increase in the intensity of the aromatic C region is observed while that of the O-alkyl C region decreases drastically. For a better understanding of the global C cycle and turnover in Mediterranean forest soils, the identification and quantification of refractory carbonous materials is necessary. The effect of different forest management practices (ie. prescribed fires) in soil refractory C forms, and in restoring some of other functional qualities of Mediterranean ecosystems deserves investigation.