Evolution of composition and content of soil carbohydrates following forest wildfires
2009
Martin, A. | Díaz-Raviña, M. | Carballas, T.
The time evolution of the content and composition of carbohydrates was studied in the surface layer of forest soils non-affected and affected by wildfires. The low- and high-severity fires caused an immediate reduction of the C present as carbohydrates of 34% and 47-55%, respectively, which was due to the decrease of both hexoses and pentoses in two hydrolysis fractions (hydrolysate-A, non-cellulosic polysaccharides; hydrolysate-B, cellulosic polysaccharides). Carbohydrates tended to recover with time; however, values had still not reached the amounts found in the corresponding unburnt samples after 12-15 months. No difference between the unburnt and burnt samples was observed in the distribution of the neutral sugars in the hydrolysates over time. On a percentage basis, 72-92% of the total neutral sugars was extracted in hydrolysate-A (59 ± 7% hexoses; 24 ± 7% pentoses) and the rest, 8-28%, in hydrolysate-B (15 ± 5% hexoses; 2 ± 1% pentoses). The contribution of hexoses and pentoses to the neutral sugar pool was different between the two hydrolysis fractions being the hexoses/pentoses ratio higher for hydrolysate-B than for hydrolysate-A. The results also showed that the proportion of soil C present as carbohydrates-C rather than the total carbohydrates content should be used for monitoring short- and medium-term changes induced by fire in soil organic matter quality.
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