Abstract
Wildfire induces soil alterations that have a long-term impact on soil organic matter (SOM) quality. We postulated that after different fire severities, the neutral sugars in soils can be used as an indicator of soil organic matter quality after fire. The aim of this study was to determine the contribution of neutral sugar, bulk and occluded particulate organic matter (oPOM) affected by wildfire, at different soil depths in an Araucaria–Nothofagus Forest, four years post-after fire. The concentration and composition of the neutral sugars in the soils clearly comprised the major fraction in the unburned soil. Medium- and high-severity fires caused a drastic reduction in soil sugars in the bulk soil as well as in the oPOM fractions. The 13C-CPMAS NMR spectroscopy analysis revealed a high contribution of recalcitrant carbon to the decomposition such as aryl–C and aryl–O derived from charred material, whereas the abundance of O–alkyl C and alkyl C functional groups were decreased. The neutral sugars (Galactose+Mannose/Xilose+Arabinose) revealed a major microbial origin in fire affected areas as the ratio was >2. Therefore. Therefore, we suggest that the neutral sugar content of soil should be used for monitoring both short- and long-term changes in SOM altered by fires.
Highlights
Wildfires are the prevailing disturbance events shaping Araucaria araucana–Nothofagus spp. forest landscapes in southern Chile and Argentina [1,2,3]
We propose that soil sugar composition can be used as a sensitive indicator to evaluate the influence of fire severity on different occluded particulate organic matter (oPOM) fractions, in temperate rain forests
1.6 g N kg−1 soil for the oPOMc and from 0.8 to 1.7 g N kg−1 for the oPOMf. These results indicate a reduction in the mass and C content in the oPOM fraction post-fire, but there was no major difference with respect to the N pattern
Summary
Wildfires are the prevailing disturbance events shaping Araucaria araucana–Nothofagus spp. forest landscapes in southern Chile and Argentina [1,2,3]. Wildfires profoundly impact soil properties [4], mostly by altering the thickness, extent and composition of soil organic matter (SOM) [5,6,7,8]. The SOM may be affected differently at each mineral soil horizon. Fire may deeply influence the particulate organic matter (POM). Compared to a more protected SOM in association with the mineral phase and SOM occluded within soil aggregates, i.e., the occluded particulate organic matter (oPOM) [9]. Different forms of organic matter have different effects on soil quality and can respond differently to SOM alteration by fire [10,11]. Studies realized by Golchin et al [12], Chan et al [10] and Kölbl and Kögel-Knabner [13], support that the POM is a sensitive indicator of the alteration of soil
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