69969

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ABSTRACT WITHDRAWN

Severe wildfire is part of the forest environment in Australia and can alter the physical, chemical and biological properties of surface soil. In 2003 more than 500,000 hectares of Eucalyptus delegatensis (alpine ash) forests were burnt in Victoria, south-eastern Australia. These high altitude (1000-1400m) forests are characterized by a deep litter layer and organic surface soils containing around 20% carbon. High intensity wildfires completely oxidize surface litter and soil organic matter and deposit large amounts of charcoal and ash on the soil surface. We measured the effects of these wildfires on soil organic carbon and attempted to characterize the differentially stabilized carbon fractions produced by wildfire using Mid Infra-red Reflectance Spectroscopy (MIRS), to evaluate the utility of MIRS in predicting the changes in chemistry of soil organic carbon due to wildfire. Soils were sampled to 20cm depth, two months before fire (November 2002), three months after fire (April 2003) and 86 months after fire (April 2010). The fine fraction (<2mm) of soil was analyzed for total carbon and then correlated using a partial least squares approach to the intensity of spectral bands derived from MIRS analyses of the soils. Total soil organic carbon was reduced by wildfire in surface soils (April 2003) with recovery to pre-fire levels by April 2010. When comparing the spectra of soils before and after fire, aliphatic carbon near the 2930cm-1 region almost vanished after fire (April 2003) but recovered in April 2010 to pre-fire levels. Also, new peaks for aromatic carbon that represent charcoal were found in the fingerprint region of post-fire soil MIRS scans. Therefore, MIRS revealed a change in the nature of the remaining organic carbon with an increase in the proportion of highly recalcitrant fractions. Results will be discussed particularly in regard to the application of MIRS to assess the impact of fire on the stability of soil organic carbon.
See more from this Division: Virtual Posters
See more from this Session: Virtual Posters