Paper No. 5
Presentation Time: 10:00 AM


BOOT, Claudia M.1, HADDIX, Michelle L.1, PAUSTIAN, Keith2 and COTRUFO, M. Francesca2, (1)Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO 80523, (2)Department of Soil and Crop Sciences, Colorado State University, Fort Collins, CO 80523,

Pyrogenic carbon (PyC) is an unaccounted for component of the C cycle, and can be up to 20% of soil organic matter in frequently burned areas. To better understand PyC dynamics in a fire-prone ecosystem, we characterized changes in soil carbon, nitrogen, and PyC content following the High Park fire that took place June 2012. We examined surface soil (0-5 cm) under pondersoa pine, one of the dominant tree species in the watershed, with two different slopes (0-5°, 5-15°), and three burn intensities (unburned, medium and high burn) using the benzene polycarboxylic acid (BPCA) method as a molecular marker for the amount of PyC in surface soils (0-5 cm). We expected lower slopes to have higher amounts of PyC and that the amount of PyC would increase with burn intensity.

Soil C stocks were highly variable post-fire and ranged from 8.7-17.7 tC ha-1 in the ponderosa pine 0-5 cm soil. The high burn intensity tended to have lower soil C stocks compared to the moderate and unburned soil. Interestingly, in the burn sites (moderate and high) the steepest slopes tended to have higher soil C stocks. BPCA results indicated low slope aspect (0-5°) always retained more PyC than higher slope aspects (5-15°) regardless of burn intensity. In the low slope aspects soils, however, the amount of PyC at different burn intensity followed the opposite pattern from what we expected, with high burn intensity having the lowest amount of PyC and the unburned sites with 50 to 400% more PyC. High amounts of PyC in unburned soils could be from previous fires, or from atmospheric deposition of PyC from burned areas to unburned sites. Additionally, low amounts of PyC in high burn intensity sites may be due to losses from wind transport or combustion of residual PyC during the High Park fire. Our initial results illustrate the importance of quantifying PyC in soils with different characteristics (e.g. burn intensity, slope), and how this type of accounting can lead to descriptive dynamics of PyC within the global C cycle.

  • GSA 2013 poster High Park BC v2.pptx (2.8 MB)