3:45 PM - 4:00 PM
[MIS03-15] Nutrient release during biodegradation of organic horizons in the Siberian taiga underlain by continuous permafrost
Keywords:Forest fire, Biodegradation, Continuous permafrost terrain, plant nutrition, burned temprature, humic substances
A sampling site located in the Evenkia province in the central Siberia. Soils are classified as Oxyaquic Cryosols or Gelic Cambisols according to the WRB classification system. Organic horizon samples were taken depending on hummock topography. Air-dried and powdered samples were heated in a muffle furnace between 105 and 550oC for 15minites. Organic residues were applied to incubation experiment to evaluate biodegradation and solutes release. Biodegradation was evaluated from mineralization rates being calculated using temporal changes in CO2 concentration during an incubation experiment and total organic carbon content in heated solid samples. During the same incubation time course, biogenic elements released from the heated samples were determined after water extraction by ICP-AES, Ion-chromatography and TOC-L with total nitrogen module unit.
Solutes release from heated organic horizon samples by water saturation was different between samples depending on the heating temperature. Larger amount of nutrient elements were released from organic horizons taken from trough points on the hummock. Samples heated at 250oC released the highest amount of solutes mainly dominated by dissolved organic C. Basic cations and major anions including phosphate, nitrate and chloride were also largely released from the sample heated at 250oC. Higher the heating temperature was, solutes concentration was lower. Solution pH was higher with increasing the heating temperature. The ratios of carbon to nitrogen in solid samples were decreased with increasing the heating temperature. The temperature dependence of solutes release was different along with hummock topography.
The maximum mineralization (%) was approximately 4% of total C in samples heated at lower temperature below 180oC. The mineralization rate was not largely different between samples, indicating that the biodegradation process in all heated samples mainly depends on the amounts of easily decomposable carbon source, such as DOC. There are significant correlations between the maximum mineralization rate and DOC or inorganic N. Solutes mainly consisting of nutrients and energy source for microorganisms can be a significant controlling factor for the biodegradation process of organic horizons. The difference in solutes composition and the biodegradation were mainly depending on heating temperature of organic horizons. Heating temperature during a forest fire is an important parameter controlling the further degradation of organic matter in organic horizons and the fate of carbon dynamics in the boreal permafrost affected forest region.