Molecular Weight Distribution of Soluble Organics from Laboratory-Manipulated Surface Soils
- Peter S. Homann and
- David F. Grigal
Transfer of organic matter from solid to solution phase is the first step in the redistribution by leaching of organic C and associated elements in forest soil profiles. To examine the effects of disturbances on solubilization of organics, three A horizons and one O horizon were exposed to air drying, waterlogging, addition of urea, addition of ash, and addition of ash in combination with heating at 250 °C. Following incuhation at 20 to 22 °C for 1 to 50 d, soluble organic C (SOC) was extracted with 0.5 mM SrCl2. The SOC was 0.2 to 0.7% of total organic C in controls. Urea and heat-plus-ash treatments yielded up to 17 times more SOC than controls, and other treatments yielded up to three times more than controls. Distribution of SOC among molecular-weight classes, as determined by dialysis, was 21 to 32% in the <3500-dalton class, 8 to 20% in the 3500 to 14 000-dalton class, and 47 to 71% in the >14 000-dalton class. Urea treatment yielded a higher proportion of SOC in the >14 000-dalton class than in the controls, while air drying resulted in a lower proportion. Both the quantity and quality of soluble organics can be influenced by soil disturbances, but the specific response varies with the type of disturbance.
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