Organic Carbon Characteristics in a Spruce Swamp Five Years after Harvesting
1996
McLaughlin, Jim (Jim W.) | Liu, Guo | Jurgensen, Martin F. | Gale, Margaret R.
Forest harvesting and regeneration may cause changes in soil and solution chemistry that adversely affect environmental quality. Organic C content in the forest floor and mineral soil, and dissolved organic carbon (DOC) fractions in the soil solution and groundwater were investigated in a black spruce [Picea mariana (Miller) BSP] swamp 5 yr after the application of two silvicultural prescriptions: whole-tree harvest only and whole-tree harvest followed by site preparation bedding. Soil organic carbon (SOC) content in the forest floor of both treatments were significantly lower than that of an uncut control stand. However, SOC in the upper 50 cm of mineral soil of the bedded treatment was similar to that of the control, while both were about 20% higher than SOC in the harvest-only treatment. Total DOC concentrations ranged from 12 to 87 mg/L in the soil solution and 6 to 46 mg/L in the groundwater and did not differ among treatments. Hydrophobic acids were the dominant DOC fraction across all treatments, but the proportion of hydrophobic strong acids increased at the expense of hydrophilic acids in the harvest-only treatment. Carboxyl content of hydrophilic acids in the soil water was 7.0 mmol/g hydrophilic compound in the control stand and 4.4 mmol/g in the treatments. Hydrophobic acid carboxyl content across treatments was 4.6 mmol/g hydrophobic substance. Relative to C loss and changes in water chemistry, these results indicate that 5 yr after whole-tree harvesting, this forest site has not yet fully equilibrated.
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