Persistence of Charcoal in Soils of the Cone Pond (New Hampshire) Watershed and Possible Effects on Soil Chemistry.

The watershed of Cone Pond, in the central White Mountains of New Hampshire, has a record of blow-down and fire, circa 1820. Charcoal can be easily found below the current forest floor. Anecdotal evidence suggests that the presence of this black carbon has had a lasting effect on the chemical properties of both the watershed soils and the pond. We took 60 samples of the Oa horizon along two transects trifurcating the watershed and measured soil chemical parameters along with potential net ammonification and nitrification rates. Cone Pond watershed soils had, by far, the lowest rates of net N transformations in a cross-site comparison of ten northeastern USA watersheds. The C/N ratios of these samples were often much higher than would be predicted from similar horizons collected at the nine other watersheds, which had no lasting evidence of fire. Charcoal was evident in the Cone Pond samples with the highest C/N deviations. This charcoal was separated manually but the weight was not sufficient to explain the deviation. Low molar ratios of H/C in these same horizons suggested an additional component of black carbon, not easily separable as charcoal. It is difficult to separate the effect of black carbon from that of coniferous vegetation on soil chemistry (and the two may interact). There is apparently a long lasting effect from the persistence of black carbon in Cone Pond watershed soils.