Monday, November 5, 2007 - 2:30 PM
113-5

Carbon and C/N Ratios Are Remarkably Linked in Northeastern USA Forest Research Sites.

Donald Ross, University of Vermont, Dept.of Plant & Soil Sci., Hills Building Uvm, Burlington, VT 05405-0082

We measured C and C/N ratios in 620 surface soil horizons (primarily Oa and A) from ten small watersheds at seven established research sites in New York, Vermont and New Hampshire. Both the C (50-530 g/kg) and C/N ratio (11.6-45.3) had a wide range. In all but the Cone Pond watershed, C/N was positively and linearly related to C content. For these nine watersheds, the average C/N = 9.7 + 0.029 X C g/kg, R2 = 0.98. Ratios at Cone were much higher than would be predicted from the other data and charcoal was found in numerous samples, suggesting a source of recalcitrant C. Across all watersheds, C was also positively correlated with the presences or absence of an E horizon, forest floor depth, and there was a good linear relationship between the soil C and soil water content, allowing the development of a ‘wetness ratio' that provides a metric for moisture status independent of C. Although sugar maple dominance was negatively correlated with C/N ratio (and C) and conifer dominance positively correlated, net nitrification rates were better predicted by red spruce basal area and density (both negative influences) than by a positive influence of sugar maple. The remarkably tight relationship between C and C/N ratio suggests that C alone might be useful as a predictor of nitrogen transformations.