Site Latitude/Longitude Organic Carbon (%) Denitrification capacity, no added nutrientsa DEA, added glucose and nitrateb µg N2 h-1 kg dry wt soil-1 ± Std Devc Nature Reserve 30° 38.335' N/87° 04.525’ W 9 4.4 ± 0.3 133 ± 13 Shoreline Park South 30° 21.109' N/87° 10.554' W 20 114 ± 86 525 ± 58 Lake Shore Trail 30° 21.127' N/87° 10.096' W 41 UDd 576 ± 98 aDenitrification reactions with only endogenous levels of nitrate and glucose. bNutrients for denitrification were made non-limiting by the addition of nitrate and glucose to the reaction vessels. cRates are expressed as the mean of triplicate determinations. Based on the results of t-tests (p>0.05), the null hypotheses were rejected. Thus, within each soil the denitrification enzyme activity rates were higher than the denitrification capacity rates. dUD, unable to determine (no increase in the N2 /Ar ratio was observed)

Table 1: Denitrification enzyme activity rates determined in short term (4 h) anaerobic assays in the presence and absence of nutrient (NO3-N, glucose-C) amendments. The nitrogen product was measured by membrane inlet mass spectrometry.