Book Description

S2Clearcutting of northern hardwood forests in New Hampshire resulted in accelerated loss of dissolved nutrients to streams similar to that shown in experimental studies at Hubbard Brook. Stream water samples were collected during 4 years from nine watersheds that had been completely clearcut and from five nearby reference watersheds that were uncut. Differences in stream chemistry between clearcut and reference watersheds were greatest during the second year after cutting. During the 4 years of the study, specific conductance of the reference streams ranged from 20 to 30 [mu] S/cm; average pH ranged from 5.0 to 5.7; nitrate ranged from less than 0.1 to about 4.0 mg/l; calcium from 1.0 to 3.0 mg/l; ammonium from less than 0.01 to 0.05 mg/l; magnesium from 0.2 to 0.8 mg/l; sodium from 0.6 to 1.6 mg/l; potassium from 0.1 to 0.7 mg/l; sulfate from 3.0 to 8.0 mg/l; and chloride from 0.3 to 0.6 mg/l. During the second year after clearcutting, specific conductance of streams draining the cuts ranged from 22 to 68 [mu] S/cm; average pH ranged from 5.1 to 6.0; nitrate ranged from 1.4 to 27.3 mg/l; calcium from 1.4 to 6.7 (ng/l; ammonium from less than 0.01 to 0.05 mg/l; magnesium from 0.3 to 1.4 mg/l; sodium from 0.8 to 3.0 mg/l; potassium from 0.1 to 1.5 mg/l; sulfate from 2.1 to 6.3 mg/l; and chloride from 0.4 to 0.9 mg/l. During the first year after cutting, streams from the cuts were more acidic than those from the reference streams; however, they were less acidic by the end of the second year. Concentrations of most ions in streams from clearcuts approached reference levels by the end of the fourth year after clearcutting, though streams from clearcuts remained less acidic by nearly a whole pH unit, sulfate remained depressed, and potassium remained elevated. During the 4 years following cutting, stream exports from cut sites exceeded those from reference sites by 57 kg/ha for inorganic nitrogen, 61 kg/ha for calcium, and 15 kg/ha for potassium.S3.