SITE PREPARATION BURNING TO IMPROVE SOUTHERN APPALACHIAN PINE HARDWOOD STANDS - NITROGEN RESPONSES IN SOIL, SOIL-WATER, AND STREAMS

Three paired watersheds treated with a fell and burn prescription were studied to determine the effects on soil, soil water, and stream wate r. Soil nitrification and mineralization were measured by in situ clos ed-core incubation. Soil water was collected with porous cup lysimeter s placed at 30 and 60 cm depths, and water samples were collected from streams draining control and burned areas on one of the three sites. All data were collected for 6 months prior to and 12 months after trea tment. Soil ammonium (NH4+) content increased significantly in all thr ee sites after burning, but the magnitude differed greatly among sites . However, there was no change in soil nitrate (NO3-) content. In situ measurements of net mineralization showed increased rates with increa sing burn severity. Net nitrification displayed no treatment response. Slight and nonsignificant increases in soil water NO3- concentration occurred after burning in two of the three sites. Stream water NO3- co ncentrations increased in the one stream sampled. Thus, while prescrib ed burning increased available soil N, there was little change in N tr ansformation rates or movement of dissolved inorganic N off site durin g the first year after burning.