Effects of Nitrogen on Temporal and Spatial Patterns of Nitrate in Streams and Soil Solution of a Central Hardwood Forest

Abstract EN

This study examined changes in stream and soil water NO3− and their relationship to temporal and spatial patterns of NO3− in soil solution of watersheds at the Fernow Experimental Forest, West Virginia.

Following tenfold increases in stream NO3− concentrations over a 13-year period (1969–1981) on untreated WS4, concentrations have declined through 2006.

Following fourfold increases in stream NO3− on treatment WS3 from pretreatment levels to a 1998 maximum, concentrations have declined through 2006, despite additions of N.

Concentrations of soil water NO3− were consistently lower for WS4 compared to WS3.

Data for soil water NO3− on WS3 versus WS4 followed patterns of net mineralization and nitrification for these watersheds.

Nitrogen additions to WS3 decreased spatial heterogeneity of N processing, which was largest in the pretreatment year and decreased significantly to a minimum by 2000-2001.

Concurrently, soil water NO3− increased on WS3 from 1.3 mg NO3−-N L−1 in pretreatment 1989 to a maximum of 6.4 mg NO3−-N L−1 in 2001.

Spatial heterogeneity in soil water NO3− on WS4 remained high during this period.

Data suggest that temporal patterns of stream NO3− may be influenced by spatial heterogeneity of watershed processes which vary over time in response to N availability.