Sources, Movement and Sequestration of Dissolved Organic Matter in Doug-fir Forests

ADAMS, ALBERT; HARRISON, ROB; AMOROSO, MARIANO; TURNBLOM, ERIC; BRIGGS, DAVE

Seattle, Washington, USA

Conferencia; 2004 ASA-CSSA-SSSA International Annual Meetings with the Canadian Society of Soil Science; 2004

American Society of Agronomy - Crop Science Society of America - Soil Science Society of America

Increasing understanding of regional variation in carbon (C) in soils, trees and soil solutions can improve management of C sequestration. We studied such variation in second growth Douglas-fir [Pseudotsuga menziesii (Mirab.) Franco] and evaluated soil C collected from 1 m pits dug in control and urea treated (multiple applications initiated during 1973-80) plots in 4 texturally different soil series in the coastal coniferous forest region of Washington State. We compared dissolved organic carbon (DOC) collected by lysimeters in the different soil types at 4 soil depths. Finer-textured, tephra-derived soils had significantly more C than coarse-textured, glacial-derived soils. The highest [DOC] was in the fertilized, upper soil horizons. [DOC] in lysimeter samples was higher in a wet summer and subsequent winter than in the preceding drier winter implying that long-term hydrology influenced DOC flux. Results also suggest that the mechanisms of C flux and location of C sequestration are different in coarser-textured materials than finer volcanic material. In less productive, coarse-textured soils fertilization was associated with C sequestration in trees. In more productive fine-textured ashy loam, urea applications were associated with C sequestration in the mineral soil.