Soil Carbon and Nitrogen Changes in Forests of Walker Branch Watershed, 1972 to 2004

• Published in: Soil Science Society of America journal Vol. 71; no. 5; pp. 1639 - 1646
• Main Authors: Johnson, D.W, Todd, D.E. Jr, Trettin, C.F, Sedinger, J.S
• Format: Journal Article
• Language: English
• Published: Madison Soil Science Society 01-09-2007; Soil Science Society of America; American Society of Agronomy
• Subjects: Agronomy. Soil science and plant productions; biogeochemical cycles; Biological and medical sciences; Carbon; Carbon dioxide; carbon nitrogen ratio; chemical composition; Earth sciences; Earth, ocean, space; Environmental changes; Exact sciences and technology; forest ecosystems; forest growth; forest litter; forest soils; Fundamental and applied biological sciences. Psychology; Leaching; losses from soil; Nitrogen; Soil science; Soils; spatial variation; Studies; surface layers; Surficial geology; temporal variation; Vegetation; Watersheds; Tennessee; USA, Tennessee, Walker Branch; USA, Tennessee; Soil science; Earth science
• ISSN: 0361-5995; 1435-0661
• DOI: 10.2136/sssaj2006.0365

Changes in soil C and N concentrations and contents in four samplings during a 32-yr period on Walker Branch watershed in Tennessee were determined and compared with previously measured C and N fluxes and with changes in ecosystem C and N pools during this period. Soils showed significant increases in C and N concentrations in surface horizons from 1972 to 2004, and most of this increase occurred between 1972 and 1982. A previously observed decline in soil C and N contents between 1982 and 1993 was reversed in 2004 such that the latter increased to near 1982 values. The changes in soil C content could be approximately accounted for by previously measured litterfall and soil CO2-C fluxes. Changes in soil N could not be accounted for by leaching, increments in vegetation, or by laboratory bias, changes during sample storage, or reasonable estimates of field sampling errors. We conclude that, although vegetation C and N pools increased steadily during the sampling period in most cases, changes in soil C and N pools on Walker Branch watershed are highly variable in both space and time, and there has been no unidirectional trend during the time period of this study.