ARS | Publication request: SPECTRA CHARACTERISTICS OF WATER EXTRACTABLE ORGANIC MATTER FROM SOILS OF DIFFERENT LAND USES IN A SUBARCTIC ALASKA ENVIRONMENT

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: May 22, 2006
Publication Date: N/A

Technical Abstract: The objective of this research was to determine characteristics of soil water extractable organic matter (WEOM) under different land uses in a subarctic environment. Soil (Volkmar, Aquic Eutrocrepts) samples were taken in October, 2005 from forestry, agricultural, and USDA Conservation Reserve Program (CRP) land. Fresh soil samples were sieved (<2 mm), and extracted with distilled water at a 1:10 of soil:water ratio. The extraction solutions were sequentially filtered through Millipore membranes of 1600 mm, 450 mm, and 1 kD, and solution pH, EC, concentrations of Al3+, Fe3+, Ca2+, Mg2+, Cu2+, Zn2+, and K+, and soluble carbon concentrations were determined. The spectra of UV-Vis were measured for each size fraction. The ratio of E4/E6 was calculated. A spectral slope coefficient was derived from simulation model. Majority (>65%) of Al3+ and Fe3+ were in 450-1600 mm size fraction in CRP and forestry soils, but most Al3+ and Fe3+ were in 1 kD - 450 mm fraction in agricultural soil. There were 57 to 72% Ca2+ in 1 kD - 450 mm fraction for CRP and forestry land in comparison with 68% Ca2+ in < 1 kD fraction for agricultural land. The E4/E6 of WEOM was similar in <1600 mm and <450 mm fractions among different land uses. But for the < 1 kD fraction, the E4/E6 ratio was apparently smaller in forestry than in CRP and agricultural soils, demonstrating a high condensation of aromatic constituents. The spectral slope coefficient at 375 nm was higher for forestry soil in <1 kD size fraction, reflecting impact of substrate sources on the small size WEOM. In summary, land use affected trivalent and divalent cations in different size fractions of WEOM. The impact of land use on spectra properties of WEOM can only be found in < 1 kD size fraction.