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Estimating Carbon and Nitrogen Pools in a Forest Soil:Influence of Soil Bulk Density Methods and Rock Content
Jurgensen, M.F.; Page-Dumroese, D.S.; Brown, R.E.; Tirocke, J.M.; Miller, C.A.; Pickens, J.B.; Wang, M. 2017.
Estimating Carbon and Nitrogen Pools in a Forest Soil:Influence of Soil Bulk Density Methods and Rock Content.
Soil Sci. Soc. Am. J. . 10.2136/sssaj2017.02.0069.
Keywords: Carbon Pools, Nitrogen Pools, Bulk Density, Fine Fraction
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Abstract:
Soils with high rock content are common in many US forests, and contain
large amounts of stored C. Accurate measurements of soil bulk density and
rock content are critical for calculating and assessing changes in both C
and nutrient pool size, but bulk density sampling methods have limitations
and sources of variability. Therefore, we evaluated the use of small-diameter
soil cores (SD), irregular soil volume excavation (IR), and a nuclear density
gauge (ND) to measure bulk density and rock content, and estimate C and
N pools in three 10-cm increments to a 30-cm depth in a glacial till soil in
northern Wisconsin. Total and fine bulk densities were lower when measured
with SD cores than with larger soil volume IR and ND methods. No differences
in C pools among bulk density sampling methods were found in the
10-cm increments, but when combined to 30 cm, the C pool estimate with IR
(81.6 Mg ha–1) was significantly higher than those of ND (75.3 Mg ha–1) and
SD (73.4 Mg ha–1). No significant differences in N pools were detected in the
10-cm increments, but the 0- to 30-cm N pool estimates by IR (5.65 Mg ha–1)
and ND (5 Mg ha–1) were higher than that of SD (4.22 Mg ha–1). Surface
rocks could lower soil C and N pools by 20% or more. Overall, the bulk density
method had little effect on soil C and N pool estimates in the surface 20
cm of this soil but did when sampled to 30 cm soil depth.
Moscow FSL publication no. 2017c
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