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Effects of Soil Sample Size and Included Root and Wood on Bulk Density in Forested Soils
Author(s) -
Terry T. A.,
Cassel D. K.,
Wollum A. G.
Publication year - 1981
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1981.03615995004500010029x
Subject(s) - loam , bulk density , soil water , silt , soil science , core sample , volume (thermodynamics) , geology , soil texture , environmental science , mineralogy , core (optical fiber) , materials science , composite material , geomorphology , physics , quantum mechanics
Obtaining reliable estimates of bulk density of forested soils can be an arduous task. Soils are not uniform as a result of variable textures and depths of surface horizons, incorporated wood and other debris, and the presence of densely matted layers of surface roots. This study was designed to determine the effects of soil sample size and root and wood volume‐weight corrections on bulk density in bedded and nonbedded plots within two 5‐year‐old loblolly pine ( Pinus taeda L.) plantations. Bulk density was measured on various sizes of cylindrical cores collected from loam and silt loam soils on the North Carolina Coastal Plain. Bulk density values were computed with and without volume and weight corrections for wood and roots. Corrections for wood and roots volumes were found to be unnecessary under the soil‐vegetation conditions sampled, because the combined roots and woody material occupied only 2 to 3% of the total sample volume. Bulk density, however, did vary significantly between bedding treatments and among core sizes. Bedding generally lowered surface bulk density values. Differences in bulk density by core size were attributed primarily to (i) variations in the depth of surface horizon included in each core size and (ii) differences in soil compression, which is a function of core diameter. Under the conditions of this study the 7.6‐cm diam core was considered to be the best size for determining bulk density. For this core size, five to 26 soil cores were needed to estimate bulk density at a precision level of ± 0.10 g/cm 8 at the 0.05 probability level.