The organic fraction–bulk density relationship and the expression of nutrient content in forest soils

Abstract

Bulk density of forest soils from nine locations in New England was closely and inversely related to the organic fraction of the soil. Measured data over the whole range of organic fractions followed the theoretical relationship Db = DbmDbo/[FoDbm + (1 − Fo)Dbo] where Db is the bulk density (Mg/m3), Fo is the organic fraction (kgo/kg), Dbo is the bulk density when Fo = 1, and Dbm is the bulk density when Fo = 0. The relation arises from assuming that (i) Dbo, the bulk density of "pure" organic matter, and Dbm, the bulk density of "pure" mineral matter, are constant and (ii) in a mixture, the volumes occupied by the organic mass and the mineral mass are additive. For forest soils on coarse-textured till in New England, Dbo = 0.11 Mg/m3 and Dbm varied from 1.45 Mg/m3 for sandy loams to 2.19 Mg/m3 for silt loams. When these parameters are known, Db can be estimated from Fo, which is more easily measured. When Fo is greater than 0.1 kgo/kg, the organic mass per unit soil volume (FoDb), or organic density, is approximately constant at 0.1 Mgo/m3. For many nutrients, separate evaluation of the organic density and the amount of nutrient per unit organic mass may facilitate intersite comparisons for studies of nutrient availability and leaching.

Disturbance Legacy on Soil Carbon Stocks and Stability within a Coastal Temperate Forest of Southwestern British Columbia, Canada

“…Périé and Ouimet (2008) recommended using the organic density approach to estimate BD from SOM because it allows BD to be predicted without significant bias and with a degree of accuracy of 14%. The values for D bm and D bo were also chosen by Grand and Lavkulich (2011) for Humo-Ferric Podzol evaluations on glacial till on the Sunshine Coast of southwestern British Columbia and are in good agreement with other studies conducted in medium to coarse-textured acid forest soils (Federer et al, 1993). BD values for soil horizons were similar to those reported by Shaw et al (2005) for the FH layer of an Orthic Humo-Ferric Podzol but lower for the mineral horizons Ah, Bf1 and Bf 2 .…”

White Spruce Plantations on Abandoned Agricultural Land: Are They More Effective as C Sinks than Natural Succession?

“…All soil samples were air-dried (48-72 h) and sieved through 2 mm mesh; subsamples were ground again through 250 µm mesh. Volumetric soil samples were weighed before and after sieving through 2 mm mesh, in order to calculate bulk density as described by Federer et al [24]. Total C content was determined on the basis of oven-dried mass (105 °C) for all ground subsamples, following dry combustion with a LECO CR-412 carbon analyser.…”

Organic carbon, organic matter and bulk density relationships in boreal forest soils

“…To estimate BD, a nonlinear model was also tested, according to the organic density concept developed by Federer et al (1993):…”

“…More recently, Pre´vost (2004) obtained reasonably good estimates of BD by using logarithmic relationships for some forest soils in Quebec (Canada). However, Federer et al (1993) proposed a new theoretical expression based on the organic density concept to relate BD and SOM. Organic density is the organic mass per unit soil volume.…”