COS 87-5 - Organic matter management effects on soil carbon fractionation in a loblolly pine (Pinus taeda L.) plantation

Thursday, August 11, 2011: 9:20 AM
Ballroom F, Austin Convention Center
Zakiya H. Leggett1, Eric B. Sucre1 and Felipe Sanchez2, (1)Southern R&D, Weyerhaeuser Company, Vanceboro, NC, (2)USDA Forest Service, Asheville, NC

Soil organic matter can serve as an indicator of soil “quality” and contributes largely to the productivity of the soil. Changes in soil organic matter stemming from changes in management practices can influence long-term site productivity and sustainability. Forest floor and logging residue removal has been shown to have no effect as well as negative effects when evaluating current literature. These effects or lack of are expected to vary by soil type, soil fertility and levels of forest floor removed.

Two studies were established to determine if the management of post harvest forest floor and organic matter significantly affect site productivity and sustainability. One study was established in 1994 in Millport, Alabama and the other study in 2006 in Pamlico County, North Carolina. Each study has three treatments: 1. Removed treatment, all forest floor and slash materials were removed using rakes; 2. Control treatment, the forest floor and slash material were unaltered, and 3. Doubled treatment, all forest floor and slash material coming from the removed treatment were uniformly added. Soil samples were collected from 3 depths: 0-20cm, 20-40cm, and 40-60cm and 3 replicates of each treatment were sampled on each site. Total soil carbon (C) was evaluated on the soil samples. A density fractionation method (using sodium polytungstate solution) was used to fractionate the soil organic matter into six different fractions (1.65, 1.85, 2.0, 2.25, 2.5 and >2.5). The degree of organic matter stability is expected to increase with increasing density. This method allows us to make inferences about the effect the study treatments have on stabilization or destabilization of the organic matter.


When evaluating the Millport site, the doubled treatment had 38, 13 and 98% more carbon (% soil carbon) as compared to the removed treatment for the 0-20, 20-40 and 40-60cm depths respectively. The fractionation for the 0-20cm depth revealed significant differences in the treatments for the 2.5 fraction. The 20-40cm depth resulted in no treatment effects for any of the fractions while the 40-60cm depth revealed significant differences in the 1.65 fraction. When evaluating the Pamlico site, there were no differences in treatments for the 0-20cm depth. However, the removed treatment had 45 and 81% more carbon (% soil carbon) as compared to the doubled treatment for the 20-40 and 40-60cm depths respectively. The fractionation revealed no significant treatment effects except for the 2.0 fraction in the 20-40cm depth.

Copyright © . All rights reserved.
Banner photo by Flickr user greg westfall.