Title

A 13C NMR study of Decomposing Logging Residues in an Australian Hoop Pine Plantation

Author(s)/Creator(s)

Chris E. Johnson, cejohns@syr.eduFollow
Timothy J. Blumfield, Griffith University
Sue Boyd, Griffith University
Zhihong Xu, Griffith University

Document Type

Article

Date

3-19-2013

Keywords

Australia, Carbon, Decomposition, Forestry, Litter, Nuclear magnetic resonance spectroscopy, Residue management, Tissue chemistry

Disciplines

Civil and Environmental Engineering

Description/Abstract

Purpose Residue retention is important for nutrient and water economy in sub-tropical plantation forests. We examined decomposing hoop pine (Araucaria cunninghamii Ait. Ex D. Don) residues – foliage, branches and stem wood – to determine the changes in structural chemistry that occur during decomposition.

Materials and methods Residues were incubated in situ using 0.05-m² microplots. We used solid-state ¹³C nuclear magnetic resonance (NMR) spectroscopy to determine the structural composition of harvest residues in the first 24 months of decomposition.

Results and discussion The spectral data for branch and stem residues were generally similar to one another and showed few changes during decomposition. The lignin content of branch and foliage residues decreased during decomposition. When residues were mixed together during decomposition the O-alkyl fraction of foliage decreased initially then increased up to 24 months, while the alkyl carbon (C) fraction exhibited the opposite pattern. The decomposition of woody hoop pine residues (branch and stem wood) is surprisingly uniform across the major C forms elucidated with ¹³C NMR, with little evidence of preferential decomposition. When mixed with branch and stem materials, foliage residues showed significant short- and long-term compositional changes. This synergistic effect may be due to the C:N ratio of the treatments and the structure of the microbial decomposer community.

Conclusions Twenty-four months of decomposition of hoop pine residues did not result in substantial accumulation of recalcitrant C forms, suggesting that they may not contribute to long-term C sequestration.

Recommended Citation

Johnson, C. E., Blumfield, T. J., Boyd, S., & Xu, Z. (2013). A 13C NMR study of decomposing logging residues in an Australian hoop pine plantation. Journal of Soils and Sediments, 13(5), 854–862. http://doi.org/10.1007/s11368-013-0676-4