Quantitative and qualitative assessment of timber harvesting residues: a case study of a balsa plantation in Papua New Guinea

Abstract

The quantity and quality of the harvesting residues in a balsa plantation in East New Britain Province of Papua New Guinea are reported in this paper. The plantation was harvested manually with a chainsaw and manpower to extract the industrial wood at age 6 years. A modified standard harvesting residue assessment method using plots on line transects was applied. The total weight of the harvest residues remaining on the site after wood extraction was 211.7 t_GREEN ha⁻¹ (tonnes (green) per hectare). The major component was un-merchantable stem wood (121.3 t_GREEN ha⁻¹; 57.3%), followed by bark (59.3 t_GREEN ha⁻¹; 28.0%). This level of harvest residue was relatively greater than that reported in other studies, reflecting the combination of the log specification applied and the nature of the stem defects in balsa trees. The level of residues indicates the possibility of additional woody material recovery for bioenergy after consideration of sustainability issues.

The average moisture content of the wood components of the residues was determined over two days. The average moisture content on the first day after harvesting was 50%, falling in the following day to about 48%. The abundance of five elements in the harvest residues was estimated using data from a single sample tree; of the elements assessed potassium was the most abundant while calcium was the least.

Keywords:

• Plantations
• harvesting
• residues
• nutrients
• moisture content
• balsa

Acknowledgements

The support of the following parties in undertaking the fieldwork is acknowledged:

Jaupo Minimulu (ACIAR Project Officer); Nathan Kotlarewski, Swinburne University of Technology, PhD student; PNG Balsa Limited; The PNG Balsa harvest team; The Papua New Guinea University of Natural Resources and Environment; Professor John Herbohn, University of the Sunshine Coast.

Notes

1. Garden system in the PNG context refers to horticulture for subsistence and/or cash crops managed on a rotational basis.

2. Jenkin, B. Personal communication. Balsa plantation management, October 2014.

3. National Agricultural Research Institute (NARI) Plant analysis results. Unpublished contract analysis data for samples received on 26 February 2015.