Carbon fraction of Pinus radiata biomass components within New Zealand

Peter N Beets,Loretta G Garrett

doi:10.1186/s40490-018-0119-5

Abstract

BackgroundCarbon fractions are applied to dry matter estimates to calculate carbon stocks in forest stands. A default carbon fraction has been applied to planted forest species in New Zealand; however, various studies have shown that the carbon fraction can differ among species and between tree components. New Zealand-specific carbon fractions were, therefore, developed to improve the accuracy of carbon stock estimates for international reporting purposes.MethodsCarbon fractions were analysed using subsamples of tree components from 684 stems, 1125 crowns and 70 root systems from 14 sites distributed throughout New Zealand. The carbon fractions for needles, branches, cones, stem wood, stem bark and roots reported by the laboratory at a drying temperature of 104 °C were corrected using published procedures to the moisture content attained after drying subsamples to constant weight at 70 °C, the drying temperature used in New Zealand biomass studies.ResultsCarbon fraction averaged 0.514 g C g−1dm in needles, 0.507 g C g−1dm in branches, 0.519 g C g−1dm in cones, 0.498 g C g−1dm in stem wood, 0.501 g C g−1dm in roots, and 0.539 g C g−1dm in stem bark of radiata pine. The stem bark carbon fraction increased asymptotically with stand age.ConclusionsThe default carbon fraction (0.50 g C g−1dm) used previously in the FCP model underestimates carbon stocks in New Zealand’s planted forest estate. Applying carbon fractions derived from New Zealand biomass studies will increase carbon stock estimates for the planted forest land by approximately 1% and also increase estimates of removals during harvesting operations. Information on in-forest debarking activities will further improve estimates of removals associated with harvesting.

Highlights

The net stocked area of planted forest in New Zealand covered approximately 1.7 million ha as of 1 April 2016, which was comprised of Pinus radiata, D.Don, Pseudotsuga menziesii (Mirb.) Franco (Douglas-fir 6%) and a range of minor species including eucalypts and cypress (NEFD 2016)
The amount of carbon contained in the dry matter component containing needles, branches, stem wood, stem bark and roots has been examined in a number of coniferous species (Balboa-Murias et al 2006; Bert and Danjon 2006; De Aza et al 2011) and is reported to vary
Robust carbon fractions have been developed for biomass components of radiata pine in New Zealand

Summary

Introduction

The net stocked area of planted forest in New Zealand covered approximately 1.7 million ha as of 1 April 2016, which was comprised of Pinus radiata, D.Don (radiata pine 90%), Pseudotsuga menziesii (Mirb.) Franco (Douglas-fir 6%) and a range of minor species including eucalypts and cypress (NEFD 2016). A weighted average carbon fraction has been derived for various species (Thomas and Martin 2012); the application of a single carbon fraction for a species implies that partitioning of components is fixed This is not the case in New Zealand’s intensively managed planted forests, where the disposition of components varies with site, stand age and the silvicultural regime (Madwick et al 1977; Beets and Pollock 1987; Beets and Madgwick 1988). Component-specific carbon fractions can be implemented within the FCP as it provides annual estimates of the dry matter content of needles by age class, live branches, dead branches, cones, stem wood, stem bark and roots from time of planting to harvesting. New Zealand-specific carbon fractions were, developed to improve the accuracy of carbon stock estimates for international reporting purposes

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