Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Carbon fraction of Pinus radiata biomass components within New Zealand

Carbon fraction of Pinus radiata biomass components within New Zealand Background: Carbon 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. Methods: Carbon 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. −1 −1 −1 Results: Carbon fraction averaged 0.514 g C g dm in needles, 0.507 g C g dm in branches, 0.519 g C g dm in −1 −1 −1 cones, 0.498 g C g dm in stem wood, 0.501 g C g dm in roots, and 0.539 g C g dm in stem bark of radiata pine. The stem bark carbon fraction increased asymptotically with stand age. −1 Conclusions: The default carbon fraction (0.50 g C g dm) 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. Keywords: Biomass, Carbon stocks, Carbon fraction, Douglas-fir, Radiata pine Introduction called the Forest Carbon Predictor (FCP) (Beets et al. The net stocked area of planted forest in New Zealand 2011). The FCP estimates the dry matter content of live covered approximately 1.7 million ha as of 1 April 2016, tree components, which is converted to carbon by apply- which was comprised of Pinus radiata, D.Don (radiata ing a carbon fraction. The amount of carbon (i.e. the car- pine 90%), Pseudotsuga menziesii (Mirb.) Franco bon fraction) in biomass components is currently −1 (Douglas-fir 6%) and a range of minor species including assumed to be 0.50 g C per gram of dry matter (g dm), eucalypts and cypress (NEFD 2016). Unbiased estimates which differs slightly from default fraction in the IPCC of carbon (C) stocks and changes in New Zealand’s guidelines (IPCC 2006), which is 0.51 in temperate and planted and natural forests are required to meet inter- boreal conifers. Given the importance of planted forests as national reporting commitments under the United a carbon sink in New Zealand, it is important to develop Nations Framework Convention on Climate Change New Zealand-specific carbon fractions. (UNFCCC) and the Kyoto Protocol. The national inven- The amount of carbon contained in the dry matter tory of planted forest provides data for developing carbon component containing needles, branches, stem wood, yield tables, which are derived from a modelling system 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 * Correspondence: peter.beets@scionresearch.com Scion, Private Bag 3020, Rotorua 3046, New Zealand © The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Beets and Garrett New Zealand Journal of Forestry Science (2018) 48:14 Page 2 of 8 between species and among biomass components, as samples were also acquired at eight Genotype × Envir- was highlighted in a recent review (Thomas and Martin onment (G × E) trial sites established in the North and 2012). For carbon estimation purposes, biomass samples South Island of New Zealand, each planted with 40 clon- need to account for within- and between-tree variation ally propagated genotypes. At these sites, stem wood, in carbon content to provide unbiased estimates of the stem bark, and needle biomass samples were obtained carbon fraction. For example, a composite sample of from 96 trees (one tree from each of the 12 genotypes mass-weighted stem wood or bark subsamples taken at per site) in 2017 in 12- to 15-year-old stands. In fixed intervals along the entire length of stems will pro- addition, branch and root samples (10 to ≤ 50 mm diam- vide representative material, while for needles and eter over bark) were acquired from recently harvested branches, mass-weighted subsamples from throughout stands at nine sites located within New Zealand com- the crown will provide representative material for chem- mercial plantations as part of woody debris decay studies ical analysis. Tree biomass sampling procedures are spe- (Garrett et al. 2008, 2010, 2012). Finally, outer bark cifically designed to provide representative samples of (cork) from disc samples taken at fixed intervals individual biomass components, thus providing suitable along the entire stem length of 19 trees (stands aged subsamples for carbon analysis. A weighted average car- 22/23 years old) at Puruki Forest was separated from bon fraction has been derived for various species inner bark (phloem and phelloderm) using a chisel, (Thomas and Martin 2012); however, the application of which was only feasible from discs in the lower part a single carbon fraction for a species implies that parti- of the stem. This corky bark was bulked into a single tioning of components is fixed. This is not the case in sample per tree and labelled “outer bark”. The inner New Zealand’s intensively managed planted forests, bark and bark from upper discs that could not be where the disposition of components varies with site, separated from the inner bark was bulked by tree and stand age and the silvicultural regime (Madwick et al. labelled “inner bark”. One 10-year-old Douglas-fir 1977; Beets and Pollock 1987; Beets and Madgwick stand was sampled at Gowan Hill, Southland, which pro- 1988). An alternative approach is to apply carbon frac- vided needle, branch and stem wood and bark samples for tions to each biomass component separately. comparison purposes. The oven-dried (70 °C) samples Component-specific carbon fractions can be imple- were processed as follows. mented within the FCP as it provides annual estimates Woody biomass samples were chipped and then of the dry matter content of needles by age class, live ground until all the material passed through a 2-mm branches, dead branches, cones, stem wood, stem bark mesh sieve, while needle samples were ground until all and roots from time of planting to harvesting. the material passed through a 1-mm mesh sieve. To improve the accuracy of carbon stock estimates for Because the samples had been exposed to air for an in- planted forests in New Zealand, carbon data from radiata definite period of time, they had gained moisture. pine biomass studies across a range of sites and ages were Carbon (C) content of these samples was determined by summarised by component and stand age, so as to incorp- thermal combustion (Leco CNS-2000, LECO Corp., St orate suitable carbon fractions within the Forest Carbon Joseph, MI, USA). Carbon fractions (CFs) reported by Predictor. In this paper, component-specific carbon frac- the laboratory were based on moisture factors of sub- tions were tabulated for radiata pine along with limited samples dried for 24 h at a drying temperature of 104 °C. data for Douglas-fir grown in New Zealand, Also, an as- The moisture factors (s.e.) averaged 1.087 (0.0008) for sessment of the impact of the revised fractions on biomass stem wood, 1.096 (0.0008) for stem bark and 1.077 carbon stock estimates is provided. (0.0008) for needles. These moisture factors provide car- bon fractions at a drying temperature of 104 °C and Methods were, therefore, back-corrected to the moisture content Oven-dried (70 °C) stem wood, stem bark, branch, cone of biomass samples oven dried to constant weight at 70 ° and needle samples for carbon analysis were obtained C, the drying temperature used in New Zealand biomass from existing and new radiata pine and Douglas-fir bio- studies. Carbon fractions were back-corrected as follows: mass studies in New Zealand. Dead needles intercepted CF =CF × (100 − 1.045)/100 (following Bert and 70 104 by branches in the lower crown were collected separately Danjon 2006), where CF is the carbon fraction applied from live needles. Biomass studies in radiata pine stands to biomass data, CF is the carbon fraction reported by were undertaken in 5- and 15-year-old stands at the laboratory and 1.045 is the percentage reduction in Kinleith, 5-, 16- and 26-year-old stands at Tarawera, 5- moisture content of biomass samples oven dried to con- and 28-year-old stands at Woodhill and a 5-year-old stant weight at 70 °C and then re-dried to constant stand at Nelson. Carbon data from the 15- and weight at 104 °C. 16-year-old stands at Kinleith and Tarawera, respect- For radiata pine, data for each component were exam- ively, were published by Oliver et al. (2011). Biomass ined for variation with tree age. The carbon fraction in Beets and Garrett New Zealand Journal of Forestry Science (2018) 48:14 Page 3 of 8 stem bark was the only component to vary significantly Results as a function of stand age. The carbon fraction in stem Carbon fractions of radiata pine tree components bark was modelled as a function of age using the NLIN The carbon fractions of radiata pine tree components are procedure (Gaus-Newton method) in SAS Version 9.4 summarised in Table 1. The mean carbon fraction across −1 statistical analysis software (SAS Institute Inc. 2011). For sites averaged (standard error in parenthesis) 0.498 g C g dm −1 components other than stem bark, the overall mean (0.001) for stem wood, 0.501 g C g dm (0.004) for coarse −1 across sites was calculated by component. roots, 0.514 g C g dm (0.002) for live needles, 0.507 −1 −1 The impact of replacing the default carbon fraction gCg dm (0.002) for branches and 0.519 g C g dm (0.004) −1 (0.50 g C g dm) by the revised carbon fractions was for cones. Dead fallen needles from upper branches assessed by applying carbon fractions to stem wood, intercepted by branches in the lower crown averaged −1 stem bark, needle, branch and cone dry matter estimates 0.514 g C g dm (data not shown), which was the from a radiata pine chronosequence study (Madwick et same as the value obtained for live needles. For stem bark, −1 al. 1977; Webber and Madgwick 1983). the overall mean carbon fraction averaged 0.539 g C g dm Table 1 Mean carbon fraction of radiata pine biomass components, age of sample stand, number of stems/crowns/roots sampled (n) and study sites in New Zealand Site Stand age n (stem/crown/ Carbon fraction (± se) −1 (years) root) (g C g dm) Stem wood Stem bark Branches Needles Cones Roots Balmoral, SI 28 0/3/6 n/a n/a 0.510 n/a n/a 0.506 Burnham, SI 28 0/4/8 n/a n/a 0.521 n/a n/a 0.510 Crater Block, NI 13 12/12/0 0.497 0.546 n/a 0.526 n/a n/a Forest Creek, SI 14 12/12/0 0.500 0.549 n/a 0.515 n/a n/a Golden Downs, SI 5 120/240/0 0.500 0.508 0.515 0.507 n/a n/a 28 0/2/4 n/a n/a 0.495 n/a n/a 0.509 Kaingaroa, NI 12 12/12/0 0.497 0.545 n/a 0.509 n/a n/a 28 0/2/4 n/a n/a 0.493 n/a n/a 0.494 Kinleith, NI 5 120/240/0 0.499 0.518 0.507 0.501 n/a n/a 10 0/0/9 n/a n/a n/a n/a n/a 0.498 15 24/47/3 0.504 0.539 0.515 0.508 0.520 0.478 Lawrence, SI 14 12/12/0 0.496 0.557 n/a 0.514 n/a n/a Lochinver, NI 14 12/12/0 0.494 0.550 n/a 0.517 n/a n/a Mahia, NI 15 12/12/0 0.498 0.556 n/a 0.520 n/a n/a Rotoehu, NI 12 12/12/0 0.496 0.545 n/a 0.517 n/a n/a 28 0/1/6 n/a n/a 0.499 n/a n/a 0.493 Tarawera, NI 5 120/270/8 0.494 0.510 0.510 0.510 n/a 0.510 11 0/0/4 n/a n/a n/a n/a n/a 0.532 16 24/48/4 0.509 0.545 0.514 0.523 0.525 0.491 26 24/48/0 0.498 0.546 0.509 0.514 0.511 n/a 28 0/2/4 n/a n/a 0.501 n/a n/a 0.498 West Coast, SI 28 0/1/6 n/a n/a 0.504 n/a n/a 0.503 Woodhill, NI 5 120/120/0 0.495 0.509 0.507 0.514 n/a n/a 13 12/12/0 0.493 0.539 n/a 0.510 n/a n/a 28 36/1/4 0.498 0.554 0.503 n/a n/a 0.497 Mean 0.498 0.539 0.507 0.514 0.519 0.501 ± se 0.001 0.004 0.002 0.002 0.004 0.004 Carbon is expressed per unit dry matter (dm) oven dried at 70 °C Live needles 10 mm to ≤ 50 mm diameter over bark Beets and Garrett New Zealand Journal of Forestry Science (2018) 48:14 Page 4 of 8 (0.004); however, the mean carbon fraction increased with increases with age, until the bark layer becomes domi- −1 −1 age from 0.508 g C g dm at age 5 to 0.554 g C g dm at nated by cork. stand age 28 years (Fig. 1). No significant trends with age were evident for other components. Carbon fraction of Douglas-fir components −1 Means and ranges in component carbon fractions av- The mean and range in carbon fraction (g C g dm) of eraged across the eight G × E trial sites, and 12 geno- biomass components for one Douglas-fir stand in New types are summarised in Table 2. Carbon fractions Zealand are summarised in Table 4. The mean carbon −1 differed significantly between sites and among clones, al- fraction was lowest in stem wood (0.502 g C g dm), inter- though the differences are relatively small and impracti- mediate in needles and branches and highest in stem bark −1 cal to implement (Table 2). (0.534 g C g dm). These results for Douglas-fir are very The carbon fraction in stem bark of New Zealand-grown similar to those reported above for New Zealand-grown radiata pine follows an asymptotic relationship with age radiata pine. (Fig. 1)given by: Discussion CF ¼ 0:551 ðÞ 1  0:291  expðÞ −0:280  Age Various studies of conifers growing in countries other stembark than New Zealand show that carbon fractions can differ The model was fitted to a total of 16 stands from 5 to 28 appreciably among species and tree components years old at 11 sites, three of which (Woodhill, Kinleith, (Table 5). The New Zealand-grown radiata pine carbon Tarawera) were sampled at multiple ages (Table 1). The fractions reported here are based on wood and bark model has an R = 0.91 and root mean square error = 0.057. samples from 684 stems, 1125 crowns and 70 root Stem bark was the only tree component where the carbon systems from a total of 14 sites distributed throughout fraction varied significantly with stand age. The asymptote New Zealand. The samples were obtained from biomass- was reached by around stand age 12 years. specific studies and are considered representative of each tree component. These data show similar trends to Carbon fraction of radiata pine bark components radiata pine in Spain (Table 5), with the C fraction in the The carbon fraction of the inner and outer bark of 22/ stem bark being the highest, needles and branches inter- 23-year-old trees at Puruki Forest is summarised in mediate and stem wood lowest. For most species, heart- Table 3. The carbon fraction of the outer bark exceeded wood has a higher carbon fraction than sapwood, and that of the inner bark by approximately 14%. The bark branches, roots and needles tend to be intermediate be- of very young trees is equivalent to the inner bark, while tween stem sapwood and stem bark (Table 5). Explana- the outer bark becomes evident as trees increase in age. tions offered for differences in carbon fractions are The results for the inner and outer bark are consistent summarised in reviews by Matthews (1993), Bert and with the finding that the carbon fraction of bark initially Danjon (2006) and Thomas and Martin (2012). Species Fig. 1 Carbon fraction of stem bark as a function of stand age in New Zealand radiata pine biomass studies. Three sites were sampled at multiple ages: Woodhill (triangles), Kinleith (dots) and Tarawera (crosses). The remaining eight sites were sampled only at one age (circles). The line shows the fitted exponential function: CF = 0.551 × (1 − 0.291 × exp(− 0.280 × Age)) stembark Beets and Garrett New Zealand Journal of Forestry Science (2018) 48:14 Page 5 of 8 Table 2 Carbon fraction—summary of G × E trials sampled at Table 4 Carbon fractions of Douglas-fir biomass components of approximately mid-rotation ages eight trees from a 10-year-old stand at Southland Component Mean Site Genotype Biomass Carbon fraction (± se) −1 component (g C g dm) Min Max Min Max Mean Minimum Maximum Stem wood 0.496 0.493 0.500 0.494 0.500 Needles 0.518 (0.003) 0.506 0.530 Stem bark 0.548 0.538 0.557 0.538 0.564 Live branches 0.513 (0.003) 0.503 0.523 Needles 0.516 0.509 0.526 0.512 0.520 Dead branches 0.521 (0.003) 0.508 0.529 Carbon is expressed per unit dry matter (dm) oven dried at 70 °C Stem wood 0.502 (0.001) 0.496 0.506 Stem bark 0.534 (0.003) 0.520 0.543 and component-related differences in carbon fractions Carbon is expressed per unit dry matter (dm) at 70 °C reflect the relative proportions of high versus low carbon fraction compounds in tissues during, for example, heartwood formation and cell suberisation in bark. The bark carbon fraction increases with tree age in New carbon content of cellulose (44.4%), lignin (66.7%) and Zealand radiata pine studies. hemi-celluloses (44.4–45.5%) are reasonably well estab- The dry mass of biomass samples and hence the car- lished (Matthews 1993). Radiata pine has produced very bon content depend on the drying temperature and hu- little heartwood by age 20–28 years, the ages at which it midity of the drying oven (Matthews 2010). To minimise is typically harvested in New Zealand, and the carbon bias, carbon fractions reported by laboratories need to fraction of stem wood varies little with tree age. Radiata be corrected to the moisture content of oven-dry bio- pine stem wood was previously estimated to be com- mass samples. In most studies, biomass samples are prised of lignin 26%, cellulose 42%, galactoglucomannan oven dried in forced ventilation ovens at 65–75 °C to 15%, arabinoglucuronoxylan 10%, arabinogalactan 4%, constant weight or after a defined period of time in the utonic acids, etc. 3% (Uprichard and Lloyd 1980), which oven. To minimise carbon and nitrogen volatilisation gives a moisture-free C fraction of 0.504, based on losses that occur at high temperatures (Samuelsson et al. methods in Matthews (1993). This value compares 2006), comparatively low drying temperatures are used −1 favourably to the value of 0.498 g C g dm (Table 1) ob- when drying biomass samples to constant weight, which tained directly from the measured stem wood carbon can take up to several weeks for large samples. Losi et fraction in the current study. al. (2003), for example, noted that charring occurred The carbon fraction in radiata pine stem bark in- when attempting to dry biomass samples to constant creased with tree age in New Zealand biomass studies. weight at a temperature of 105 °C. Results of chemical Other studies have shown that the carbon fraction of analysis conducted by laboratories are based on very stem bark is generally highest at the base of the stem small samples which are dried quickly at comparatively where the proportion of mature bark is greatest (De Aza high drying temperatures. For this study, the approach et al. 2011). More particularly, it has been shown that used by Bert and Danjon (2006) to correct the carbon the outer bark has a higher carbon fraction than inner data reported by various laboratories was followed. They bark, which was ascribed to higher levels of extractives, noted that the moisture factor applied in the analytical lignin, tannins and suberin (Bert and Danjon 2006). The laboratory was based on subsamples dried at 103 °C, outer bark has a significantly higher carbon fraction than whereas the biomass samples had been dried to constant the inner bark in the current study which was based on weight at 65 °C, which resulted in a moisture content 19 radiata pine stems, presumably owing to the higher about 2% lower than that in their biomass samples. Mat- content of lignin and suberin in the outer bark. The pro- thews (2010) found approximately 2.5% of additional portion of the outer bark in the lower part of the stem moisture in pine samples dried at 65 °C compared to increases with tree age, which explains why the stem when samples were dried at 103 °C in an air-conditioned laboratory at 20 °C and 40% relative humidity. Likewise, the moisture factor of the bulked radiata pine biomass Table 3 Carbon fraction summary of inner and outer stem bark samples in the current study was 1.01045. These samples in 22/23-year-old radiata pine trees at Puruki Forest had been dried to constant weight at 70 °C and then fur- Component Carbon fraction ther dried to constant weight at 104 °C. −1 (g C g dm) Based on the data obtained here, the values for carbon n Mean Minimum Maximum −1 fractions applied in the FCP should be 0.514 g C g dm for −1 −1 Stem bark—inner 19 0.503 0.472 0.558 needles, 0.507 g C g dm for branches, 0.519 g C g dm for −1 −1 Stem bark—outer 19 0.575 0.549 0.628 cones, 0.498 g C g dm for stem wood and 0.501 g C g dm Carbon is expressed per unit dry matter (dm) oven dried at 70 °C for roots. For stem bark, the carbon fraction (the mean Beets and Garrett New Zealand Journal of Forestry Science (2018) 48:14 Page 6 of 8 Table 5 Component carbon fraction, number of sample trees per stand (n), country of study and source of data for various Pinus species Species Component Age (years) Number Carbon Fraction Biomass Country Source −1 (g C g dm) samples dried (°C) P. nigra Stem sapwood 27–39 112 0.465 75 Spain De Aza et al. 2011 Stem bark 106 0.499 P. pinaster Stem heartwood 29–50 87 0.495 Stem sapwood 156 0.458 Stem bark 137 0.501 P. sylvestris Stem heartwood 36–53 76 0.523 Stem sapwood 166 0.453 Stem bark 166 0.485 P. radiata Stem wood Unknown 54 0.504 65 Spain Balboa-Murias et al. 2006 Stem bark 54 0.541 Large branches 54 0.513 Small branches 54 0.525 Twigs 54 0.532 Needles 54 0.527 P. pinaster Stem wood 125 0.471 Stem bark Unknown 125 0.508 Large branches 125 0.479 Small branches 125 0.505 Twigs 125 0.497 Needles 125 0.497 P. pinaster Stem heartwood 50 4 0.544 65 France Bert and Danjon 2006 Stem sapwood 4 0.523 Stem inner bark 4 0.510 Stem outer bark 4 0.559 Dead branch 4 0.534 Live branch 4 0.535 Cones 4 0.534 Needles 4 0.536 Taproot wood 4 0.517 Taproot bark 4 0.549 Coarse root wood 4 0.513 Coarse root bark 4 0.544 Tree total 0.532 Bert and Danjon (2006) reported carbon fractions (the analytical laboratory used 103 °C) corrected to 65 °C, which was the temperature used in their biomass dry matter determinations. Other reported values that are assumed were as provided by the analytical laboratory used −1 −1 −1 value is 0.534 g C g dm) increases significantly with stand gCg dm by age 9 years to a maximum of 0.55 g C g dm age, and, therefore, an age-adjusted carbon fraction should by stand age 17 years and older. The revised carbon frac- be applied to this component for stands aged 5 years or tions are applied in the FCP as shown in Table 6 for actual older. For stand less than 5-years-old, the CF = 0.503 (the biomass data. value for inner bark). Consequently, the mean carbon frac- Compared to the use of the default carbon fraction −1 tion in radiata pine bark increases rapidly from approxi- (0.50 g C g dm), the revised carbon fractions increase the −1 mately 0.50 g C g dm at stand age 4 years to 0.54 amount of aboveground live (AGL) carbon stored in Beets and Garrett New Zealand Journal of Forestry Science (2018) 48:14 Page 7 of 8 Table 6 Carbon stock (t/ha) and sequestration (t/ha/year) estimates calculated by applying carbon fractions to radiata pine stand dry −1 matter estimates in Madwick et al. (1977) and Webber and Madgwick (1983): (a) using a default carbon fraction of 0.50 g C g dm and (b) using tree component-specific carbon fractions for radiata pine in New Zealand −1 a Carbon stock estimates based on a carbon fraction of 0.50 g C g dm Stand age (years) Stem Stem Branches Needles Cones AGL AGL C wood bark C seq 2 0.09 0.03 0.06 0.18 0.00 0.36 0.36 4 3.60 0.64 3.28 3.58 0.00 11.1 5.37 6 11.3 1.46 7.49 5.78 0.00 26.0 7.48 8 23.0 2.63 11.9 2.96 0.05 40.5 7.24 9 14.5 1.80 2.77 1.70 0.30 21.1 10 24.8 2.39 5.69 2.93 0.11 35.9 14.8 17 107.4 10.9 11.0 5.41 2.51 137.3 14.5 22 121.8 13.7 13.7 4.64 1.61 155.4 3.61 29 168.7 16.2 12.8 4.10 4.65 206.4 7.29 Residues following harvesting of stem 25.3 2.4 12.8 4.10 4.65 49.3 wood plus bark Residues following harvesting of stem 25.3 16.2 12.8 4.10 4.65 63.0 wood only b Carbon stock estimates based on the revised component-specific carbon fractions for radiata pine Stand age (years) Stem Stem Branches Needles Cones AGL AGL C C sequestration C stock wood bark C seq change (%) change (%) 2 0.08 0.03 0.06 0.19 0.00 0.36 0.36 1.6 1.6 4 3.58 0.64 3.33 3.68 0.00 11.2 5.43 1.2 1.2 6 11.3 1.5 7.6 5.94 0.00 26.3 7.55 1.0 1.1 8 22.9 2.8 12.1 3.04 0.05 40.9 7.27 0.4 0.8 9 14.5 1.9 2.8 1.75 0.31 21.3 0.8 10 24.7 2.6 5.8 3.01 0.11 36.2 14.9 0.6 0.7 17 107.0 12.0 11.2 5.56 2.61 138.3 14.6 0.8 0.8 22 121.3 15.0 13.9 4.76 1.67 156.6 3.66 1.2 0.8 29 168.0 17.8 13.0 4.21 4.83 207.8 7.31 0.3 0.7 Residues following harvesting of stem 25.2 2.7 13.0 4.21 4.83 49.9 1.3 wood plus bark Residues following harvesting of stem 25.2 17.8 13.0 4.21 4.83 65.0 3.2 wood only The resulting percentage changes in aboveground live (AGL) C stocks and C sequestration are shown (in part b) by stand age, as are the expected effects of harvesting the 29-year-old stand (Webber and Madgwick 1983), assuming stem wood plus bark extraction (85%) or assuming stem wood only extraction (85%), on carbon stocks of residues and stock changes (%) C sequestration of the 9-year-old stand was not calculated because this stand had been thinned, which explains why the AGL C stock decreased relative to the AGL C stock at age 8 years mature stands by approximately 1%. The amount of car- bark) carbon fractions for radiata pine are applicable to bon retained on site as harvest residues during conven- other coniferous species in New Zealand’s planted forest tional stem-harvesting operations, which typically remove estate. 85% of the stem wood plus bark, increased by 1.3%, unless harvested stems were entirely debarked at the stump in Conclusions which case the amount of carbon retained on site as har- Robust carbon fractions have been developed for biomass vest residues increased by 3.2%, when using the revised in- components of radiata pine in New Zealand. Analysis −1 stead of the default carbon fractions (Table 6). shows that the default carbon fraction (0.50 g C g dm) Component carbon fractions are similar in Douglas-fir used in the FCP model underestimates carbon stocks in and radiata pine biomass components. It was, therefore, New Zealand’s planted forests by approximately 1%. Ap- assumed that the component- and age-specific (for stem plying the revised carbon fractions derived above from Beets and Garrett New Zealand Journal of Forestry Science (2018) 48:14 Page 8 of 8 specific biomass components of commonly planted spe- Beets, P. N., & Madgwick, H. A. I. (1988). Above-ground dry matter and nutrient content of Pinus radiata as affected by lupin, fertiliser, thinning, and stand cies in New Zealand in the FCP model will improve the age. New Zealand Journal of Forestry Science, 18,43–64. accuracy of carbon stock estimates for planted forest. Beets, P. N., & Pollock, D. S. (1987). Accumulation and partitioning of dry matter Moreover, operational information on in-forest debarking in Pinus radiata as related to stand age and thinning. New Zealand Journal of Forestry Science, 17, 246–271. activities that provide estimates of the percentage of stem Bert, D., & Danjon, F. (2006). Carbon concentration variations in the roots, stem bark mechanically removed during harvesting operations and crown of mature Pinus pinaster (Ait.). Forest Ecology and Management, will further improve estimates of removals associated with 222, 279–295. De Aza, C. H., Turrion, M. B., Pando, V., & Bravo, F. (2011). Carbon in heartwood, harvesting, and additional work is required to achieve this. sapwood and bark along the stem profile in three Mediterranean Pinus species. Annals of Forest Science, 68, 1067–1076. Abbreviations Garrett, L. G., Kimberley, M. O., Oliver, G. R., Pearce, S. H., & Beets, P. N. (2012). AGL: Aboveground live biomass; C: Carbon; CF: Carbon fraction; Decomposition of coarse woody roots and branches in managed Pinus CF : Carbon of samples dried to constant weight at 104 °C; CF : Carbon 104 70 radiata plantations in New Zealand – a time series approach. Forest Ecology fraction of samples dried to constant weight at 70 °C; FCP: Forest Carbon and Management, 269, 116–123. Predictor; IPCC: Intergovernmental Panel on Climate Change; NI: North Island Garrett, L. G., Kimberley, M. O., Oliver, G. R., Pearce, S. H., & Paul, T. S. H. (2010). of New Zealand; SI: South Island of New Zealand; UNFCCC: United Nations Decomposition of woody debris in managed Pinus radiata plantations in Framework Convention on Climate Change New Zealand. Forest Ecology and Management, 260, 1389–1398. Garrett, L. G., Oliver, G. R., Pearce, S. H., & Davis, M. R. (2008). Decomposition of Acknowledgements Pinus radiata coarse woody debris in New Zealand. Forest Ecology and Funding to facilitate the preparation of this manuscript was provided by the Management, 255, 3839–3384. New Zealand Ministry for the Environment under Head Agreement 20059, IPCC. (2006). 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Statement of Work 21078. Tree component biomass samples included in this Prepared by the National Greenhouse Gas Inventories Programme and H. S. analysis were acquired from biomass studies that had been undertaken Eggleston, L. Buendia, K. Miwa, T. Ngara, & K. Tanabe (Eds.). Kanagawa: using funding from a range of sources, including Growing Confidence in Institute for Global Environmental Strategies. Forestry’s Future GCFF research programme funded by MBIE, SLMACC Losi, C. J., Siccama, T. G., Condit, R., & Morales, J. E. (2003). Analysis of alternative projects funded by Ministry of Primary Industries, and an Underpinning methods for estimating carbon stock in young tropical plantations. Forest Research Contract funded by Ministry for the Environment. The authors Ecology and Management, 184, 355–368. acknowledge the contribution of Mark Kimberley for statistical assistance. Madwick, H. A. I., Jackson, D. S., & Knight, P. J. (1977). Above-ground dry matter, energy, and nutrient content of trees in an age series of Pinus radiata plantations. New Zealand Journal of Forestry Science, 7, 445–468. Funding Matthews, G. (1993). The carbon content of trees. [Technical Paper 4]. Edinburgh: Funding to facilitate data analysis and publication of this manuscript was Forestry Commission. provided by the Ministry for the Environment under Head Agreement Matthews, S. (2010). Effect of drying temperature on fuel moisture content Reference 20059, Statement of Work 21078. measurements. International Journal of Wildland Fire, 19, 800–802. NEFD. (2016). National Exotic Forest Description as at 1 April 2016. Wellington: Availability of data and materials Ministry for Primary Industries. Please contact author for data requests. Oliver, G. R., Beets, P. N., Pearce, S. H., Graham, J. D., & Garrett, L. G. (2011). Carbon accumulation in two Pinus radiata stands in the North Island of New Authors’ contributions Zealand. New Zealand Journal of Forestry Science, 41,71–86. PNB developed the concept for this manuscript and was the primary author. Samuelsson, R., Nilsson, C., & Burvall, J. (2006). Sampling and GC-MS as a method LGG contributed towards data collation from decay studies and contributed for analysis of volatile organic compounds (VOC) emitted during oven drying to writing the paper. Both authors have read and approved the final version of biomass materials. Biomass and Bioenergy, 30, 923–928. of the manuscript. SAS Institute Inc. (2011). Base SAS® 9.3 Procedures Guide. Cary, NC: SAS Institute Inc. Thomas, S. C., & Martin, A. R. (2012). Carbon content of tree tissues: a synthesis. Ethics approval and consent to participate Forests, 3, 332–352. Not applicable Uprichard, J. M., & Lloyd, J. A. (1980). Influence of tree age on the chemical composition of radiata pine. New Zealand Journal of Forestry Science, 10, 551–557. Webber, B., & Madgwick, H. A. I. (1983). Biomass and nutrient content of a 29-year- Consent for publication old Pinus radiata stand. New Zealand Journal of Forestry Science, 7,445–468. Not applicable Competing interests The authors declare that they have no competing interests. Publisher’sNote Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Received: 21 February 2018 Accepted: 13 November 2018 References Balboa-Murias, M. A., Rodriguez-Soalleiro, R., Merino, A., & Alvarez-Gonzalez, J. G. (2006). Temporal variations and distribution of carbon stocks in aboveground biomass of radiata pine and maritime pine pure stands under different silvicultural alternatives. Forest Ecology and Management, 237,29–38. Beets, P. N., Kimberley, M. O., Paul, T. S. H., & Garrett, L. G. (2011). Forest carbon monitoring system – forest carbon model validation study for Pinus radiata. New Zealand Journal of Forestry Science, 41, 177–189. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png New Zealand Journal of Forestry Science Springer Journals

Carbon fraction of Pinus radiata biomass components within New Zealand

Loading next page...
 
/lp/springer-journals/carbon-fraction-of-pinus-radiata-biomass-components-within-new-zealand-GTWvmpCGx2
Publisher
Springer Journals
Copyright
Copyright © 2018 by The Author(s).
Subject
Life Sciences; Forestry
eISSN
1179-5395
DOI
10.1186/s40490-018-0119-5
Publisher site
See Article on Publisher Site

Abstract

Background: Carbon 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. Methods: Carbon 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. −1 −1 −1 Results: Carbon fraction averaged 0.514 g C g dm in needles, 0.507 g C g dm in branches, 0.519 g C g dm in −1 −1 −1 cones, 0.498 g C g dm in stem wood, 0.501 g C g dm in roots, and 0.539 g C g dm in stem bark of radiata pine. The stem bark carbon fraction increased asymptotically with stand age. −1 Conclusions: The default carbon fraction (0.50 g C g dm) 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. Keywords: Biomass, Carbon stocks, Carbon fraction, Douglas-fir, Radiata pine Introduction called the Forest Carbon Predictor (FCP) (Beets et al. The net stocked area of planted forest in New Zealand 2011). The FCP estimates the dry matter content of live covered approximately 1.7 million ha as of 1 April 2016, tree components, which is converted to carbon by apply- which was comprised of Pinus radiata, D.Don (radiata ing a carbon fraction. The amount of carbon (i.e. the car- pine 90%), Pseudotsuga menziesii (Mirb.) Franco bon fraction) in biomass components is currently −1 (Douglas-fir 6%) and a range of minor species including assumed to be 0.50 g C per gram of dry matter (g dm), eucalypts and cypress (NEFD 2016). Unbiased estimates which differs slightly from default fraction in the IPCC of carbon (C) stocks and changes in New Zealand’s guidelines (IPCC 2006), which is 0.51 in temperate and planted and natural forests are required to meet inter- boreal conifers. Given the importance of planted forests as national reporting commitments under the United a carbon sink in New Zealand, it is important to develop Nations Framework Convention on Climate Change New Zealand-specific carbon fractions. (UNFCCC) and the Kyoto Protocol. The national inven- The amount of carbon contained in the dry matter tory of planted forest provides data for developing carbon component containing needles, branches, stem wood, yield tables, which are derived from a modelling system 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 * Correspondence: peter.beets@scionresearch.com Scion, Private Bag 3020, Rotorua 3046, New Zealand © The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Beets and Garrett New Zealand Journal of Forestry Science (2018) 48:14 Page 2 of 8 between species and among biomass components, as samples were also acquired at eight Genotype × Envir- was highlighted in a recent review (Thomas and Martin onment (G × E) trial sites established in the North and 2012). For carbon estimation purposes, biomass samples South Island of New Zealand, each planted with 40 clon- need to account for within- and between-tree variation ally propagated genotypes. At these sites, stem wood, in carbon content to provide unbiased estimates of the stem bark, and needle biomass samples were obtained carbon fraction. For example, a composite sample of from 96 trees (one tree from each of the 12 genotypes mass-weighted stem wood or bark subsamples taken at per site) in 2017 in 12- to 15-year-old stands. In fixed intervals along the entire length of stems will pro- addition, branch and root samples (10 to ≤ 50 mm diam- vide representative material, while for needles and eter over bark) were acquired from recently harvested branches, mass-weighted subsamples from throughout stands at nine sites located within New Zealand com- the crown will provide representative material for chem- mercial plantations as part of woody debris decay studies ical analysis. Tree biomass sampling procedures are spe- (Garrett et al. 2008, 2010, 2012). Finally, outer bark cifically designed to provide representative samples of (cork) from disc samples taken at fixed intervals individual biomass components, thus providing suitable along the entire stem length of 19 trees (stands aged subsamples for carbon analysis. A weighted average car- 22/23 years old) at Puruki Forest was separated from bon fraction has been derived for various species inner bark (phloem and phelloderm) using a chisel, (Thomas and Martin 2012); however, the application of which was only feasible from discs in the lower part a single carbon fraction for a species implies that parti- of the stem. This corky bark was bulked into a single tioning of components is fixed. This is not the case in sample per tree and labelled “outer bark”. The inner New Zealand’s intensively managed planted forests, bark and bark from upper discs that could not be where the disposition of components varies with site, separated from the inner bark was bulked by tree and stand age and the silvicultural regime (Madwick et al. labelled “inner bark”. One 10-year-old Douglas-fir 1977; Beets and Pollock 1987; Beets and Madgwick stand was sampled at Gowan Hill, Southland, which pro- 1988). An alternative approach is to apply carbon frac- vided needle, branch and stem wood and bark samples for tions to each biomass component separately. comparison purposes. The oven-dried (70 °C) samples Component-specific carbon fractions can be imple- were processed as follows. mented within the FCP as it provides annual estimates Woody biomass samples were chipped and then of the dry matter content of needles by age class, live ground until all the material passed through a 2-mm branches, dead branches, cones, stem wood, stem bark mesh sieve, while needle samples were ground until all and roots from time of planting to harvesting. the material passed through a 1-mm mesh sieve. To improve the accuracy of carbon stock estimates for Because the samples had been exposed to air for an in- planted forests in New Zealand, carbon data from radiata definite period of time, they had gained moisture. pine biomass studies across a range of sites and ages were Carbon (C) content of these samples was determined by summarised by component and stand age, so as to incorp- thermal combustion (Leco CNS-2000, LECO Corp., St orate suitable carbon fractions within the Forest Carbon Joseph, MI, USA). Carbon fractions (CFs) reported by Predictor. In this paper, component-specific carbon frac- the laboratory were based on moisture factors of sub- tions were tabulated for radiata pine along with limited samples dried for 24 h at a drying temperature of 104 °C. data for Douglas-fir grown in New Zealand, Also, an as- The moisture factors (s.e.) averaged 1.087 (0.0008) for sessment of the impact of the revised fractions on biomass stem wood, 1.096 (0.0008) for stem bark and 1.077 carbon stock estimates is provided. (0.0008) for needles. These moisture factors provide car- bon fractions at a drying temperature of 104 °C and Methods were, therefore, back-corrected to the moisture content Oven-dried (70 °C) stem wood, stem bark, branch, cone of biomass samples oven dried to constant weight at 70 ° and needle samples for carbon analysis were obtained C, the drying temperature used in New Zealand biomass from existing and new radiata pine and Douglas-fir bio- studies. Carbon fractions were back-corrected as follows: mass studies in New Zealand. Dead needles intercepted CF =CF × (100 − 1.045)/100 (following Bert and 70 104 by branches in the lower crown were collected separately Danjon 2006), where CF is the carbon fraction applied from live needles. Biomass studies in radiata pine stands to biomass data, CF is the carbon fraction reported by were undertaken in 5- and 15-year-old stands at the laboratory and 1.045 is the percentage reduction in Kinleith, 5-, 16- and 26-year-old stands at Tarawera, 5- moisture content of biomass samples oven dried to con- and 28-year-old stands at Woodhill and a 5-year-old stant weight at 70 °C and then re-dried to constant stand at Nelson. Carbon data from the 15- and weight at 104 °C. 16-year-old stands at Kinleith and Tarawera, respect- For radiata pine, data for each component were exam- ively, were published by Oliver et al. (2011). Biomass ined for variation with tree age. The carbon fraction in Beets and Garrett New Zealand Journal of Forestry Science (2018) 48:14 Page 3 of 8 stem bark was the only component to vary significantly Results as a function of stand age. The carbon fraction in stem Carbon fractions of radiata pine tree components bark was modelled as a function of age using the NLIN The carbon fractions of radiata pine tree components are procedure (Gaus-Newton method) in SAS Version 9.4 summarised in Table 1. The mean carbon fraction across −1 statistical analysis software (SAS Institute Inc. 2011). For sites averaged (standard error in parenthesis) 0.498 g C g dm −1 components other than stem bark, the overall mean (0.001) for stem wood, 0.501 g C g dm (0.004) for coarse −1 across sites was calculated by component. roots, 0.514 g C g dm (0.002) for live needles, 0.507 −1 −1 The impact of replacing the default carbon fraction gCg dm (0.002) for branches and 0.519 g C g dm (0.004) −1 (0.50 g C g dm) by the revised carbon fractions was for cones. Dead fallen needles from upper branches assessed by applying carbon fractions to stem wood, intercepted by branches in the lower crown averaged −1 stem bark, needle, branch and cone dry matter estimates 0.514 g C g dm (data not shown), which was the from a radiata pine chronosequence study (Madwick et same as the value obtained for live needles. For stem bark, −1 al. 1977; Webber and Madgwick 1983). the overall mean carbon fraction averaged 0.539 g C g dm Table 1 Mean carbon fraction of radiata pine biomass components, age of sample stand, number of stems/crowns/roots sampled (n) and study sites in New Zealand Site Stand age n (stem/crown/ Carbon fraction (± se) −1 (years) root) (g C g dm) Stem wood Stem bark Branches Needles Cones Roots Balmoral, SI 28 0/3/6 n/a n/a 0.510 n/a n/a 0.506 Burnham, SI 28 0/4/8 n/a n/a 0.521 n/a n/a 0.510 Crater Block, NI 13 12/12/0 0.497 0.546 n/a 0.526 n/a n/a Forest Creek, SI 14 12/12/0 0.500 0.549 n/a 0.515 n/a n/a Golden Downs, SI 5 120/240/0 0.500 0.508 0.515 0.507 n/a n/a 28 0/2/4 n/a n/a 0.495 n/a n/a 0.509 Kaingaroa, NI 12 12/12/0 0.497 0.545 n/a 0.509 n/a n/a 28 0/2/4 n/a n/a 0.493 n/a n/a 0.494 Kinleith, NI 5 120/240/0 0.499 0.518 0.507 0.501 n/a n/a 10 0/0/9 n/a n/a n/a n/a n/a 0.498 15 24/47/3 0.504 0.539 0.515 0.508 0.520 0.478 Lawrence, SI 14 12/12/0 0.496 0.557 n/a 0.514 n/a n/a Lochinver, NI 14 12/12/0 0.494 0.550 n/a 0.517 n/a n/a Mahia, NI 15 12/12/0 0.498 0.556 n/a 0.520 n/a n/a Rotoehu, NI 12 12/12/0 0.496 0.545 n/a 0.517 n/a n/a 28 0/1/6 n/a n/a 0.499 n/a n/a 0.493 Tarawera, NI 5 120/270/8 0.494 0.510 0.510 0.510 n/a 0.510 11 0/0/4 n/a n/a n/a n/a n/a 0.532 16 24/48/4 0.509 0.545 0.514 0.523 0.525 0.491 26 24/48/0 0.498 0.546 0.509 0.514 0.511 n/a 28 0/2/4 n/a n/a 0.501 n/a n/a 0.498 West Coast, SI 28 0/1/6 n/a n/a 0.504 n/a n/a 0.503 Woodhill, NI 5 120/120/0 0.495 0.509 0.507 0.514 n/a n/a 13 12/12/0 0.493 0.539 n/a 0.510 n/a n/a 28 36/1/4 0.498 0.554 0.503 n/a n/a 0.497 Mean 0.498 0.539 0.507 0.514 0.519 0.501 ± se 0.001 0.004 0.002 0.002 0.004 0.004 Carbon is expressed per unit dry matter (dm) oven dried at 70 °C Live needles 10 mm to ≤ 50 mm diameter over bark Beets and Garrett New Zealand Journal of Forestry Science (2018) 48:14 Page 4 of 8 (0.004); however, the mean carbon fraction increased with increases with age, until the bark layer becomes domi- −1 −1 age from 0.508 g C g dm at age 5 to 0.554 g C g dm at nated by cork. stand age 28 years (Fig. 1). No significant trends with age were evident for other components. Carbon fraction of Douglas-fir components −1 Means and ranges in component carbon fractions av- The mean and range in carbon fraction (g C g dm) of eraged across the eight G × E trial sites, and 12 geno- biomass components for one Douglas-fir stand in New types are summarised in Table 2. Carbon fractions Zealand are summarised in Table 4. The mean carbon −1 differed significantly between sites and among clones, al- fraction was lowest in stem wood (0.502 g C g dm), inter- though the differences are relatively small and impracti- mediate in needles and branches and highest in stem bark −1 cal to implement (Table 2). (0.534 g C g dm). These results for Douglas-fir are very The carbon fraction in stem bark of New Zealand-grown similar to those reported above for New Zealand-grown radiata pine follows an asymptotic relationship with age radiata pine. (Fig. 1)given by: Discussion CF ¼ 0:551 ðÞ 1  0:291  expðÞ −0:280  Age Various studies of conifers growing in countries other stembark than New Zealand show that carbon fractions can differ The model was fitted to a total of 16 stands from 5 to 28 appreciably among species and tree components years old at 11 sites, three of which (Woodhill, Kinleith, (Table 5). The New Zealand-grown radiata pine carbon Tarawera) were sampled at multiple ages (Table 1). The fractions reported here are based on wood and bark model has an R = 0.91 and root mean square error = 0.057. samples from 684 stems, 1125 crowns and 70 root Stem bark was the only tree component where the carbon systems from a total of 14 sites distributed throughout fraction varied significantly with stand age. The asymptote New Zealand. The samples were obtained from biomass- was reached by around stand age 12 years. specific studies and are considered representative of each tree component. These data show similar trends to Carbon fraction of radiata pine bark components radiata pine in Spain (Table 5), with the C fraction in the The carbon fraction of the inner and outer bark of 22/ stem bark being the highest, needles and branches inter- 23-year-old trees at Puruki Forest is summarised in mediate and stem wood lowest. For most species, heart- Table 3. The carbon fraction of the outer bark exceeded wood has a higher carbon fraction than sapwood, and that of the inner bark by approximately 14%. The bark branches, roots and needles tend to be intermediate be- of very young trees is equivalent to the inner bark, while tween stem sapwood and stem bark (Table 5). Explana- the outer bark becomes evident as trees increase in age. tions offered for differences in carbon fractions are The results for the inner and outer bark are consistent summarised in reviews by Matthews (1993), Bert and with the finding that the carbon fraction of bark initially Danjon (2006) and Thomas and Martin (2012). Species Fig. 1 Carbon fraction of stem bark as a function of stand age in New Zealand radiata pine biomass studies. Three sites were sampled at multiple ages: Woodhill (triangles), Kinleith (dots) and Tarawera (crosses). The remaining eight sites were sampled only at one age (circles). The line shows the fitted exponential function: CF = 0.551 × (1 − 0.291 × exp(− 0.280 × Age)) stembark Beets and Garrett New Zealand Journal of Forestry Science (2018) 48:14 Page 5 of 8 Table 2 Carbon fraction—summary of G × E trials sampled at Table 4 Carbon fractions of Douglas-fir biomass components of approximately mid-rotation ages eight trees from a 10-year-old stand at Southland Component Mean Site Genotype Biomass Carbon fraction (± se) −1 component (g C g dm) Min Max Min Max Mean Minimum Maximum Stem wood 0.496 0.493 0.500 0.494 0.500 Needles 0.518 (0.003) 0.506 0.530 Stem bark 0.548 0.538 0.557 0.538 0.564 Live branches 0.513 (0.003) 0.503 0.523 Needles 0.516 0.509 0.526 0.512 0.520 Dead branches 0.521 (0.003) 0.508 0.529 Carbon is expressed per unit dry matter (dm) oven dried at 70 °C Stem wood 0.502 (0.001) 0.496 0.506 Stem bark 0.534 (0.003) 0.520 0.543 and component-related differences in carbon fractions Carbon is expressed per unit dry matter (dm) at 70 °C reflect the relative proportions of high versus low carbon fraction compounds in tissues during, for example, heartwood formation and cell suberisation in bark. The bark carbon fraction increases with tree age in New carbon content of cellulose (44.4%), lignin (66.7%) and Zealand radiata pine studies. hemi-celluloses (44.4–45.5%) are reasonably well estab- The dry mass of biomass samples and hence the car- lished (Matthews 1993). Radiata pine has produced very bon content depend on the drying temperature and hu- little heartwood by age 20–28 years, the ages at which it midity of the drying oven (Matthews 2010). To minimise is typically harvested in New Zealand, and the carbon bias, carbon fractions reported by laboratories need to fraction of stem wood varies little with tree age. Radiata be corrected to the moisture content of oven-dry bio- pine stem wood was previously estimated to be com- mass samples. In most studies, biomass samples are prised of lignin 26%, cellulose 42%, galactoglucomannan oven dried in forced ventilation ovens at 65–75 °C to 15%, arabinoglucuronoxylan 10%, arabinogalactan 4%, constant weight or after a defined period of time in the utonic acids, etc. 3% (Uprichard and Lloyd 1980), which oven. To minimise carbon and nitrogen volatilisation gives a moisture-free C fraction of 0.504, based on losses that occur at high temperatures (Samuelsson et al. methods in Matthews (1993). This value compares 2006), comparatively low drying temperatures are used −1 favourably to the value of 0.498 g C g dm (Table 1) ob- when drying biomass samples to constant weight, which tained directly from the measured stem wood carbon can take up to several weeks for large samples. Losi et fraction in the current study. al. (2003), for example, noted that charring occurred The carbon fraction in radiata pine stem bark in- when attempting to dry biomass samples to constant creased with tree age in New Zealand biomass studies. weight at a temperature of 105 °C. Results of chemical Other studies have shown that the carbon fraction of analysis conducted by laboratories are based on very stem bark is generally highest at the base of the stem small samples which are dried quickly at comparatively where the proportion of mature bark is greatest (De Aza high drying temperatures. For this study, the approach et al. 2011). More particularly, it has been shown that used by Bert and Danjon (2006) to correct the carbon the outer bark has a higher carbon fraction than inner data reported by various laboratories was followed. They bark, which was ascribed to higher levels of extractives, noted that the moisture factor applied in the analytical lignin, tannins and suberin (Bert and Danjon 2006). The laboratory was based on subsamples dried at 103 °C, outer bark has a significantly higher carbon fraction than whereas the biomass samples had been dried to constant the inner bark in the current study which was based on weight at 65 °C, which resulted in a moisture content 19 radiata pine stems, presumably owing to the higher about 2% lower than that in their biomass samples. Mat- content of lignin and suberin in the outer bark. The pro- thews (2010) found approximately 2.5% of additional portion of the outer bark in the lower part of the stem moisture in pine samples dried at 65 °C compared to increases with tree age, which explains why the stem when samples were dried at 103 °C in an air-conditioned laboratory at 20 °C and 40% relative humidity. Likewise, the moisture factor of the bulked radiata pine biomass Table 3 Carbon fraction summary of inner and outer stem bark samples in the current study was 1.01045. These samples in 22/23-year-old radiata pine trees at Puruki Forest had been dried to constant weight at 70 °C and then fur- Component Carbon fraction ther dried to constant weight at 104 °C. −1 (g C g dm) Based on the data obtained here, the values for carbon n Mean Minimum Maximum −1 fractions applied in the FCP should be 0.514 g C g dm for −1 −1 Stem bark—inner 19 0.503 0.472 0.558 needles, 0.507 g C g dm for branches, 0.519 g C g dm for −1 −1 Stem bark—outer 19 0.575 0.549 0.628 cones, 0.498 g C g dm for stem wood and 0.501 g C g dm Carbon is expressed per unit dry matter (dm) oven dried at 70 °C for roots. For stem bark, the carbon fraction (the mean Beets and Garrett New Zealand Journal of Forestry Science (2018) 48:14 Page 6 of 8 Table 5 Component carbon fraction, number of sample trees per stand (n), country of study and source of data for various Pinus species Species Component Age (years) Number Carbon Fraction Biomass Country Source −1 (g C g dm) samples dried (°C) P. nigra Stem sapwood 27–39 112 0.465 75 Spain De Aza et al. 2011 Stem bark 106 0.499 P. pinaster Stem heartwood 29–50 87 0.495 Stem sapwood 156 0.458 Stem bark 137 0.501 P. sylvestris Stem heartwood 36–53 76 0.523 Stem sapwood 166 0.453 Stem bark 166 0.485 P. radiata Stem wood Unknown 54 0.504 65 Spain Balboa-Murias et al. 2006 Stem bark 54 0.541 Large branches 54 0.513 Small branches 54 0.525 Twigs 54 0.532 Needles 54 0.527 P. pinaster Stem wood 125 0.471 Stem bark Unknown 125 0.508 Large branches 125 0.479 Small branches 125 0.505 Twigs 125 0.497 Needles 125 0.497 P. pinaster Stem heartwood 50 4 0.544 65 France Bert and Danjon 2006 Stem sapwood 4 0.523 Stem inner bark 4 0.510 Stem outer bark 4 0.559 Dead branch 4 0.534 Live branch 4 0.535 Cones 4 0.534 Needles 4 0.536 Taproot wood 4 0.517 Taproot bark 4 0.549 Coarse root wood 4 0.513 Coarse root bark 4 0.544 Tree total 0.532 Bert and Danjon (2006) reported carbon fractions (the analytical laboratory used 103 °C) corrected to 65 °C, which was the temperature used in their biomass dry matter determinations. Other reported values that are assumed were as provided by the analytical laboratory used −1 −1 −1 value is 0.534 g C g dm) increases significantly with stand gCg dm by age 9 years to a maximum of 0.55 g C g dm age, and, therefore, an age-adjusted carbon fraction should by stand age 17 years and older. The revised carbon frac- be applied to this component for stands aged 5 years or tions are applied in the FCP as shown in Table 6 for actual older. For stand less than 5-years-old, the CF = 0.503 (the biomass data. value for inner bark). Consequently, the mean carbon frac- Compared to the use of the default carbon fraction −1 tion in radiata pine bark increases rapidly from approxi- (0.50 g C g dm), the revised carbon fractions increase the −1 mately 0.50 g C g dm at stand age 4 years to 0.54 amount of aboveground live (AGL) carbon stored in Beets and Garrett New Zealand Journal of Forestry Science (2018) 48:14 Page 7 of 8 Table 6 Carbon stock (t/ha) and sequestration (t/ha/year) estimates calculated by applying carbon fractions to radiata pine stand dry −1 matter estimates in Madwick et al. (1977) and Webber and Madgwick (1983): (a) using a default carbon fraction of 0.50 g C g dm and (b) using tree component-specific carbon fractions for radiata pine in New Zealand −1 a Carbon stock estimates based on a carbon fraction of 0.50 g C g dm Stand age (years) Stem Stem Branches Needles Cones AGL AGL C wood bark C seq 2 0.09 0.03 0.06 0.18 0.00 0.36 0.36 4 3.60 0.64 3.28 3.58 0.00 11.1 5.37 6 11.3 1.46 7.49 5.78 0.00 26.0 7.48 8 23.0 2.63 11.9 2.96 0.05 40.5 7.24 9 14.5 1.80 2.77 1.70 0.30 21.1 10 24.8 2.39 5.69 2.93 0.11 35.9 14.8 17 107.4 10.9 11.0 5.41 2.51 137.3 14.5 22 121.8 13.7 13.7 4.64 1.61 155.4 3.61 29 168.7 16.2 12.8 4.10 4.65 206.4 7.29 Residues following harvesting of stem 25.3 2.4 12.8 4.10 4.65 49.3 wood plus bark Residues following harvesting of stem 25.3 16.2 12.8 4.10 4.65 63.0 wood only b Carbon stock estimates based on the revised component-specific carbon fractions for radiata pine Stand age (years) Stem Stem Branches Needles Cones AGL AGL C C sequestration C stock wood bark C seq change (%) change (%) 2 0.08 0.03 0.06 0.19 0.00 0.36 0.36 1.6 1.6 4 3.58 0.64 3.33 3.68 0.00 11.2 5.43 1.2 1.2 6 11.3 1.5 7.6 5.94 0.00 26.3 7.55 1.0 1.1 8 22.9 2.8 12.1 3.04 0.05 40.9 7.27 0.4 0.8 9 14.5 1.9 2.8 1.75 0.31 21.3 0.8 10 24.7 2.6 5.8 3.01 0.11 36.2 14.9 0.6 0.7 17 107.0 12.0 11.2 5.56 2.61 138.3 14.6 0.8 0.8 22 121.3 15.0 13.9 4.76 1.67 156.6 3.66 1.2 0.8 29 168.0 17.8 13.0 4.21 4.83 207.8 7.31 0.3 0.7 Residues following harvesting of stem 25.2 2.7 13.0 4.21 4.83 49.9 1.3 wood plus bark Residues following harvesting of stem 25.2 17.8 13.0 4.21 4.83 65.0 3.2 wood only The resulting percentage changes in aboveground live (AGL) C stocks and C sequestration are shown (in part b) by stand age, as are the expected effects of harvesting the 29-year-old stand (Webber and Madgwick 1983), assuming stem wood plus bark extraction (85%) or assuming stem wood only extraction (85%), on carbon stocks of residues and stock changes (%) C sequestration of the 9-year-old stand was not calculated because this stand had been thinned, which explains why the AGL C stock decreased relative to the AGL C stock at age 8 years mature stands by approximately 1%. The amount of car- bark) carbon fractions for radiata pine are applicable to bon retained on site as harvest residues during conven- other coniferous species in New Zealand’s planted forest tional stem-harvesting operations, which typically remove estate. 85% of the stem wood plus bark, increased by 1.3%, unless harvested stems were entirely debarked at the stump in Conclusions which case the amount of carbon retained on site as har- Robust carbon fractions have been developed for biomass vest residues increased by 3.2%, when using the revised in- components of radiata pine in New Zealand. Analysis −1 stead of the default carbon fractions (Table 6). shows that the default carbon fraction (0.50 g C g dm) Component carbon fractions are similar in Douglas-fir used in the FCP model underestimates carbon stocks in and radiata pine biomass components. It was, therefore, New Zealand’s planted forests by approximately 1%. Ap- assumed that the component- and age-specific (for stem plying the revised carbon fractions derived above from Beets and Garrett New Zealand Journal of Forestry Science (2018) 48:14 Page 8 of 8 specific biomass components of commonly planted spe- Beets, P. N., & Madgwick, H. A. I. (1988). Above-ground dry matter and nutrient content of Pinus radiata as affected by lupin, fertiliser, thinning, and stand cies in New Zealand in the FCP model will improve the age. New Zealand Journal of Forestry Science, 18,43–64. accuracy of carbon stock estimates for planted forest. Beets, P. N., & Pollock, D. S. (1987). Accumulation and partitioning of dry matter Moreover, operational information on in-forest debarking in Pinus radiata as related to stand age and thinning. New Zealand Journal of Forestry Science, 17, 246–271. activities that provide estimates of the percentage of stem Bert, D., & Danjon, F. (2006). Carbon concentration variations in the roots, stem bark mechanically removed during harvesting operations and crown of mature Pinus pinaster (Ait.). Forest Ecology and Management, will further improve estimates of removals associated with 222, 279–295. De Aza, C. H., Turrion, M. B., Pando, V., & Bravo, F. (2011). Carbon in heartwood, harvesting, and additional work is required to achieve this. sapwood and bark along the stem profile in three Mediterranean Pinus species. Annals of Forest Science, 68, 1067–1076. Abbreviations Garrett, L. G., Kimberley, M. O., Oliver, G. R., Pearce, S. H., & Beets, P. N. (2012). AGL: Aboveground live biomass; C: Carbon; CF: Carbon fraction; Decomposition of coarse woody roots and branches in managed Pinus CF : Carbon of samples dried to constant weight at 104 °C; CF : Carbon 104 70 radiata plantations in New Zealand – a time series approach. Forest Ecology fraction of samples dried to constant weight at 70 °C; FCP: Forest Carbon and Management, 269, 116–123. Predictor; IPCC: Intergovernmental Panel on Climate Change; NI: North Island Garrett, L. G., Kimberley, M. O., Oliver, G. R., Pearce, S. H., & Paul, T. S. H. (2010). of New Zealand; SI: South Island of New Zealand; UNFCCC: United Nations Decomposition of woody debris in managed Pinus radiata plantations in Framework Convention on Climate Change New Zealand. Forest Ecology and Management, 260, 1389–1398. Garrett, L. G., Oliver, G. R., Pearce, S. H., & Davis, M. R. (2008). Decomposition of Acknowledgements Pinus radiata coarse woody debris in New Zealand. Forest Ecology and Funding to facilitate the preparation of this manuscript was provided by the Management, 255, 3839–3384. New Zealand Ministry for the Environment under Head Agreement 20059, IPCC. (2006). 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Statement of Work 21078. Tree component biomass samples included in this Prepared by the National Greenhouse Gas Inventories Programme and H. S. analysis were acquired from biomass studies that had been undertaken Eggleston, L. Buendia, K. Miwa, T. Ngara, & K. Tanabe (Eds.). Kanagawa: using funding from a range of sources, including Growing Confidence in Institute for Global Environmental Strategies. Forestry’s Future GCFF research programme funded by MBIE, SLMACC Losi, C. J., Siccama, T. G., Condit, R., & Morales, J. E. (2003). Analysis of alternative projects funded by Ministry of Primary Industries, and an Underpinning methods for estimating carbon stock in young tropical plantations. Forest Research Contract funded by Ministry for the Environment. The authors Ecology and Management, 184, 355–368. acknowledge the contribution of Mark Kimberley for statistical assistance. Madwick, H. A. I., Jackson, D. S., & Knight, P. J. (1977). Above-ground dry matter, energy, and nutrient content of trees in an age series of Pinus radiata plantations. New Zealand Journal of Forestry Science, 7, 445–468. Funding Matthews, G. (1993). The carbon content of trees. [Technical Paper 4]. Edinburgh: Funding to facilitate data analysis and publication of this manuscript was Forestry Commission. provided by the Ministry for the Environment under Head Agreement Matthews, S. (2010). Effect of drying temperature on fuel moisture content Reference 20059, Statement of Work 21078. measurements. International Journal of Wildland Fire, 19, 800–802. NEFD. (2016). National Exotic Forest Description as at 1 April 2016. Wellington: Availability of data and materials Ministry for Primary Industries. Please contact author for data requests. Oliver, G. R., Beets, P. N., Pearce, S. H., Graham, J. D., & Garrett, L. G. (2011). Carbon accumulation in two Pinus radiata stands in the North Island of New Authors’ contributions Zealand. New Zealand Journal of Forestry Science, 41,71–86. PNB developed the concept for this manuscript and was the primary author. Samuelsson, R., Nilsson, C., & Burvall, J. (2006). Sampling and GC-MS as a method LGG contributed towards data collation from decay studies and contributed for analysis of volatile organic compounds (VOC) emitted during oven drying to writing the paper. Both authors have read and approved the final version of biomass materials. Biomass and Bioenergy, 30, 923–928. of the manuscript. SAS Institute Inc. (2011). Base SAS® 9.3 Procedures Guide. Cary, NC: SAS Institute Inc. Thomas, S. C., & Martin, A. R. (2012). Carbon content of tree tissues: a synthesis. Ethics approval and consent to participate Forests, 3, 332–352. Not applicable Uprichard, J. M., & Lloyd, J. A. (1980). Influence of tree age on the chemical composition of radiata pine. New Zealand Journal of Forestry Science, 10, 551–557. Webber, B., & Madgwick, H. A. I. (1983). Biomass and nutrient content of a 29-year- Consent for publication old Pinus radiata stand. New Zealand Journal of Forestry Science, 7,445–468. Not applicable Competing interests The authors declare that they have no competing interests. Publisher’sNote Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Received: 21 February 2018 Accepted: 13 November 2018 References Balboa-Murias, M. A., Rodriguez-Soalleiro, R., Merino, A., & Alvarez-Gonzalez, J. G. (2006). Temporal variations and distribution of carbon stocks in aboveground biomass of radiata pine and maritime pine pure stands under different silvicultural alternatives. Forest Ecology and Management, 237,29–38. Beets, P. N., Kimberley, M. O., Paul, T. S. H., & Garrett, L. G. (2011). Forest carbon monitoring system – forest carbon model validation study for Pinus radiata. New Zealand Journal of Forestry Science, 41, 177–189.

Journal

New Zealand Journal of Forestry ScienceSpringer Journals

Published: Dec 7, 2018

References