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TECHNICAL REPORT
GREENHOUSE ALLIES PROJECT

Measurement of carbon sequestration
in small non-industrial forest plantations.
(continued)

2 Harvests
The purpose of these harvests are several:

(i) to allow allometric equations to be developed for each species to provide for more accurate (?) estimations of their biomass than using the conversion figures in the Vegetation Sinks Workbook; and
(ii) to compare the harvest indices and root:shoot ratios with those presented in the Vegetation Sinks Workbook.

2.1 Methods used
Six species were sampled, two in each of the regions. The species were chosen using the following criteria: (i) general popularity in the regions; and (ii) availability. Sampling consisted of a measurement of the standing trees in a plantation and then selection of a range of representative diameter classes for harvest. A maximum of six trees were sampled at each site of each species (one species per site). As outlined in the Scope report the protocol to be followed is as below.

Destructive sampling is undertaken on seven of the fully measured trees across the range of sizes as follows:

(i) tree is felled at 0.5m;
(ii) total height and free bole height are measured;
(iii) wood core samples are taken at 10%, 20%, 30%, 40%, 50%, and 70% of total height and at 0.5, 0.7, 0.9, 1.1, 1.3, and 1.5 metres
(iv) the stem is cut every 10th of total height and diameter and bark thickness is measured, including the diameter at ground level;
(v) foliage and branches are separated and weighed; and
(vi) subsamples of foliage and branches are dried in an oven.

If time and funds permit there may also be root sampling by excavation.

2.2 Results
The Harvest Indices and root:shoot ratios for each of the species harvested varied somewhat from the values used in the Vegetation Sinks Workbook (Table 2).

Table 2: Harvest indices and root:shoot ratios for the six species harvested. The Vegetation Sinks Workbook (VSW) recommends a Harvest Index of 0.68 to be used for Pinus radiata and 0.7 for eucalypts. There are no figures for rainforest species. The VSW recommends a root:shoot ratio to be assumed to be 0.20 for all species. Means and standard deviations are shown.
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The partitioning of biomass into the component parts of the plant can be used as an above-ground indicator of the variation between species (Figures 1 to 3).

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Figure 1: Biomass partitioning for the two species harvested in the Northern Rivers region: (a) Eucalyptus microcorys at the Moody property, and (b) Grevillea robusta at Rocky Creek Dam (Rous County Council).
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Figure 2: Biomass partitioning for the two species harvested in the Mid-North Coast region: (a) E. grandis at the Morton property, and (b) E. saligna at the Robinson property.

The allometric relationships developed from encouraging, with a good relationship between biomass and diameter at breast height above these are as follows:

Northern Rivers
Grevillea robusta above-ground biomass = 0.035 dbhob2.739 r2 = 0.998 total biomass = 0.079 dbhob2.515 r2 = 0.97
Eucalyptus microcorys above-ground biomass = 0.238 dbhob2.146 r2 = 0.96 total biomass = 0.246 dbhob2.225 r2 = 0.95

Mid-north Coast
E. grandis above-ground biomass = 0.313 dbhob2.107 r2 = 0.986 total biomass = 0.203 dbhob2.197 r2 = 0.984
E. saligna above-ground biomass = 0.167 dbhob2.205 r2 = 0.986 total biomass = 0.238dbhob2.181 r2 = 0.996

New England
E. nitens above-ground biomass = 0.281 dbhob1.985 r2 = 0.982 total biomass = 0.419 dbhob1.849 r2 = 0.992
Pinus radiata above-ground biomass = 0.186 dbhob2.112 r2 = 0.97 total biomass = 0.204 dbhob2.15 r2 = 0.98

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Figure 4: The relationship between diameter at breast height (dbhob) and above-ground and total biomass for trees sampled at properties in each of three regions of northern New South Wales. Northern Rivers: (a) Eucalyptus microcorys, (b) Grevillea robusta; Mid-north Coast: (a) E. grandis and (b) E. saligna; and New England: (a) E. nitens and (b) Pinus radiata.

The difference in these relationships between the species appear not to be very significant at this young age, however, for when all the data points are amalgamated disregarding species, the resulting relationship is almost as strong as for the individuals. As these relationships are for power curves, this closeness will possibly become less the larger the diameter as the species grow (Figure 5). There are some arguments which support the cross-species, and indeed cross-genera similarity in growth allometrics, with variation being simply ‘noise’ within major life-form types (e.g. woody versus non-woody) and major age classes (Niklas 1994, p. 183-4).

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Figure 5:over bark (dbhob) when all the non-coniferous species are amalgamated, and with the coniferous species.

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