Indicative Forest Sequestration Tables
Methods
Used regimes and species
MAF requested the modelling of forest biomass and carbon tables for various tree species and different management regimes and in the case of Radiata pine at specified levels of site productivity represented by specified values of 300Index. For other species medium/average site productivity was assumed. The species and regimes modelled are shown in Table 1.
Table 1: Species and associated regimes for modelling afforestation carbon stock tables
| Species | Site Quality300Index | Management regime | |||||
|---|---|---|---|---|---|---|---|
| Rotation length (years) | Planting (sph) | Pruning | comments | Thinning | comments | ||
| Radiata Pine | three classes 20/25/31 |
50 y | 1000 | 375 sph to 2.5m | Age 4-5 | To 350 sph | Thinned to waste at age 7-8 |
| 350 sph to 4.5m | Age 5-6 | ||||||
| 325 sph to 6.5m | Age 7-8 | ||||||
| Radiata Pine | 20/25/31 | 50 y | 1000 | None | To 500 sph | Thinned to waste at age 10 | |
| Radiata Pine(2nd rotation) | Average site class | 1st Rot: 28 y 2nd Rot: 50 y |
1000 | None | To 500 sph | Thinned to waste at age 10 | |
| Douglas-fir | Average site class | 80 y | 1400 | None | to 500 sph | Thinned to waste at age 15 | |
| Redwood | Average site class | 60 y | 900 | 400 sph to 2.5m | Age 4 | To 300 sph | Thinned to waste at age 11 |
| 350 sph to 4.5m | Age 6 | ||||||
| 300 sph to 6m | Age 9 | ||||||
| E. fastigata | SI of 25** | 40 y | 800 | None | None | ||
| Cypresses | Averaged | 35 y | 1000 | None | To 500 sph | Thinned to waste at age 10 | |
| Totara | Medium site | 80 y | 1000 | None | None | ||
| Kauri | Medium site | 80 y | 1000 | None | None | ||
* assumed mortality is 95% in the first year
** Site index as the height of the dominant trees at age 15
*** Averaged yield table based on five runs for average stands of both C. macrocarpa and C. lusitanica
Index300 and Site Index used
The modelling of the pruned and unpruned Radiata pine regimes was based on three site qualities, reflected by the 300 Indices of 20, 25 and 31.
Based on these values we calculated site index based on the relationship between 300Index and site index:
SI=0.517*I300+16.968 R2=0.5164
For the unpruned – two rotation Radiata pine regime we used the average national values of a 300 Index of 25 and a site index of 29.9.
With these values of site index and 300Index we modelled stem total volume inside bark and stand carbon stocks by stand age class for radiata pine.
Models used
Volume and carbon yield tables were developed using a combination of various stem volume growth models and C_Change (Beets et al 1999).
The 300 Index Growth model (Kimberley et al 2005) was used for Radiata pine, using a new national volume equation (Kimberley and Beets 2007), in combination with the biomass partitioning model C_Change.
For Douglas-fir, the 500 Index Growth model (Knowles 2005) as implemented in the Douglas-fir Calculator (MacLaren and Knowles 2005), was used in combination with C_change.
For Eucalyptus fastigata the Eucalyptus fastigata Growth model (van der Colff, Kimberley 2005) was used in combination with C_Change.
For redwood the redwood model (Kimberley and Dean 2006 unpublished) was used in combination with C_Change.
For planted totara and kauri we used recently developed yield tables, based on data from Bergin and Kimberley (2003) and Pardy et al (1992), in combination with C_Change.
For cypresses the preliminary cypress growth model (Berrill, 2004) was used in combination with C_Change.
Wood densities
We estimated wood densities for Radiata pine based on site quality. We used C/N ratios depending on site quality to estimate wood density and kept the temperature for all three site qualities constant (national average based on distribution of plantation forests is 11°C). The used C/N ratios are:
| Site quality (300Index) | C/N ratio used for Wood density |
|---|---|
| 20 | 30 |
| 25 | 23 |
| 31 | 16 |
The calculated outerwood density values were used to predict density for each growing year (Beets et al 2007).
Wood density for Douglas-fir was taken from the Douglas-fir calculator. Density was input by stand age class into the C_Change model.
Wood density for redwood, E. fastigata, cypress, totara and kauri were taken from various sources and in some instances assumed to be constant over the live of the tree.
The wood density of redwood was assumed to be constant over the development of the stand ( 332 kg/m3). For totara we assumed a constant tree density of 373 kg/m3 and for kauri 404 kg/m3. The latter based on an unpublished study from Taranaki.
Wood density (whole tree basic density) data for Eucalyptus fastigata was taken from McKinley et al 2000 for available ages and then interpolated for each year.
For cypress we assumed a constant whole tree density of 420 kg/m2 based on McKinley et al 2000.
Further specifications for Douglas-fir and other species
The Douglas-fir calculator was used to produce a national stem volume yield table. However ages less than 7 years old are not provided by this program. To estimate appropriate volumes at ages younger than 7 years we used the following formulae based on Kimberley & Beets (2007 in press)
AgeY = reference age
AgeX = current age
The national yield table for Douglas-fir were based on:
• a site index of 31.3 m
• a 500 Index of 18.4 m3/ha/year
• a latitude of 40 degrees
representing an average site.
For redwood the used average Site Index was 37 (MTH at age 40yrs). For Eucalyptus fastigata a site index of 25 was used, representative for an average site. The planted totara yield table is based on data from Bergin and Kimberley 2003. The planted kauri yield table is based on Pardy et al 1992. For these yield tables we used the average productivity of all planted stands with the mentioned regime (planted at 1000 stems per hectare, no thinning nor pruning) described in Pardy et al (1992) and Bergin and Kimberley (2003).
For cypress we averaged five runs of the preliminary cypress growth model (Berrill 2004) covering average stands for both species (C. macrocarpa and C. lusitanica) and in both South Island and North Island. A North Island high quality site for C. lusitanica was also included. The model runs showed higher productivity from C.macrocarpa compared to C. lusitanica. The higher productivity may be an artefact of the higher number of growth plots in the model especially in the South Island.
2nd Rotation Radiata pine
Young second rotation stands show higher carbon stocks then first rotation stands (afforestation), because dead woody litter and fine woody litter residues are carried over from the previous rotation. For one average Radiata pine regime we modelled the residues from the previous rotation, assuming the same thinning and pruning regimes were applied in both rotations, and assuming that the first rotation stand was clearfelled at ages 28. Furthermore an extraction of 85% of the stem volume during the clearfelling was assumed.
Scaling factor
A fixed scaling factor was derived from the average actual clearfell yield for Radiata pine, reported in the 2006 NEFD report. The average recovered volume at 1st April 2006 was 486 m3/ha at age 28.2 years. Assuming a mean recovery of 85%, this results in 486/0.85 = 572 m3/ha of total stem volume.
The comparison of this total stem volume at age 28 (572 m3/ha) with the modelled weighted average volume of 781 m3/ha (weighted by area for pruned and unpruned regimes in each region) gives a scaling factor of 26.8% (or 0.732). This factor was used to scale the modelled volume yield tables for radiata pine as well as Douglas-fir, redwood, cypress, Eucalyptus fastigata, kauri and totara - because insufficient data exists from the NEFD regarding species other than Radiata pine.
As this scaling factor is based on the average actual clearfell yield in 2006 i.e. from the clearfelling of pre-1990 stands, it may be conservative for post-1989 stands that may in general have higher yields.
Contact for Enquiries
Sustainable Land Management and Climate Change
MAF
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PO Box 2526, Wellington
Tel: 0800 CLIMATE (254 628)
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