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Determining Biomass in Residues Following Harvest in Pinus radiata Forests in New South Wales RIRDC Publication No. 11/177

RIRDC

Innovation for rural Australia

Determining Biomass in Residues Following Harvest in Pinus radiata Forests in New South Wales by Fabiano Ximenes1, Jorge Ramos1, Dr. Huiquan Bi1, Nick Cameron2, Dr. Bhupinder Pal Singh1, and Mirella Blasi1 1

NSW DPI, 2Forests NSW

April 2012 RIRDC Publication No. 11/177 RIRDC Project No. PRJ-005725

© 2012 Rural Industries Research and Development Corporation. All rights reserved.

ISBN 978-1-74254-354-3 ISSN 1440-6845 Determining Biomass in Residues Following Harvest in Pinus radiata Forests in New South Wales Publication No. 11/177 Project No. PRJ-5725 The information contained in this publication is intended for general use to assist public knowledge and discussion and to help improve the development of sustainable regions. You must not rely on any information contained in this publication without taking specialist advice relevant to your particular circumstances. While reasonable care has been taken in preparing this publication to ensure that information is true and correct, the Commonwealth of Australia gives no assurance as to the accuracy of any information in this publication. The Commonwealth of Australia, the Rural Industries Research and Development Corporation (RIRDC), the authors or contributors expressly disclaim, to the maximum extent permitted by law, all responsibility and liability to any person, arising directly or indirectly from any act or omission, or for any consequences of any such act or omission, made in reliance on the contents of this publication, whether or not caused by any negligence on the part of the Commonwealth of Australia, RIRDC, the authors or contributors. The Commonwealth of Australia does not necessarily endorse the views in this publication. This publication is copyright. Apart from any use as permitted under the Copyright Act 1968, all other rights are reserved. However, wide dissemination is encouraged. Requests and inquiries concerning reproduction and rights should be addressed to the RIRDC Publications Manager on phone 02 6271 4165. Researcher Contact Details Fabiano Ximenes PO BOX 100 Beecroft NSW 2119 Phone: 0458 760 812 Fax: 02 9871 6941 Email: [email protected]

In submitting this report, the researcher has agreed to RIRDC publishing this material in its edited form. RIRDC Contact Details Rural Industries Research and Development Corporation Level 2, 15 National Circuit BARTON ACT 2600 PO Box 4776 KINGSTON ACT 2604 Phone: Fax: Email: Web:

02 6271 4100 02 6271 4199 [email protected]. http://www.rirdc.gov.au

Electronically published by RIRDC in April 2012 Print-on-demand by Union Offset Printing, Canberra at www.rirdc.gov.au or phone 1300 634 313

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Foreword Australia’s response to climate change opens new areas of opportunity for improved use of production forests and the development of new bioenergy crops. Public and private plantations contain significant volumes of biomass that must be managed on site or removed in order to allow for re-establishment; to reduce fire risk; and/or to improve forest health. Alternatively, at least some of this material could be utilised in a sustainable manner to contribute to national and state targets for cleaner energy production and reduce costs of plantation reestablishment. The very significant volumes of biomass which are currently left on site after harvesting result in high site preparation and reestablishment costs. Utilisation for heat, electricity or liquid fuel production could partially, or completely, offset these costs. In order to develop a market for biomass there is a need to establish available volumes that could be removed sustainably, biomass harvesting costs and potential savings that could be generated for plantation establishment. This research, through pilot projects in the Macquarie region of NSW, aimed to determine quantities of the different biomass fractions in the residues, and a preliminary cost benefit analyses from extracting that resource. The main focus was on underutilised material from softwood plantations for which commercial values are low and markets are currently small or nonexistent. Some biomass must be retained to ensure appropriate nutrient levels and minimise soil compaction and erosion. This will vary for soil type and site. Key findings of this study include: •

Total above-ground biomass varies considerably according to site quality and silvicultural treatment;



The predicted total above-ground stand biomass (based on pre-harvest measurements and biomass equations) varied between 210 and 566 tons/ha among the forty sample plots;



The actual measured total above ground stand biomass varied between 200 and 507 tons/ha among the eight sites;



Residual biomass accounted for between 13 – 25% of the total above ground biomass;



Waste logs and branches (> 80 mm diameter) combined accounted for 35% of the total residual biomass;



There were no clear differences between the relative proportions of residual biomass on thinned sites and unthinned sites;



Less than 40% of the study sites carried sufficient biomass to be obvious candidates for a stand-alone biomass harvesting operation;



Site impacts and production costs can be reduced where biomass is extracted with other products through an integrated operation, also avoiding the minimum yield thresholds that apply to stand alone operations;



Removal of available volumes of biomass does not seem to be cost-effective for any of the sites studied under current biomass pricing and renewable energy policies, and current extraction systems. The financial costs of biomass production currently outweigh the financial benefits by $21.31/green metric tonne;

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Removal of residues off-site has a lower greenhouse footprint than retention of residues on site and/or burning on site;



Removal of waste logs and large branches off-site does not lead to significant immediate nutrient losses.

The results of this project suggest that there is potential for removal of additional biomass from the Macquarie region pine forests. The results also clearly suggest that there will be a high degree of variability in the volumes and types of residues generated, according to silvicultural status and biomass productivity of the site. Removal of biomass off-site for energy generation or fibre production also leads to the most favourable greenhouse outcome for the forest. Under current market values for bioenergy production and considering the extraction systems included in the cost-benefit analysis, it is currently uneconomical to remove the additional biomass from the forest. However, should demand for bioenergy and biofuels grow into the future as expected, and should more economical ways of extracting the biomass be developed, it may become economically viable to do so. This project was supported by funding from the Australian Government Department of Agriculture, Fisheries and Forestry under its Forest Industries Climate Change Research Fund program, and also from RIRDC Core Funds which are provided by the Australian Government. This report is an addition to RIRDC’s diverse range of over 2000 research publications and it forms part of our Bioenergy, Bioproducts and Energy R&D program, which aims to meet Australia’s research and development needs for the development of sustainable and profitable bioenergy and bioproducts industries. Most of RIRDC’s publications are available for viewing, free downloading or purchasing online at www.rirdc.gov.au. Purchases can also be made by phoning 1300 634 313.

Craig Burns Managing Director Rural Industries Research and Development Corporation

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Acknowledgments Support provided by Forests NSW Macquarie Region Office, in particular Gavin Jeffries (Regional Manager), Mike Freeman (Timber Merchandising Manager), William Shearman (Planning Manager) and Field Workers is gratefully acknowledged.

v

Contents Foreword ................................................................................................................................................ iii Acknowledgments ................................................................................................................................... v 1. Introduction and Objectives ................................................................................................................ 1 2. Materials and Method .......................................................................................................................... 2 3. Results ................................................................................................................................................. 9 5. Analysis of nutrient contents and removal in biomass fractions of Pinus radiata ............................ 29 6. Greenhouse gas implications of removal of residues ........................................................................ 41 7. Cost-benefit analyses ......................................................................................................................... 44 Implications .............................................................................................................................. 59 Recommendations .................................................................................................................... 60 Appendices ............................................................................................................................... 61 References ................................................................................................................................ 63

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Tables Table 1

Description of study sites ..................................................................................................................... 2

Table 2

Log grading specifications used in the study ........................................................................................ 4

Table 3

Stand attributes of the 61 sample plots. .............................................................................................. 11

Table 4

Predicted component and total aboveground biomass for the 61 sample plots. ................................ 13

Table 5

Total fresh and oven-dry biomass per site and total fresh and oven-dry biomass per hectare ............ 15

Table 6

Mean fresh biomass weight and range for stem components ............................................................. 17

Table 7

Total biomass in stem and branch components per plot .....................................................................18

Table 8

Proportion of biomass (fresh weight) in branches of different diameter classes by plot .................... 20

Table 9

Proportion of all branches in crown and stem grouped by diameter class .......................................... 21

Table 10

Summary of waste sections 0-1 m in length by site ........................................................................... 23

Table 11

Summary of waste sections 1- 5 m in length by site .......................................................................... 23

Table 12

Summary of waste sections > 5 m in length by site............................................................................ 24

Table 13

Descriptive statistics of moisture content (stem and bark), green and basic density of stem sections by site....................................................................................................................................26

Table 14

Descriptive statistics of moisture content (stem and bark), green and basic density of stem sections by silvicultural regime .......................................................................................................... 27

Table 15

Tree total biomass weight and weight of extractable residues (t/ha, dry wt.), from sites across different thinning regimes (unthinned, UT; thinned twice T2) and biomass productivity (low biomass, LB; high biomass, HB), as determined in the field and derived from biomass equations developed for the study sites. ............................................................................................. 28

Table 16

Concentration (kg/t, dry wt) of total C and nutrient (major) in soil samples from sites of different thinning regimes (unthinned, UT; thinned twice T2) and biomass productivity (low biomass, LB; high biomass, HB)................................................................................................ 30

Table 17

Concentration (kg/t, dry wt) of total C and nutrient (major) in litter samples from selected UT and T2 sites. ........................................................................................................................................31

Table 18

The weights (t/ha, dry wt.), and total C and nutrient concentrations (kg/t), of biomass components of Pinus radiata from sites across different thinning regimes (unthinned, UT; thinned twice T2) and biomass productivity (low biomass, LB; high biomass, H B). ....................... 33

Table 19

Total nutrient content (kg/t) in biomass fractions of a 29-yr old Pinus radiata (Webber and Madgwick 1983).................................................................................................................................35

Table 20

Weights (t/ha) and total nutrient concentration (kg/ha) of harvestable biomass fractions in eight stands of Pinus radiata with differences in thinning regimes (unthinned, UT; thinned twice T2) and biomass productivity (low biomass, LB; high biomass, HB). .....................................39

Table 21

Field activities included in the GHG assessment................................................................................ 41

Table 22

Reductions in GHG emissions (tonnes CO2 –e ha -¹) as a result of alternative management scenarios (results expressed on an oven-dry weight basis) .................................................................43

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Table 23

Greenhouse emissions (kg CO2 –e ha -¹) from operational activities ................................................ 43

Table 24

Wood processing companies that source softwood logs from Macquarie Region radiate pine plantations .......................................................................................................................................... 47

Table 25

Plantation establishment cost savings arising from sale of biomass ................................................... 54

Table 26

Cost-benefit summary ........................................................................................................................ 57

Figures Figure 1.

Collection of litter samples prior to tree harvest ................................................................................ 3

Figure 2

Weighing a saw log ........................................................................................................................... 5

Figure 3

Weighing a pulp log........................................................................................................................... 5

Figure 4

Weighing a waste log......................................................................................................................... 5

Figure 5

Branch segregation (background) and staff measuring branch diameters .........................................5

Figure 6

Top, mid and butt disc samples used for moisture content, density and nutrient determinations ......7

Figure 7

Nitrogen (N) concentration (kg/t) of branches of varying diameter class across selected UT, T1 and T2 sites.................................................................................................................................36

Figure 8

Phosphorus (P) concentration (kg/t) of branches of varying diameter class across selected UT, T1 and T2 sites ......................................................................................................................... 36

Figure 9

Potassium (K) concentration (kg/t) of branches of varying diameter class across selected UT, T1 and T2 sites ......................................................................................................................... 37

Figure 10

GHG emissions comparison under different residue management scenarios (results expressed on an oven-dry weight basis) ........................................................................................................... 42

Figure 11

Radiata pine harvest slash ................................................................................................................ 44

Figure 12

Macquarie Region showing location of radiata pine plantations managed by FNSW ..................... 46

Figure 13

Clearfall Harvest Type by Proportion of Log Yield - 2011 ............................................................. 46

Figure 14

Biomass uses and associated processing technologies ....................................................................48

Figure 15

Growth projections for renewable energy by type ........................................................................... 49

Figure 16

Growth projection for fuels by type .................................................................................................49

Figure 17

Log products as proportion of total above ground biomass (42 plot sites) ......................................51

Figure 18

Biomass Harvesting Residue Yields by Site (excluding branches 80 mm diameter) combined accounted for 35% of the total residual biomass;



Biomass harvesting residue yields by site (excluding branches 10

Pulp

> 10 cm sweep along any 3 meter length

8

N/A

N/A

Sawlog

2.5-3

26

N/A

4.0-6.0, >6.0-8.0 and >8.0 cm) and weighed (Figure 5).

Figure 2. Weighing a saw log

Figure 3. Weighing a pulp log

Figure 4. Weighing a waste log

Figure 5. Branch segregation (background) and staff measuring branch diameters

5

2.7 Weight of crown biomass Crown was defined as the top part of the tree remaining after the last log section was cut. Each individual tree crown -or crown pieces- were transported to the landing bay, delimbed and weighed. The diameter of each branch of the crown was measured at 10 cm from the base of the branch and grouped by diameter class (0-2.0, >2.0-4.0, >4.0-6.0, >6.0-8.0 and >8.0 cm). The weight of each group was recorded.

2.8 Weight of stump The weight of stumps was calculated by multiplying their estimated volume by the green density of the “butt” portion of the log. Measurements were made of average stump diameter and height and these used to calculate stump volume. Stump volume was calculated assuming the stump resembled the shape of a cylinder.

2.9 Weight of needles The weight of needles was determined for each tree based on the total weight of needles determined in a previous study for mature (35-yeard old) Radiata pine trees harvested at Greenhills State Forest, near Tumut, NSW. In that study (unpublished), the fresh weight of the needles accounted on average for 4.4% of the above-ground fresh weight of the trees, and this factor was applied here.

2.10 Weight of bark The weight of stem bark was determined for each tree based on the weight of bark in commercial logs determined in a previous study for mature (35-yeard old) Radiata pine trees harvested at Greenhills State Forest, near Tumut, NSW. In that study (unpublished), a large number of logs (173) were weighed before and after debarking, and the proportion of biomass in bark determined. The fresh weight of bark accounted on average for 15.3% of the above-ground fresh weight of the trees, and this factor was applied here. For branches, we determined the proportion of bark for each branch diameter class included in the study based on the weight of the branch samples collected in the field before and after debarking.

2.11 Biomass sampling Three trees per plot (one from each of suppressed, intermediate and dominant classes) were randomly selected for moisture content and density analysis in the laboratory. The same samples were also used for nutrient analysis. Discs of approximately 5 cm in thickness were cut from the selected trees at 3 length intervals along the stem (butt, mid and top section) (Figure 6). At each of these intervals, branch samples were taken from each diameter class (0-2.0, >2.0-4.0, >4.0-6.0, >6.0-8.0 and >8.0 cm). The samples were identified according to tree number, compartment number, diameter class and position in the tree and bagged for transport to the laboratory for preparation and analysis. All biomass samples were stored at 5 m (Table 10, Table 11 and Table 12).

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Table 10.

Summary of waste sections 0-1 m in length by site

State Forest

Cpt

AC

Current Silv

% of Waste 0-1 m

UT

Total Weight Waste 0-1 m (kg) 452

19.4

Average Weight (kg) 45.2

Max Weight Measured (kg) 113.0

Average Length (m) 0.8

Max Length (m) 1.0

Total Waste Sections (kg) 2326

Dog Rocks Gurnang

26

1970

354

Gurnang

355

1977

T2

716

19.8

1977

T2

841

22.8

22.4

70.0

0.4

1.0

3609

27.1

100.0

0.6

0.9

3690

Gurnang

373

1982

T1

908

17.3

33.6

156.0

0.7

1.0

5244

Gurnang

375

1982

T2

788

25.1

29.2

110.0

0.7

1.0

3135

Sunny Corner Sunny Corner Vittoria

131

1982

T1

558

12.8

14.3

64.0

0.5

1.0

4360

779

1983

T1

499

23.9

13.5

38.0

0.7

1.0

2089

31

1969

UT

79

2.6

8.8

16.0

0.5

1.0

3033

23

Table 11 Summary of waste sections 1- 5 m in length by site State Forest

Cpt

AC

Current Silv

% of Waste 1-5 m

UT

Total Weight Waste 1-5 m (kg) 1345

Max Weight Measured (kg) 145.0

Average Length (m) 2.9

Max Length (m)

Total Waste Sections (kg)

57.8

Average Weight (kg) 42.0

Dog Rocks Gurnang

26

1970

4.9

2326

354

1977

T2

2451

74.6

106.6

359.0

2.5

4.2

3609

Gurnang

355

1977

T2

2585

70.1

73.9

249.0

2.2

4.2

3690

Gurnang

373

1982

T1

3858

73.6

133.0

490.0

2.3

4.8

5244

Gurnang Sunny Corner Sunny Corner Vittoria

375

1982

T2

2059.

65.7

76.3

296.0

2.3

5.0

3135

131

1982

T1

3107

71.2

56.5

412.0

2.4

4.5

4360

779

1983

T1

1347

64.5

61.2

183.0

2.5

4.4

2089

31

1969

UT

2734

90.1

50.6

445.0

2.7

4.8

3033

Table 12.

Summary of waste sections > 5 m in length by site

State Forest

Cpt

AC

Current Silv

% of Waste > 5m

UT

Total Weight Waste > 5 m (kg) 529

Max Weight Measured (kg) 108.0

Average Length (m) 7.6

Max Length (m)

Total Waste Sections (kg)

22.7

Average Weight (kg) 66.1

Dog Rocks Gurnang

26

1970

12.2

2326

354

1977

T2

202

5.6

202.0

202.0

5.2

5.2

3609

Gurnang

355

1977

T2

264

7.2

264.0

264.0

5.5

5.5

3690

Gurnang

373

Gurnang

375

1982

T1

478

9.1

95.6

145.0

6.2

7.7

5244

1982

T2

288

9.2

96.0

138.0

6.5

8.5

3135

Sunny Corner Sunny Corner Vittoria

131

1982

T1

696

16.0

69.6

179.0

5.7

7.7

4360

779

1983

T1

243

11.6

243.0

243.0

5.9

5.9

2089

31

1969

UT

220

7.3

55.0

116.0

8.1

15.9

3033

24

4.5 Moisture content and density of biomass fractions The moisture content (wet basis) of the stem sections generally increased from the butt to the top section of the trees, as expected (Table 13). The average moisture content of the wood is similar to that of 35-year old Pinus radiata stem samples for the Tumut area of NSW reported previously (Ximenes et al, 2008). The basic density of the stem sections decreases as the tree height increases, which was also expected (Table 13). The basic density of the wood is typically lower than that reported for Pinus radiata stem samples of similar age for the Tumut area of NSW reported previously (Ximenes et al, 2008). The basic density of UT stem samples was greater than that of T1 and T2 stem samples whereas the moisture content of the wood and bark from UT sites was lower than that of T1 and T2 sites (Table 14). The age of UT trees (significantly older than trees in the other stands) may explain to some extent the differences in density and moisture content described here. Interestingly the mean moisture content of UT stem wood reported here was exactly the same as the mean moisture content reported previously for radiata pine trees of similar age in Tumut, NSW (Ximenes et al, 2008).

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Table 13.

Descriptive statistics of moisture content (stem and bark), green and basic density of stem sections by site

State Forest

Cpt.

AC

Current Silv

Sample ID

Green Density kg/m (Mean,SD)

Dog Rocks

26

1970

UT

Butt

900.8 (52.8)

Dog Rocks

26

1970

UT

Mid

Dog Rocks

26

1970

UT

Vittoria

31

1969

Vittoria

31

Vittoria

3

Basic Density kg/m (Mean,SD)

3

26

Moisture Content % Mean (SD)

Moisture Content (Bark) % Mean (SD)

454.2 (19.3)

49.3 (3.2)

27 (2.4)

847.5 (50.3)

438.3 (29.5)

48 (3)

40.5 (6.5)

Top

871.7 (60)

397.5 (26.7)

54.4 (4.5)

61.5 (8.5)

UT

Butt

883.3 (92)

453.3 (36.5)

48.5 (4)

25 (7.4)

1969

UT

Mid

815 (55.7)

415.8 (30.9)

48.5 (4.2)

42.3 (9.3)

31

1969

UT

Top

841.7 (20.4)

378.3 (11.7)

55.1 (0.9)

64.3 (0.6)

Gurnang

373

1982

T1

Butt

984.2 (50.2)

405.8 (26.4)

58.6 (1.6)

34.1 (15.4)

Gurnang

373

1982

T1

Mid

904.2 (47.4)

360 (23)

60.2 (1)

55.8 (4)

Gurnang

373

1982

T1

Top

919.2 (55)

327.5 (22.2)

64.5 (2)

72 (2.4)

Sunny Corner

131

1982

T1

Butt

977.9 (81.3)

452 (21.5)

53.5 (3.6)

35.3 (3.9)

Sunny Corner

131

1982

T1

Mid

890.2 (66.4)

398.2 (22.3)

55.1 (2.7)

47.6 (5.2)

Sunny Corner

131

1982

T1

Top

987.4 (26)

364.4 (25.9)

63.1 (2.5)

66.7 (3)

Sunny Corner

779

1983

T1

Butt

955 (33.4)

450 (29.5)

52.6 (3.6)

34.8 (2.1)

Sunny Corner

779

1983

T1

Mid

854.2 (42.7)

396.7 (22.7)

53.5 (4.2)

52 (5.8)

Sunny Corner

779

1983

T1

Top

958.3 (48.2)

353.3 (16.1)

63.1 (2)

69.3 (3)

Gurnang

354

1977

T2

Butt

968.5 (46)

446.2 (22.6)

53.8 (2.7)

38.8 (3.3)

Gurnang

354

1977

T2

Mid

910.7 (121.6)

414.3 (54.9)

54.3 (3.9)

46.7 (12.7)

Gurnang

354

1977

T2

Top

928.6 (72.2)

376.4 (20.2)

59.4 (4.5)

67.6 (6.9)

Gurnang

355

1977

T2

Butt

955.3 (72.7)

447.1 (35.1)

52.9 (5.1)

35.3 (3.8)

State Forest

Cpt.

AC

Current Silv

Sample ID

Green Density kg/m (Mean,SD)

Gurnang

355

1977

T2

Mid

918.8 (97.8)

Gurnang

355

1977

T2

Top

Gurnang

375

1982

T2

Gurnang

375

1982

Gurnang

375

1982

Table 14.

3

Basic Density kg/m (Mean,SD)

3

Moisture Content % Mean (SD)

Moisture Content (Bark) % Mean (SD)

390 (41.5)

57 (7.1)

53.8 (5.4)

950.8 (72.8)

365 (21.1)

61.3 (4.7)

59.8 (4.9)

Butt

968.3 (51.5)

462.5 (16)

52.1 (2.4)

36.7 (5.4)

T2

Mid

911.7 (34.6)

407.5 (13.6)

55.3 (2.5)

53.3 (5)

T2

Top

928.3 (36.9)

363.3 (18.3)

60.8 (2.6)

71.3 (3.9)

Descriptive statistics of moisture content (stem and bark), green and basic density of stem sections by silvicultural regime

27

Silv.

Green Density 3 kg/m (Mean,SD)

Basic Density 3 kg/m (Mean,SD)

Moisture Content % Mean (SD)

Moisture Content (Bark) % Mean (SD)

T1

936 (67)

390 (47)

58.2 (5.2)

51.7 (15.7)

T2

932 (74)

407 (44)

56.1 (5.1)

51.5 (13.7)

UT

861 (67)

427 (38)

50.2 (4.5)

41.5 (16.0)

4.6 Comparison of predicted biomass and biomass determined in the field On table 15 the biomass of the eight study sites derived from weighing in the field is compared with the biomass for the same study sites derived from pre-harvest tree and stand measurements and the use of biomass equations. The biomass equations estimates of total tree biomass for UT sites were consistently robust, with a slight overestimation of the biomass (6.5% on average). The biomass equations were also robust in predicting the weight of extractable biomass from UT sites, underestimating it by 10.9%. The biomass equation estimates for T1 and T2 sites on the other had were significantly more variable. For T1 sites, the equations were very robust in the prediction of total biomass from Sunny Corner SF Cpt 131; however they overestimated the tree biomass from the other Sunny Corner site by 12% and underestimated the tree biomass for Gurnang SF Cpt 373 by 23% (Table 15). The equations underestimated the weight of extractable biomass from 33.5 to 40% for two sites (Snny Corner Cpt. 779 and Gurnang SF Cpt 373) and overestimated the total tree biomass of the remaining T1 site by 40% (Table 15). For T2 sites, the equations consistently overestimated the tree total biomass by between 13-24%. The estimated of the weight of extractable biomass were very variable, underestimating it by between 17 to 69% for two sites (Gurnang SF Cpts 354 and 375) and overestimated the weight of extractable biomass of the remaining T2 site by 34% (Table 15). The better performance of the biomass equations in predicting the biomass from UT sites suggests that the inclusion of the extra plots for the refinement of the biomass equations (all in UT sites) was essential. Table 15.

Tree total biomass weight and weight of extractable residues (t/ha, dry wt.), from sites across different thinning regimes (unthinned, UT; thinned twice T2) and biomass productivity (low biomass, LB; high biomass, HB), as determined in the field and derived from biomass equations developed for the study sites.

Site Dog Rocks SF (Cpt 26) Vittoria SF (Cpt 31) Sunny Corner SF (Cpt 779) Sunny Corner SF (Cpt 131) Gurnang SF (Cpt 373) Gurnang SF (Cpt 354) Gurnang SF (Cpt 355) Gurnang SF (Cpt 375)

Biomass -field Total tree >8 cm branches + biomass stem residues

Biomass - equations Total tree >8 cm branches + biomass stem residues

Management

Age class

UT, LB

1970

360.3

34.6

390.1

31.2

UT, HB

1969

489.2

43.8

517.4

39.4

T1, LB

1983

271.4

26.0

308.2

19.5

T1, HB

1982

322.7

14.7

321.8

21.8

T1, HB

1982

408.2

37.5

331

26.8

T2, LB

1977

244.3

18.0

282.2

15.4

T2, LB

1977

239.7

14.4

315.6

21.9

T2, HB

1982

201.9

15.6

249.7

9.2

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5. Analysis of nutrient contents and removal in biomass fractions of Pinus radiata This section relates to the following milestone: -

“Calculation of nutrient removal for different intensities of biomass harvesting for the assessment of the environmental implications of biomass harvesting on site productivity”

In this report we present carbon (C) and major nutrient data for soil and biomass samples collected from all study sites. The carbon and nutrient data for litter samples was restricted to four sites (UT and T2), and the average across those sites used for the calculations of nutrient composition of the litter layer of the remaining site, as the variability in the data for the selected UT and T2 sites was typically low.

5.1 Carbon and nutrient concentrations of soil and litter samples In Table 16Error! Reference source not found., the total C and major nutrient concentrations of soil to 30 cm depth (0-10 cm, 10-30 cm) from all selected sites are presented. The C concentration in the topsoil (0-10 cm) was invariably significantly higher than at lower depths (10-30 cm), (Table 16). In general, the N and P concentrations of the topsoil were similar or higher than at lower depths (Table 16). The nutrient concentrations of the soil from Dog Rocks site SF were significantly higher than that of the other unthinned site (Vittoria SF) and higher than for any other site tested (Table 16). These results are consistent with differences in biomass productivity between the two UT sites, i.e. there could have been greater extraction of soil nutrients in commercial and harvestable biomass fractions at the productive Vittoria SF site than the Dog Rocks SF site. The differences in the nutrient concentration of the soil at T1 and T2 sites were not as evident (Table 16), perhaps in part due to their closeness in age and lack of biomass productivity differences for the T1 and T2 sites. As expected, the C and nutrient concentrations (kg t-1) of litter surface litter (needles plus fine woody debris to 8 cm branches plus woody residues) from a hectare of Pinus radiata stand

Site Vittoria SF (Cpt 31)

Dog Rocks SF (Cpt 26)

Management UT, HB

UT, LB

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Sunny Corner SF (Cpt 131)

T1, HB

Sunny Corner SF (Cpt 779)

T1, HB

Gurnang SF (Cpt 373)

T1, HB

Gurnang SF (Cpt 375)

T2, HB

Age class 1969

Harvestable biomass fractions 8 cm branches + stem residues Litter layer (