Trees for Wood and Animal Production in Northern Australia

Home , Albizia, Albizia lebbeck, Albizia procera, Archidendropsis

by J. Brian Lowry

October 2008

RIRDC Publication No 08/164 RIRDC Project No CSC-58A

ISBN 1 74151 753 2 ISSN 1440-6845

Trees for Wood and Animal Production in Northern Australia Publication No. 07/164

Project No. CSC-58A

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 J. Brian Lowry Formerly: CSIRO Livestock Industries 39 Tucker Street Long Pocket Laboratories Chapel Hill QLD 4069 120 Meiers Road Indooroopilly QLD 4068 Phone: 07-3378 1795 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: 02 6271 4100 Fax: 02 6271 4199 Email: [email protected]. Web: http://www.rirdc.gov.au

Electronically published in October 2008

Foreword

This project investigates the feasibility of a more sustainable and productive farming system in the tropical woodlands of Northern Queensland through the use of rainforest species. In particular, the report examines the potential use of Albizia lebbeck as animal fodder, its effect on the sub-canopy pasture, and its timber quality.

This research will benefit farmers, agricultural advisors, farm forestry extension officers and other agroforestry researchers. The results of this study should also inform agricultural policy and research and development (R&D) funding agencies.

Findings from this project indicate that fallen leaf from some deciduous trees in the dry season can be used as fodder, though it contains more fibre and less protein than green leaf. However, eating fallen leaf may help animals digest low quality dry season grass in some species. Results also demonstrate that effects of isolated trees of all species tested in this project on the quality of sub-canopy pasture are positive

The tropical woodlands, for some, seem an improbably harsh environment to grow trees for wood and animal production. However both vegetational history and current ecology suggest that native non- sclerophyll trees have the potential to play a greater role in the landscape than is currently the case.

This project was funded by the Joint Venture Agroforestry Program (JVAP), which is supported by three R&D Corporations – Rural Industries Research and Development Corporation (RIRDC), Land & Water Australia (L&WA), and Forest and Wood Products Research and Development Corporation (FWPRDC). The Murray-Darling Basin Commission (MDBC) also contributed to this project. The R&D Corporations are funded principally by the Australian Government. State and Australian Governments contribute funds to the MDBC.

This report was prepared in March 2005. It is an addition to RIRDC’s diverse range of over 1800 research publications. It forms part of our Agroforestry and Farm Forestry R&D program, which aims to integrate sustainable and productive agroforestry within Australian farming systems. The JVAP, under this program, is managed by RIRDC.

Most of our publications are available for viewing, downloading or purchasing online through our website: • downloads at www.rirdc.gov.au/fullreports/index.html • purchases at www.rirdc.gov.au/eshop

Peter O’Brien Managing Director Rural Industries Research and Development Corporation

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Acknowledgements

The author acknowledges access, information or advice from:

Dr David Taylor, Forest Research Institute, Gympie. Dr Paul Ryan, Forest Research Institute, Gympie Mr David McGowan “Yandilla” Mr Bob Clem, QDPI, Brian Pastures Mr John Wildin, Farnborough, Yeppoon. Dr Ross Gutteridge, University of Queensland Mr Ernie Ryder, Department of Natural Resources Mr Scotty McVeigh, Department of Natural Resources Mr Col Middleton, Department of Primary Industry Mr Mike Nasser, Department of Primary Industry. Dr Eric Anderson, Department of Primary Industries. Mr John Baker “Booroondarra” Mr John Elliot, Mackay Mr Mike Whiting, CSIRO Townsville Mr David Coates, CSIRO, Townsville Mr Arthur Rosser and Mrs Carol Rosser, Eungella. Mr Andrew Grodecki, Department of Natural Resources Mr Peter Pomroy, QDPI Forestry, Cardwell Oxley Library, for access to a rare copy of Bailey (1888).

The project also acknowledges the efforts of Ms Marnie Matthews and Mr Dean Gibson in the Tropical Beef Centre, Rockhampton, and the considerable amount of effort in generating in vitro data and trying to elucidate grass/leaf synergy by Dr Peter Kennedy, CSIRO, Long Pocket Laboratories. Mrs Grace Lowry provided valuable help with field observations.

The author is particularly indebted to Mr Ron Holme, Mrs Sue Holme and Mr Richard Holme of “Glendhu” for access to their plantings of various trees and their interest.

Abbreviations

NDF Neutral Detergent Fibre VFA Volatile fatty acids TBC Trpocial Beef Centre, Rockhampton

Contents

Foreword ______iii Acknowledgements______iv Executive Summary ______vi 1. Introduction ______1 2. Objectives ______2 3. Methodology______3 3.1 Tree selection and phenological recording ______3 3.2 Feed from Large Trees ______4 3.3 Tree canopy – grass interaction ______8 3.4 Wood Quality Aspects______8 4. Overall Results ______9 4.1 Tree performance ______9 4.2 Tree Products as Feed ______10 4.3 Tree-Grass Interaction______19 4.4 Wood Use ______19 5. Discussion – General ______22 5.1 Feed from Large Trees ______22 5.2 Fallen leaf and synergies______26 5.3 Canopy Effects – General ______28 5.4 Wood potential ______28 6. The outlook for Albizia lebbeck (siris, Indian siris, flea tree) ______32 6.1 Status as native tree______34 7. Results and Discussion for Other Tree Species ______37 7.1 Trees not considered ______37 7.2 Trees with fodder value and softer, low density timbers ______48 8. Implications______50 9. Recommendations______52 10. References ______53 Appendix 1. Summary of sites ______58 Appendix 2. Agroforestry in Northern Australia – the Wider Context ______61

Executive Summary

What the report is about This report investigates the feasibility of a more sustainable and productive farming system in the tropical woodlands of Northern Queensland through the use of rainforest species. In particular, the report examines the potential use of Albizia lebbeck as animal fodder, its effect on the sub-canopy pasture, and its wood quality.

This project sought new information through a study of existing trees in a number of locations, sampling of sub-canopy pasture and fallen leaf, and laboratory and feeding experiments. This project produced further evidence that an agroforestry system could be based on trees for both wood and animal production, and that such a system is yet to be actively developed.

Who is the report targeted at? The report is for use by farmers, agricultural advisors, farm forestry extension officers and researchers. The results of this study should also inform agricultural policy and research and development (R&D) funding agencies.

Background Alibizia lebbeck was identified as a tree legume that could supplement dry season pasture through leaf fall and provide high value timber. Traditionally, A. lebbeck has been frequently used for shade but has never been planted for fodder. Anecdotal evidence suggested that most of the animal production benefits come from fallen leaf material from trees in paddocks, rather than in the hedged or shrubby form associated with “browse”. Elsewhere in the world, A. lebbeck is highly valued for its timber.

In 1997, The Joint Venture Agroforestry Program published a review of the potential for dual purpose trees, The Potential for Tropical Agroforestry in Wood & Animal Feed Production. RIRDC 97/73. The current project nominated five species that shed leaf during the dry season for particular attention, with 11 others to be addressed according to opportunity and emerging evidence. The review also highlighted the enhancement of pasture growth in association with A. lebbeck.

Aims/Objectives To demonstrate the feasibility of more sustainable and productive farming systems through the use of trees that promote animal production and also yield a valuable timber crop.

This report investigates the nutritional benefits of fallen tree leaf, wood quality, and the impact of the species on the sub-canopy pasture associated with the trees. In investigating the nutritional role of fallen tree leaf a number of aspects were addressed: 1. the general question of whether animals eat fallen tree leaf 2. the nutritional value of fallen leaf 3. nutritional interactions that improved the nutritional value of the feed.

Methods used Five species that shed leaf during the dry season were selected for the project: A. lebbeck (siris), A. procera, Gmelina arborea (yemene), Tipuana tipu (tipuana) and Melia azedarach (white cedar), with 11 others examined according to opportunity and emerging evidence (see Appendix 1 for a detailed list). Data was collected from existing trees in a variety of locations including: wayside, on grazing or cropping land, planted or volunteer. These were located by contacts with landholders, information from DNR and other professionals, herbarium notations, previous knowledge, and by direct observation and reconnaissance.

Tree girths were measured with a tape to +1 mm, usually at height 1.2 m. If major low branching or other factors made this impractical, the actual height and reason were recorded. Tree height was

measured either by sighting on a ‘height stick’ marked in strongly contrasting (black and white) 200 mm sections, or with a Sunto PM5-1520 hypsometer that necessitated taping out a distance of 15 or 20 m from the stem. Canopy diameter was measured on both an east-west and north-south axis, as the horizontally taped distance from below the tips of the outermost branches.

Where practicable the following was recorded: - tree species - tree girth - location both by description and GPS reading - tree habit, height - girth at 1.2 m - canopy diameter - nature of sub-canopy vegetation - tree phenology (flowering, fruiting, leaf condition) - nature of the immediate landscape.

Repeat observations were made on particular trees or populations to find out when or if fall of leaf, flower or fruit occurred. Where possible, observations were made about one year apart to determine the annual increment of girth and height over the 1997–98 period. At some sites fallen leaf or flower samples were collected for analysis, for in vitro experiments, or if possible, for voluntary intake experiments.

Results/Key findings 1. Fallen leaf from some deciduous trees in the dry season does get eaten by animals in dry season pasture. The evidence comes from animal experiments, observations, and other records. 2. Fallen tree leaf had less protein and more fibre than green leaf. With some trees, considerable protein was retained. In general, compared with dry-season grass, fallen tree leaf does not yield as much energy in the rumen, but what energy there is is yielded much more quickly. Tree leaf is also rapidly fragmented within the rumen and combined with rapid initial fermentation suggesting that the animal could extract nutrients quickly. 3. Acceptability of fallen leaf to animals varies greatly between tree species; however, animals strongly preferred freshly fallen leaf. 4. Eating fallen leaf may help the animal make use of low quality dry season grass in some species. The promotion of digestion was associated with the soluble fraction. A similar activity was found in extracts of lucerne. 5. Effects of isolated trees on the quality of sub-canopy pasture were positive for A.lebbeck. A. procera, A. canescens, Tipuana tipu and Melia azedarach. 6. No species produced a dry-season fall of edible flowers and pods as profusely as A. lebbeck. 7. Pruning after one year should ensure further development of a clear main stem; however, further data was not collected due to the short-term nature of this project. 8. A. lebbeck is often avoided by wood turners because of the irritant dust; however, the use of full protective equipment combats the irritant.

Implications for relevant stakeholders The tropical woodlands, for some, seem an improbably harsh environment to grow trees for wood and animal production. However both vegetational history and current ecology suggest that native non- sclerophyll trees have the potential to play a greater role in the landscape than is currently the case.

This project highlighted the potential value of A. lebbeck as a multi-purpose agroforestry species. A. lebbeck may supplement dry season pasture and enhance the digestibility of low-quality dry season grass. Effects of isolated trees on the quality of sub-canopy pasture were positive for A. procera, A. canescens, Tipuana tipu and Melia azedarach.

Due to the irritant dust associated with A. lebbeck, full protective equipment is recommended when milling.

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Recommendations A workshop investigating agroforestry potential for A. lebbeck is recommended. The following issues could be addressed:

1. With the possibility of divergent views on usefulness of A. lebbeck it would be beneficial to find common ground, discuss what the problems might be, and how to accommodate them.

2. As indicated in this report, wood and forage aspects tend to be covered by different agencies. Some attempt at integration is warranted.

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1. Introduction

Planting trees on farms is actively endorsed by the media, promoted by various agencies and occurs to varying degrees, mainly in southern Australia. Planting is usually for timber, shelter, hydrology or environmental benefits. There is also interest in woody plants as fodder, for example tagasaste in temperate areas, and leucaena in tropical areas. To keep within the reach of grazing animals, plants are generally maintained as shrubs and rarely grown as trees.

The approach described in this report originated with work in Townsville in 1987–1992.

An investigation into woody legumes as supplementary fodder species in the tropical woodlands of Northern Australia, identified Albizia lebbeck as a tree legume that could supplement dry season pasture through leaf fall and provide high value timber. Traditionally, A. lebbeck has been frequently used for shade but has never been planted for fodder. Anecdotal evidence suggested that most of the animal production benefits come from fallen leaf material from trees in paddocks, rather than in the hedged or shrubby form associated with “browse”. Elsewhere in the world, A. lebbeck is highly valued for its timber. The aim was to investigate whether A. lebbeck could fulfil the dual purpose of animal production for the majority of its growing life, and also provide a final timber yield.

In 1997, The Joint Venture Agroforestry Program published a review of the potential for dual purpose trees, The Potential for Tropical Agroforestry in Wood & Animal Feed Production (referred to in the text as RIRDC 97/73). We recommend that this report be read in conjunction with RIRDC 97/73. The arguments developed on fallen leaf and canopy effect in that report are just as relevant, as are most of the species notes. This report is intended to take the subject forward.

RIRDC 97/73 highlighted four species in particular along with a number of others. The current project nominated five species that shed leaf during the dry season for particular attention (A. lebbeck (siris), A. procera, Gmelina arborea (yemene), Tipuana tipu (tipuana) and Melia azedarach (white cedar)), with 11 others to be addressed according to opportunity and emerging evidence (see Appendix 1 for a detailed list). Direct observations and findings while conducting this project changed our estimation of some of these subsidiary species, and also highlighted some that were not previously considered. The review highlighted the improvement of pasture growth in association with A. lebbeck, and although strange in the Australian context, was in line with reported effects elsewhere in the dry tropics.

This report deals with both general questions on the potential of dual purpose trees and the results and observations as they apply to particular species. The general aspects are covered in Sections 3, 4 and 5; and the appraisal for individual tree species in Sections 6 and 7.Finally, implementing agroforestry systems with the native trees studied in this project has wider philosophical implications. Although currently rare in the native rangelands, studies both of vegetational history and of contemporary ecology, suggest that these trees once occupied a much wider place in the landscape, and certainly could do so in the future. The background argument on this is presented in Appendix 2.

2. Objectives

To demonstrate the feasibility of more sustainable and productive farming systems through the use of trees which promote animal production and also yield a valuable timber crop.

The report investigates the nutritional benefits of fallen tree leaf, wood quality, and the impact of the species on the sub-canopy pasture associated with the trees. In investigating the nutritional role of fallen tree leaf a number of aspects were addressed:

1. the general question of whether animals eat fallen tree leaf 2. the nutritional value of fallen leaf 3. nutritional interactions that improved the nutritional value of the feed.

3. Methodology

3.1 Tree selection and phenological recording Five species that shed leaf during the dry season were selected for this project: A. lebbeck (siris), A. procera, Gmelina arborea (yemene), Tipuana tipu (tipuana) and Melia azedarach (white cedar), with 11 others examined according to opportunity and emerging evidence (see Appendix 1 for a detailed list). Data was collected from existing trees in a variety of locations including: wayside, on grazing or cropping land, planted or volunteer. These were located by contacts with landholders, information from DNR and other professionals, herbarium notations, previous knowledge, and by direct observation and reconnaissance.

Where practicable the following was recorded:

- tree species - tree girth - location both by description and GPS reading - tree habit - height - girth at 1.2 m - canopy diameter - nature of sub-canopy vegetation - tree phenology (flowering, fruiting, leaf condition) - nature of the immediate landscape.

Repeat observations were made on particular trees or populations to determine when or if fall of leaf, flower or fruit took place. Where possible, observations were made about one year apart to calculate the annual increment of girth and height over the 1997–98 period.

Position of the trees was determined with a Magellan GPS2000 global positioning system. This model required a wide sector of unobstructed sky and would sometimes take several minutes to acquire satellite signals. However, the accuracy of c. +100 m, together with any other location details recorded at the time should be sufficient to find the particular tree again. It will also more easily allow results to be expressed through a GIS package.

Tree girths were measured with a tape to +1 mm, at height 1.2 m. If major low branching or other factors made this impractical, the actual height and reason were recorded. Tree height was measured either by sighting on a ‘height stick’ marked in strongly contrasting (black and white) 200 mm sections, or with a Sunto PM5-1520 hypsometer that necessitated taping out a distance of 15 or 20 m from the stem. Canopy diameter was measured on both an east-west and north-south axis, as the horizontally taped distance from below the tips of the outermost branches.

Samples of fallen leaf or flower were collected from some sites for analysis, for in vitro experiments, or if possible for voluntary intake experiments. The large-scale collection of Gmelina arborea leaf is described in Section 3.2.3.

3.2 Feed from Large Trees

3.2.1 Evaluation of fallen leaf, flower, pod Feed Evaluation Crude protein content (N x 6.24) was estimated by measuring nitrogen using the traditional Kjeldahl method in the Tropical Beef Centre, Rockhampton, and in the Analytical Services Section, CSIRO Cunningham Laboratory, Brisbane.

Fibre (neutral detergent fibre, NDF) content of bulk samples was measured by the Van Soest method (Goering and van Soest 1970, van Soest and Robertson 1985). This is usually equated with the cell wall content. We have found some qualifications to this, such as changes to the lignocellulose (Kennedy et al. 1999) and a substantial lignin fraction being extracted (Lowry unpubl). However it was used here because of the almost universal adoption of it as a measure of fibre..

Saponins were suspected in some samples. To detect the presence of substantial levels the phytochemical screening test (formation of a stable foam) was carried out against plants of known saponin content.

Tannins were likely to be present in any tree forage, and the analyses, or at least their interpretation, is complex. Here a simple assessment was done by autocoagulation. The fresh plant material was homogenised with water in the presence of an antioxidant and immediately squeezed through a 50 micron cloth. The smooth green suspension was then stood at 25o C. Separation of the suspension into a clear supernatant and a green coagulum, due to tannin binding with leaf protein and forming an insoluble precipitate, was taken as indicating nutritionally significant tannin. The levels could be estimated by the speed of this reaction against known plants.

Digestibility was estimated in vitro by incubation with rumen fluid in a prescribed medium under anaerobic conditions. Gas production has been used as an index of digestion for some time, particularly for conventional feeds, but recently applied to browses (Kaitho et al. 1997). We used a recently described but widely adopted method (Pell and Schofield 1993). This method provides both the determination of actual fibre (NDF) loss, and of the amount of substrate fermented. Automated monitoring of gas pressure allows one to follow the kinetics and progress of fermentation, and the use of a bicarbonate buffer links gas pressure directly to production of volatile fatty acids (VFA), which are the pathway by which the ruminant obtains energy from the feed As it was used for not only evaluating substrates but also for exploring the synergistic interactions between tree leaf and grass, the procedure is described in detail below.

The plant material was dried at 60o C and milled to pass a 1 mm screen. A small sample (100 mg) was accurately weighed in a 50 ml glass serum bottle. Each sample was replicated three times.. Each 100 mg sample was wetted with 1 ml of degassed water, and a small magnetic stirrer bar added to each bottle. The samples were transferred to a chamber where they could be manipulated under anaerobic conditions. To each bottle was added a deoxygenated medium containing bicarbonate buffer (to stabilise pH during release of volatile fatty acids), casein (empirically found to keep microbial culture alive during shocks and transfers) and some trace minerals. Finally, rumen fluid, freshly collected, strained through a 50 micron mesh, and kept under continuous stirring, was added to each bottle.

Both medium and rumen fluid were kept close to 39o C. The bottles were then closed with a diffusion- proof elastomer stopper and sealed by crimping with an aluminium cap. The array of bottles was transferred to an incubator at 39o C in which each bottle was positioned above a small motor to actuate the stirrer. Gentle stirring took place at preset intervals to simulate rumen movements. Gas pressure was monitored by a pressure transducer mounted on a syringe, inserted through the elastomer stopper and connected to a computer with software that enabled 16-channel data logging. Gas pressure for larger numbers of samples was measured individually with a pressure sensor at particular times and the data recorded manually.

Following the period of fermentation, samples were either: used for the determination of undigested fibre; centrifuged and the supernatant analysed for VFA; or analysed for purines, as measure of total microbial biomass. Analysis of undigested fibre required the addition of a neutral detergent reagent to each bottle, which was then resealed and autoclaved for 1 hour. All microbial biomass was considered to be solublised by this treatment. The solid residues were collected quantitatively, washed, dried and considered to be undigested NDF.

In a parallel procedure triplicate samples of non-incubated plant material were treated with neutral detergent to determine the original NDF content. From this the NDF digestibility was calculated as:

Original NDF - residual NDF ------Original NDF

This provides a single final value for a particular fermentation and refers only to the fate of the plant fibre. It does not give any information about the non fibre components. In contrast the gas pressure, being directly related to the production of VFAs, provides an indication of the progress of the fermentation – lag times, rates, and when fermentation stopped. It has contributions both from the fermentation of NDF and of the non-NDF components (usually assumed to ferment rapidly at the beginning).

3.2.2 Synergy Experiments – leaf and grass

Preliminary experiments were conducted on fallen leaf from a collection of species from an RIRDC agroforestry trial that included rainforest species (at Mt Mee near Brisbane; Dr David Lamb, University of Queensland). Incubations consisted of grass, tree leaf, and a 1:1 mixture of grass and tree leaf. The NDF residue of the mixture was compared with the NDF of the grass and the tree samples. If the residue was less than predicted it was concluded that additional NDF had been digested due to some synergistic interaction between the substrates.

This was followed by experiments in which Gmelina leichartii (white beech) was investigated in considerable detail. These included: A. investigating the effect of different ratios of leaf and grass (1:4, 1:1, 4:1) B. prior extraction of the leaf with water, and comparison of extracted and non-extracted substrate and the water extract C. purine determination following fermentation to see if there were any differences in total microbial biomass D. treatment of NDF residues with acid detergent and the UV absorbance of the filtrates measured to see if there had been any increase in dispersible lignin E. extension of results for fibre recovery and gas pressure to determine the production of volatile fatty acids F. examination of the role of microbial consortia by a batch transfer experiment in which the medium from fermentation on the three substrate (leaf only, grass only, mixture) was used as an inoculum (rather than rumen fluid) for a second fermentation.

Experiments with freshly fallen leaf of Gmelina arborea, mainly mixed with Angleton grass and carpet grass, with fibre recovery at different times and use of two types of inoculum. Sequential extraction of the leaf with ethanol and water was carried out to ascertain the effect of total extractable constituents (both polar and non-polar).

Experiments with fallen leaf of A. lebbeck and T. tipu, initially as is, and then with sequential extraction with ethanol and water. Other experiments used natural microbial consortia of different fibrolytic capacity originating from wild ruminants. The finding that A. lebbeck extract seemed to be promotory led to the infusion experiment described in 3.2.3.

To identify the active factor in A. lebbeck extract, we developed a specialised system with cotton thread as a substrate. This was digested to completion (>95%), the time required for this being readily determined from the gas pressure trace. Extracts that reduced the time required were considered promotory.

3.2.3 Animal Experiments Voluntary Intake experiments At intervals, at both Long Pocket Laboratories and Tropical Beef Centre, three sheep in pens (but sometimes two or four) on a basal diet of carpet and Rhodes grass or Angleton grass, usually supplemented with 100 g/day of cottonseed meal, were offered fallen leaf, pod or flower from a number of different tree species as the material became available. Sheep behaviour and intakes of the tree material and the basal diet were recorded.

Fate of tree seed in the bovine tract This experiment employed fistulated steers on a maintenance diet in pens at the Tropical Beef Centre. A counted sample of whole (single-seeded) T. tipu pods was introduced into the rumen through the rumen cannula. The following morning the accumulated faeces were sluiced through a fine mesh screen which was then examined for intact seeds or recognisable fragments. This procedure was repeated each morning for seven days. In addition whole pods were placed in a dacron bag (50 micron mesh) suspended in the rumen and examined at intervals. Similar observations were made with sheep and A. lebbeck pods at Davies Laboratory Townsville.

Feeding Trial with Gmelina arborea Material and Methods Fallen leaf from G. arborea came from the Shell multispecies trials in Kennedy State Forest, near Cardwell, North Queensland. It was collected by raking the ground below the trees at the time leaf was falling in October. The bulk collection of about 300 kg was organised by Mr Peter Pomroy, QDPI Forestry, Cardwell. The leaf was transported to the Tropical Beef Centre (TBC), Rockhampton. On arrival it was visibly darker than freshly fallen leaf and contained some forest floor debris. It was stored in hay shed with free air circulation until feeding commenced in February. At that time, when feed was being weighed out, a rough screening was carried out to eliminate obvious foreign or woody material. The mature tropical grass used in the experiment was from a bulk supply of Angleton grass (Dicanthium sp) used for other experiments at TBC.

The sheep were 15 Wiltshire Merino cross wethers. They were assigned sequentially in order of liveweight to three groups of five animals, and were each housed in individual metabolism cages for daily collection of faeces and urine. Water was provided ad libitum. They were fed Angleton grass and lucerne for a 3-day adjustment period.

Following this the three groups were initially fed the following diets: 1. Angleton grass hay fed ad libitum with an approximately 10% excess 2. fallen leaf of G. arborea, fed ad libitum with an approximately 10% excess 3. Angleton grass and G. arborea leaf (1:1 mixture) placed in opposite ends of the bin to allow observation of feeding behaviour, animal preferences, and between-animal variation. Both were supplied with a 10% excess.

The intended sequence was: Week 1 • began designated diets with monitoring intake • feed offered was calculated from previous day’s intake, allowing 10% excess • uneaten residues were stored • if intakes of any diet became too low to maintain the animal, feeding of that diet was suspended Week 2 • continue feeding designated diets, with measurement of daily dm intake • uneaten residues from each pen were stored • began collection of faeces and urine • faeces were oven dried and daily faecal dm output determined • a subsample (100g) of faeces was collected from each animal at end of week, freeze-dried (or frozen) and stored • collected urine into 2M H2SO4 (100 ml) • measured volume of urine. • stored 50 ml sample of urine each day. • pooled urine on the basis of daily volume at end of week for N analysis and purine determination Week 3 • continued feeding designated diets but supplemented with 2% urea, applied as a 25% solution sprayed on the feed. • continued faecal collections

Analyses Nitrogen and fibre (NDF) was determined on bulk feed samples, uneaten residues, faeces; and nitrogen was determined in urine. Nitrogen was analysed at TBC, and fibre at Cunningham Laboratory. Relative intakes of leaf and grass for individual animals were calculated from fibre values of residues.

As the actual procedure was affected by the sheep responses, this is described in the Results, Section 4.2.3.

Infusion Experiment Freshly fallen A. lebbeck leaf from Townsville was brought to Long Pocket Laboratories, dried and milled to pass a 1 mm screen. Milled leaf (2 kg) was stirred with boiling deionised water (10 litres) with gentle heating to keep the mixture close to boiling without excessive local heating. The slurry was strained through a 50 micron dacron mesh, and the solids stirred with further boiling water and strained again. The extract was allowed to stand for 30 minutes, decanted clear of fine particles, and kept under refrigeration until use. The soluble solids content of the extract was 45 g/litre, and the extraction removed 22% of the original dry matter. A similar extract was made from lucerne to act as a positive control.

Three fistulated sheep in separate pens were maintained on a diet of Rhodes grass and intakes recorded each day for the period of the experiment. On day 2 one sheep was infused intraruminally with 400 ml of the A. lebbeck extract (corresponding to about 20% leaf in the diet), one with the lucerne extract and the control sheep was not infused. This treatment was continued for 3 days. There was then a period of 4 days with no infusion, followed by a 3–day infusion period with different sheep. Thus the three treatments were carried out on each sheep over the 3–week period. Each day, three dacron bags with 20 micron mesh, each containing 2.5 g of milled grass, were placed in the rumen at 0900 h. They were withdrawn at 1600 h and three new ones put in place, to be recovered the following day at 0900 h. After removal from the rumen the bags were washed and the dry matter residue determined by the standard method.

Cattle Feeding Experiment An experiment directly testing the value of fallen A. lebbeck leaf as a supplement to dry season grass, not part of this project, but initiated because of the results emerging from it (Kennedy et al. 2002), is discussed in Section 5.2.

Experiments at both Long Pocket Laboratories and Tropical Beef Centre were approved by the respective Animal Ethics Committees.

3.3 Tree canopy – grass interaction Isolated trees were selected for the experiment with clearly defined canopy in an area of reasonably uniform sub-canopy vegetation, and where access by grazing animals could be prevented or controlled. Any obvious species difference between sub-canopy and extra-canopy ground cover was recorded. Grass was harvested in 1 m x 1 m quadrats at uniform intervals along a transect chosen to sample both the sub-canopy and extra-canopy area. Grass was collected oven dried at 60oC, and the dry weights determined. A sub-sample was milled and analysed for fibre and nitrogen. Where biomass measurement was impractical nitrogen and fibre content was determined on whole plants.

Attenuation of direct sunlight by the tree canopy was measured with a 250 mm linear photocell array under a diffusing glass cover, hand-held horizontally at 500 mm above the ground. Output was measured in the open, clear of the canopy, before and after measuring it at several positions along a transect below the canopy. Canopy transmission was taken as the average output below the canopy expressed as a fraction of that in the open.

3.4 Wood Quality Aspects A Sunto increment borer with a 250 mm reach and a 5 mm core was used to attempt to take wood samples, mainly to ascertain the position and extent of the heartwood core in A. lebbeck trees of known age. When this procedure proved difficult, we used a brace and bit with a 6 mm auger. Shavings were extracted every few millimetres. Contact with the heartwood was easily detected by the change in appearance of the shavings. Holes were subsequently closed with sealant.

Radial discs of 10–year–old A. lebbeck wood were cut for determination of sapwood age by annual rings.

Milling of selected trees was carried out with a privately owned Lucas Mill at “Booroondara”. Boards were cut to a thickness of 20 mm, usually to the full width attainable with the 8 inch blade. The boards were air-dried, planed and polished on one surface, and allowed to stand. They were examined occasionally for sap stain and checking.

Pruning treatments were carried out at a number of sites on A. lebbeck trees, T. tipu and M. azedarach, and broadly followed the prescriptions of Bragg (1998), a recent guide published for those growing rainforest timbers. Trees selected were those that were not grossly malformed, sweeping, or multistemmed and appeared to have the potential to yield at least 3 m of clear stem. Pruning was carried out from the ground to a height up to 3.5 m, using a pruning saw with a 1.5 m extension. Branches were removed of all diameters up to 50 mm. The cut was made as vertically as possible, but primarily at right angles to the side branch, and positioned to minimise the cut surface area. The aim was to avoid leaving a protruding stub, but also to avoid leaving an excessively large cut surface by taking it flush with the main stem. Where possible, sites were visited about 1 year after pruning to record effects on individual trees. We also looked for trees that had branches previously lopped or cut in order to get an appreciation of what happened to protruding stubs and how well cut surfaces callused over.

Several woodcraft displays and individuals were visited to find out about aspects of the timber’s use and to seek comment from those using the timbers.

4. Overall Results 4.1 Tree performance Study sites A summary of sites from which data was obtained is shown in Appendix 1. Some entries relate to individual trees, others to local populations of trees. It is envisaged that this list, and the associated records on which it is based, will be a future resource for anyone pursuing further interest in dual purpose trees, and wishing to later check on individual tree performance, survival, changes in habitat or the response to pruning treatments. Tree phenology Tree growth, leafing and flowering phenology and other observations are presented in the results and discussion for individual species in Section 6. Tree canopy diameter measurements, although useful for indicating canopy area, generally required a subjective assessment of the location of the outer canopy. As a result, measurements in successive years were sometimes inconsistent with previous measurements, possibly due to irregular growth at the edge of the canopy ( increments in growth are not reported here). Due to the deciduous habit of A. lebbeck and A. procera, canopy expansion could be estimated not long before leaf drop. Just before leaf drop it could be assumed that the full leaf- bearing length of any stem could be counted as current season’s growth. It was found that A. lebbeck had a canopy expansion of 2 – 2.2 m/year (Lowry et al. 1991); and that A. procera had a canopy expansion 2 – 2.5 m/year in smaller trees. This method did not work well with the other species considered because many stems branched during the one season of growth making it difficult to assign a simple length increment. Measuring girths gave consistent results and, converted to basal area, is directly related to wood volume.

Only A. lebbeck showed significant amounts of fallen flower. It was negligible for A. canescens and A. procera, and not observed at all with Paraserianthes toona. In the case of M. Azedarach, flowering was conspicuous but the visible biomass on the ground was so low that it was not recorded. T. tipu had a profuse flowering in southeast Queensland in October 1997 with a dry matter yield below the canopy of large trees of 40–80 g/m 2 but production was much smaller in 1998. Flower production from Cassia brewsteri was surprisingly copious, with dry matter production of 150 g/m 2 below a large tree. Large trees of Gmelina arborea had a conspicuous flower fall but this was not investigated further.

Pod production was most conspicuous with A. lebbeck. In the case of A. procera, pods were highly visible in August to November because of their red colour, but they were not dropped evenly. Collection of individual bunches from A. procera suggested production of 1 kg from smaller trees, and 3 – 5 kg from larger trees. A. canescens pods were similar to A. lebbeck but produced less abundantly – about 1 kg per tree.

4.2 Tree Products as Feed 4.2.1 Feed evaluation Composition of fallen leaf, flower or pod of a number of species is shown in Table 1. In some cases results for green (mature, fully expanded) leaf are also given, to demonstrate that fallen leaf had less protein and higher fibre content than the green leaf. Fallen leaf had NDF content in the range 27 – 54%, considerably less than typical values for mature tropical grasses (70 – 80%). A. canescens pods were found to have no detectable saponin, unlike A. lebbeck pods which do have significant levels. The leaf of A. canescens A. lebbeck was virtually free of tannin.

Table 1 Composition and digestibility of tree materials

Species Substrate Protein Fibre Dig. (1) Ferm. (2) Albizia lebbeck Fallen leaf 46.0 24 20 Fallen leaf 11.3 47.7 26 Fallen pod 59.0 24 Albizia canescens Fallen leaf 14.6 37.5 Green leaf 23.0+1.9 65.0 20 Pods 14.3 Albizia procera Fallen leaf (1) 8.7 54.7 13 11.6 Fallen leaf (2) 38.8 4 10.5 Green leaf (1) 12.4 48.1 Green leaf (2) 38.7 Acc 19.1 Pods 71.7 Melia azedarach Fallen leaf 5.9 + .7 28.6 43 25.1 Green leaf 17.1+ 2.7 29.1 Tipuana tipu Fallen leaf 8.4 46.3 18 19.2 Mature pods 9.3 76.2 Green pods 70.0 Paraserianthes toona Green leaf 13.2 43.4 <1 15.0 Gmelina arborea Fallen leaf Bulk collection for feeding trial 4.2 42.3+ Field sample, freshly fallen 10.2 27.8 26 25 Green leaf 24.9 18 24.5 Gmelina leichardtii Fallen leaf 49.2 0–11 14 Archidendropsis Green leaf 13.1 + .6 41.1 5 16.5 basaltica Brachychiton discolor Fallen leaf 8.8 + 1.2 40.4 15 27.7 Dalbergia sissoo Fallen leaf 1.95 43.8 Green leaf 2.24 35.9 Bauhinia carronii Fallen leaf 31.3 Acc 6.2 Green leaf 29.9 Acc Acacia salicina 11.8 Casia brewsteri Fallen leaf 10.8 (1) NDF digestibility in vitro. (2) Fermentability in terms of final gas production (mV/g)

In vitro results The maximum in vitro digestibility of leaf NDF varied widely but was always much less than for grasses. When NDF residue was measured for a series of different incubation times to determine the time course for fibre digestion it was found that most fibre was lost in the first 24 hours and change was slow after that. In the same experiment grass substrates would show continuing loss up to 72 hours with a much greater final extent of digestion.

However, a major unexpected problem with the method was discovered – in some tree species the NDF residue recovered following incubation was actually higher than the initial value. This accretion occurred within the first 6 hours in some species with fibre decreasing thereafter, but in other species it persisted. Eliminating casein from the medium had little effect.

Monitoring in vitro gas production showed the different patterns of fermentation of fallen tree leaf and mature grass (see figure 1). In general, compared with dry season grasses, fermentation of leaf started sooner and proceeded initially at a faster rate. After about 24 hours the rate slowed and production was limited for the following 48 hours, while fermentation of grass continued for another 24 – 48 hours. Thus the substrates had equal VFA production in the range 12 – 24 hours, but final production from the grass was much greater. The significance of this in conjunction with differences in fragmentation and rate of passage is discussed later. Although this was a recurring pattern, and highly consistent for grasses, tree species varied widely in final gas production and initial rates.

Fig. 1. Gas pressure traces comparing fermentation of fallen A. lebbeck leaf with that of Angleton grass. Data was recorded at 10–minute intervals but plotted here using the 2–hour values to avoid cluttering the trace.

4.2.2 Synergy – In Vitro Experiments 1. Preliminary results The initial findings that prompted this work were with fallen leaf from trees in an agroforestry trial with rainforest species at Mt Mee. The effects on enhanced fibre digestion were presented as an Appendix to RIRDC 97/73. These immediately highlighted Eleocarpus grandis and Flindersia sp. as having a marked negative effect when co-fermented with spear grass. They also showed that white beech, Gmelina leichardtii, had an apparent synergistic effect. These results were presented in terms of NDF digestibility, which led to some confusion when comparing substrates of widely differing NDF content. Thus from now on results are presented in terms of actual NDF residues.

2. Experiments with Gmelina leichardtii Several subsequent experiments involving Gmelina leichardtii showed that the lower-than-expected fibre residue for the mixed substrate was repeatable.

Fermentations with different ratios of leaf and grass showed that the synergistic effect was observed best with 1:1 mixtures but also occurred with a higher content of grass indicating that it was the grass fibre that was being affected. Thus, for a 72–hour fermentation with spear grass:

Mixture Actual residue Predicted 20% fallen leaf 39.49 + .08 40.05 50% fallen leaf 41.44 + .30 43.11 80% fallen leaf 46.32 + .36 46.17

Conducting fermentation for different times showed that most of the positive effect was detected between 24 and 72 hours. Shorter times gave difficult to reproduce results, while actual and expected values tended to converge after very long incubation times.

Purine content at end of incubation did not show any major change in total microbial populations (Table 2). Solution from acid detergent treatment of NDF residues did not show any change to the dispersible lignin fraction.

Table 2. Fermentation of fallen leaf of Gmelina leichardtii and spear grass, separately and as a 1:1 mixture

Substrate NDF residue(1) Acetate(2) Propionate(2) Purines(3)

Spear grass 38.01+ .12 1.60+.08 0.55+.02 0.21

Gmelina leaf 48.21+ .33 0.65+.01 0.18+.00 0.18

Mixture 41.44 + .30 1.28+.10 0.40+.03 0.19 Predicted 43.11 1.13+.09 0.37+.02

Water extracted leaf 57.26 + .40 0.49+.04 0.15+.01 0.16

Mixture 46.37 + .17 1.16+.12 0.35+.03 0.18 Predicted 47.64 1.04+.12 0.35+.03

Water extract 0.0 0.19 0.04 0.04

Mixture 39.99 + .63 1.93 0.62 0.18 Predicted 38.01 1.79 0.59 1. Percent of original dry matter after 72 h incubation. 2. Mg/ml of medium 3. Absorptivity/g of substrate

Measurements showed that production of VFA from the mixed substrate was higher than expected, indicating some synergistic interaction when grass and leaf were fermented together (Table 2); and the reduced fibre recovery did correspond with higher VFA production. The water- extracted leaf also gave a positive interaction, while the soluble fraction did not. This implied that the interaction was occurring between the cell wall materials, either through morphological or chemical reasons, and was not due to a soluble constituent.

Batch transfer experiment When the supernatant medium from incubations with rumen fluid on grass, leaf, or the 1:1 mixture was used as the inoculum for new incubation, the inoculum from the mixed substrate was more effective at fermenting spear grass than that from speargrass only (Fig. 2).

Fig. 2. Gas pressure curves for a 2–stage fermentation. All refer to the fermentation of a pure spear grass substrate. The inoculum is from the previous fermentation of three types of substrate. The microbial consortium arising from fermentation of the mixed substrate appears to be able to ferment spear grass better than that from spear grass alone.

3. Range of Species This section presents results for a number of species before going on to consider those of most interest. They all involve 1:1 mixtures of the fallen tree leaf with the grass, standard media unless otherwise indicated, and rumen fluid as inoculum. They compare the NDF recovered from the mixture following incubation with that expected from grass and leaf fermented separately.

Tree Species Grass Incubation NDF NDF Effect Time Residue Expected Albizia procera Angleton 48 36.9 39.4 Promote Bauhinia carronii Angleton 48 +N 39.62 38.45 Inhibit -N 40.34 39.54 Brachychiton Spear 72 h 34.41 + .54 35.58 Promote populneum Angleton 114 32.5 34.2 Promote Dysoxylon Spear 72 37.22 + .87 31.38 Inhibit molissimum Eucalyptus Angleton 18 45.61 44.53 Inhibit platyphylla 42 38.65 34.64 114 33.98 31.0 Gmelina arborea Spear 72 25.18 25.94 Promote Melia azedarach Angleton 41 32.15 31.37 Inhibit Samanea saman Angleton 48 +N 40.8 43.0 Promote 48 -N 40.5 44.7

G. arborea Although they are closely allied taxonomically, NDF production from the leaf of G. arborea was different to G. leichardtii. Not only was the NDF content of G. arborea much lower but it digested at a significant rate in vitro; however, it also showed a synergistic effect when mixed with spear grass (see above).

When mixed with Angleton grass, there was considerable synergy. Gas pressure curves (Fig. 3) show the course of fermentation, with the faster initial rate for the leaf, and the curve for the mixture lying well above that expected for no interaction, which would be midway between the leaf only and grass only curve. Data from stopping fermentation and measuring residual NDF for the mixture at different times are shown in Fig. 4. There was enhanced fibre digestion throughout, but it maximised at 48 hours. The effect was greater when the amount of inoculum was reduced (x 1/10) indicating that the

mixed substrate probably provided a better medium for a cellulolytic consortium to grow. It occurred in the usual medium containing nitrogen and also in a nitrogen-deficient medium. Solvent-extracted leaf showed a similar synergistic effect. The water extract had a slight inhibitory effect on fermentation of the grass substrate. It should be noted that these experiments were done with a sample of fallen leaf collected for analysis, not the bulk lot used for the feeding experiment, which was of much lower quality.

Fig. 3 Fermentation of G. arborea fallen leaf, Angleton grass, and the 1:1 mixture. As with Fig. 1 they show the more rapid initial fermentation but lower final pressure for the fallen tree leaf compared with grass. The curve for the mixture would be expected to come midway between those for the pure substrates. Instead it is considerably higher after 24 hours.

Fig. 4 Actual fibre recoveries from fermentation for different times of a mixture of fallen G. arborea leaf and Angleton grass, compared with those expected from the results of incubating each separately. The result at 48 hours represents an increase of NDF digestibility from 38% to 48%.

4. Results for A. lebbeck and T. tipu Green leaf of A. lebbeck was co-fermented with spear grass. The mixing induced a small increase in the amount of NDF fermented; the residue was 33.33% versus 34.36%. This corresponded to an increase of NDF digestibility from 41.8% to 43.6%. Subsequent experiments gave the following NDF residues with mixed substrates:

• Fallen leaf of T. tipu with Angleton grass 33.37 v 36.30 expected • Fallen leaf of T. tipu with carpet grass (Axonopus compresus) 35.18 v 36.69 • Fallen leaf of A. lebbeck with Angleton grass 32.47 v 34.62

In each case the mixture had enhanced fibre loss and gas production.

T. tipu was mixed with Angleton grass in three ratios (1:3, 1:1, 3:1) and fermented in media containing nitrogen or media deficient in nitrogen. Synergy was greater in the absence of nitrogen, suggesting a role for protein, but was also present at lower levels in the presence of abundant protein or non-protein nitrogen. There was enhanced gas production but little effect on fibre recovery.

A. lebbeck was mixed with Angleton grass in three ratios (1:3, 1:1 and 3:1), and fermented with media containing nitrogen, or media deficient in nitrogen. There was enhanced fibre loss in all treatments.

The total extracts from sequential extraction with ethanol and then water of A. lebbeck and T. tipu were added to Angleton grass at a level corresponding to a 1:1 mixture. Addition of each extract cause increased fibre disappearance.

Carpet grass was fermented with and without A. lebbeck extract using different microbial consortia as inoculum. The extract produced enhanced fermentation, particularly with the microbial consortium (dominated by Ruminococcus) from the addax antelope.

Separate extracts were prepared from A. lebbeck by sequential extraction with ethyl acetate and water giving non-polar and polar constituents. These were added to fermentations of carpet grass with the different consortia. Enhanced fermentation occurred with the water-soluble fraction and not the ethyl acetate extract.

5. A. lebbeck extract on cotton thread Previous results showed that the water soluble fraction from fallen leaf of A. lebbeck was capable of promoting grass digestion in vitro. The following experiment was designed to determine the actual agent responsible for the digestion. The effects of various soluble compounds or extracts were tested on the time required for complete digestion of a pure cellulose substrate, cotton thread.

Fig. 5 Gas pressure from the fermentation of pure cellulose (cotton thread) by rumen fluid in a complete medium with and without the presence of solubles from fallen leaf of A. lebbeck and from lucerne. Digestion of the cellulose was completed 30 hours earlier in the presence of the extracts.

The activity of A. lebbeck extract in promoting cellulose fermentation was determined before and after ultrafiltration through a 3000 Dalton membrane. Activity was unaffected by ultrafiltration, indicating that it was due to a low molecular weight component. In case the activity was due to an easily hydrolysable component we also tested A. lebbeck extracts before and after acid hydrolysis. Activity was largely retained on treatment, suggesting that it could not be due to a specific peptide or oligosaccharide.

The effect in the same system of some possible compounds that could be responsible was determined. These included different levels of cyclitols (inositol, pinitol and quebrachitol), starch, sugars and sugar alcohols (mannitol). Some extracts did enhance gas production through their own fermentation but did not affect the time at which cellulose digestion was competed.

Extracts prepared from a number of high quality pasture legumes were also tested in the system, and found to have effects similar to that from A. lebbeck fallen leaf (see Discussion).

4.2.3 Animal Experiments 1. Voluntary intake experiments with fallen tree leaf With most of the species available in sufficient quantity to determine voluntary intake, sheep would eat more than 100 g/day in addition to the basal grass diet. The voluntary intakes (g/head/day) for sheep offered both mature grass and fallen tree leaf were as follows:

Tree species Grass species Days Grass intake Leaf intake Celtis sinensis Carpet / Rhodes 9 422 + 126 321 + 115 3 none supplied 670 + 109 Melia azedarach1 Carpet / Rhodes 4 602 + 63 102 + 48 Cassia brewsteri Carpet / Rhodes 7 557 + 97 102 + 33 Flindersia australis2 Carpet / Rhodes 4 not determined 183 + 62 Bauhinia variegata Angleton 3 not determined 302 + 73 Tipuana tipu Carpet / Rhodes 4 570 + 220 nil Ficus benjamina Carpet / Rhodes 4 670 + 105 64 + 55

The most obvious observation was the sheep’s non-acceptance of fallen leaf or pods of T. tipu. The leaf had been stored for some weeks, but the pods were freshly fallen. Apart from T. tipu there was an obvious and consistent preference for freshly fallen leaf (offered within 24 hours of falling) for all species where this comparison could be made. In some cases sheep were able to distinguish between this material and a batch only 24 hours older. With M. azedarach, intake decreased sharply after three days. This is sometimes an animal response to the presence of toxins. Although unlikely, there had been no application to test toxic substrates, and feeding of this leaf was stopped. There were very large between-animal differences with the Flindersia leaf.

In addition to the above, more rudimentary observations were made with small amounts (up to 1 kg) of material as follows:

Albizia canescens Pods Eaten over 2 days in the presence of maintenance diet Green leaf Eaten readily, including stem material Bombax ceiba Freshly fallen flower Eaten readily, sought out actively among basal feed Brachychiton discolor Fallen leaf Eaten readily Pongamia pinnata Green leaf Eaten readily Archidendron thozetiana Green leaf Eaten readily Barklya syringifolia Green leaf Eaten readily Cassia tomantella Green leaf Eaten readily Cassia brewsteri Green leaf Avoided at first, a little eaten after 1 day Cassia brewsteri Fallen flower Not eaten

Among other observations, the sheep strongly preferred Brachychiton discolor (lacebark) fallen leaf to the basal diet. The large and fragile individual leaves were picked up and carefully manipulated to ingest the entire leaf without dropping any pieces.

Field Observation In two cases it was evident that cattle were using fallen leaf in the field.

At Fairymead Road, near Rockhampton, a very large M. azedarach tree was located on a fence line with about half the canopy over a heavily grazed paddock and half over a road reserve. In early July, the tree was leafless but only recently so. The sub-canopy area in the road reserve had large amounts of freshly fallen leaf, difficult to estimate because of rough vegetation, but about 50 g/m2. Virtually no fallen leaf was on the ground in the sub-canopy area within the paddock – which was so well grazed that every leaf was visible. It was clear that cattle had been eating fallen leaf. The only qualifier to this

finding was that this paddock was so heavily grazed that it may not reflect behaviour of animals when pasture is plentiful.

Near Woodstock, inland from Townsville in an area of flat plain with fine textured duplex soils were scattered infestations of Zizyphus mauritania (chinee apple) a shrub or small tree that is a woody weed in Australia but valued as a fruit and fodder tree in much of the dry tropics. It is facultatively deciduous and had shed almost all leaf during an October dry period. A number of shrub canopies straddled the fence line between a heavily grazed paddock and ungrazed reserve, in both of which the ground was fairly bare. It was obvious that there was much less fallen leaf on the ground on the grazed side compared with the ungrazed side. Further observations from other sources and recent relevant research are in the Discussion.

2. Feeding Experiment with Gmelina arborea The bulk collection of fallen leaf by the time it arrived at the Tropical Beef Centre was considerable darker than freshly fallen material. There was a gross difference in composition not known at the time of collection; the fibre content was 42% instead of 27% for freshly fallen leaf, and protein was 4.3% instead of 10.2%.

The leaf-only diet The expectation of high intakes arising from previous fragmentation studies and in vitro and intra- ruminal nylon bag results were not realised in the actual feeding experiment. For two days intakes were close to those on the mature grass (about 700 g/day) then dropped abruptly to about 350 g/day. Although there was considerable between-animal variation, on the sixth day, when the average intake was about 300 g/day, it was decided this treatment could not continue for ethical reasons as sheep would be below maintenance level. The treatment was terminated, and the group of sheep were supplied a leaf/grass (2:1) mixture. An attempt to calculate the nutritional parameters from the limited data gave the following results:

Dry matter intake: 471 + 71 g/day Dry matter digestibility: 41 + 9% NDF digestibility: 36% Nitrogen digestibility: 18%

A parameter that turned out to be of unexpected interest (see Discussion 5.1) was the faecal dry matter content. At 58 + 5% it was significantly less than that for the grass diet: 70 + 2%.

Mixture of dry-season grass and fallen leaf Full monitoring of the grass only and mixed diets commenced in week 2, with both the grass and the mixed diet being supplied with a 10% excess. It was evident that intakes of the mixed diet did not show any evidence of enhanced dry matter intake. As previously noted, the leaf being used was scarcely palatable to sheep. Furthermore when a limited amount of freshly fallen leaf was obtained from a local source, sheep immediately ate this in preference to the bulk supply on offer. It was also evident that the leaf material was quite heterogeneous. There were visible differences in colour and texture and because of the large leaf size sheep were able to be quite selective about what they ate from it. As well as this the feed residues from the chopped Angleton grass contained very coarse stem material that the sheep were clearly selecting against. On the grass only diet there was sufficient excess for this not to affect total intake, but on the mixture, with less total grass present, it could result in lower grass intakes through sheep being forced to eat a lower quality fraction. For this reason in the third week we increased the amount of both leaf and grass on offer so that sheep on the mixed diet had at least the possibility of selecting acceptable leaf, and of being able to select the grass component of equal quality as that on the grass-only diet.

The original protocol envisaged urea supplementation in week 3 in case synergy effects could occur only in the presence of adequate nitrogen. In the event we supplied all sheep with cottonseed meal at 100 g/day as a protein supplement. This had the overall effect of increasing intake, and the generally

expected effects with the all grass diet. Supplementation and the increased opportunity for selection introduced large between animal variation on the mixed diet. Even with increased grass availability some animals selected a substantial proportion of leaf. The intake and digestibility data were as follows:

Week 2 Week 3 Grass only Grass/leaf Grass only Grass/leaf Dry matter intake 636 + 21 598 + 46 784 + 26 807 + 62 Dry matter digestibility 43 + 5 24 + 4 43 + 4 44 + 12 Faecal dry matter (%) 70 + 2 58 + 3 70 + 2 59 + 5 Faecal nitrogen (%) 1.37 + .19 1.70 + .15 NDF digestibility (%) 43 + 2 39 + 13 Proportion of leaf selected (range,%) 0 – 43

These results are further discussed in Section 5.1.

3. Synergy – Infusion experiment with A. lebbeck fallen leaf Infusion with the water extract from fallen leaf of A. lebbeck appeared to have a remarkable effect on feed intake, which was about 100 g/day higher than that for the control animal. The positive control, an extract of lucerne also showed an increased intake. This was to be expected as it should have had enough soluble nutrient to give an effect akin to supplementation. During the infusion periods (three sheep x three days) average daily feed intakes were as follows:

Sheep infused with A. lebbeck extract 676 + 33 Sheep infused with Lucerne extract 663 + 89 Control sheep infused with water only 565 + 69

Unfortunately there were no significant results on the digestibility of samples in intra-ruminal dacron bags during the infusion periods.

4. T. tipu Seed in the Bovine Tract No seed or recognisable seed fragments were found by washing and sieving faeces for the week following the introduction of intact pod in the rumen. When the whole pods were placed in the rumen in dacron bags for up to one week the non-vascular tissue was extensively digested leaving much of the fibre as a web surrounding the seed. There was no indication of the seed itself imbibing water or softening.

4.3 Tree-Grass Interaction Measurements done on the main species of interest are shown in Table 3. There were promotional effects with A. procera, A. canescens, C. brewsteri, M. azedarach and T. tipu. P. toona had markedly inhibitory effects at the site studied. More data on A. lebbeck are presented in Section 6. Section 6 also summarises the new data on the effect of isolated trees on sub-canopy grass.

4.4 Wood Use When the Sunto increment borer was used to attempt to locate the position of the boundary between sapwood and heartwood in A. lebbeck trees it proved impractical to get cores of more than about 75 mm depth. The device became very difficult to turn, possibly due to the wood grain in A. lebbeck, as previous attempts had worked well with softwoods and eucalypts. However one could say that in trees up to 7 years old it was not possible to detect any heartwood. Simple drilling with a 6 mm auger on large trees known to have been fast growing showed sapwood depth was 100 mm – 110 mm. Radial sections showed ill-defined rings but these were due to the distribution of large ducts. No variation in xylem could be detected at x100 under a binocular microscope and nothing resembling the annual rings of temperate woods. However, assuming the distribution of ducts had a seasonal basis, it seemed likely that sapwood contained 7–8 years’ growth.

Pruning was carried out on A. lebbeck at Yandilla, Brian Pastures, Lansdown and Glendhu, on red A. lebbeck and M. azedarach at Amity Creek and on T. tipu at Glendhu.

Table 3 Production and quality of sub-canopy grass cover (canopy) compared with that growing outside the canopy (open).

Crude Protein Fibre (NDF) Dry Matter (g/m2) Canopy Open Canopy Open Canopy Open Albizia lebbeck 1 * 10.4 5.5 301 157 2 ** 395 + 63 248 + 12 Albizia procera 1 19.5+.4 8.1+.2 67.1 + .2 71.9 + .9 2 10.7+.9 3.2+1.4 62.0 + 1.4 75.8 + 1.5 3 4.8 1.1 69.1 71.1 Albizia canescens 1 13.2 8.1 70.8+1.7 76.6+1.7 2 17.8+.6 11.7+2.1 68.7+2.2 69.0+.2 3 16.7+ .7 9.4+2.8 69.1+ .9 70.6+3.9 4 11.1+1.1 4.1+.9 5 378 + 174 89 + 14 Tipuana tipu 1 10.2+.2 8.2+.7 72.9+.9 72.3+1.6 175+11 143+22 2 63.2 + 1.6 66.7 + 2.9 102 + 22 80 + 32 Melia azedarach 1 12.5 + 1.5 6.3 + .6 2 3.9+.4 4.1+.2 236+73 174+34 3 12.5+1.5 6.9+.6 4 *** 12.1 + 3.6 7.6 + 2.7 68.1 + 2.3 71.5 + 5.1 Paraserianthes toona 5.5+.7 3.2+.4 109+75 299+85 Cassia brewsteri 7.5 + 1.1 6.0 + 0.0 76.6 + 1.8 77.3 + 0.1

Results for individual sites in the dry season. * Summary of previous unpublished data for July ** Radial transect, see Section 4.4 *** Mean of single samples from 4 different sites

From observing growing seedlings and existing A. lebbeck trees it was clear that the first appropriate time for pruning would be after about 1 year when there is often major branching of the main stem at about 2 m height. Simple pruning with secateurs should ensure further development of a clear main stem with minimal effort; however, no trees in early initial growth were available and we carried out pruning on larger trees of height 4 m – 6 m, with a variety of branching patterns below 3 m. There was no difficulty in positioning the cut, as the lateral branches had a distinct flare where they joined the main stem, enabling a cut with minimum surface area, but still close to the main stem and the thicker more actively callus-forming cambium. Records from this exercise will be available for future evaluation.

The difference in callus potential is shown by the regrowth at an old obliquely lopped branch (Fig. 6). Where the cut was close to the main stem, wood was growing over the old cut surface. The stem bark on the other side showed little regrowth.

As mentioned in RIRDC 97/73, Mr Ron Holme of “Glendhu” had earlier carried out pruning of Dalbergia sissoo trees on his property. Some useful information resulted from this. It is evident from his trees that heavy or early pruning may result in formation of epicormic shoots that would not

otherwise occur. This is no problem as they are very easy to remove, but does suggest checking the trees about two years after pruning.

Milling was carried out on logs of A. lebbeck, A. canescens, A. basaltica, Acacia bidwillii and C. brewsteri (see Section 7). The sawn timber resulting from this is currently held at Tropical Beef Centre.

A number of turned articles using the species of interest are currently in Brisbane or at Tropical Beef Centre, and are available for displays, or otherwise promoting the use of dual purpose trees. A list is as follows:

• Albizia lebbeck Square concave clock mounting, 240 mm x 240 mm Three-drawer trinket box Pedestal clock mountings (two only) Vase (very darkly figured wood), 110 mm x 60 mm Turned vase displaying inner and outer wood • Tipuana tipu Open bowl 220 mm x 80 mm Recurved bowl 200 mm x 50 mm Flask 140 mm x 120 mm • Melia azedarach Platter 390 mm Platter 200 mm • Albizia basaltica Vase 170 mm x 70 mm, uses whole stem, displays heartwood contrast Vase 130 mm x 80 mm, as above • Moreton Bay fig Fluted vase 150 mm x 90 mm • Bauhinia variegata Open bowl 210 mm

Figure 6 Pruning of A. lebbeck

This large (90 mm diameter) branch was cut obliquely to the main stem. At the top the cut was right on the collar of maximum callus-forming potential, and there has been an outgrowth of new wood. At the lower edge the cut is about 20 mm away from the main stem (not obvious because of perspective) and the only cambium exposed is that of the thinner bark of the side branch. Almost no new wood has formed on this edge. Obviously pruning of such large branches is not contemplated; however this shows the importance of positioning the cut on smaller branches to get the most rapid closure with minimum defect potential.

5. Discussion – General

5.1 Feed from Large Trees 5.1.1 Flower and Pod, Green Leaf The production of fallen flower or pod in substantial amounts by large A. lebbeck prompted the hope that on investigation there may be other species that could also make a significant nutritional contribution. However none of the principal species in this study produced flower or pod as profusely. Of the two species that did produce substantial amounts (T. tipu pods and C. brewsteri flowers), the pod and flowers turned out to be unpalatable. Other observations are in the notes on individual species. At the moment the only recorded case of flower fall being used by grazing animals is with cocky apple, Planchonia careya (Lowry 1992), which is not one of the tree species in this study.

The potential role of green leaf may be much higher than envisaged in RIRDC97/73. This is because of the indications that with species such as A. lebbeck, heavy lopping of the green crown should be carried out for a number of years before log harvest in order to increase wood quality.

5.1.2 Using Fallen leaf Many trees in the dry tropics shed all or some leaf during the dry season. For the purpose of this project species were selected that dropped all leaves over a limited period in the dry season. This may or may not involve the tree being visibly leafless as some trees undergo complete leaf change during which the entire canopy is shed as new leaf is produced. However in the dry tropics many trees are completely leafless in the late dry season, which makes both the fallen leaf and the new leaf potentially important for livestock feed.

Do animals actually eat fallen tree leaf? In terms of evidence for the significance of fallen leaf as feed, it is now apparent that considerably more exists than the few cases cited in RIRDC97/73. Additional reports include: • For northern coniferous and hardwood forest, foliage fall is a food source for wintering white-tail deer in Maine (Ditchkoff and Servello 1998). In British Columbia, litterfall has been reported as a feed source for mule deer (Waterhouse et al. 1991) and for black-tailed deer (Rochelle 1981). This even included foliage fall from a conifer, Douglas fir. In Japan sika deer use fallen leaf in mountain forests (Borkowski and Furubashi 1998). • In cool temperate forests, white tailed deer on Stewart Island (New Zealand) obtained most of their food as fallen leaves and fruit (Nugent and Challies 1988), and from a wider range of species than in a previously cited report for South Island. • In the dry tropics, leaf fall from Commiphora africana, Sterculia rhynchocarpa and Terminalia spp was an important part of the dry season diet of goats and cattle in Kenya (Scholte 1992). There also, goats are said to thrive on the leaf fall of Acacia meliflora (Dougall and Bogdan 1958). Within Australia there are several reports that large amounts of fallen leaf of yellow-wood (Terminalia oblongata) are occasionally eaten by sheep or cattle (Carroll 1985). This has been noted in the context of a sporadic toxicity problem with yellow-wood, which generally is regarded as a useful browse tree. An interesting point here is that the fallen leaf is considered innocuous compared with new growth (Anderson 1993). • In the Mediterranean environment, goats in Northern Greece rely heavily on autumn leaf fall of ash and hornbeam (Papachristou and Nastis 1996). In Crete livestock use fallen leaf of kermes oak, but it is not highly preferred (Papanastasis and Misbah 1998). In Tunisia fallen leaves of many species are used by milking goats (Scheurmann 1981). Fallen oak leaves are an important food source for red deer in north east France (Picard et al. 1991). In South Africa freshly fallen dicotyledonous leaf is an important part of the diet of blue duiker and red duiker (Bowland and Perrin 1998). Even more surprising, Suni antelope, which were regarded as browsers are now thought to feed largely on freshly fallen leaf of a large number of plant species (Lawson, 1989). In China, the fallen leaf of Paulonia is fed to pigs

(Gutteridge and Norton 1992) and should thus be quite acceptable to ruminants. Fallen leaf of Populus nigra is a feed of sheep in China (Li 1984) and in Spain (Orensanz et al 1983).

• Unpublished records include: Fallen leaflets of Parkinsonia aculeata are eaten by goats in Mexico (Dr Janet Stewart, Oxford Forestry Institute). In plantations of Gmelina arborea in West Africa, fallen leaf is carried out of plantations for village livestock (Dr J. Lambourne, consultant). In Kenya woodlands, cattle eat fallen leaf of Grewia sp, the crunching sound being audible when the cattle are not visible (J. Stuth, Texas A&M University). Various unpublished observations from inland Australia refer to sheep eating the fallen leaflets from Acacia nilotica and the fallen phyllodes of Acacia cambagei, although the green leaf is toxic, and cattle eating the fallen leaf of native Bauhinia spp. Horses actively seek out the freshly fallen leaf of Chinese elm, Celtis sinensis. Sheep are sometimes moved from Mitchell grass paddocks into Acacia cambagei woodland to use leaf fall (Dr David Taylor, Forest Research Institute, Queensland).

The results obtained in this project together with the above published and unpublished and earlier records together comprise 14 tree species in Australia, which indicates that fallen leaf may be a significant feed source.

In contrast to the above additional field-based observations, there are no further reports indicating intake and digestibility of fallen leaf from pen feeding trials. Despite the number of reports or observations in individual systems there seems to be no published comments, apart from those of the author (Lowry and Wilson 1999), about any possible general significance of fallen leaf as a feed resource.

Indirect Evidence Recently, there has been striking indirect evidence for use of fallen leaf in northern Australian rangelands. In a major study on stocking rates and land condition, Ash et al. (1995) used faecal C13 measurements to determine the proportion of C4 (tropical grasses) and C3 (forbs, browse, legumes) plants in the diets of grazing cattle. They found that on degraded lands in the dry season cattle had up to 30% C3 plants in the diet. This was under conditions where no green legumes or forbs could be found, which suggests a high proportion of the diet was likely to be fallen tree leaf, even that of eucalypts.

Faecal analysis by near infra red reflectance spectroscopy (NIRS), which can indicate the proportion of non-grass species in the diet, has recently been applied to grazing cattle in northern Australia. This has shown high intakes of C3 species in the dry season at some sites, and also even in the late wet season at a site that was noteworthy for a high incidence (up to 40%) of browse species (Coates 2000, Oerlemans 1999). These suggest that non-grass contributions are at much higher levels on dry-season pasture than had been thought possible. It seems likely that at a proportion of this is fallen leaf rather than browse.

Another relevant recent paper reviews the relation between stocking rate and animal condition (Ash and Stafford Smith 1996). It highlights and addresses the paradox that animal condition may remain anomalously high when pasture indices suggest animals should be in very poor condition. This suggests that animals could be using feeds in the environment not included in the usual pasture assessments eg fallen tree leaf Of interest is whether the synergy of co-fermentation of grass with certain leaf may have occurred in the and contributed to better use of the remaining dry season grass, to help account for animals retaining condition.

The paradox – senescent leaf is best fresh Fallen leaf, regardless of metabolic state was used in the experiments because it would be present in grass that had been dead for many months; however, observations in this project showed that ‘freshness’ of fallen leaf was very important to animals – animals clearly selected for the most recently fallen leaf within a particular batch.

The physiological changes following leaf abscission will be different from those in hayed-off grass, because of the phenolics commonly present in tree leaf. As cell membranes break down there will be an opportunity for the remaining protein to become bound with leaf phenolics. The phenolics will be exposed to the action of polyphenoloxidases before these are denatured, and will then be exposed to aerial oxidation. Both processes could yield quinonoid products that may be toxic to micro-organisms. The chemistry involved is similar to the enzymic browning that occurs on the cut surface of fresh food such as apples.

An interesting situation applies with Cassia brewsteri, in which freshly fallen leaf was preferred to green leaf. This observation has considerable implications (Section 7; Cassia brewsteri). However we note here it is not without precedent. Something similar may happen with Acacia argyrodendron (gidgee) as noted at Noonbah. Together with the experiments and observations in the current project it seems evident that: 1. There are at least some and probably many tree species from which animals will eat considerable amounts of fallen leaf in the presence of mature grass. 2. The freshness of the fallen leaf is important. 3. Cassia brewsteri is particularly interesting in that the fallen leaf is preferred to green leaf..

5.1.3 Composition

Protein contents of fallen leaf while lower than the green leaf (Table 1) were generally higher than for dry-season grasses.

The results for fibre highlight an aspect not obvious from the general paradigms on grazing animal nutrition, in which it is assumed that: 1. Neutral detergent fibre (NDF) is an acceptable measure of cell wall content of all forages. 2. The non-fibre NDF fraction is fully digestible and of high nutritional quality. 3. Low quality forages have high NDF content and most of the energy for animals fed on them comes from digestion of fibre.

Thus for mature grasses, nutritional quality is thought to be determined (inversely) by the NDF content and (positively) by the rate and extent to which it can be digested. The most important variables are the rate and extent to which NDF is fermented.

This model does not fit well the results presented here. Firstly, the chemistry of grass and dicotyledonous tree leaf is different and thus NDF is different.

Secondly, the technique for NDF determination was not suitable when used on incubated material of some tree species. The solid fraction recovered as NDF, was sometimes higher than in the samples prior to incubation, giving rise to apparent “negative digestibility”. Fermentation was undoubtedly occurring but there was also an interaction that resulted in production of material that resisted dispersion in the neutral detergent reagent. Some of the more obvious explanations were tested but did not account for the effect. .

Although fallen tree leaf would be regarded as a low quality fibrous feed and would be expected to have more fibre than the green leaf, we found the NDF content of fallen tree leaf (25 – 55%) was much less than in grasses (70 – 80%). Furthermore the NDF itself was much less digestible. Allowing for problems with the method, it was clear that in some species it was virtually unchanged during incubation. Thus the nutritional value is more dependent on the non-NDF (ND-soluble) fraction. With green leaf it has been assumed that most of the non-NDF fraction is protein, lipid, soluble carbohydrate and mineral, as well as soluble secondary compounds such as phenolics, and that, as with grasses, most of it is digestible for the animal. This is not the case for fallen leaf and there are big differences in the amount and availability of this non-NDF fraction, which will have a major influence on the net nutritional value of the material. In the absence of broad spectrum anti-microbial activity it

is quite reasonable that some compounds can interfere with attachment or function of the cellulolytic organisms while other organisms dealing with the easily fermented solubles are unaffected. Thus there can be some gas pressure increase in the absence of fibre digestion. A further complication is that we have found that certain common leaf phenolics, normally thought of as adverse factors, can be rapidly degraded to acetate by rumen organisms, and thus can be regarded as nutrients.

Despite the uncertainty of the factors involved in the fibre digestion, the final VFA production from fallen tree leaf is about half that from mature tropical grass, which indicates that there are more accessible nutrients in the grass. However to obtain these, the grass would have to stay in the rumen for 72 hours or more, which would represent a rate of passage so slow that the animal would starve. In fact, feed particles break down and leave the rumen according to size, whether or not they are digested, and there is a trade off between rate of digestion and rate of passage.

Morphologically tree leaf is different from grass: it has a more reticulate structure and less tensile strength. Under the mechanical process of chewing it should break down more readily and yield less linear particles (Kennedy and Lowry 1996). In these experiments G. arborea was notable for the speed and ease with which it fragmented. Thus although tree leaf has less total available nutrients than the grass, the rapid fragmentation coupled with the rapid initial fermentation suggest that the animal could extract these nutrients quickly and increase its intake. It should also be noted that tree leaf is important as a source of protein.

A further aspect with pinnate legumes such as A. lebbeck is that leaflets separate from rachis and rachillae on senescence, and it is really only the leaflets that are likely to be eaten. Loss of quality on senescence will be to some extent offset by the shedding of the more highly fibrous rachillae. In the case of A. lebbeck the respective NDF content of leaflets and rachii were 42.9 and 53.6.

Gmelina arborea feeding experiment It was originally hoped that this experiment would fulfil two objectives.

There was sufficient preliminary information to suggest the leaf would be eaten. The in vitro and intra-ruminal bag results showed that the leaf should be highly digestible and could be eaten in large amounts because of its fragmentability, making it a feed of potentially high value. This would point to a remarkable agroforestry role for G. arborea, hitherto seen only as a plantation forestry tree. G. arborea showed synergy in co-fermentation of leaf and grass.

The degraded material used in the experiments were likely to have lowered the digestibility. The much higher fibre and lower protein values of this material indicated that much of the original dry matter was by autolytic or microbial changes and this would be the fraction that was readily metabolisable and digestible.

However, even with a poor intake, we would have expected from the intra-ruminal nylon bag results a higher digestibility than observed. We believe a novel factor could be contributing to this result. Fragmentation studies showed problems wet-sieving suspensions of G. arborea leaf and in filtering neutral detergent extractions and in vitro cultures because the water phases were often highly viscous. This was attributed to a soluble polymeric fraction which it was assumed would be fully fermentable under rumen conditions. It was an experimental inconvenience but almost certain to be part of the digestible fraction. However the consistently higher water content of faeces on the leaf-only and leaf/grass diet suggest strongly that the leaf has a non-degradable water-soluble component that is contributing bulk to the digesta. Simple comparative viscosity checks on water extracts from the faeces suggest this is the case. If so, it explains one anomaly with the intra-ruminal bag results: an indigestible but soluble component would diffuse out of the bags and could be counted in the digestible dry matter fraction even if it was not utilised in the tract. Such a component would be regarded as desirable “soluble fibre” in human nutrition but almost unheard of in ruminants.

A further interesting implication is that, if we assume gut volume is more or less constant, the higher digesta water content with the leaf diets means that the animals are not able to accommodate as much dry matter in the whole tract as on the grass diet. In fact in week 3 dry matter intakes and digestibility were comparable. This means that there may be a synergy with the mixed diet enabling the animals to process it more effectively.

It was notable that despite the poor acceptance of leaf on its own, when animals on the mixed diet had access to just as much grass as those on the grass diet some of them selected substantial amounts of leaf. The in vitro experiments show high gas production for the relatively small amount of fibre being fermented, indicating that a lot is coming from the non-fibre fraction.

It is also possible that from the very great variation between animals, the gut microflora in some animals may be becoming adapted to the unusual substrates in the leaf.

5.2 Fallen leaf and synergies Clearly not all trees are browsed by ruminants. Some are overtly toxic, and some are avoided for other reasons. The differences are due to the secondary compounds that are much more diverse and abundant in trees than in grasses. Whatever the effect on the whole animal, these compounds are also capable of affecting rumen function. It is perfectly possible for a leaf constituent with broad spectrum anti-microbial activity to interfere with digestion, as seen with shrubs containing essential oils. Other compounds are inhibitory but there are also microbial routes for degrading them. It was expected that there will be little gain from mixing leaf and mature tropical grasses in available nutrients and that a possibility existed of some compound interfering with cellulolytic activity. Despite this, experiments by A.C. Schlink in Townsville indicated that the effects of pasture legume supplements in promoting fibre digestion were greater than could be accounted for by the protein in the legume. Other studies suggested that there have been indications of positive associative effects with high quality supplements (Wood and Manyuchi 1997, Nahsahli et al. 1995). Experiments on low quality roughage had not been conducted and provided further rationalisation for the experiments with fallen tree leaf and mature tropical grasses. . Additionally, the very different nature of the lignocellulose in tree leaf and tropical grass suggested opportunities for different micro-organisms to exploit different parts of the system. These experiments concentrated on fallen leaf because: • Fallen leaf was the substrate actually available in a dual-purpose tree system. • With green leaf one might expect some kind of enhancement akin to that found with supplementation by pasture legumes. • The difference in protein of green and fallen leaf would be unlikely to affect the outcome as the fermentation medium contained added protein (see Methodology).

If synergistic effects did occur it would have important implications, namely that animals grazing pastures with leaf fall of the appropriate species will perform considerably better than otherwise expected. It would clearly be important for the use of trees in pasture. Since this is an important question in principle, this section is devoted to considering if such a synergy can be demonstrated in any species.

The first experiment was mentioned in an appendix to RIRDC 97/73 and used a collection of tree species from an RIRDC experimental site at Mt Mee, north-west of Brisbane.

Following this, work concentrated on G. leichardtii (white beech) because it was already under trial for planting in pasture (fallen leaf was collected), it was dry-season deciduous with a relatively large leaf (i.e. easy for animals to pick up), and because in initial exploratory experiments it appeared to yield synergistic effects. This was confirmed by a series of subsequent experiments, as described.

Work with this species and others exposed unexpected problems with the method, largely because it was an unusual substrate. For this and other reasons we turned to species of more direct interest as dual purpose trees, or at least those having some significance as browse, as well as looking at a wider range of trees. G. arborea gave unequivocally positive results. In Gmelina sp., despite differences in levels and digestibility of the NDF, synergy was associated with the fibre or at least insoluble fraction, and not with the solubles.

After investigating the phenomenon in G. leichartii, where it was first observed but of little forage interest, we found it far better manifested in fallen leaf of A. lebbeck, the species already of most interest as a dual purpose tree. Here it was associated with both the fibre and the soluble fraction. The soluble component promoted the attack on pure cellulose by rumen bacteria. The agent responsible was a low molecular weight, polar, non-hydroysable compound. A similar activity was found in extracts of lucerne,and thus it was concluded the phenomenen was not peculiar to A. lebbeck – any further investigation could be mainstream nutritional research.

Of the other species studied, it seems that the larger inhibitory effects were found with the trees that had little known significance as browse, while the positive effects were with those that were good feeds. This is an interesting inference as most studies on acceptability of forages assume that this depends on action on the animal – acute or subclinical toxicity and taste aversion. These results suggest effect on rumen microbes could also be a factor affecting choice of forage. The single result presented for A. procera is probably real but there were some odd results with this species, despite its closeness to A. lebbeck. The result for poplar gum Eucalyptus platyphylla is of interest because this is a common eucalypt that, unusually, does shed much leaf in the dry season.

Infusion Experiment This was an attempt to see if the fibrolytic effects seen in vitro could occur in the whole animal. Given the in vitro results we included lucerne extract as a positive control. This would be expected to have some positive effects because of known soluble nutrients in it and would be akin to carrying out a supplementation treatment. An external factor was that some weather changes during the experiment caused intakes and probably digestion to vary widely. Despite this, in two of the infusion periods sheep treated with A. lebbeck and lucerne extracts both had markedly higher intakes than the control sheep. The third period appeared anomalous only in that the control sheep had a surprisingly high intake (a difference of 100 g/day) If so, it is possible to say that water solubles from A. lebbeck fallen leaf were as good or better than those from an equal weight of lucerne for promoting intake, although they would certainly have contained less protein.

We expected to observe dry matter loss in the intra-ruminal dacron bags. Improved fibre digestion in the rumen may be reflected in higher dry matter digestibility in the whole tract, but it may also lead to higher intake with little change to digestibility. The system processes it faster rather than increasing the extent of digestion. However for samples retained in the rumen in bags, we would expect to see an increase in extent. Unfortunately the bag data was inconclusive

Dry matter loss during the A. lebbeck treatments was somewhat greater than during the lucerne treatments implying that the A. lebbeck is more directly promoting fibre breakdown (in increasing intake the lucerne may have been acting more on the whole animal).

Synergy observed in feeding experiments 1. Two separate earlier in vivo experiments provide evidence of A. lebbeck fallen leaf promoting the digestion of spear grass. In one experiment (Schlink et al. 1990) fallen leaf, flower and pod were each fed as supplements to spear grass for a period of 5 weeks followed by a 1–week period when digestibility measurements were carried out. The digestibility of the spear grass alone was 29.8 and of the diet supplemented with fallen leaf was 34.2. On this diet the intake of spear grass was 403 g/day and of the fallen leaf 95 g/day. In a separate experiment (Lowry 1989) the digestibility of the fallen leaf on its own was 42.5%.

If we assume that the digestibility of the fallen leaf, which came from the same sources, is the same in each experiment, and was not be affected by being mixed with the spear grass, then the digestibility of the spear grass in the mixed diet was 32.1%; an increase of 2.3%. As it was, other parameters (animal liveweight, wool growth) were improved by the inclusion of this modest amount of fallen leaf. Synergy may have been contributing to this result.

2. Results from this project prompted a feeding experiment with cattle in which fallen A. lebbeck leaf and flower were fed as supplement to a hay from a very poor quality native pasture (Kennedy et al. 2002). Their value was compared with other supplements of known value. The results were dramatic; A. lebbeck leaf, at only 15% of total intake, had the effect of increasing grass intake by 50% and the total digestible dry matter intake by 62%. This provided unequivocal in vivo evidence in support of the promotion of cellulose digestion seen in vitro. It showed that fallen A. lebbeck leaf (and flower) is valuable as a supplement to poor quality grass.

5.3 Canopy Effects – General Evidence for the ability of isolated trees in semi-arid environments to promote sub-canopy herbage was reviewed in RIRDC97/73. Since then awareness of it seems to have strengthened, to the extent of being referred to as the “savanna effect” (van Noordwijk and Ong 1999) and leading to more general studies (Moyo et al. 1999). In a comprehensive recent review Cruz et al. (1999) outlined the conditions under which positive canopy effects can occur. Awareness of this has been slower in Australia, no doubt because of the preponderance of eucalypts, but it appears that the possibility of certain trees having a “net stimulatory effect” is becoming recognised (Quirk 2000). In RIRDC 97/73 we drew attention to the reported tree-grass relationship in the Dehasa region of Spain. Since then we understand from an unsourced newsletter that Meat and Livestock Australia has sponsored Dr Anna Ridley of the Institute for Integrated Agricultural Development, Rutherglen, Victoria to study this region.

An effect of the tree canopy of which we were unaware in RIRDC97/73 was that on soil acidity, and of the two independent processes involving cation inputs by litter fall and complexing of cations by leaf leachates. From the work of Noble and Randall (1998) it is clear that there are very important differences between tree species in the net effect on remediating soil acidity. Furthermore the effect of the eucalypts tested was negative while that of M. azedarach was the most beneficial. This adds another dimension to the effects of tree canopy and it would be of considerable interest to find out the parameters for the other tree species in this project.

From the current study it seems that there are other trees in addition to A. lebbeck that can have positive canopy effects. They are discussed by individual species. It should be emphasised that any positive canopy effects are associated with isolated trees. As spacings decrease there develops an adverse effect on grass cover from all species, including A. lebbeck. On the other hand when trees or shrubs are grown at close spacings and heavily cut or hedged there may be promotion of grass, but here there is little shading and presumably the dominant effect is release of nitrogen, akin to having a legume in pasture.

The other general point to make is that increased sub-canopy dry matter production is not as important as the effect on quality. Even if the trees produced no net increase in pasture biomass the creation of a mosaic with islands of higher quality grass would benefit animal production. It also requires more careful management, as the sub-canopy green panic undergoes greater grazing pressure.

5.4 Wood potential 5.4.1 Cabinet woods – enhanced heartwood formation Recognition in this project of the considerable sapwood zone in well-growing A. lebbeck trees, presumably applying to forest A. lebbeck also, suggests that trees at 25 years that have a merchantable volume of wood may lack sufficient heartwood to be valuable as cabinet wood. In RIRDC97/73 it was suggested that a distinctive management option for A. lebbeck was the heavy lopping of mature trees

for drought feeding, and that although this would reduce wood growth the conversion of sapwood to heartwood should continue regardless. Thus the trees would “add value but not volume”. In fact the situation appears much more promising. In biological terms, it appears that the amount of functioning sapwood is determined by the amount of active tree canopy (Bamber 1976). Removal of a portion of the canopy reduces the need for conductive sapwood and the conversion of some of this to heartwood begins immediately. Thus the progression of sapwood to heartwood in heavily pruned trees does not merely continue as in intact trees but is actually accelerated. This has been confirmed in forestry research, for both softwood (Ihara 1972) and hardwood (Polge 1985) species. However this has been reported largely as an incidental observation. In forestry the purpose of pruning is to obtain good stem form and improve wood quality by reducing knots and occlusions, and the main constraint is the effect on wood volume growth. The use of heavy lopping prior to harvest would be a unique feature of the dual purpose tree system, being done late in the rotation with the main aim of increasing wood quality through heartwood content.

This has important implications for a dual-purpose agroforestry system, depending on the time taken for sapwood to heartwood conversion in the particular species. It is remarkably difficult to find published data for this for a range of species, apart from a number of cases given by Hillis (1977). These included 5–7 years in several eucalypts, and 2–3 years in the only tree legume cited, Robinia pseudoacacia. If the time required is five or more years in a fast-growing species then, because of exponential wood volume growth, a 25–year old tree would have a high proportion of sapwood. This suggests that heavy crown lopping, perhaps three times in the five years before harvest, not only could, but should be done. This in turn would generate a much larger feed component for the whole system; trees could be lopped during the dry season but while in full leaf. The operation would be an unsubtle slashing of the outer branches; not technically difficult. Timing could be opportunistic according to feed requirements.

This management operation to both increase wood value and produce more feed would be a distinctive feature of the dual purpose tree system.

In discussing A. lebbeck use with woodworkers there was a clear dichotomy between those who knew the timber but would not touch it because of having had a problem with the dust, and those who worked it but used full protective equipment. Keating and Bolza (1989) refer to “nasal irritation” associated with working with A. lebbeck. Inhaling dust of this and the other allied species, in particular red siris, can produce headaches and flu-like symptoms (S. McVeigh, DNR, Mackay). There is considerable literature on the chemical constituents of A. lebbeck and A. procera but nothing published on the wood constituents seems to account for this effect. The problem is certainly no constraint on use because for many woodworkers the need for protection is taken for granted when working with high-value tropical timbers.

The suggestion put forward in RIRDC97/73 that an agroforestry system could be based on producing short clear logs if the wood was of high value is directly supported by a survey in Western Australia (Challis 1989). The suggestion also that marketing such timbers would not require large scale production is supported by a recent sale of rainforest timbers in Gympie, where a series of very small lots achieved very high prices (Capill 1999).

On-farm milling is now even more a reality (JVAP 1999) than two years ago when we saw it as an essential factor for a dual purpose tree system. In Queensland the activity is now virtually dominated by one type of machine, the Lucas Mill. This cuts precisely dimensioned sawn timber but not large slabs. The only alternative, with only one rig operating as far as we know, is the “Dinasaw”. This uses a large horizontal band saw, which can cut wide slabs from large irregular pieces of wood. Its main use appears to be for salvaging valuable timbers such as red cedar stumps.

There has been some scepticism about growing timber in non-coastal areas from those who see the rangelands as primarily for grazing. In fact the Department of Natural Resources have a Vegetation Management Extension Officer (Ms Ellie Fairbairn) based in Barcaldine, promoting and developing

the use of outback timbers (Fairbairn 1999). Furthermore the Queensland Forest Research Institute has had an ACIAR project specifically on dry land agroforestry with sites such as Noonbah near Longreach. See also Appendix 2.

5.4.2 Is there a place for low density timbers? In RIRDC 97/73 we noted the fodder value of the kurrajong tree, but with an emphasis on cabinet woods. There seemed little but curiosity value in kurrajong wood because of its softness and low density. The applications mentioned by Bootle (1983) (stage sets, hat blocks,) suggested a similarity to balsa. It was therefore interesting that a display of the Queensland Forest Service, entitled “Forestry in the War Years” has the following statement: “Research was conducted to find an alternative to balsa, traditionally used in aircraft interior construction. Grey Corkwood (Erythrina vespertilio) and White Kurrajong were found to have the necessary characteristics”.

Having assumed that the applications of balsa wood since then were limited to Kon Tikis and model aeroplanes, it was surprising to find that it is used as part of composite materials for a number of high value applications, such as surfboards, boat building, and even aerospace. The salient point here is that despite its softness balsa still contains the basic lignocellulose composite – just in a more expanded morphology. As with other low density woods its mechanical strength is, on a unit weight basis, if anything greater than those traditionally regarded as strong. Enclosed within a laminate it confers far greater rigidity than an amorphous filling material such as polystyrene foam. As a building or interior material its use in lightweight composites would seem to have the additional advantage, in the event of fire, of not giving off the toxic fumes that come from some synthetic polymers. Some Australian companies import balsa, but from the Australian Forest Products Statistics it is impossible to know how much. It is not listed separately in Miscellaneous Forest Products and it is hard to know which category it would come under.

Used in Australian made surfboards and windsurfers it is not difficult to envisage the use of local (plantation grown) lightweight native timbers being employed as a desirable attribute for marketing purposes. Corkwood (Erythrina vespertilio), commonly known now as batswing coral tree, has the lowest density of all the timbers listed by Cause et al. (1989); at 190 kg/m3 it is very close to balsa.

It is clear also that for some craft applications such as carving, softer low density timbers are preferred as long as the appearance is desirable. Moreton Bay fig often gets used in this way.

A market for limited volumes of soft low density timbers would allow a quite different set of species to be considered as dual purpose trees. Notes on some of them are in Section 7.

Tree establishment – is there a missing factor? It is generally evident that many rainforest trees grow well in a wide range of habitats. It is also evident that many attempts to establish these trees have been disappointing. As reported in Section 4, the same observation applies to the species of interest in this project. One possible limiting factor to trees being established in new areas is the absence of symbiotic soil organisms. In the case of tree legumes the importance of nitrogen fixation and the relatively visible nature of the root nodules hosting rhizobia have ensured an awareness of the need for rhizobial colonisation. There has not been much concern about other root symbiotes. In a study of 70 woodland species, Reddell and Milne (1992) showed that 90% had specialised nutrient-gathering mechanisms, 82% had mycorrhizae and 16% had both ecto- and vesicular arbuscular mycorrhizae. Work at the Tropical Forest Research Centre at Atherton has also shown the importance of vesicular arbuscular mycorrhizae in enabling rainforest species to be established in open woodland (P. Reddell personal communication). These organisms do not persist in the open without a suitable host. It may be that including other inocula when raising seedlings will increase the establishment success rate. The crudest approach would be to incorporate soil from healthy existing stands in the seedling medium. This has in fact been demonstrated for two deciduous monsoon forest species including Bombax ceiba mentioned elsewhere in this report (Bowman and Panton 1993).

Another possible factor is the claim that many North Queensland soils lack the trace amounts of molybdenum required for tree legumes, and that A. lebbeck may stagnate until the root system reaches a lower horizon with adequate molybdenum (Dr Eric Heidegger, Geology Department, University of Queensland, personal communication).

6. The outlook for Albizia lebbeck (siris, Indian siris, flea tree)

For animal production A. lebbeck has a remarkable range of attractive features: green leaf as browse; dry season fall of edible leaf, flower and pod; promotion of yield; and quality of sub-canopy grass. These were set out in RIRDC 97/73. There have been no new findings that diminish any of these. In this project we found that leaf-grass synergy in ruminal digestion, first seen and investigated in a relatively obscure species, in fact occurs with A. lebbeck as strongly as in any species. Thus the fallen leaf, already demonstrated to be a good feed in its own right, can have additional value in promoting the use of dry season grass. This has recently been directly demonstrated in an animal experiment (Kennedy et al. 2002).

In considering potential uses it is worth noting the degree of recognition and changing attitudes that exist. Firstly as noted in RIRDC97/73 A. lebbeck is almost omnipresent as a shade tree in northern and inland towns and on properties. It is hard to imagine a town like Charters Towers without it. Yet earlier general books on trees on farms, including northern and inland areas, (Cremer 1990, Hall et al. 1972, Brown and Hall 1968) make almost no mention of it. The levels of recognition may be increasing; it now has full coverage in Doran and Turnbull (1997) whereas it did not feature in the preceding edition (Turnbull 1986). In looking at future pastoralism it is mentioned favourably by Gramshaw and Lloyd (1993).

From this project two findings stand out.

1. Unequivocal evidence for the ability of A. lebbeck to establish itself on a variety of subcoastal sites N of 26 o A woodland area worth describing in detail is on the Ross River plain on the outskirts of Townsville. Part of it was under periodic grazing, all of it subject to various disturbances but otherwise untended. Some trees were used in earlier published research. The area was progressively developed for real estate from 1991 and is now totally under housing. Retrospective estimates of tree growth are possible from previous data on individual trees combined with a study of air photo coverage taken in 1961, 1965, 1974 and 1986. The scale of these varies but canopy diameters can be compared because the concrete ribs of a weir are clearly visible and provide a convenient reference. Mango and tamarind trees can be identified by their dense dark crown, eucalypts (mostly E. tesselaris) by the lighter crown and the more erect habit which gives rise (in non-noon photos) to a more elongated shadow, sometimes showing the lower stem. A. lebbeck and rain tree are recognised by the lighter crown and bushy habit but are hard to distinguish. However, there was only one rain tree in the area in 1988.

At the time the site was being visited for research purposes (1987–89) a particular ungrazed area of about 3 ha contained a number of big trees (about a 15 m canopy diameter), which were used for estimating canopy-grass interactions. A number of medium sized trees (300 – 400 mm dbh) were harvested for feeding experiments. There was no attempt to enumerate the total tree population but the area could be regarded as patchy, A. lebbeck-dominated woodland with a few scattered eucalypts. This is in accord with the 1986 cover that shows at least 48 A. lebbeck trees of canopy diameter greater than 5 m. This is in marked contrast to the 1965 cover which shows an almost bare area. There are only five A. lebbeck and an equal number of eucalypts. The 1961 cover shows only three A. lebbeck and a number of other trees some of which subsequently disappeared. Thus A. lebbeck woodland has emerged in 25 years with most of the tree growth occurring in the last 12 years.

Another part of the area of about 5 ha, subject to grazing, contained rather fewer trees (about 30, though counting is more difficult) but these included the biggest ones in the area (dbh 935, 893, 734 mm with canopy diameters in the range 25 m – 28 m). These largest trees were almost certainly present in the 1961 photo but identification is confused by the presence of eucalypts that have subsequently gone. From the 1965 cover it seems likely that canopy diameter for these three trees then

was 0.4–0.45 of that in 1986. They were large trees some 25 years previously, but had made substantial growth in the last 20 years.

The most unequivocal observation is that for two trees on the embankment at the south end of the weir. The largest of these in 1987–88 featured strongly in a study of folivory by fruit bats. Unfortunately the canopy and stem diameter were not measured but would have been at least 15 m and 450 mm respectively. Immediately to the south was a smaller tree with a crown that was mostly separate but merged at the closest point. Both are clearly visible in the 1986 photo cover, with the smaller tree having a crown diameter about 0.6 that of the large one and only just in contact. In the 1974 cover the larger tree is seen clearly, with a diameter less than half that in 1986. Surprisingly, the smaller tree can not be seen at all. In the 1965 cover there are no distinct tree crowns but a number of small diffuse objects that could be shrubs or saplings about 1 m in diameter. Because of the bareness of the particular site and the detail visible in this lower altitude photo one can be certain that if either of these trees were present then they would have been very small. Thus one can be certain that a considerable tree has developed in 20 years, and a smaller but substantial one in 12 years.

Other cases include near Kilkivan, where a forester (Mr E. Ryder, DNR) noted a site where there was a solitary isolated tree some 15 years ago. Today the tree is large (703 mm dbh, height 13.4 m), still growing (dbh increment 10 mm), and surrounded by a population of about 30 trees from seedling size to 190 mm dbh.

In Central Queensland there is abundant evidence of naturalisation on road reserves. Of particular interest is a population above Lakes Creek Road, Rockhampton, because it is on a dry ridge that would appear to be a harsh site. At all locations it is evident that this establishment occurs only in the absence of grazing. We thus have the frequent sight of volunteer trees appearing in road reserves, where they are ultimately a nuisance, and none on the other side of the fence where they would be useful, but are eaten by livestock as soon as they appear.

A particular site at Lansdown near Townsville is interesting in that a wire netting fence enclosing a plot containing rows of shrub legumes acted to trap wind-blown A. lebbeck pods from a large tree 100 m away. Seeds subsequently established, creating an additional row that, with the removal of the fence, looked as though it was part of the original plot.

Overall, the observations are very encouraging on the feasibility of establishing A. lebbeck but clearly indicate caution on its management.

2. A contrast is apparent between the robust appearance of many untended wayside trees compared with their sometimes indifferent performance following deliberate planting, even on some research sites. This can to some extent be attributed to a series of very bad years for tree establishment. However we believe it is also affected by the planting stock; container-grown trees rapidly become root-bound. Absence of the right root symbiotes may also be responsible.

RIRDC 97/73 refers to a number of experimental sites where A. lebbeck has been planted in multispecies evaluations. We now refer to two sites where it has been planted at wide spacings as part of an actual agroforestry trial.

One, planted in 1990, is at Warrill View near Mutapilly in south-east Queensland. It initially performed poorly (2.6 m height in 3 years [Dunn et al. 1994]). However in the last two years it has shown rapid growth and its potential is being reassessed (D. Taylor unpubl.). In September 1999 the trees on this site were about 7 m high with diameter 165 mm, and sub-canopy grass enhancement appeared to be starting under some trees.

Another true agroforestry trial has been established at the QDPI Kairi Research Station on the Atherton Tableland. On this site A. lebbeck was initially attacked by white-tailed rats that burrowed

down to eat the roots, an unexpected problem unlikely to occur in grazing land. It does, however, add to the legends concerning these formidable north Queensland native rainforest animals. Despite initial problems most trees have survived, but are lagging well behind the Pinus carribea. This site is better watered and fertile than most places that would be considered for A. lebbeck agroforestry, an effect of which is that the trees were swathed in glycine – not something seen at any other site.

Over the last 3 years there have been a number of plantings on grazing properties.

Apart from the Shell multispecies trials all planting of A. lebbeck has been for its role in animal production. None have included treatments to do with wood value.

There is no simple summary for growth performance because there is such wide variation. Areas not previously reported include “Yandilla” where nine trees planted in 1993 had an average height of 6.0 + 0.6 m and diameter of 132 + 22 mm. At “Glendhu” in a block of 40 A. lebbeck planted in 1993, trees selected for pruning had average height of 7.2 + .8 m and over the last year had a diameter increment of 25% (144 mm to 180 mm).

It is probably justified to quote some of the best results because in a large scale planting the elite trees will determine the system’s performance. The best performing tree at “Glendhu”, 4–years old and given no special treatment, had in the next year a 28% diameter increment (192–245 mm) and grew from 5–7.2 m in height. The canopy diameter expanded from 9.3–11.4 m, meaning it covered an extra 33 m2 during the year. Also of interest were trees planted by direct seeding in stump holes in 1994 (cf Lake 1997) where the best had dbh of 70 mm, a clear stem to 2.8 m, and was 5 m high. A tree planted by the author in Townsville in 1987 was in 1998 16.5 m high with a diameter of 401 mm. In terms of potential size in the semiarid tropics, possibly the biggest tree, said to be over a metre in diameter, is at “Conjuboy” a grazing property between Greenvale and Mt Garnet (R. Holme personal communication). Logs of 1 m diameter have been obtained in Central Queensland (D. Cranston personal communication).

In 1990 the author planted two 1 ha blocks each with 70 A. lebbeck at “Lansdown”. The experiment was abandoned due to relocations, but the trees were left in place. Most were eventually destroyed incidentally through control of chinee apple infestations. They provided an unexpected demonstration of site effects. One block, on red duplex soil, survived and some grew quite well. The other block was on a cracking clay and survival was very poor.

6.1 Status as native tree In the previous review it seemed clear that A. lebbeck was a native tree in parts of northern Australia, although it had been widely introduced and most of the trees seen in eastern Australia would be of exotic origin. This is the consensus of botanists who have worked in areas where it occurs naturally. In addition to previous references, Dr Paul Forster of the Queensland Herbarium has said that he can point to the actual zone on Cape York where there is a boundary between indigenous populations and the introduced form. Mr Geoff Tracey (of the pioneering Webb and Tracey studies on northern forest types) regards it as indisputably one of the complex of species that have a distribution throughout the seasonally wet/dry regions of Asia and northern Australia. However the situation is clouded by the recent publication of the volume on Mimosaceae in “Flora of Australia” (Cowan 1998). The late Dr Cowan described it as “thoroughly naturalised” for the northern areas where others have regarded it as indigenous, and distinguishes between early and recent naturalisation – the latter the sort of populations described above for Central Queensland. Given that it was not known in Australia last century except as a local introduction, by “early naturalisation” he must have meant prior to European settlement. This may well apply to trees such as tamarind, but it is hard to see any Bugis traders carrying A. lebbeck with them. Given the ecological congruence of the monsoon forest habitats of northern Australia and eastern Indonesia, and the lower sea levels in the Pleistocene, it would be very remarkable if it had not arrived here before European settlement. Although it might seem pointless to

be concerned whether a tree was indigenous or thoroughly naturalised prior to European settlement, perceptions are important, and the status of A. lebbeck will continue to be an issue.

Most recently, unequivocal affirmation of its native status has come from the Society for Growing Australian Plants (Ross et al. 1999). The native form is distinguished by a number of leaf characters, including additional glands on the rachis.

6.1.1 A. lebbeck as a problem species? A. lebbeck’s status as a native tree has perhaps taken on greater significance because of the tendency in some quarters to treat it as a problem species. Although invaluable as a shade and shelter tree in many inland areas, it must be acknowledged that A. lebbeck is not the ideal suburban tree. The dry- season fall of leaf, flower and pods that would be valuable for livestock becomes a litter problem for drains and guttering. The fallen flower if wetted ferments rapidly with an unpleasant smell. The tree is also claimed to be allergenic although this remains to be confirmed. More serious is the question of whether it could become a weed tree. As noted above there are volunteer populations in some areas. It is hard to see much problem with the tree itself because it is not toxic, thorny or thicket forming and is beneficial to much wildlife. However the question is not whether the existence of these populations is desirable but whether if it was established on a large scale in pasture, it would pose a threat to any other environment. The relevant points are these:

1. There is abundant evidence it will not establish by itself under grazing because of the palatability of seedlings. 2. Seed is not dispersed by birds (bird dispersal is a common feature of weed trees). 3. Seed is dispersed largely by wind blown pods over limited distances. 4. A. lebbeck is not very hard seeded. It seems certain that seed would not remain dormant and viable through more than one wet season. 5. Seed eaten by sheep did not survive in the tract and almost certainly would not in cattle.

There is the possibility of storm and flood events carrying pods down watercourses out of grazing land to areas with no cattle where it might establish.

6.1.2 Effect on Pasture In RIRDC 97/73 we speculated that the sub-canopy grass enhancement would be seen mainly in the wet/dry tropics. This is supported by recently published results from a trial at Narayen where the grass yields under 7–year–old A. lebbeck were slightly less than in the open. They were however, considerably higher than under Eucalyptus argophloia, Acacia stenophylla and leucaena in the same experiment (Wilson 1998). Here the dominant factor was that the trees were clearly in competition with the grass for water. Whether this would continue to be the case remains to be seen.

Sub-canopy grass enhancement by this species has already been published and accepted as reason for looking at other species. However we report here additional results in the form of grass production along a series of radial transects out to 50 m from a single large isolated tree. This was specifically to address the question as to whether the enhanced sub-canopy area would be associated with a ‘depleted’ zone immediately surrounding the tree. This could happen if tree roots reach out past the edge of the canopy, depleting soil water without the reduced insolation due to the canopy. The results (mean of six transects) carry a hint of this, but show there would still be a large net increase in dry matter production (Fig. 7). They also show that for a large tree like this the enhancement extended out past the edge of the canopy. A further observation at this same site where the sub-canopy grass was green panic and the extra canopy grass was urochloa, was that a zone of urochloa close to the tree was also enhanced.

Grass associated with siris canopy

600 sub-canopy extra-canopy 500

400

300

200

100 Grass dry matter (g/m2) 0 0 5 10 15 20 25 30 35 40 45 50 55 60 Distance from tree stem (m)

Fig. 7. Grass production (mean of six radial transects) out to 50 m from a large A. lebbeck.

6.1.3 Wood Potential In RIRDC 97/73 we compared the high value of A. lebbeck as cabinet wood as indicated by overseas sources. From the references seen it was unclear if the trade was still current or extended further than the UK. It is worth mentioning that a recent book has it as one of the world’s 200 best or most useful woods and comments from a North American perspective (Flynn 1994). Another, earlier manual has a description which is worth quoting: “Of all the timbers the colour of this might be said to be the most difficult to describe, as in different lights the grain reflects curious and unexpected colours and displays a unique, lustrous sheen, so that while it would be correct to describe the wood as brown, it can also be seen golden, almost golden-yellow, and sometimes a distinct green shade. It is a very attractive wood for a great variety of decorative woodwork.” (Howard 1948). Despite book references to a trade in A. lebbeck timber as East Indian walnut it is, given the number of internet sites concerned with tropical timbers, surprisingly hard to find any current data. It is not listed in the data of the International Tropical Timber Organisation, which should provide the most systematic coverage and has much information on plantation grown A. falcataria. The only quoted price found for A. lebbeck was from a dealer in Hawaii (Winkler Wood Products, Inc) who offered it at a higher price than Australian red cedar ($6.50 versus $4.25 / board foot).

In this project we had boards sawn from a log at Belmont to compare with A. canescens. Central Queensland wood turners are certainly aware of the timber – most avoid it because of the irritant dust, but it is used actively by those that employ full protective equipment.

Observations of pruned trees showed almost no epicormic branching from removal of larger branches (40 mm), unlike T. tipu. There was good callusing of the surface from smaller branches (10–20 mm) but at one site (“Lansdown”) the pruning seemed to encourage wood moth attack. At Glendhu the diameter increment in the year following pruning (11.3 + 1.7%) was not much less than that for unpruned trees (13.5 + 2.9%).

7. Results and Discussion for Other Tree Species

7.1 Trees not considered The number of trees appearing on this list, including ones not mentioned in RIRDC 97/73, may give the impression that it is expanding indiscriminately. One could pause here to note the trees not considered to have dual purpose potential. These include all species of eucalypts sensu lato, other allied Myrtaceae, and also all native and exotic conifers. That rules out most of the commercial timber species, simply because they have almost no forage value or benefit to pasture production. No phyllodinous acacias are included although the exclusion is not so clear cut. Trees with poisonous or otherwise adverse characteristics are ruled out. Thus a native tree legume Peltophorum pterocarpum although it is widely planted and dry-season tolerant is simply not eaten to any extent. Clearly, trees designated as woody weeds are ruled out, although with a twinge of regret in the case of Chinese elm because of the high palatability of the fallen leaf and the timber value.

The list is in effect drawn from those non-sclerophyll trees capable of growing in open rangeland and is still selective within that group. The fact that there can, even so, be a substantial number of species is a reflection of Australian biodiversity. For some species, see also notes in RIRDC 97/73.

7.1.1 Albizia procera (forest siris) The mystery concerning A. procera is why it is not more highly regarded, or indeed why it is so little known. Why is this attractive, fast growing and valuable tree not widely planted for rainforest restoration? One possible reason is that it might have been somewhat uncommon in old growth primary forest and did not get the recognition of the forest giants yielding valuable wood. Trees seen by the author in primary forest behind Ingham, although very tall and straight, were not of great girth. They would not carry the timber volume of the prized timber species. It is not mentioned by Swain (1928), suggesting that it was not being used in significant amounts at that time. Although it is one of the Queensland timbers highlighted by Bailey (1888) for an international exhibition in Melbourne with the comment “wood of a dark colour resembling walnut, a useful cabinet wood”, his account of it seems to be based largely on the existing trade in it in India.

If not abundant in old growth forest, it is one of the species that can respond to forest disturbance. Today the tree is very abundant as a pioneer species in certain areas that were formerly forested. A significant timber resource is developing, some in World Heritage areas some not. Quite large trees are being destroyed by road works or property development without the timber value being recognised. Recruitment and growth is so good in some localities that, perversly, there is a danger of this beautiful and valuable native tree being ignored for native tree plantings – because it looks so vigorous it suspected of being weedy. However it is not in these areas where it has most potential for agroforestry, but in those with a harsher dry season.

Of the trees in this project, it is the only one for which it is said that the leaves can be used as a vegetable (Zabala 1997, p. 161). However in some in vitro experiments we found leaf to have strong antimicrobial activity.

Growth Wayside trees of A. procera in the wetter coastal area were actively growing. Over the size range 80– 320 mm dbh, the 1997/98 diameter increment averaged 9.6%. There was no simple relationship between tree size and increment and it was some of the largest trees that showed most growth (13% diameter increment). This may be because competition effect varied widely between trees. There were some indications that when trees grew in proximity, particular trees became dominant.

An encouraging finding was that in drier areas where there may be a sparse natural occurrence but not the above mentioned vigorous self-establishment trees also showed high growth rates. Diameter increment ranged from 0% to 23%. This supports its wider agroforestry potential. For this provenance is likely to be very important. Some natural populations on Cape York are multistemmed and shrubby, quite different from the good tree form seen further south.

Feed drop Both leaf and pod drop were found to occur earlier over its current range than had previously been observed in Townsville. Pods retained their seeds when they dropped (important for feed value) and tended to come off in bunches along with a terminal branchlet. Yield was definitely lower than for A. lebbeck; estimated at about 1 kg for medium sized trees, 3–5 kg for larger trees.

Effect on pasture In the dry tropics the promotional effect of A. lebbeck and now other species is noteworthy for fostering in the sub-canopy area the growth of green panic, a shade-tolerant form of Panicum maximum, which might be hard to find in the surrounding area. This species difference in itself almost guarantees higher quality for the sub-canopy grass. The abundant natural populations of A. procera occur in wetter areas, and many trees were located in areas dominated by Panicum maximum both below and outside the canopy. It was thus of interest that on such sites the dry season sub-canopy grass was also of higher quality, with a more than two-fold difference in protein and a corresponding but less marked difference in fibre (Table 3 ). At a site in the dry tropics there was marked disjunction in the grass cover; with green panic below the canopy; spear grass and a mixture of other grasses away from it. Here the difference in quality was even more extreme; protein content below the canopy 4.8% compared to 1.1% extra-canopy. Unfortunately these sites were unsuitable for measuring grass dry matter production, and the two trees that had been envisaged for that purpose were destroyed shortly before sampling.

Although some useable timber has been lost incidentally where forest A. lebbeck has been felled, we have also been told of logs being salvaged by those who know its value and sold for good prices in the Mackay area.

7.1.2 Albizia canescens (“Belmont A. lebbeck”) Albizia canescens is most closely allied to A. lebbeck and A. procera. Under recent revisions only these three remain as true albizias; the other Australian species formerly Albizia are now Paraserianthes, Archidendron, Archidendropsis. It occurs scattered in eucalypt woodland and has an open crown and glaucous foliage much like eucalypts. Anyone who recognises it as a tree legume is likely to equate it with A. lebbeck. However, there are obvious differences, particularly in the flowers (large and fluffy in A. lebbeck; very small in A.canescens) and in the bark (tessellated and flaking in A. lebbeck, vertically fissured and corky in A. canescens). It is entirely tropical, found across northern Australia from the Kimberleys to near Rockhampton, but apparently rarely abundant. Surprisingly, it is quite common on ‘Belmont’, a MLA-owned grazing property near Rockhampton that has been used for CSIRO cattle breeding research for many years.

It is certainly not well known. It is not mentioned in “Plants of Central Queensland” (Anderson 1993). It does not feature in any other current book on Australian plants, other than a formal taxonomic treatment in Flora of Australia. It is not found in the Kershaw Gardens, Rockhampton, or the Tondoon Gardens, Gladstone – both excellent native botanic gardens for the region where it occurs. Nor is it in the Mt Cootha Botanic Gardens in Brisbane. There are a few public places where it can be seen, such as a solitary tree in the Heritage Village, Rockhampton, and a small group of trees in council reserve at Thozet Creek. Recently, following representations from the author, the Environment Department of Townsville City Council has become interested in the species, has located more trees, and has highlighted a population on the outskirts of Townsville as part of a biodiversity celebration. An interesting aspect is that, as with A. lebbeck, the tree may produce a copious carbohydrate gum

exudate. According to an internet site of the Kowanyama Aboriginal Community Council this is regarded as a bush food (“toffee”) on Cape York.

A major phenological observation is that the species seems to have a growth habit rather different from A. lebbeck or any other trees in this project. Although it can occur as a large clean stemmed tree, it appears A. canescens has a greater tendency to coppice under natural conditions than A. lebbeck. Some trees had a series of major stems arising, not by very low branching as with A. lebbeck, but from at or below ground level from what appears to be a massive woody lignotuber. This probably enables the tree to regenerate after fire more effectively than A. lebbeck and may account for its presence in dry eucalypt woodland. Furthermore the corky bark appears to be more fire resistant; it had an outer charred layer on otherwise healthy trees from fires of a year or two previously. However the difference is marginal; compared to eucalypts, all albizias are fire sensitive.

At several locations there were young trees making rapid growth (3 m height in less than 2 years). Among the medium sized trees were some heavily attacked by wood moth and by leaf feeding insects. However, some made substantial growth (8% diameter increment). Two larger trees (395 mm dbh) made very little diameter growth (2%) over the study period.

Flower yield was negligible because the very small flowers and pods, although of similar size to A. lebbeck, were produced much more sparingly in 1997, but some trees produced a larger crop (2–3 kg) in 1998. Leaf fall occurs later (November) and is less conspicuous than with A. lebbeck as it is almost concurrent with new leaf flush.

Fodder value The fallen pods are similar to A. lebbeck, are palatable to sheep, and have lower saponin content, which should make them more acceptable to stock. They are however produced more sparingly. The green leaf is highly palatable and like A. lebbeck has almost no tannin content. Fallen leaf has similar properties but leaf fall is not as profuse.

Effect on pasture At Belmont near Rockhampton, where A. lebbeck and A. canescens occur in the same area, it was clear that canopy effects of A. canescens generally mirrored those of A. lebbeck. Here we report that the early wet season grass growth differential associated with the A. canescens canopy is probably the most dramatic seen so far, with a four-fold difference in dry matter production. The yield found on a radial transect out from the stem is shown in Fig. 8. Higher quality for sub-canopy grass was found at all sites sampled in Central and North Queensland, although the largest difference was found with a somewhat moribund tree and could reflect release of nutrients from the tree itself.

Despite the similarity of the seeds and pods there are important differences. Surprisingly there was no trace of hard-seededness. Hot water treatment suitable for A. lebbeck killed all the seeds. With no pre- treatment at all there was 90% germination within 5 days. Initial seedling mortality was high but could certainly be improved. Seed was also heavily attacked by weevils.

Wood is described by Bailey (1888) “wood brown, resembling walnut, very suitable for cabinet work”. The fact that this tree was recognised as a Queensland timber at that time, but is not mentioned in the rather larger list of Cause et al. (1989), or by Swain (1928) suggests that it must have become less common in the intervening period. Similarly the reference to it by von Mueller (1888) while recommending the introduction of A. lebbeck (not knowing it was already present in parts of northern Australia) suggests it was reasonably well known. Milling of a selected log in the current project yielded wood essentially like A. lebbeck, with coloured and patterned heartwood strongly demarcated from pale outerwood.

Grass associated with A. canescens canopy

800 sub-canopy extra-canopy )

2 700 600 500 400 300 200

Grass drymatter (g/m 100 0 0123456789101112131415 Distance from tree stem (m)

Fig. 8. Grass production on a radial transect from a tree of Albizia canescens .

Comparing it to A. lebbeck, the most promising species for wood and animal production:

Advantages 1. It is not only unequivocally native over a wide range of northern Australia, but also found only in Australia (A. lebbeck has a small native range, a wide Malesian distribution, and is often regarded as an exotic). This may be a subjective difference but can be important to some individuals or agencies involved in tree establishment. 2. Unlike A. lebbeck it already occurs in eucalypt woodland. In the first instance, implementation would mean locating and promoting it in situ.

Disadvantages 1. It lacks the full range of productive attributes of A. lebbeck and appears to be subject to the same pests. 2. Seed would be less available. 2. It probably yields smaller log size.

However, there seems no doubt about it being a valuable species to have in the pastoral system. In the context of tree clearing and land management in general it would seem important to draw attention to it so that full consideration can be given to currently existing trees where they do occur. The same applies to several other undervalued species, but this looks like one of the best examples.

For this purpose the author considers a sensible common name is required. This should consist of ‘siris’ with an appropriate qualifier. In Australia the Queensland Forest Service has designated A. procera as ‘forest siris’, A. toona as ‘red siris’ and A. xanthoxylon as ‘yellow siris’. It seems appropriate to refer to A. canescens as ‘Belmont siris’. Belmont appears to be one of the best locations for it; geographical terms are often used in plant variety names, and the association with the beef industry is appropriate because of its potential value.

7.1.3 Melia azedarach (white cedar, Persian lilac) M. azedarach is remarkably widespread within Australia and overseas. In the remnant rainforest of Wongabel State Forest on the Atherton tableland it is a lofty dominant, with a compact dense canopy

carried on a clear straight bole, unbranched to 25 m. In the same area, outside Yungaburra there was a tree half that height, but large and spreading with a stem diameter of 800 mm and a canopy diameter of 16.3 m. From the habit it could only have grown after the forest was cleared. It is observed in many drier areas as a tree of good form or highly branched and coppiced, often inconspicuous except prior to leaf fall when it punctuates the landscape with brilliant yellow. Other distinctive locations are the lower slopes of the Bunya Mountains and Forty Mile Scrub National Park in North Queensland.

Elsewhere there has been considerable interest it its insecticidal properties. An excellent recent review of this and other aspects is included within a book on the related neem tree Azadirachta indica, (Schmutterer et al. 1997) a source that would be hard to find by doing a search on Melia. The insecticidal constituents of M. azedarach apparently protect it totally against locusts and grasshoppers, but there is an equally long list of insects that have adapted to the toxic compounds. From adapted insects, because of its high nutritional value, it is subject to heavy attack. This can result in total defoliation but the tree apparently recovers readily. It is no longer in favour as a street tree in Rockhampton because of the occasional proliferation of urticating caterpillars.

M. azedarach is also known for mammalian toxicity (Oelrichs 1983). However this toxicity seems to apply only to the berries, and only towards monogastric animals. M. azedarach is regarded as browse both in Australia and overseas.

There is no doubt about M. azedarach’s palatability. In an area planted with native browse trees at Brian Pastures the species grew well, but when the shrubs were considered large enough for cattle to have free access it was decimated while the acacias and casuarinas were hardly touched. There cattle eat the stems up to 20 mm, and other observations indicate that young plants are literally eaten to the ground. Our results (Table 1) show M. azedarach is remarkable for the efficiency with which protein is removed from the senescing leaves. However, there seems little doubt that fallen leaf is highly digestible and, given our preliminary results, would be eaten.

The tree has more than one leaf change during the year. Almost all trees drop leaves around June, but individual trees may shed leaf at other times as well. The estimated yield from a tree of 240 mm dbh was 8.0 kg.

An obvious feature of M. azedarach was the rapid growth of young stems (height growth 2–3 m/year) in wayside locations. Most of this was regrowth and root suckers rather than new seedlings, but was still impressive. Some trees in the Brisbane area have shown a 55–80% diameter increment during the third year after planting. Larger wayside trees (170–325 mm dbh) had substantial diameter increments during the year (5–14%).

Effect on Pasture Initially in this project we thought the tree had a neutral effect on pasture with an apparent positive effect at one site attributed to the tree releasing nutrient due to its size and state of decline. However further results (Table 3) suggest it is often positive, a surprising result given that the tree is not nitrogen fixing. However it is now known that this species has a remarkable potential to remediate soil acidity (Noble and Randall 1998) and this may be responsible. It was a frequent observation that although biomass of sub-canopy grass appeared little higher, it was visibly greener with a higher incidence of green panic.

Canopy transmission was similar for large and medium sized trees, and even in ungrazed trees did not come close to the ground, allowing plenty of lateral light penetration.

The timber of M. azedarach does not have clearly demarcated heartwood so the late lopping suggested for A. lebbeck may not apply. Although listed as cabinet wood, it does not seem to be in favour with some wood workers because of a tendency to produce a woolly grained surface. Prices for slabs do not seem to be as high as for other rainforest hardwoods. Some people have dismissed any timber potential in trees in open country because of the poor form compared with forest trees. There is

indeed a massive difference. However its clearwood potential is apparent in wayside plants and can be achieved by selecting a few potentially good stems from a coppice or thicket, pruning them and removing the rest. M. azedarach regrowth with a straight stem to 4–5 m is frequently seen with one or two simple branches off it – ideal for a pruning treatment. M. azedarach that grow close to eucalypts or other trees, almost certainly originating from seed dropped by birds generally are overshadowed, misshapen and unlikely to develop. A simple option is to poison or remove the original tree, which would allow the possibility of development of a fine M. azedarach specimen.

7.1.4 Tipuana tipu (tipuana, racehorse tree, Pride of Bolivia) In RIRDC 97/73 T. tipu was believed to have great potential as a dual purpose tree. Actual results from this project have been mixed. It certainly has a promotional effect on sub-canopy grass, at least in central and northern Queensland. However, the value in the fallen pod is contentious because animals will not eat it. It seems also that animals do not eat the fallen leaf, although this should be tested again with freshly fallen material. At Glendhu, Mr Holme has seen cattle in yards eating leaf as it falls. However there is also the disadvantage that the leaf fall occurs over rather a long period. This is now seen as a real problem for use.

The increasing in T. tipu planted as a shelter tree has lead to some worries about it establishing where it is not wanted. We have found volunteer seedlings in south-east Queensland but very few in relation to the amount of seed produced. There is little evidence of untoward establishment.

Furthermore if T. tipu was being used in a dual purpose system, cattle might spread seed. From the results of this project this seems very unlikely. Animals show little inclination to eat the ripe pods, and when placed in the rumen no seed emerged in the faeces. Thus fallen pods make no contribution to the animal production value, but are also unlikely to become a weed via seed distributed by cattle faeces.

The single-seeded winged pods tend to fall over a prolonged period but much of it with the leaf. Flower fall was very heavy in September 1997 (about 100 g/m2 below big trees) but much less in 1998. In early December there is a small but possibly significant fall of leaf-like green pods where seed has failed to set.

“Racehorse tree” is a locally used common name reflecting high growth rates. This has already been reported for south-east Queensland but is certainly true in the north as well. At Glendhu large trees (230–290 mm dbh) had diameter increments of 20% for the year of study while for recently planted trees (55 mm dbh) the diameter increments were 22–49%.

Effect on Pasture At a site near Rockhampton late dry season grass production associated with two large 12–year–old trees was as follows:

Sub-canopy dry matter 175 + 11 g/ m2 protein content 10.2 + .2 Extra-canopy 143 + 22 8.2 + .7

This covered a period very difficult for plant growth and it would be surprising if there was a large differential. The landholder was very positive that in recent years the arrival of the wet season had brought a massive flush of sub-canopy grass growth. On this site it was possible to enumerate individual clumps of green panic in a prevailing Bothriochloa sward. This showed 4–10 clumps / m2 in the sub-canopy area and none at all extra-canopy. This would ensure that when conditions allowed, grass production and quality would be higher in the sub-canopy area. From this and other observations there seems little doubt that T. tipu can exert a positive effect on sub-canopy grass in the dry tropics. The situation is not as clear at a S.E. Queensland site where early dry season production was not significantly different: sub-canopy 102 + 22 , and extra-canopy 80 + 32 g/m2 .

For wood quality, the big question with this species concerns tree form. The majority of wayside and shelter trees have low and strongly divergent branching. If this is an obligate growth form, there is

little chance of producing useful timber. However it is apparent from populations of recently planted trees that it is possible to select individual trees for which acceptable stem form could be obtained by pruning. At Glendhu a number of trees were pruned as part of this project. Observation one year later showed a further problem in that pruning of branches more than 15 mm diameter stimulated epicormic branching from the main stem. At Brian Pastures there are plantings that allowed an estimate to be made of the size and spacing at which growth is restricted by between-tree competition (about 150 mm dbh; 2 m).

T. tipu is abundant enough in south-east Queensland for several wood turners to specialise in its use.

7.1.5 Paraserianthes toona (Mackay cedar, red siris ) It was extraordinarily difficult to observe flowering or fruiting in this species, either in wild populations visited on field trips, or on a number of trees in cultivation, throughout the period of this project. Apart from a few branches on one of a group of five trees in Rockhampton, it simply did not occur. However it turns out that P. toona is a mast fruiting species. Mr Scotty McVeigh of the Queensland Department of Natural Resources, Mackay, who collects the seed for DPI Forestry, confirmed that there had not been any fruiting during this period. It was evident that leaf change occurred September–October, but this was also difficult to observe. The trees were never leafless, but bronze new leaf flush could be seen in a few cases. Given also the very small leaflets, it is clear that P. toona produced no animal feed from fall of leaf, flower or pod.

For a tree commonly regarded as a rainforest species it was interesting to find not only that P. toona occurs naturally in dry eucalypt country, but that these trees were making significant growth (diameter increment 3–4%). The species has proved to be fast-growing under cultivation at two sites but slow to establish in a CRRP planting at Eungella.

Effect on Pasture In contrast to A. lebbeck and the other albizias, open grown trees of P. toona markedly suppressed vegetation below the canopy (Table 3). This was seen in grassland in both dry and wet tropics, and with mixed understorey vegetation in open forest habitat

The effect is likely to be due to heavy shading, due to two factors: 1. In open grown trees of P. toona side branches spread out horizontally, and branching occurs from a low level, so that the tree forms a domed crown reaching to the ground. 2. Interception of direct sunlight by the tree canopy was measured for the first time in this project for this and other species. We found transmission (15–25%) to be much lower than A. lebbeck (45– 55%), confirming the subjective observation of a very dark dense canopy.

This however does not eliminate it from consideration. The foliage is palatable and once the tree was exposed to grazing, dense foliage would not reach so close to the ground. Further purposeful pruning to about 3 m would allow more lateral light penetration and ensure that the type of shading observed did not occur. The tree is almost certainly nitrogen-fixing and indications from a large old tree with canopy well clear of the ground were that green panic was encouraged close to the tree base. A series of considerations together suggest this species, while not as attractive as A. lebbeck, could have a distinct role.

Of all the species in this study, P. toona is the one often used for timber. All the tables and bench seating in the Hogs Breath Café at Airlie Beach have been constructed from large planks and slabs which display the visual characters of the species very well. A different application is at the Coolum Hyatt Hotel which sports a massive pair of entrance doors sculpted from P. toona.

7.1.6 Gmelina arborea G. arborea is of interest given its reputation as a fast growing hardwood for plantation forestry and the indications that it has distinctive nutritional value, making it attractive as a dual purpose tree for agroforestry.

Little phenological observation was done on this species because there are few trees outside the research plots in the wet tropics. However, it was surprising to find some large isolated trees previously seen in the dry tropics although of unknown age, were still growing (500 mm dbh; 6% diameter increment). Leaf drop in the dry tropics was total and occurred in early August in Townsville, later in Rockhampton. Large trees (about 500 mm dbh) drop at least 10 kg of leaf dm. There is a copious flower fall, not previously noted, in October.

Value as feed There are further reports of G. aborea’s use as feed in addition to those few noted in RIRDC 97/73. In their coverage of the timber, Keating and Bolza (1989) note “the leaves are plucked as fodder”. There is also an observation from Dr J. Lamborne, an experienced agriculturalist and development assistance worker, of villagers in West Africa carrying loads of fallen leaf from plantations to feed livestock. It seems likely that freshly fallen leaf would be a good feed, and it is regrettable that the opportunity to prove it in this project was wasted.

7.1.7 Gmelina leichardtii, Gmelina fasciculiflora These closely allied native species both go by the name white beech. G. leichardtii is the more widespread; G. fasciculiflora is found only in the tropics. Dr Elwyn Hegarty has noted that total loss of leaf canopy in G. fasciculiflora can occur in 1 – 2 days. This has interesting implications. Leaves are still green when they fall and, given that a small sample was eaten readily after being stored for some months, are likely to be palatable. In an agroforestry planting it is reasonable to expect this sudden leaf drop would occur on different trees over a period of some weeks, so the fallen leaf supply from this species, which had a very synergistic effect on grass digestion, would be delivered much more effectively to grazing animals.

7.1.8 Dalbergia sissoo This tree yields one of the most valuable of the world’s timbers (Brazilian rosewood). In RIRDC 97/73 we regarded it as virtually unknown in Australia and refer to it only in terms of its robust performance in Browsenet tree forage trials at Brian Pastures, and Mr Ron Holme having carried out a pruning treatment at Glendhu. In fact D. sissoo has a rather more substantial presence in Australia and presents unique problems and opportunities. The species was introduced several decades ago as a fast growing tree to stabilise sandy sites following major coastal engineering work near Mackay. Since sugar cultivation and harvesting became fully mechanised, and in doing so became restricted to largely level sites, hill slopes that had been cleared for sugar cultivation became neglected. D.sissoo, with its small winged seed, and presumably a large local seed source, was able to colonise such sites. Today there are local but dense naturalised populations around the Pioneer Valley. It can be seen both as a D. sissoo woodland or forest of quite substantial trees on certain slopes, and as dense thickets of small trees. Its thicket forming tendency has led to it being regarded locally as a woody weed. However there are also some local landholders who have quite large trees on their property and have become aware of the wood value. Timber is already being milled on farm and a small local group has formed to develop the marketing of it under the assumption that short clear logs are marketable if the wood is valuable enough.

If D. sissoo is a problem species in some locations, it is difficult to see how this is the case on grazing properties in this region. D. sissoo is unequivocally a fodder tree, and there is little chance of unwanted seedlings appearing under grazing. It also appears that existing thickets are opened up considerably through browsing and trampling when cattle have access. On at least one property the landholder has left large isolated trees of good stem form as shade trees to continue growing and be harvested at a future date. This same property has substantial D. sissoo trees in which the crown has

been lopped for drought feeding and the stem left intact for timber – exactly as suggested for A. lebbeck in RIRDC 97/73.

D. sissoo is deciduous with most leaf falling in August to September. It would probably not be used by cattle in the Pioneer Valley area because it is a wetter area and the dry-season pastures would usually not be of as low quality as those inland. However, we found that there was a high retention of protein in the fallen leaf and that it did not show enzymic browning. D. sissoo’s acceptability and the effect of isolated trees on pasture remain to be determined.

Whatever the problem feral dalbergia may present in the Mackay area, it is hardly likely to present any problem away from the wet coast. Robust trees at Brian Pastures have not given rise to a single seedling. They show however, that it can be established in drier areas. The experience developing around Mackay there certainly suggests it presents a remarkable opportunity.

7.1.9 Cassia brewsteri (Leichhardt bean)

As a native flowering tree this species is surely undervalued. It is comparable to the exotic C. fistula, but with the flowers in varying combinations of orange and yellow. The species is variable but often occurs as a large tree of good form in open woodland. It is also the only species tasted by humans in the course of this project. The name “Leichardt Bean” is to be taken literally. Leichardt was almost as adventurous in his approach to bush foods as in physical exploration. He did note, however, that while some of his party liked it, he experienced severe purging from eating this Cassia and since then few people have even thought of trying it.

C. Brewsteri was well rated by Vercoe (1989) because of high in vitro digestibility (63.6%) and protein (20.8%) levels.

The living foliage is definitely to be regarded as unpalatable to cattle in the field, although horses may browse it without apparent ill effects (M. Matthews unpubl). It is not among the browse trees listed by Everist (1986). According to Anderson (1993) it is not eaten by animals and this has been confirmed by several people, as well as being obvious from the absence of a “browse line” on established plants. However a more shrubby Cassia near Belmont was readily eaten – this was probably C. tomantella, which in some treatments is included in the same super-species. This raises the question of whether there might be some variation in the arboreal forms such that some are acceptable as browse in the green state. C. brewsteri has been regarded as a problem regenerating following tree clearing in Brigalow country.

Thus the finding that fallen leaf was eaten readily is a remarkable feature of this species. Sheep ate the fallen leaf without hesitation and in total contrast to their behaviour when offered fresh leaf. Leaf fall occurred in July in south-east Queensland and later in the north. There is no reason to believe that fallen leaf would not be eaten in the field under the usual condition of dry season pasture. Leaflet size is no constraint to animals using it; at about 75 x 30 mm they are considerably larger than those of A. lebbeck. The yield of fallen leaf is considerable, estimated at 8 kg from a tree of 630 mm dbh.

Although a significant amount of flower fell from a large tree (150 g/m 2), surprisingly sheep would not eat it, despite it not have the rank smell associated with many cassias. Although some trees produced a copious crop of pods, a high proportion of the seed was destroyed by a beetle that bored along the cylindrical pod, perforating most of the seeds by the time the pod fell.

Although sometimes perceived as slow growing by native plant enthusiasts, this may well depend on circumstance. It “grows quickly” according to Nicholson and Nicholson (1988). Large old trees at Sherwood Arboretum (790 mm dbh) had a negligible annual increment but coppice stems on one had a large increment. A 30–year–old tree at Long Pocket had reached significant size (340 mm dbh; 18.5 m high) with strong competition from neighbouring trees and had a 2% diameter increment. The

appearance of trees in road reserves and its being regarded as a regrowth problem also suggest rapid growth rates are possible.

Individual trees at Booroondarra had a higher incidence of green panic below the canopy, visibly greener than the surrounding area. However both sub-canopy and extra-canopy grass cover was very heavy at the time, which may account for a relatively small difference in composition (Table 3).

The timber is moderately well known among wood turners as being easy to work and having an attractive red colour. We produced some sawn timber in this project, which did indeed look attractive, although the red colour faded on exposure to full light. The timber potential is enhanced by the tree height and straight trunk.

The indications of a positive pasture effect and edible fallen leaf suggests C. brewsteri may have been much undervalued. While often regarded as a woody regrowth problem it may actually have been contributing a significant feed resource. The claim that use of fallen leaf has been generally overlooked may have its strongest example with this tree.

7.1.10 Acacia bidwilli, A. sutherlandii (corkwood wattles) These are two of the relatively few Australian acacias with fine bipinnate leaves rather than fibrous phyllodes. Both are readily browsed, have medium density timber and pale corky bark. A. sutherlandii has a more inland distribution (Fairbairn 1999). Although browsed by stock A. bidwillii seems to be thriving in some areas, has a tendency to be thicket forming, and is regarded with some suspicion as a potential problem species. However, we also heard from a landholder who considered it to promote grass growth on his property, where it occurrs as larger scattered trees. We saw a site near Rockhampton where a single large tree did indeed appear to have a positive effect.

Anderson (1993) describes the timber as essentially similar to Archidendropsis basaltica. Because the latter is of some value we milled a log of corkwood wattle on this project but found it to be very different; medium density, easy to cut. The timber was described by Bailey (1888) as “close grained, light, easy to work”.

7.1.11 Archidendropsis basaltica (dead finish, red lancewood) The implication of the common name “dead finish” is that just when it is needed as browse the tree is bare. As discussed elsewhere this may not be quite fair; the fallen leaf may in fact be used, despite the small size of the leaflets. We did not monitor any A basaltica in this project, or obtain fallen leaf. The green leaf was not high in protein and of rather low fermentability, but did show some synergy with Angleton grass. We milled a log from the Middlemount area to have a sample of the dense red timber on hand for comparative and display purposes.

7.1.12 Archidendropsis thozetiana (southern siris, scrub tea tree) A. thozentiana is a tree legume that until recently was considered another species of albizia. In this project we have seen it at only two locations but from observations on the ground, the habitat, and herbarium collections, it is likely that it would be locally common in the range 23 – 27 o S. It extends well inland, to the Zig Zag Range west of Emerald.

It is listed as a Queensland timber (density 960 kg/m3) under the name “brown siris”. The Queensland Herbarium refers to it as “southern siris”—appropriate in terms of its location—and has it as a key species defining a largely vanished dry rainforest vegetation type “Southern siris / Booyong Closed Forest”.

The green leaf is highly palatable for sheep. Leaflet size is highly variable, sometimes as large as A. lebbeck but usually (from herbarium collections) much smaller. From the nature of the canopy it is

unlikely that fallen leaf would be a significant feed resource. The pods are large and very similar to A. lebbeck but on the trees seen were carried sparsely.

The interesting thing about A. thozetiana is that given its similarity to melaleuca, it would be expected to have an adverse effect on pasture. In fact, as a tree legume it will contribute nitrogen and with a rather open canopy may well be beneficial.

As it is almost certainly fire sensitive and highly palatable the chances of young trees getting established seem remote, but may be improved through simple management.

Timber was described by Bailey (1888) as “wood of a red colour, hard, heavy, durable, very tough and close-grained.”

7.1.13 Barklya syringifolia (Crown of gold tree) B. syringifolia is a tree legume (Caesalpiniaceae, but in some books inexplicably listed as Papillionaceae) of the dry rainforests from central Queensland to northern NSW. It is remarkably unknown yet has magnificent yellow flowers that make the tree crowns visible for a few weeks in October.

The leaves are simple and of an unusual spatulate shape, about 35 x 40 mm, and highly palatable to sheep. It was deciduous in July in Brisbane. There were large trees (20 m) in dry rainforest near Rockhampton, but also small ones in isolated patches. Finding a site where such trees could be protected and released from competition would provide a low cost method of evaluating their potential. This is one of the species that could raise the appreciation of dry rainforest communities as having the potential for production as well as conservation.

The species is not among those listed as Queensland timbers by Cause et al. (1989), implying it is too uncommon to bother about, but it did not escape Bailey (1888) who noted “wood blackish grey, close to grain and very tough, suitable for tool handles”.

7.1.14 Bauhinia variegata (orchid tree) This attractive tree with large bilobed leaves and large orchid-like flowers is cultivated as far south as Brisbane. It is exotic but appears to be very similar to B. monandra which may or may not be native on Cape York (Williams 1984). This bauhinia (unlike the native inland species) seemed so much a tree of cultivation in the wet tropics, or well watered gardens of the dry tropics, that it has been a surprise during the course of this project to find that it is capable of not only surviving but naturalising in some harshly seasonal environments. Thus while previously it might have seemed impractical to talk of establishing it, now any mention of this species starts off with the disadvantage that it is already perceived in some places as an environmental weed.

Specific locations for volunteer populations include: road verges of Bruce Highway just north of the Burnett River; southern approaches to Rockhampton; and lower parts of a road to Mt Archer summit, Rockhampton.

In the wet tropics the tree is evergreen and flowers continuously. In the seasonally dry tropics it is completely deciduous with much of the flower production occurring while it is leafless.

The reason for considering it as a fodder tree is that the green leaf is already known to be of very high nutritional quality (Lowry et al.1992), and that there is a conspicuous dry season leaf drop. In the event, both fallen leaf and flower were readily eaten by sheep.

The timber is used by wood turners, surprisingly it is of medium density and easily worked. In both Rockhampton and Brisbane this was under the name of “Bohemia”. This seemed sufficiently

ambiguous, despite verbal descriptions, for the author to make sure by having the tree pointed out at first hand.

7.1.15 Carthormion umbellatum This mimosoid tree legume has no common name. It has a very northern range and is locally common in parts of Cape York and the Gulf country. It has been mentioned by several respondents as reaching considerable size, having good timber and being a good browse tree. Planted trees in Rockhampton were deciduous in November. The leaflets are somewhat smaller than those of A. lebbeck.

7.1.16 Flindersia maculata, F. collina (leopard wood), Flindersia spp. The first two are very much trees of the inland. Flindersia came to my attention through a wood turner citing it as having excellent wood and being a good fodder tree. Everist (1986) also comments on their value as browse. Furthermore, from trees seen on the Darling Downs, F. maculata appears to drop all its leaf over a short period. The genus Flindersia is rich in secondary compounds including bitter limonoids and does not seem likely to used for browse, but we found that fallen leaf of F. australis (Crows ash, teak) was eaten readily in significant amounts. This being so there seems no reason fallen leaf of the other species should not also be eaten.

7.1.17 Pongamia pinnata (pongamia tree) This is one of the species with the timber value abundantly evident from overseas references, which is also native in northern Australia, but which has never been taken seriously. It is listed as browse by Everist (1986) but can occur as a substantial tree, usually in dry watercourses in the seasonal tropics. It is a papillionate rather than mimosoid legume. The pods are too woody to be of feed value but the tree is completely deciduous and the leaflets are large (180 x 60 mm). The tree is widely planted south of the tropic but in this region the leaf is heavily attacked by a leaf miner in the latter part of the year, which would certainly degrade its feed value.

7.2 Trees with fodder value and softer, low density timbers 7.2.1 Bombax ceiba (silk cotton tree) This is a spectacular flowering tree (Family Bombacaceae) of the monsoon forests of northern Australia, but planted trees have grown well in Townsville and Rockhampton. Large red fleshy flowers are produced and dropped in abundance immediately after leaf fall. Fallen leaf and particularly flower was highly palatable to sheep. Timber density is 350 kg/m 3.

7.2.2 Brachychiton populneum, B. discolor, B. diversifolius, B. rupestre (kurrajong) These are well known as fodder trees. We have one verbal record of fallen leaf being eaten. From the behaviour of sheep offered fallen leaf this seems very likely. Kurrajong is also well known for not having an adverse effect on grass or crop growth. Traditionally in wheat areas, kurrajong trees have been left and the ground cropped right to the base on the observation that the yield is as good there as elsewhere. As indicated in section 5.4 the timber (density 450 kg/m 3) was found to be adequate as a substitute for balsa wood in wartime.

7.2.3 Commersonia bartramiana (brown kurrajong) This is a fast growing pioneer species of rainforest fringes and dry rainforests, and is capable of volunteer establishment in south east Queensland. Being highly palatable as browse and being deciduous with membranous leaves it is probable that fallen leaf would be eaten. Volunteer populations are sometimes dense and shrubby but individual trees become tall with clear straight stems. Density is 500 kg/m 3

7.2.4 Erythrina vespertilio (bat-wing coral tree) This tree occurs scattered through eucalypt woodlands, suddenly revealed in the late dry season by its crop of red flowers. There is no indication that leaf is browsed (most erythrinas contain alkaloids, but

some are fodder trees) but it is completely deciduous and it may be that the fallen leaf is eaten. In this project we found the in vitro fermentability of the fallen leaf to be very high (data not shown). This native coral tree has the lowest density of any of the Queensland timbers listed by Cause et al. (1989) – at 190 kg/m3 it could indeed be a substitute for balsa.

7.2.5 Ficus macrophylla (Moreton Bay fig) This was one of the few species noted in RIRDC97/73 as having on record that the fallen leaf was used by cattle. It was not included in the present project because it was assumed the wood was of little value. In fact a number of wood turners do use it and it is regarded as easy to work. The density at 335 kg/m 3 (Cause et al. 1989) is definitely in the low density group.

7.2.6 Macaranga tanarius (macaranga) This is a common pioneer species, very fast growing, with a large peltate leaf. It is also capable of growing well in drier areas. Macaranga did not rate well in the in vitro evaluations here but is noted as one of the important fodder trees in Timor (Zabala 1997; p. 32) and the leaf was also said to have been used by aborigines to wrap food for cooking (Aboriginal Plant trail, Mt Cootha Botanic Garden). It thus seems likely that it has feed value, and if so the conspicuous dry season leaf drop would probably be used. The tree is very fast growing and the wood is light, soft and easily worked, but the density (560 kg/m 3) is not as low as other species in this group.

8. Implications

The opportunity The results presented here, together with the wider aspects canvassed in Appendix 2, suggest that a major opportunity is available. They indicate the potential productivity and sustainability on much of the northern Australian rangelands could be higher than is usually supposed.

There are still real research needs There sometimes appears to be a tendency to assume that most of the science necessary for resource management has been done and is available, and that the most effective strategy is modelling with existing data to define the most appropriate system. This may well be true in many situations. However the author suggests that for the northern rangelands major research needs exist, the results from which could strongly affect the way we approach the system. As dealt with in this report, these include the role of deciduous trees, and the tree–grass interactions of the non-sclerophyll trees.

Fear of adverse impacts There has also been a tendency for researchers to tacitly recognise that in many ways agriculture has had a destructive effect on the Australian environment and to retreat from any thought of bold interventions. Researchers are now defensive about work on sown pastures. The success and enthusiasm for leucaena rather than leading to a search for new shrub forages has instead inspired concern (well founded when it has been planted near water courses) for its weed potential. However the issues arising from introduction to the rangelands of African grasses and South American legumes is a very different from encouraging native non-sclerophyll trees to reclaim territory that they probably occupied at the time of the megafauna.

The need to integrate Another implication is the need to integrate different disciplines. It could be that the reason dual- purpose agroforestry systems have not been proposed before is that those aware of one component have been unaware of the possibilities in the other component. Those interested in growing wood would not want to go to the trouble of establishing most of the species used in pasture. Those interested in shrub forages have not seen any virtue in having large out-of-reach trees in pasture. In Queensland these interests are represented by different agencies. The Queensland Department of Primary Industries has an interest in browse species, and planted A. lebbeck on both research sites and on properties, but exclusively as a browse species. The Queensland Department of Natural Resources is also involved in establishing trees, for wood, shelter or environmental purposes but never for forage.

In Queensland the “Managing and Growing Trees Training Conference” in 1996 and 1998, jocularly anagrammed as MAGOTT I and MAGOTT II, organised by Greening Australia and Queensland Department of Natural Resources have brought together a wide variety of experience and interests; however, the only presentations on forage aspects were those of the author.

Grazing management Any agroforestry system would obviously involve more grazing management than has been traditionally practiced, and this must be seen as a disadvantage. However, independently, there has been a growing interest in intensively managed grazing (“cell grazing”), often from innovative producers. This would be valuable if incorporated in an agroforestry system, allowing heavy stocking at the time of leaf drop to ensure use but then allow the area to recover.

Weed trees One could note here that the problem status of trees such as Chinese elm often results because of prolific seed production and efficient dispersal, usually by birds. Introduction of a biocontrol agent to drastically reduce seed production would remove this problem. The benefits of biocontrol are usually

evaluated in terms of the economic cost of the problem. Surely, however, it should include benefits if it can make a problem species an asset.

Carbon Credits There have been rapid developments in this but it looks increasingly certain that trading in carbon credits will become a reality. Establishing trees in a dual purpose system will certainly result in carbon sequestration.

There would of course have to be special considerations for this system including biomass exported as cattle liveweight and timber, increased soil organic matter, and the fate of the various biomass components. It will be a disadvantage if accreditation were only available for large scale plantation forestry enterprises.

One possibility would be to refrain from wood harvest to gain greater carbon credits. If this provided funds for tree establishment the landholder could establish a more productive pasture system for no cost.

Methane reduction Quite apart from the question of carbon fixation, this agroforestry system could contribute to greenhouse gas reduction by the nutritional route in two distinct ways. The key fact here is that methane emissions per unit of feed are relatively high for animals on low quality diets.

For much of the year grazing animals in the dry tropics are consuming mature grass but merely maintaining, or even losing liveweight. During this time, methane production takes place with no net liveweight gain. Provision of the higher quality feed associated with this agroforestry system would enable animals to continue growing, would mean fewer animals were needed to achieve the same production, and would greatly reduce methane emission per unit of liveweight gain.

Additionally, the different microbial ecology of animals getting a higher quality diet may reduce methane production per unit of feed consumed. This would need to be investigated for the actual system concerned.

9. Recommendations

Workshop: “A. lebbeck – and trees for wood and animal production”.

There are three reasons why it would be worth holding a small workshop:

1. With the possibility of divergent views on the nature of A. lebbeck developing, it would be beneficial to get relevant people together to find common ground, and determine what the problems might be and how to accommodate them.

2. To bring together those already interested in A. lebbeck for forage and those involved in tree planting for other reasons, but who have shown no interest in A. lebbeck.

3. As indicated in Section 8, wood and forage aspects tend to be covered by different agencies. Some attempt at integration is warranted.

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Appendix 1. Summary of sites

Abbreviations used for Data Sought inc = measurements for growth increments coll = collections of fallen flower leaf or pod, timber tgi = studying tree-grass interaction obs = phenological observations.

Place Name Location No Data Sought Acacia bidwillii (corkwood wattle) Rockhampton 23 14.06 150 28.98 1 tgi, obs Rockhampton 23 14.39 150 29.31 2 tgi obs Albizia chinensis “Glendhu” s. Mt Garnet 18 25.50 145 04.22 2+ inc, tgi,obs Albizia canescens (Belmont siris) Sebastopol Creek 23 39.65 150 05.70 5 tgi, coll, inc Poison Creek 23 34.90 150 25.41 1 obs, inc Thozet Creek 23 21.80 150 32.91 1 + 7 inc, obs “Belmont”, Rockhampton 23 13.72 150 23.20 1 obs, coll, tgi 23 13.84 150 23.22 1 23 13.84 150 23.08 1 Heritage Village, Rockhampton 23 18.55 150 30.93 1 inc, obs Caves Village, Olsens caves 23 10.09 150 29.40 4 inc Stuart, nr Townsville 19 24.12 146 54.84 ∞ obs Townsville 19 19.04 146 46.05 2 obs “Lansdown” nr Townsville 19 39.75 146 50.50 1 tgi, obs, inc Double Barrel Ck 18 39.98 146 50.79 12 obs, inc Albizia lebbeck (siris) Long Pocket, Brisbane 27 30.68 152 59.84 3 obs, coll, media University of Queensland, Gatton 10+ coll “Yandilla” nr Kilcoy 26 47.47 153 34.12 14 prn, obs Kilkivan 26 05.15 152 16.16 1 + ∞ tgi,, inc, obs Gunalda 25 59.26 152 34.22 3 + ∞ obs Brian Pastures 25 40.81 151 44.26 7 prn, obs Brain Pastures (Browsenet) 25 35.91 151 45.61 26 inc “Narayen”, Munduberra ∞ tgi Lake Creek 23 23.08 150 34.07 ∞ obs Etna Creek, Browsenet 23 13.82 150 28.78 8 obs Mundingburra 19 18.08 146 47.20 1 inc “Lansdown” 18 39.97 146 50.05 ∞ prn, inc, tgi “Glendhu” s. Mt Garnet 18 25.50 145 04.22 14 prn, inc, tgi,obs Kairi Res. Stat. 17 13.56 145 34.56 ∞ inc, obs Albizia procera (forest siris) Mt Cootha B.G., Brisbane, 27 29.84 152 58.23 1 obs, inc, coll Sarina Range 21 30.14 149 07.20 1 obs, inc Sarina Range 21 30.02 149 07.42 1 obs, inc Sarina, Hwy Reserve 21 27.43 149 13.35 1 tgi inc Kuttabul 20 58.51 148 50.20 1 inc, obs Alligator Ck 19 25.42 146 56.79 2 ?tgi Stuart Creek, nr Townsville 19 23.32 146 49.74 2 inc, obs, tgi Killymoon Ck 19 23.54 146 59.13 2 inc, obs, tgi

Place Name Location No Data Sought “Glendhu” s. Mt Garnet 18 25.50 145 04.22 4 inc, obs Cardwell Range 18 32.08 146 11.21 8 inc, obs “Lansdown” 18 39.97 146 50.05 6 obs, col Yorkeys Knob, Cairns 16 50.44 145 42.41 1 obs, inc N of Cairns 16 46.05 145 33.87 5 tgi, obs, coll Palm Cove 16 45.17 145 39.60 1 tgi, inc, coll Archidendropsis basaltica (dead finish) “Booroondarra” 22 50.62 148 24.42 ∞ coll, obs Middlemount 22 53.79 148 18.97 12 + ∞ obs Waterford 22 45.39 148 12.47 ∞ obs Archidendropsis thozetiana (southern siris, scrub tea tree) Moores Creek 23 19.75 150 33.52 9 obs, coll, inc Barklya syringifolia (crown of gold tree) Sherwood Arboretum 27 31.97 152 58.32 1 obs Glenwood 25 57.99 152 35.26 1 obs Moores Creek 23 19.75 150 33.52 2 coll Cassia brewsteri (Leichhardt bean) Sherwood, Brisbane 27 31.97 152 58.32 4 coll, inc obs Long Pocket, Brisbane 27 30.75 152 59.85 2 coll, inc, obs Glenwood 25 57.99 152 35.26 1 obs “Booroondarra” nr Middlemount 22 49.42 148 29.87 1 + ∞ tgi, coll S. of Greenvale 19 10.51 145 22.16 1 + ∞ obs, inc, tgi Dalbergia sissoo Brian Pastures 25 35.91 151 45.61 14 obs Mackay, Peak Downs Hwy 21 10.03 149 08.74 30+ inc, coll, obs Farleigh 21 06.90 149 06.50 3 inc, coll, obs Gmelina arborea (yemane) Mt Cootha BG 27 29.84 152 28.23 2 coll, obs Rockhampton 23 23.97 150 29.42 1 coll James Cook University 19 19.54 146 45.73 2 inc, coll Annandale 19 18.82 146 46.27 2 inc, tgi, coll Kennedy State Forest 20 coll Melia azedarach (white cedar) Brisbane, Sherwood 27 30.48 152 59.91 3 inc, obs “Yandilla” nr Kilcoy 26 47.47 153 34.12 1 obs Booyal 25 12.54 152 01.75 1 inc Granite Creek 24 36.84 151 40.07 5 inc tgi obs

Gracemere 23 24.50 150 25.51 1 coll Sebastopol Creek 23 39.65 150 05.70 1 obs, inc Ubobo 24 24.13 151 19.16 3 inc, obs Westwood 23 38.54 150 09.18 1 obs, inc Marmor 23 41.01 150 42.77 3 + 7 obs Marmor 23 41.71 150 42.89 1 obs, tgi Yungaburra 1 obs Holloways Beach, Cairns 16 50.44 145 44.36 1 inc, prn

Paraserianthes toona (red siris, Mackay cedar ) Mt Cootha B.G., Brisbane 27 28.84 152 58.23 1 inc, obs, coll Amity Creek 22 32.88 149 29.42 6 inc, tgi, obs Nr St Lawrence 22 13.88 149 29.32 1 obs St Lawrence Creek 22 18.87 149 26.64 1 obs Eungella 21 07.03 148 29.70 3 obs Mt Stuart 2 inc, obs Nr Port Douglas 16 33.77 145 29.49 1 tgi obs inc Cook Hwy 16 38.48 145 33.87 10 tgi, obs Rockhampton B. G. 23 24.05 150 29.31 1 obs

Pongamia pinnata (pongamia tree) Sherwood, Brisbane 27 31.97 152 58.32 4 inc, obs Murray, Townsville 19 19.23 146 45.96 3 obs Mt Stuart

Samanea saman (rain tree) “Glendhu” s. Mt Garnet 18 25.50 145 04.22 1 inc, tgi, obs

Tipuana tipu ( tipuana) Yamato, nr Ipswich 27 39.72 152 45.24 1 tgi “Yandilla” nr Kilcoy 26 47.47 153 34.12 5 prn, inc, obs Connondale 26 47.81 152 44.70 26 tgi Fathen Creek 26 05.51 152 17.25 1 tgi, inc Brian Pastures 25 35.91 151 45.61 20 inc, obs Etna Creek, Browsenet 23 13.82 150 28.78 10 obs Belmont 23 13.65 150 22.96 3 obs Farnborough 23 04.80 150 43.10 2 inc, tgi “Glendhu” s. Mt Garnet 18 25.50 145 04.22 6 prn, inc, tgi,obs

Appendix 2. Agroforestry in Northern Australia – the Wider Context

In arguing the potential for agroforesty with dual-purpose trees in northern Australia one labours against the apparent improbability of establishing, in dry eucalypt woodland, trees that are more easily viewed as rainforest trees. The evident harshness of dry eucalypt woodland, and the well-known adaptations against dessication and insolation seen in eucalypts, tends to give the impression that these are the only suitable trees for this environment. This appendix presents arguments that the trees of interest can indeed be seen as appropriate for establishing and managing in the native rangelands.

There are three elements to be considered 1. the nature of the Australian tropical woodlands 2. studies of vegetational history 3. contemporary observation.

1. It is well known that northern Australia is characterised by harsh conditions. The soils are infertile, the climate severe, the rainfall unreliable. Conditions will not sustain a closed forest and so we have the tropical and subtropical woodlands. Over a vast tract of this country beef cattle production is an obvious land use. Apart from socioeconomic factors, it makes ecological sense to have large herbivores in the savanna ecosystem. Every year grass grows vigorously in the wet season and then matures, becoming indigestible to anything but a fibre-digesting herbivore. It is much better to have some of that biomass processed by an animal than burnt, which would otherwise happen eventually. That way, at least some of the organic matter gets to the soil, minerals are recycled, microbial activity supported. Certainly, fire is a natural part of the system; but too-frequent fires lead to loss of nutrients and biodiversity, particularly of fire-sensitive plants and the invertebrates. The best way to avoid hotter or more frequent fires is by having animals that digest fibre. However there are major constraints on animal production from two underlying biological factors: A. tropical grasses (C4 grasses) become of low feed value in the dry season everywhere in the seasonal tropics B. although the country is mostly woodland, the dominant eucalypts and acacias have highly lignified and cutinised sclerophyllous leaves that by their nature are of little feed value. The eucalypts also provide very thin shade and compete with grass. Their dominance is very much an Australian phenomenon.

Because of this it has been traditional for beef producers to view trees as a problem. Pulling trees appears to produce more grass. Yet increasingly it is recognised that trees are essential to prevent land degradation. There seems to be a trade-off between environmental protection and increased production. When people say ‘’trees’’ they almost always mean eucalypts. Do we have to accept their dominance as inevitable as the scorching sun and drought?

It should be said that sclerophyllous leaves are not an inevitable response to a seasonally harsh environment. An alternative is for trees to have lighter, membranous leaves that function when conditions are suitable and are dropped under harsh conditions. The plant invests less biomass but renews it more frequently. The deciduous habit may be an equivalent strategy as a dry-season adaptation but it has profoundly different consequences in terms of feed value; non-sclerophyll leaves are more digestible. On the ground, they are more easily degraded, unlike the sclerophyll litter which is long lived and inflammable. Eucalypts are not only fire tolerant, but fire-promoting. Native deciduous trees may be scattered through woodland, but most tend to occur in discrete patches of vegetation collectively known by the paradoxical term “dry rainforests”. They are a minor element, in terms of area, although they are known to have important wildlife values.

2. Vegetational history. There is a large amount of palynological evidence that about 50,000 years ago Australia’s vegetation was very different. There was less eucalypt dominance and a higher

proportion of the dry rainforest types (Kershaw 1986). This would include some of the species seen here as having potential for dual-purpose agroforestry. This vegetation was present under climate conditions not markedly different from today. Thus there is, first, an indication that deciduous mesic trees have in the past grown well in areas where we do not see them occurring naturally today. This would appear to be as close to empirical fact as we are likely to get. However the circumstances that led to this vegetation change and eucalypt dominance tend to be seen as controversial. This is because it is associated with an increase of fire frequency, the disappearance of a megafauna of large herbivores, and the first appearance of humans on the Australian continent (Flannery 1994). Despite abundant evidence here and elsewhere that man as hunter-gatherer was capable of profoundly altering his environment, this is for various reasons still disputed in Australia. Rather than reviewing this debate, we just note what seems to be an empirical fact; that a landscape rich in dry rainforest plant communities was able to sustain large herbivores that have since vanished. It has been pointed out that the arrangement of thorns in many dry rainforest shrubs and trees, which have no adaptive significance against native herbivores today, are living evidence of these species co-evolving with large herbivores. This is also an indication of their feed value compared to sclerophyll trees. In fact apart from some acacias, the woody plants recognised as having browse value are non-sclerophyllous, and tend to be members of various dry rainforest associations. Their production value tends to be neglected because of the relatively small areas for this vegetation.

3. Contemporary observations. Not only have elements of the mesic vegetation that supported the megafauna persisted for 50 000 years, there is evidence that they can recolonise eucalypt woodland, given the right conditions. First there is the spontaneous advance of rainforest into wet sclerophyll forests when fire is suppressed, which has been documented in several places. This is so obvious in North Queensland national parks that the Department of Environment carries out deliberate burning to prevent "rainforest encroachment" into eucalypt forest. It seems reasonable to assume the same effect would be seen in drier areas; i.e. of dry rainforests extending their range, except that most of these are either under continuous grazing or subject to frequent fires. Recent studies on dry rainforests in Queensland indicate that in many cases their present boundaries are not determined by nutrients or rainfall but by past fire history. The potential for extending their range can be seen also in the behaviour of certain native species such as Macaranga tanarius, Schefflera actinophylla or Pittosporum umbellatum which can vigorously colonise eucalypt woodland in the absence of fire to the extent of being regarded as a problem. Then there is the vigour with which some highly undesirable non-sclerophylls such as rubber vine and Ziziphus invade native woodland. Trees do not have to be sclerophyllous to thrive in the north Australian environment.

This is particularly pertinent to A. lebbeck. Today its native habitat is at the closed forest-open woodland ecotone in parts of the Kimberleys, Northern Territory and Cape York. But when planted it can thrive over a vast area of northern Australia, and it is naturalised in Central Queensland and elsewhere. Its limited distribution as a native tree is certainly not because of soil and climate limitations; it seems more likely to be the result of millenia of past fire regimes. Similarly the limited distribution of A. procera and A. canescens may be due to previous fire and present grazing.

There may well be practical problems in establishing dual purpose trees for agroforestry, but an inherent unsuitability for the north Australian environment is not one of them.