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Analysis of Plant-Host Relationships in Tropical Sandalwood (Santalum album)

RIRDC Publication No. 08/138

ESSENTIAL OILS AND PLANT EXTRACTS

RIRDCInnovation for rural Australia

Analysis of Plant-Host Relationships in Tropical Sandalwood (Santalum album)

by Dr Liz Barbour

August 2008

RIRDC Publication No 08/138 RIRDC Project No PRJ-000019

ISBN 1 74151 727 3 ISSN 1440-6845

Analysis of Plant-Host Relationships in Tropical Sandalwood (Santalum album)

Publication No. 08/138 Project No. PRJ-000019

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.

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Researcher Contact Details Dr Liz Barbour Assoc. Prof Julie Plummer and Kevin Murray Forest Products Commission University of Western Australia Phone: (08) 9475 8888 Phone: (08) 6488 1786 or (08) 6488 1838 Fax: (08) 9475 8899 Fax: (08) 6488 1108 or (08) 6488 1028 Email: [email protected] Email: [email protected] [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

Published in August 2008 by Union Offset

ii Foreword

Tropical sandalwood is fast becoming a major industry in the North of Australia, particularly in the Ord River Irrigation Scheme (ORIS). This has arisen from a need in the world market for sandalwood oil sourced from the species Santalum album for the valuable perfume markets and growing religious requirements of the Asia –Pacific region. The natural distribution of this species is across the Asia – Pacific region mainly focussing in India, Indonesia and across the islands to a small population in the north of Australia. However, exploitation, fire, regeneration, browsing and diseases have made the required level of harvest to meet world demand unsustainable.

The development of plantations, as has occurred in the ORIS, has the potential to make a significant contribution to the rural economics of Australia and provide a sustainable resource of sandalwood. Cultivation of sandalwood is, however, not easy due to its hemi-parasitic nature and the dependence on suitable host plants, as well as suitable environmental conditions.

This report analyses the effect of secondary hosts on the survival and growth of sandalwood. The balance of the secondary host to optimise sandalwood growth through to full rotation has been a major concern in the developing industry. This will be the first information provided on secondary host performance and the resultant wood growth that can be expected from Tropical sandalwood after 9 years of growth. This information is required for the industry and investors in this industry, both to assist with growth modelling as well as provide silviculture information for future establishment.

This project was funded from industry revenue from the Forest Products Commission, Western Australia, which is matched by funds provided by the Australian Government.

This report, an addition to RIRDC’s diverse range of over 1800 research publications, forms part of our Essential Oils and Plant Extracts R&D program, which aims to support the continued development of a sustainable and profitable essential oils and plant extracts industry that has established international leadership in production, value-adding, and marketing.

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

iii Acknowledgements

The files indicate that this trial was originally discussed and established from a collaboration of managers and scientists whom were employed by a former entity of Forest Products Commission, Department of Conservation and Land Management. The scientists and managers involved were Dr. Syd Shea, Dr. Andrew Radomiljac, Frank McKinnell, Pat Ryan, Matt Williams and Tanya Vernes who organised the planting of the trial.

Forest Products Commission undertook the thinning of the trial supervised by Peter Jones and undertaken by John Streatfield and Wayne Tatnell. The continued management of the trial has been the responsibility of John Streatfield since 2004.

Trial measurement and data input was undertaken by Len Norris and John Streatfield, Forest Products Commission with help from Julie Plummer and Chris Jones from the University of Western Australia.

It has been a pleasure working with Kevin Murray and Assoc. Prof Julie Plummer from the University of Western Australia to record the outcomes of the last 9 years of this trial.

Abbreviations

ORIS Ord River Irrigation System Sph stems per hectare

iv Contents

Foreword...... iii Acknowledgements...... iv Abbreviations...... iv List of Tables...... vi List of Figures...... vi Introduction ...... 1 Objectives...... 2 Methodology ...... 3 Plant material...... 3 Trial design...... 6 Land preparation and trial establishment ...... 7 Results ...... 8 Trial measurement in 2001...... 8 Trial measurement in 2002...... 9 Observations from 2003 - 2007...... 10 Trial measurement in 2008...... 14 Discussion of results ...... 21 Implications...... 23 Recommendations ...... 24 References ...... 25

v List of Tables

Table 1: The layout of the Randomised complete block design used in this trial divided into 5 replicates...... 6 Table 2: The original layout for each block planted in 1999...... 7 Table 3: Due to over-crowding, the second, fifth, eighth and eleventh rows of long term hosts (Table 2) were removed in 2003 to leave a final layout of 8 rows 3.6 m apart...... 7 Table 4: Trial assessment of the sandalwood after two years of growth for average tree height (cm) and survival (%)...... 8 Table 5: The average survival (%) of the pot host, Alternantha, and the primary host, Acacia trachycarpa, after two years of growth...... 8 Table 6: Trial assessment of the secondary hosts after two years of growth for tree height (cm), stem diameter (cm) and survival (%)...... 9 Table 7a: Trial assessment of the sandalwood after three years of growth...... 10 Table 8 : Tree survival within each secondary host treatment in the trial over the nine years of growth...... 15 Table 9: Stems per hectare (sph) of Tropical sandalwood and the secondary host treatment and their resultant ratio...... 16 Table 11: Tropical sandalwood bole length (m) after 9 years of growth with different secondary host treatments...... 18 Table 12: Comparing the basal area (m2) of sandalwood with the 6 different secondary hosts tested. 18 Table 13: Average sandalwood tree volume at nine years of age with the six different secondary host treatments...... 19 Table 14: Sandalwood tree volume per hectare at nine years of age with the six different secondary host treatments...... 20

List of Figures

Figure 1: Overhead photograph of the secondary host trial at eight years of age with a table indicating the host treatments below...... 11 Figure 2: The correlation between sandalwood heights and breast height diameters...... 11 Figure 3: The correlation between tree height and breast height diameter for Pongamia pinnata...... 12 Figure 4: The correlation between tree height and breast height diameter for Cathormium umbellatum ...... 12 Figure 5: The correlation between tree height and breast height diameter for Cedrela odorata...... 12 Figure 6: The correlation between tree height and breast height diameter for Dalbergia latifolia...... 13 Figure 7: The correlation between tree height and breast height diameter for Pterocarpus indicus...... 13 Figure 8: The correlation between tree height and breast height diameter for Khaya senegalensis...... 13 Figure 9: The survival (%) for (A) sandalwood with the six host treatments at two, three and nine years; and (B) the survival of the six secondary host treatments at two and nine years...... 16 Figure 10: The breast height diameter (cm) of (A) sandalwood when grown with the six secondary host treatments at two, three and nine years; and (B) host species at two and nine years...... 17 Figure 11: The relationship between sandalwood and host basal area per hectare (m2)...... 19

vi Executive Summary

What is the report is about The Forest Products Commission (FPC) and former entities of this Western Australian State agency, has been researching tree crops in the Ord River Irrigation Area (ORIA) since 1987. This report is an analysis of one of the trials established in 1999 at the Frank Wise Institute. Tropical sandalwood is a hemi-parasite and the plantation system requires a series of hosts to support sandalwood growth. This trial is of current interest as the trial has progressed through the primary host stage and is now reliant upon the various secondary hosts for sustained growth of the Tropical Sandalwood. The need for additional hosts beyond the primary host, and the identification of a superior secondary host, has been regularly questioned and this trial provides an insight to the role and value of this long-term host.

Who is the report targeted at? This report is targeted at Tropical and Native sandalwood plantation growers as it provides information on the development and optimisation of sandalwood plantation systems. It also provides productivity information that can be used both by economists and investors alike.

Background Investigations into the domestication of Tropical sandalwood (Santalum album) in the Ord River Irrigation Scheme (ORIS) in Kununurra, Western Australia started in the 1980’s. From this research, a sandalwood plantation industry now exists in the ORD with major companies such as Integrated Tree Cropping, Tropical Forestry Services as well as local landowners profiting. In forestry terms, this is a young industry and whilst the basic silviculture techniques are known, research is continuing to further improve systems for Australian conditions. Knowledge regarding performance of mature plantations in Australia can only be gained from these first host/tree trial plantings undertaken by the Forest Products Commission.

Aims/Objectives/Methods used The measurement and analysis of this trial was to quantify the effect of six different secondary hosts on Tropical sandalwood growth. The secondary host species selected were from the Meliaceae and Leguminosae. The trial was assessed whilst the primary host was still alive, and the final measurement was when all the primary hosts had died and only the secondary host was meeting the hemi-parasitic requirements of the Tropical Sandalwood.

Key findings Key findings from this trial analysis were that of the secondary hosts tested, the two Meliaceae species, Khaya senegalensis and Cedrela odorata both had good survival but did not provide the necessary support for Tropical sandalwood growth in the Cununurra clay ORIS system. Species belonging to the Leguminoseae family were superior in their support of Tropical sandalwood growth although performance between the species differed. The best performing secondary host system in this trial, Dalbergia latifolia, had a survival of 390 stems per hectare and a Tropical sandalwood production of 2 m3 per hectare in the ninth year of growth. This Tropical sandalwood growth rate was closely followed with the host support of Pongamia pinnata and Cathormium umbellatum.

vii Implications This outcome will provide great confidence to the industry in attaining the required production rates to meet market demand as Cathormium umbellatum has been a dominant secondary host in the ORIS plantings. This project does identify two alternate hosts that should be considered for greater use, especially Dalbergia latifolia as its wood would have high sawlog demand and add value to the plantation system.

Recommendations It is recommended that this trial and the monitoring of this trial be continued. The difference between the top three legume hosts could have been due to spatial differences rather than species differences. Culling to a more even stocking and further analysis will resolve this question. Additionally, the correlation of host performance to Tropical Sandalwood oil production still needs to be answered and can be reliably measured when the trees are over 10 years of age.

viii

Introduction

The Forest Products Commission (and former entities of this Western Australian State agency) established a research program into the domestication and genetic conservation of Tropical sandalwood in Kununurra at the Frank Wise Institute. This work started in the 1980’s with collaborations with Murdoch University and more recently with University of Western Australia. From this research, a sandalwood plantation industry now exists in the ORD with major companies such as Integrated Tree Cropping, Tropical Forestry Services, Capricorn Timbers as well as local landowners profiting.

Sandalwood refers to a tree species from the Santalum genus that is commercially harvested for its fragrant, essential oil heartwood. Tropical sandalwood (Santalum album) is the most widely known and valued of the sixteen species. This species produces both the highest amount of santalol, the most sought after component of the oil, and the total oil extracted does not vary in its composition within the species. Sandalwood oil is used for a range of products as additives to the finest perfumes and cosmetics, whilst the wood has been traditionally used in carving and in religious ceremonies as a component of joss sticks. More recently, sandalwood has been recognised as a mosquito repellent and the powder is made into sticks for burning.

Tropical sandalwood (Santalum album) is an aggressive hemi-parasite with 70 percent of seedlings able to generate haustoria within 30 days from germination (Nagaveni and Srimathi 1985). Rao (1904) documented the great effect hosts have on sandalwood growth and development and provided a list of 70 possible species by association. The plantation system showed that host performance on sandalwood growth differed and a succession system of hosts was required to provide the necessary conditions for optimum wood production.

The silviculture system devised utilises three hosts, the first being an herbaceous plant introduced to the container-grown sandalwood one month prior to field planting. The short-term host aims to produce rapid sandalwood growth and will die 2-4 years after establishment, leaving the long-term host to grow and support the sandalwood over its production life. The short and long term hosts are planted at the same time as the sandalwood, with plantation establishment usually occurring in May- June, or at least before the escalation in temperatures.

Structurally, hosts provide protection from sun, wind and grazing as well as a possible source of nutrients and amino acids. Nutrients such as calcium and iron (Rao, 1933); nitrogen and phosphate (Iyengar, 1960) potassium, phosphate and magnesium (Rangaswamy et al. 1962) have been shown to be supplied by the host to Tropical sandalwood. The presence of basic amino acids indicates that leguminose plants are more efficient hosts for sandalwood growth than non-leguminose plants, however performance between leguminose plants varies (Srimathi et al. 1961; Radomiljac et al. 1998, Nagaveni and Vijayalakshmi, 2003). Studies beyond one year of growth defining the success of long- term hosts in a plantation system on Tropical sandalwood growth are lacking.

In forestry terms, the Tropical sandalwood grown in Kununurra forms a young industry and whilst basic silviculture techniques are known, research is continuing to further improve systems for flood irrigation in Australian conditions. Knowledge regarding performance of mature plantations in Australia can only be gained from these first host/tree trial plantings undertaken by the Forest Products Commission. Information from the analysis of the trial presented here has great value for improvement of host/tree productivity and the future development of the industry.

In the late 90’s, there were negotiations with India to undertake an ACIAR project to ensure the sustainability of Tropical sandalwood through genetic conservation and further investigation of plantation systems. Whilst this ACIAR project did not proceed, a number of trials proposed for the project were planted. This report covers the history and present status of one of those trials.

The trial selected was planted on Forest Products Commission land at the Frank Wise Institute in July 1999. It compares the effect of Meliaceae and Legumimose long-term host plants on Tropical sandalwood (Santalum album) growth.

There are major differences between these two families selected: • Meliaceae are mostly evergreen, but some are deciduous, either in the dry season or in winter. The family includes about 50 genera and 550 species, with a pan-tropical distribution; one genus (Toona) extends north into temperate China and south into southeast Australia, and another (Melia) nearly as far north.

• Fabaceae (Leguminosae) are a large and economically important family of flowering plants, which is commonly known as the legume family, pea family, bean family or pulse family. Many Fabaceae host bacteria in their roots within structures called root nodules. These bacteria, known as rhizobia, have the ability to take nitrogen gas (N2) out of the air and convert it to a form of nitrogen that is usable to the host plant ( NO3- or NH3). This process is called nitrogen fixation. The legume, acting as a host, and rhizobia, acting as a provider of usable nitrate, form a symbiotic relationship.

The Fabaceae comprise three subfamilies (with distribution and some representative species): • Mimosoideae: 80 genera and 3,200 species. Mostly tropical and warm temperate Asia and America. Mimosa, Acacia.

• Caesalpinioideae: 170 genera and 2,000 species, cosmopolitan. Senna, Cassia.

• Faboideae: 470 genera and 14,000 species, cosmopolitan. Astragalus, Lupinus.

This report captures what is known of the first 9 years of this trial.

Objectives

The production of sandalwood oil is the fastest growing essential oil and plant extract industry in Western Australia. It is evolving from sustainable gathering through regeneration to include a plantation system to meet world demand. RIRDC have recognised this with their recent review of the industry (RIRDC Publication No 06/131). This project investigates the new Tropical sandalwood plantation system and adds to the industry knowledge base to attain profitability and thus industry sustainability through product reliability.

The analysis of this trial comes at a time when the role of long-term hosts in the Tropical sandalwood silviculture system is being questioned. One approach being developed is to forgo the presence of a long-term host and focus on short-term leguminose crops and chemical application for host nutrient supplementation. On the other hand, other growers are seeking the balance between maximising Tropical sandalwood growth and producing a high value timber product from the secondary host. The analysis of this trial will provide information to assist in this debate.

Methodology

Plant material Six long term host species were selected from the Meliaceae and Fabaceae. Khaya senegalensis and Cedrela odorata from the Meliaceae and Cathormium umbellatum, Dalbergia latifolia , Pongamia pinnata and Pterocarpus indicus from the Fabaceae. The short-term host was Acacia trachycarpa and Alternantha was used at the pot host. Each of the species is described with notes included on their seed source (if known) and nursery management.

Secondary host treatment 1: Cathormium umbellatum (Vahl.). Fabaceae subfamily Mimosoideae

A native species distributed in the most northern areas of Western Australia around Kununurra through to the Northern Territory. The species grows in alluvial soils, wet river sites, mangroves, dune swales, sandstone screes and rainforest and is described as a tree or shrub 3 – 24 m high. Leaves are bipinnate with opposite leaflets. The tree produces cream flowers between September and October, which develop into a pod with one seed.

A local seed source was used for the trial and the seedlings were grown in a 67 cell tray. This was found to be too small a tray volume due to drying our in the field prior to planting.

Secondary host treatment 2: Cedrela odorata L. Meliaceae

Known as Cedro Hembra or Spanish, Mexican or Cigar-box cedar, the species is one of the world’s most important timber species and occurs naturally from the Mexican Pacific coast, through central America and the West Indies to its southern limit in Argentina. The species prefers well-drained soils, occasionally limestone and is able to tolerate a long, dry season. It does not flourish in areas of rainfall greater than 3000 mm or on sites with water-logged soils. The species is a monoecious, semi- deciduous tree ranging in height from 10 to 30 m with pinnate compound leaves grouped towards the end of the branches.

The seed source used in this trial was sourced from Mtibwa, Tanzania. Early observations record that it was thought that the species was attacked by red spider, increasing defoliating in the dry season causing sunburn on tree bole.

Secondary host treatment 3: Dalbergia latifolia Roxb. Fabaceae subfamily Faboideae

Dalbergia is a large genus of approximately 500 species from small to medium-size trees, shrubs and lianas with a wide distribution, native to the tropical regions of Central and South America, Africa, Madagascar and southern Asia. Dalbergia latifolia is known as (East) Indian rosewood or sonokeling and can be found in India, Nepal and Malaysia. Naturally the species can receive a rainfall between 750 and 5000 mm and survive maximum temperatures of 37 – 50’C. The species grows best on deep loams or clays containing lime with poor drainage stunting tree growth. The tree is predominantly a single stemmed deciduous tree with a dome shaped crown of lush, green foliage. The bark is grey, thin with irregular short cracks with a root system that will produce suckers when near the surface. The trees can reach a height of 20 – 40 m and a girth of 1.5 – 2 m.

The seed was sourced from central India and sown into seeding trays with a media mix of perlite: peat: kracker dust (1:1:1) and completed by 25 March 1999. In hindsight this was determined to be too late and seedling quality was poor when planted which was reflected in their poor trial survival. An additional reason for this low growth rate was thought to be due to the lack of inoculants being added to the sterile nursery media.

Secondary host treatment 4: Khaya senagalensis Meliaceae Khaya is a genus of seven species of trees in the mahogany family Meliaceae, native to tropical Africa and Madagascar. K. senegalensis is known as the dry zone Mahogany and is distributed from the Congo across to Senegal. A deciduous tree, usually 15 – 20 m tall with diameters up to 1.5 m with 8 – 16 m of clean bole and often buttressed at the base. The leaves are pinnate, with 4-6 pairs of leaflets, the terminal leaflet absent; each leaflet is 10-15 cm long abruptly rounded toward the apex but often with an acuminate tip. The flowers are produced in loose inflorescences, each flower small, with four or five yellowish petals and ten stamens. The fruit is a globose four or five-valved capsule 50-80 mm diameter, containing numerous winged seeds. The seed was sourced from Tanzania, Morogoro and was grown in a 24 Hiko tray.

Secondary host treatment 5: Pongamia pinnnata (L.). Fabacaea. (recently renamed Millettia pinnata)

Indian beech is an Indo-malaysian species common on alluvial and coastal situations to 1200m altitude from India to Fiji. The species can withstand temperatures slightly below 0’C to 50’C and an annual rainfall of 500 – 2500 mm. The tree grows wild on sandy and rocky soils including oolitic limestone, but will grow in most soil types even with its roots in salt water.

The tree is described as a fast-growing deciduous tree up to 25 m tall. The trunk can reach 60 cm in diameter with smooth grey bark. Leaves are imparipinnate, with young leaves showing pinkish-red tinge which matures into a glossy, deep green grouped into 5-9 leaflets with the terminal leaf larger than the others. Flowers are fragrant, white to pinkish, paired along a rachis in axillary, pendent, long racemes of panicles reminiscent of wisteria. The pod is stalked, oblique-oblong, flat, smooth, thickly leathery to sub-woody, indehiscent with one reinform seed per pod.

The wood is yellowish-white, coarse, hard and beautifully grained but is not durable limiting its use to cabinet-making and fuel. The wood has a calorific value of 4600 kcal/kg. The tree has been used extensively in folk medicine with both the oil and residues being toxic containing a high level of alkaloids. The seed contains pongam oil, a bitter red-brown, thick, non-drying oil which lends itself for use in the tanning leather process, soap, as linament to treatment for scabes, herpes and rheumatism and as illuminating oil. Recently it has been recognised for its bio-diesel potential. Trees reach seed bearing at the age of 4 -7 years with a single tree able to yield between 9 -90 kg seed per tree of which approximately 25% of this weight is pongam oil.

The seed used in this trial is thought to have originated from India. It was sown directly into 40 cell Hiko trays although this was regarded to be too small a volume for the seed size and seedling vigour.

Secondary host treatment 6: Pterocarpus indicus (Willd.). Fabacaea

This species comes from the western limit of southern Burma, extending eastwards through to the Solomon Islands and can tolerate an annual precipitation of 960 – 2180 mm and pH range of 4.0 – 7.5. It is able to tolerate water-logging but it can not tolerate shallow soils and stiff clays.

The tree is a large deciduous tree 30m or more high with large and high buttresses. Leaves are 12 – 22 cm long in all with 5 – 13 leaflets and greyish brown to green in colour. Seeds are winged with the seed-bearing part covered by a woody protection. The seed is dark brown and smooth in appearance and ripens within 4 – 6 months.

The wood harvested from these trees is regarded one of the best furniture timbers having a density of 625 kg/m3 and can be air-dried with no difficulty.

The seed came from an unknown source and on the 15th February 1999 was sown directly into 40 cell trays with 2 seeds per cell. Germination was complete by 10th March 1999 and a fertigation routine introduced. The resultant seedlings were regarded as small for planting especially as they had poor root growth.

Intermediate host treatment: Acacia trachycarpa E. Pritz. Fabacaea subfamily Mimosoideae

Known as Sweet-scented minnieritchie, the species is an arid to tropical Australian shrub or small tree ideal for planting in frost free regions. It grows in neutral to alkaline soils in 120-400 mm rainfall zones but in the drier parts of its distribution it becomes riverine growing in dry creeks. The tree can reach 15 m high with a spreading crown of up to 10 m in diameter. The trunk has a curling , 'minni ritchi' bark texture with a pine scent which is unique and interesting for an arid tree. The leaf is made up of soft, pine needle-like, narrow phyllodes, 12-50 mm long and produces yellow, rod-shaped flowers in spring. It propagates by seed and its coppicing is assumed weak.

Hemi-parasite plant treatment: Santalum album Santalaceae

Tropical sandalwood (Santalum album) is a small tropical tree of the Santalaceae family, commonly known as the source of sandalwood. The species occurs from India through to the South Pacific to the northern coast of Australia. The height of the evergreen tree is between 4 and 9 metres and may live to one hundred years of age. The tree is hemi-parasitic tree, variable in habit, usually upright to sprawling, and may intertwine with other species. The plant parasitises the roots of other tree species, with an haustorium adaptation from its own roots. An individual will form a non-obligate relationship with a number of other plants. Up to 300 species (including its own) can act as hosts, supplying macronutrients, phosphorus, nitrogen and potassium, and shade, especially during early phases of development. It may propagate through seed or root suckering, establishing small stands. The heartwood is darker in colour than the sap wood and contains the essential oils. The leaves are opposite and ovate to lanceolate in shape. Fruit is produced between one and three years and with a black pulp exterior and hence distributed by birds.

The seed used for the trial was collected in April and August 1998 from previous trials established on the FPC estate. The pulp was removed from the seed and stored until required. On 1 December 1998, the seed was aerated with Giberrellic acid (GA3) (0.05%) for approximately 14 hours and then sown in nursery media of perlite: peat: charcoal (1:1:1). Benlate and Rogor were applied to control fungal attack. Once germinated, the seedlings were pricked out and transferred to a media of perlite: peat: kracker dust (1:1:1) on 12 February 1998.

14 days after transplanting, chemical nutrients were given to the seedlings. The seedlings were exposed to the following treatments:

• Thrive (8 g/9 l water watering and area of 3 m x 1.75 m) or

• Nurserycote (4 g/140 ml pot) fortnightly.

Supplementary fertilisers were also added on alternate fortnights and included:

• Fetrilon combi 2 (30 g/9l water watering and area of 3 m x 1.75 m

• Wuxal calcium (3 ml/9l water watering and area of 3 m x 1.75 m)

• Where applicable, the supplementary fertilisers, Wuxal and Fetrilon, were used in combination.

A nutrition experiment was established with these treatments but this will not be reported. The treatments were balanced across the secondary host experiment and thus any nursery effect was balanced across the trial.

There are records of pest attack during the propagation of the sandalwood seedlings. Leaf minor (Gnathifera spp.) was observed as a major concern in the nursery as the pest attacks the growing tip causing plants to generate axillary buds producing a multi-branched seedling. The insecticide Dimethoate was found to be unsuccessful and Cabaryl was a successful replacement.

Trial design

The trial occupies a total area of 3.11 ha plus additional area within the rows for surrounds. The six long-term host treatments were planted in blocks which were replicated 5 times. The ratio of sandal to intermediate host within these blocks was 1:1, and the trial was established with a ratio of sandal to long-term host of 1:2. Hosts were established in a Randomised Complete Block design (Table 1).

Table 1: The layout of the Randomised complete block design used in this trial divided into 5 replicates. 1 = Cathormium umbellatum, 2 = Cederela odorata, 3 = Dalbergia umbellatum, 4 = Khaya senegalensis, 5 = Pongamia umbellatum, 6 = Pterocarpus indicus.

5 4 3 Rep 5

2 6 1

2 4 6 1 4 3 1 6

6 1 5 3 1 2 3 5 5 6 2 4 3 5 4 2

Rep 1 Rep 2 Rep 3 Rep 4

Within the block, each sandalwood (S) is separated by a distance of 6 m with Acacia trachycarpa (A) planted 1.5 m either side of the sandal. Long term hosts (H) are planted at 3 m spacing from the sandalwood and there is 6 m between each long term host. Hosts occur in all rows. At planting, a guard row of no trees was left every fourth row. Each treatment has 48 sandalwood and 96 long-term hosts. Overall, the stocking of sandalwood is 462 stems per hectare (sph) and the long term hosts are 924 sph at planting (Table 2). The plot size was 0.10 ha.

Table 2: The original layout for each block planted in 1999. Each column was 1.8 m apart although of the 16 rows prepared, only 12 were planted. Thus the spacing at planting was 1.8 m between rows.one, two and three Between three and four the spacing was 3.6m. This pattern continued through the trial.

rows 1 2 3 4 5 6 7 8 9 10 11 12 S H S H H S H S H H A A A A A A A A H H S H S H H S H S A A A A A A A A S H S H H S H S H H cont …

The second, fifth, eighth and eleventh host rows were removed in 2003 (Table 3) so that there were 48 hosts and 48 sandalwood per each plot. The plot size remained the same at 0.10 ha. The overall sandalwood stocking remained at 462 sph but the long term hosts were reduced from 924 sph to 464 sph (Table 3).

Table 3: Due to over-crowding, the second, fifth, eighth and eleventh rows of long term hosts (Table 2) were removed in 2003 to leave a final layout of 8 rows 3.6 m apart. rows 1 2 3 4 5 6 7 8 S S H H S S H H A A A A A A A A H H S S H H S S A A A A A A A A S S H H S S H H cont ….

Land preparation and trial establishment

Plantation establishment at the Frank Wise Institute occurs in the Cununurra clay soil type. Northcote Key classification is Ug 5.29. The soil is described as a dark brown (2.5Y 4/2) heavy clay, very plastic when wet and very hard when dry. Typical analysis of a composite sample of soil would indicate the topsoil (0 – 150 mm) consists of sand, silt and clay fractions at about 44%, 18% and 38% respectively, 2.5% organic matter, a pH (1.5 soil : water) of 7.4 and bulk density of 1.26 g/cm3.

The standard agriculture land preparation was undertaken. This involved the laser levelling of the land to ensure efficient flood irrigation and then the preparation of mounds in which the tree would be planted and the water directed to the drainage channels. The mounds were prepared 1.8 m apart and given a final herbicide spray to control the weeds whilst the trees established.

The trial was planted in July 1999 and immediately irrigated by hand and flood irrigated when a section of planting completed. The flood irrigation remained on the land for 24 hours after planting and was re-applied every seven days for the first three months.

Results

Trial measurement in 2001

The first measurement of the trial was undertaken in August 2001 when the trial was 2 years old. All the sandalwood and secondary host trees were assessed for:

• Survival (%)

• Tree height (cm) and

• Stem diameter (cm)

The presence or absence of the pot host, Alternantha and the primary host, Sesbania formosa was recorded.

Analysis of this data (Table 4) shows that there is no statistical difference in performance between the secondary host treatments for sandalwood height. The sandalwood associated with Khaya showed significantly lower survival after two years of growth.

Table 4: Trial assessment of the sandalwood after two years of growth for average tree height (cm) and survival (%) – mean (standard error). Means with same letter following are not statistically significantly different from each other.

Sandalwood with the Sandalwood Sandalwood secondary host height (cm) survival (%) Pterocarpus 113.35a (3.46) 86.67a (2.68) Dalbergia 108.55a (5.69) 89.75a (3.42) Cathormium 111.95a (5.51) 87.08a (3.51) Pongamia 109.93a (5.40) 84.17a (5.61) Cedrela 115.28a (4.62) 83.75a (2.67) Khaya 104.33a (5.44) 72.92b (4.90) Trial average 110.57 83.26

During this two year period there was good survival of the pot host (Table 5). Only the Khaya secondary host treatment showed a significantly lower pot host survival and this may relate to the lower sandalwood survival observed (Table 4). There was no significant difference in survival between the different secondary host treatments and the primary host, Acacia trachycarpa (Table 5).

Table 5: The average survival (%) of the pot host, Alternantha, and the primary host, Acacia trachycarpa, after two years of growth. Means with same letter following are not statistically significantly different from each other.

Alternantha Acacia trachycarpa Treatment survival (%) survival (%) Pongamia 97.92a (1.32) 95.83a (0.66) Cedrela 96.25a (1.21) 95.00a (0.83) Dalbergia 98.33a (0.42) 94.58a (1.93) Khaya 85.00b (5.25) 84.58a (7.02) Cathormium 96.25a (1.38) 92.92a (2.43) Pterocarpus 94.58a (2.52) 88.75a (4.25) Trial average 94.72 91.94

The survival and growth performance of the secondary hosts after two years of growth showed significant differences (Table 6). Dalbergia had a low survival of 47.7% which was significantly lower than the other secondary hosts used in the trial. Pterocarpus, Khaya and Cathormium also had significantly lower survival than Cedrela and Pongamia, which were the species with the highest survival.

The height of the secondary hosts fell into three groups with Khaya and Pongamia being the tallest and Khaya having the greatest stem diameter (Table 6). Cedrela was also tall with the second highest stem diameter. The other three hosts were significantly shorter with the smallest diameters. Thus the Meliaceae appeared to occupy the canopy area far quicker than the Leguminoseae species.

Table 6: Trial assessment of the secondary hosts after two years of growth for tree height (cm), stem diameter (cm) and survival (%). Means with same letter following are not statistically significantly different from each other.

Host Host average height average stem diameter Host survival Treatment (cm) (cm) (%) Cedrela 2 130.32b (5.19) 13.35c (0.40) 98.92c (0.66) Pongamia 5 162.27c (10.49) 9.17b (0.38) 96.25c (1.12) Khaya 4 179.20c (9.60) 15.6d (0.58) 87.29bc (6.10) Cathormium 1 78.62a (4.42) 5.97a (0.70) 90.63bc (1.19) Pterocarpus 6 83.94a (4.34) 5.48a (0.40) 82.29b (6.93) Dalbergia 3 82.33a (6.81) 5.86a (0.60) 47.7a (7.68) Trial average 119.45 9.24 83.68

Trial measurement in 2002

The second measurement of the trial was undertaken in August 2002 when the trees were three years old. Only the sandalwood was measured and the following measurements were made:

• Survival (%)

• Dominance where 2 = sapling, 3 = small tree, branched, 4 = co-dominant, 5 = dominant

• Tree height (cm)

• Breast height diameter (DBH) (cm)

• Base diameter at 100 mm from the ground (Bdiam) (cm)

• Clear bole height, which is defined as ground to first branch (CBH) (cm)

• Height to crown break (HTOCB) (cm)

• Crown diameter (Cdiam) (cm)

This assessment showed that the Tropical sandalwood with Khaya, Cedrela and Pongamia had significantly lower survival than with the other secondary host treatments (Table 7a). Sandalwood dominance did not alter with secondary host treatment and this was reflected in the evenness of the tree height and breast height diameter of the surviving sandalwood trees.

Table 7a: Trial assessment of the sandalwood after three years of growth. The trial was assessed for survival (%), dominance, tree height (cm) and breast height diameter (DBH) (cm). Means with same letter following are not statistically significantly different from each other.

Sandalwood with the Survival (%) Dominance Tree height (cm) DBH (cm) secondary host Cathormium 85.83b (3.63) 3.29a (0.10) 221.75a (7.14) 2.51a (0.14) Cedrela 82.08ab (3.52) 3.38a (0.11) 225.85a (11.00) 2.62a (0.13) Dalbergia 85.83b (3.81) 3.27a (0.16) 215.93a (15.48) 2.33a (0.22) Khaya 74.17a (2.68) 3.18a (0.07) 215.60a (4.16) 2.24a (0.07) Pongamia 81.25ab (5.23) 3.35a (0.09) 226.60a (7.34) 2.38a (0.10) Pterocarpus 85.00b (2.59) 3.34a (0.06) 228.06a (4.77) 2.45a (0.05) Trial average 82.36 3.30 222.13 2.42

Whilst at breast height (Table 7a) there was not difference in diameter between the treatments, differences were picked up in the basal diameter of the tree (table 7b). No differences were detected between clear bole height, height to crown break and crown diameter.

Table 7b: Trial assessment of the sandalwood after three years of growth. The trial was assessed for base diameter (Bdiam) (cm), clear bole height (CBH) (cm), height to crown break (HTOCB) (cm) and crown diameter (Cdiam) (cm). Means with same letter following are not statistically significantly different from each other.

Sandalwood with the Bdiam (cm) CBH (cm) HTOCB (cm) Cdiam (cm) secondary host Cathormium 6.06bc (0.10) 34.33a (1.62) 106.76a (1.86) 144.53a (9.67) Cedrela 6.13c (0.28) 34.85a (1.22) 108.98a (1.65) 141.90a (8.58) Dalbergia 5.58abc (0.29) 36.94a (0.99) 103.62a (3.82) 138.43a (8.07) Khaya 5.25a (0.14) 34.46a (1.61) 111.25a (2.81) 133.39a (1.70) Pongamia 5.48ab (0.16) 36.82a (1.82) 111.75a (3.14) 133.06a (9.57) Pterocarpus 5.97bc (0.18) 33.40a (1.33) 108.82a (4.14) 140.05a (5.89) Trial average 5.75 35.13 108.36 138.56

Observations from 2003 - 2007

In 2003, due to host over-crowding, rows dedicated only to long-term hosts were removed. These were second, fifth, eighth and eleventh rows of long term hosts. This left the trial plots with an equal number of hosts and sandalwood and the row spacing between the rows even at 3.6 m apart.

The whole site has been regularly watered using a flood and drain irrigation system. Whilst records are vague prior to 2004, from July 2004 there has been no fertiliser added to the site. During a site review in 2006, when the trial was seven years old, it was noted that all the Acacia trachycarpa had died. Some of the long-term hosts had also died but host species, host density and tree shape appeared to have an effect on sandalwood performance.

A satellite picture (Figure 1) highlighted the differences in canopy cover between the treatments. The treatments showing the highest canopy density are Khaya and Pongamia. This was followed by Dalbergia with Cathormium showing some canopy cover. Plots with Pterocarpus and Cedrela appeared vacant.

Dalbergia Pongamia Cathormium Pterocarpus Khaya Cedrela Cedrela Pongamia Pongamia Pterocarpus Cedrela Cathormium Dalbergia Khaya Pterocarpus Khaya Khaya Cedrela Dalbergia Pongamia Cathormium Pterocarpus Cathormium Dalbergia Cedrela Khaya Pongamia Dalbergia Pterocarpus Cathormium

Figure 1: Overhead photograph of the secondary host trial at eight years of age with a table indicating the host treatments below

Walking through the trial, there were large differences in height between the species. To provide an indication of the variation of this height, a number of heights and diameters were taken and the correlation between height and breast height diameter calculated. Tropical sandalwood (Figure 2) was shown to have a high correlation.

900

800

700

) 600

500

400

Tree height (cm 300

200 y = 34.028x + 221.95 R2 = 0.6131 100

0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 DBH (cm)

Figure 2: The correlation between sandalwood heights and breast height diameters

Undergoing similar correlations, with the secondary host treatments, Cathormium umbellatum had an average height of 441 cm (Figure 3), Pongamia pinnata 653 cm (Figure 4), Cedrela umbellatum 598 cm (figure 5), Dalbergia latifolia 733 cm (Figure 6), Pterocarpus indicus 638 cm (Figure 7) and Khaya senegalensis 1195 cm (Figure 8).

1000 900 800 700 600 500 400 300 y = 18.8x + 379.45 200 R2 = 0.6201 100 Pongamia tree height (cm) height tree Pongamia 0 0 5 10 15 20 25 30 DBH (cm )

Figure 3: The correlation between tree height and breast height diameter for Pongamia pinnata

700 y = 27.664x + 107.31 600 R2 = 0.6668 500

400

300

200

100 Cathormium height (cm) Cathormium 0 0 5 10 15 20 DBH (cm )

Figure 4: The correlation between tree height and breast height diameter for Cathormium umbellatum

900 800 700 600 500 400 300 200 y = 18.399x + 352.23 2 Cedrela heightCedrela (cm) 100 R = 0.4207 0 0 5 10 15 20 25 DBH (cm )

Figure 5: The correlation between tree height and breast height diameter for Cedrela odorata

1000 900 800 700 600 500 400 300 y = 13.205x + 507.93 200 R2 = 0.3677 100 Dalbergia treeheight (cm) 0 0 5 10 15 20 25 30 DBH (cm )

Figure 6: The correlation between tree height and breast height diameter for Dalbergia latifolia

900 800 700 600 500 400 300 y = 20.198x + 359.65 200 R2 = 0.5667 100 Pterocarpus tree height tree (cm) Pterocarpus 0 0 5 10 15 20 25 DBH (cm )

Figure 7: The correlation between tree height and breast height diameter for Pterocarpus indicus

16 14 12 10 8 6 4 y = 0.1938x + 8.2379 R2 = 0.3057

Khaya tree height (m) 2 0 0 10203040 DBH (cm )

Figure 8: The correlation between tree height and breast height diameter for Khaya senegalensis

Trial measurement in 2008

In January 2008, a full measurement of the trial was undertaken. This assessment included the following parameters:

• Survival (%)

• Dominance where 2 = sapling, 3 = small tree, branched, 4 = co-dominant, 5 = dominant

• Breast height diameter (DBH) in cm over bark of up to 3 major stems was measured

• Mean DBH was calculated from these measurements using the following formula:

/(DBH1)2+(DBH2)2+(DBH3)2

• Base diameter (Bdiam) at 100 mm from the ground (Bdiam) in cm

Tree basal area (m2) for each tree was calculated using the formula: Tree basal area (m2) = 3.143 x (Bdiam/200)2

Tree basal area per hectare (m2/ha) was calculated using the formula: Total Tree basal area of all surviving trees x plot area (Where plot area = 0.1036 ha for a single treatment in a replicate)

Base stem area (Barea) (m2) was calculated using the formula: Barea (m2) = 3.143 x (Bdiam/1002)/4

• Stem diameter at crown break (cm) (Cdiam)

Crown stem area (Carea) (m2) was calculated using the formula: Carea (m2) = 3.143 x (Cdiam/1002)/4

• Stem bole length (Sbole) (m), which is defined from the ground to the breaking of the bole into a crown

Stem bole volume (m3) was calculated using the formula: Sbole vol= (Carea + Barea)/2 X Sbole

• Tree volume (m3) is the sum of the stem bole volume and the branch volume using the formula:

Tree vol = Sbole vol + Carea x (Tree height – Sbole)

Survival

Survival of the sandalwood trees in the trial did not vary statistically between year two and three except for those sandalwood associated with Pterocarpus indicus. With this secondary host, the sandalwood survival declined from 92.08 % to 85.0 %. The secondary host itself had the second lowest survival when assessed at 2 years. Dalbergia latifolia had the lowest secondary host survival (47.7% survival) and yet the survival of the sandalwood associated with this species was unaffected. The poor survival of sandalwood with the Pterocarpus secondary host treatment maybe due to the significantly lower survival of the Acacia trachycarpa (Table 5) associated with this treatment than the influence of the secondary host.

The survival of the secondary hosts changed dramatically between the three and nine year assessment. 50% of this change was due to the heavy host culling that occurred in the fourth year of the trial and

thus this change was due more to artificial than natural changes. What is of interest is the minimal effect this heavy culling had on sandalwood survival with the Cathormium, Dalbergia and Pongamia treatments. This culling effect was not as great for the Dalbergia treatment as compared to the other treatments as survival had been so poor directly after planting.

The graphical presentation of these survival trends (Figure 9A) clearly shows the rapid decline of sandalwood survival with the two Meliaceae hosts, Cederela odorata and Khaya senegalensis. The Leguminoseae hosts generally maintained sandalwood survival. A trend of a slow decline in sandalwood survival with Pterocarpus is evident and it will be interesting to observe in the future.

The culling in the fourth year of the trial made the number of hosts in each treatment more even (Figure 9B). The smaller decline in stocking is evident with Dalbergia.

Table 8 : Tree survival within each secondary host treatment in the trial over the nine years of growth. Sandalwood and the hosts were measured in years two and nine but only sandalwood was measured in year three. * Indicates sandalwood different from secondary host. Means with same letter indicate not significantly different to other hosts within the column.

3 years 4 years 2 years old 9 years old Secondary old old hosts Sandal 2ndry Sandal Sandal 2ndry host wood host wood wood Cathormium 87.08a 90.63bc 85.83b *80.00d 34.79ab (3.51) (1.19) (3.63) (2.99) (3.93) Cedrela *83.75a 98.92c 82.08ab *33.3a 43.13bc (2.67) (0.66) (3.52) (4.42) (0.85) 50 % of Dalbergia *89.75a 47.70a 85.83b *84.17d 25.83a 2ndry host (3.42) (7.68) (3.81) (3.33) (2.92) culled Khaya *72.92b 87.29bc 74.17a 50.42b 48.13c (4.90) (6.10) (2.68) (5.87) (0.90) Pongamia *84.17a 96.25c 81.25ab *77.08c 45.63c (5.61) (1.12) (5.23) (5.59) (0.61) Pterocarpus 86.67a 82.29b 85.00b *71.67c 32.29a (2.68) (6.93) (2.59) (3.88) (3.09)

100 90 A 80 70 Cathormium

) Cedrela

% 60 Dalbergia 50 Khaya 40

Survi val ( Pongamia 30 Pterocarpus 20 10 0 2 yrs3 yrs9 yrs

100 90 B 80 70 Cathormium ) Cedrela 60 Dalbergia 50 Khaya 40

Survival (% Survival Pongamia 30 Pterocarpus 20 10 0 2 yrs 9 yrs

Figure 9: The survival (%) for (A) sandalwood with the six host treatments at two, three and nine years; and (B) the survival of the six secondary host treatments at two and nine years

The loss of sandalwood in each treatment has a major impact on the expected stems per hectare with each secondary host treatment (Table 9). Whereas 462 sph were initially planted, after nine years of growth, overall the trial has 331 sph surviving. Dalbergia retained the highest stocking with 390 sph and this was followed by Cathormium and Pongamia. What is of interest is the ratio of sandalwood to host plants supporting this survival. Dalbergia has the lowest ratio and this is followed by Cathormium and Pterocarpus. Pongamia has a relatively high ratio whereas the two Meliaceae are stocked at close to or greater than the original stocking ratios.

Table 9: Stems per hectare (sph) of Tropical sandalwood and the secondary host treatment and their resultant ratio

9 years old Ratio of Secondary hosts 2ndry Sandalwood (sph) sandalwood to Host (sph) host (sph) Cathormium 370 322 1 : 0.9 Cedrela 154 399 1 : 2.6 Dalbergia 390 239 1 : 0.6 Khaya 233 446 1 : 1.9 Pongamia 357 424 1 : 1.2 Pterocarpus 332 299 1 : 0.9

Breast height diameter

The surviving sandalwood trees had their diameter at breast height measured at two, three and nine years and the average of these measurements is compared to the average breast height diameter of the host trees which were measured at two and nine years of age (Table 10).

Table 10: Breast height diameters of the sandalwood and host trees with the six secondary host treatments measured at two, three and six years. * Indicates sandalwood different from secondary host. Means with same letter indicate not significantly different to other hosts within the column.

4 2 years old 3 years old years 9 years old Secondary old hosts 2ndry Sandal Sandal 2ndry host host wood wood Cathormium 5.97a (0.70) 2.51a (0.14) 50 % *8.98c (0.33) 13.08a (0.41) Cedrela 13.35c (0.40) 2.62a (0.13) of *7.53b (0.52) 13.50ab (0.57) a a 2ndry * d d Dalbergia 5.86 (0.60) 2.33 (0.22) 10.85 (0.28) 19.08 (0.39 d host Khaya 15.6 (0.58) 2.24a (0.07) *4.38a (0.29) 24.25e (0.34) culled Pongamia 9.17b (0.38) 2.38a (0.10) *10.67d (0.16) 14.50b (0.21) a Pterocarpus 5.48 (0.40) 2.45a (0.05) *7.55b (0.36) 17.88c (0.63)

10 A

Cathormium 8 Cedrela Dalbergia 6 Khaya Pongamia 4 Pterocarpus

Breast height diameter (cm) 2

0 2yrs 3yrs 9 yrs

25 B

Cathormium 20 Cedrela Dalbergia 15 Khaya Pongamia 10 Pterocarpus

Breast height diameter (cm) 5

0 2 yrs 9 yrs

Figure 10: The breast height diameter (cm) of (A) sandalwood when grown with the six secondary host treatments at two, three and nine years; and (B) host species at two and nine years

At two and three years of age, there was no significant difference between the breast height diameters of the sandalwood with the different secondary host treatments. The change in this relationship occurred between year three and nine, so that by this latter measurement, sandalwood breast height diameter was significantly greater with secondary host treatments of Dalbergia latifolia and Pongamia pinnata. The next best treatment was Cathormium which was followed by Pterocarpus, Cedrela and Khaya. This divergence of diameter growth is clearly shown in Figure 10A. Comparing the breast height diameter of the secondary hosts (Fig 10B), the greatest increase was shown by Dalbergia whilst Cedrela changed little and all the other secondary hosts showed a similar growth trend.

Stem bole length

Bole length of the sandalwood was measured as there is discussion that this will be sold separately to the branches as it will contain the highest levels of santalol oil. Sandalwood trees associated with Pongamia pinnata had the longest bole (Table 11). This was followed by the rest of the secondary hosts with only Cedrela being significantly shorter in bole length.

Table 11: Tropical sandalwood bole length (m) after 9 years of growth with different secondary host treatments. Means with same letter indicate not significantly different to other hosts within the column.

Host treatment Bole length (m) Cathormium umbellatum 1.61ab (0.05) Cedrela odorata 1.50a (0.07) Dalbegia latifolia 1.76b (0.10) Khaya senegalensis 1.70ab (0.05) Pongamia pinata 2.02c (0.07) Pterocarpus indicus 1.64ab (0.07)

Basal stem area stem

The basal stem diameter was measured to give an indication of the area that the tree is occupying in the trial site (Table 12). On an individual tree basis, sandalwood trees with Pongamia pinnata and Dalbergia latifolia produced the greatest mean basal area per tree. The proportion of host area to sandalwood area was always greater than 1.0 with Cathromium showing the lowest proportion and Khaya the highest.

Table 12: Comparing the basal area (m2) of sandalwood with the 6 different secondary hosts tested. The proportion of the sandalwood to host treatments is presented on a per stem basis. Means with same letter indicate not significantly different to other hosts within the column.

Secondary host species Average basal area Average basal area Proportion of host: (m2) (m2) sandalwood basal per host species tree per sandalwood tree area Pongamia pinnata 5 0.0411c (0.0024) 0.0203d (0.0015) 2.0:1 Dalbegia latifolia 3 0.0498d (0.0012) 0.0196b (0.0011) 2.5:1 Cathormiun umbellatum 1 0.0253a (0.0009) 0.0162c (0.0008) 1.6:1 Pterocarpus indicus 6 0.0498d (0.0036) 0.0123b (0.0015) 4.0:1 Cedrela odorata 2 0.0353b (0.0024) 0.0124d (0.0011) 2.8:1 Khaya senegalensis 4 0.0924e (0.0027) 0.0051a (0.0007) 18.1: 1

When the basal area of host and sandalwood trees are compared on a per hectare basis, it is evident that the Meliaceae inhibit sandalwood growth. Khaya senegalensis appears to dominate the site, whilst Cedrela odorata has not produced a high basal area nor provided the parasitic support for sandalwood

growth (Figure 10). The leguminous species are showing superior relationships to stimulate sandalwood growth but there is great variation between these treatments. Basal area proportions whether based on a stem or per hectare basis, appear to be more successful when in a proportion of an host basal area double that of sandalwood (Table 12).

5 Dalbergia 4.5 Pongamia 4 3.5 Cathormium 3 2.5 Pterocarpus 2

1. 5 1 Cedrela Khaya 0.5 0 0 5 10 15 2 0 2 5 3 0 Host basal area (m2/ ha)

Figure 11: The relationship between sandalwood and host basal area per hectare (m2)

Sandalwood tree volume

The production of wood from sandalwood is only an estimate as the equations used may not be the best fit to tree shape. Nevertheless, these results give an indication of the wood volume expected per tree at the age of 9 years with the different host treatments.

As expected from the previous results, the greatest sandalwood volume was produced using Dalbergia and Pongamia as secondary hosts. A tree can be expected to give an average wood volume of 0.005 m3 of wood. Cathormium will produce 0.004 m3 of wood whilst Pterocarpus and Cedrela will produce 0.003 m3 of wood and Khaya only 0.0015 m3 of wood.

Table 13: Average sandalwood tree volume at nine years of age with the six different secondary host treatments. Means with same letter indicate not significantly different to other hosts within the column.

Secondary host Average bole volume Average branch Total average tree species (m3) volume (m3) per volume (m3) per per sandalwood tree* sandalwood tree* sandalwood tree* Cathormium 0.0014c (0.000085) 0.0026c (0.000095) 0.0041c (0.00017) Cedrela 0.0011ab (0.000099) 0.0022b (0.00031) 0.0033b (0.00036) Dalbegia 0.0018d (0.00013) 0.0035d (0.00016) 0.0053d (0.00020) Khaya 0.0008a (0.000077) 0.0007a (0.00096) 0.0015a (0.00017) Pongamia 0.0020d (0.000076) 0.0030c (0.000099) 0.0050d (0.00017) Pterocarpus 0.0013bc (0.00010) 0.0019b (0.00013) 0.0031b (0.00023)

On a per hectare basis (Table 14), the highest wood volume was produced when the sandalwood tree was grown in conjunction with Dalbergia or Pongamia and was between 1.7 and 2.0 m3/ha. Cathormium closely followed these two hosts in sandalwood growth performance. The lowest sandalwood growth was in conjunction with the Meliaceae species, Khaya and Cedrela.

Table 14: Sandalwood tree volume per hectare at nine years of age with the six different secondary host treatments. Means with same letter indicate not significantly different to other hosts within the column.

Total bole volume Secondary host Total branch volume Total tree volume (m3/ha) species (m3/ha) (m3/ha)

Cathormium 0.532b (0.034) 0.971c (0.048) 1.503c (0.077) Cedrela 0.171a (0.030) 0.330a (0.053) 0.501a (0.080) Dalbegia 0.705c (0.066) 1.366d (0.100) 2.072d (0.144) Khaya 0.190a (0.030) 0.156a (0.030) 0.346a (0.059) Pongamia 0.713c (0.072) 1.079c (0.094) 1.791cd (0.166) Pterocarpus 0.426b (0.056) 0.627b (0.072) 1.053b (0.127)

Discussion of results

This trial was established with a good coverage of the pot host Alternantha as well as the dense planting of the primary host, Acacia trachycarpa. The initial results indicate that this combination of hosts were successful in retaining sandalwood survival and maintaining growth through the first years of the trial. Whilst it has been recommended that the Alternantha host be introduced to the sandalwood seedling between 109 and 134 days prior to planting for the highest survival of sandalwood (Radomiljac and McComb, 1998a), there was no record to whether this had been undertaken for this trial. The success of the treatment indicates that nursery practices must have been acceptable as an overall trial survival of 83 % was achieved after two years. The only treatment to have a significantly lower recording of Alternantha was the secondary host treatment Khaya senegalensis in the second year and this was mirrored in the lower sandalwood survival with the species in these first assessments.

The success of Acacia trachycarpa as a primary host in this trial was expected from reported observations from a pot trial (Radomiljac and McComb 1998b) comparing the leguminous species, Sesbania formosa, Acacia ampliceps and Acacia trachycarpa with Eucalyptus camaldulensis (Myrtaceae), and no host control. The leguminous species supported significantly greater growth in the sandalwood compared to the Eucalypt and the control with no host. It is thus evident that even at this stage, a host that can provide nitrogen has growth benefits to the sandalwood.

The trial changed dramatically with two events that occurred between year three and nine of the trial. The first was the artificial reduction of the secondary hosts to half their original planned stocking and the second, the natural death of the primary host, Acacia trachycarpa, which by observation, were all completely dead by the sixth year of the trial. Thus by the time the trial was measured in its ninth year, the trial only contained sandalwood and the different secondary host treatments in each plot.

The difference in performance between the Meliaceae and the Leguminaceae was clearly evident with the latter being superior in its interaction with sandalwood. It is assumed that the major difference between these two families is the ability of the legumes to fix nitrogen through a symbiotic rhizobia relationship. As the trial did not receive any fertiliser for the last 4 years or more, a nitrogen source via the nitrogen-fixing rhizobia would be an important contribution if nitrogen was a critical factor for sandalwood growth. Radomiljac et al. (1998) showed that a substantial growth benefit can be gained from a well nodulated host and this was related to the nitrogen gain accrued from the xylem solutes. This is reflected in the increase of foliar N in sandalwood (Radomiljac et al., 1998).

The impact of the Meliaceae on sandalwood was difficult to clearly separate as two aspects were clearly being tested in the choice of species to represent this family in the trial. In the case of Khaya senegalensis, the species rapidly occupied the site and suppressed competition with other species. Khaya senegalensis dominating the canopy area filtering any light and thus suppressed the growth of the sandalwood. The growth of this secondary host species was impressive in relation to the other species chosen and this has been recognised by the industry.

The other Meliceae species, Cedrela odorata, had the highest establishment survival at two years of growth. This relatively good survival persisted to the ninth year of the trial (taking into account that 50% of the stocking was removed in the fourth year). Sandalwood associated with this species had the lowest survival in the trial and even though this made the ratio of sandalwood to Cedrela 1: 2.6, the sandalwood did not show any growth stimulation. All the sandalwood growth measurements were significantly lower than the other Leguminosae treatments with the resultant wood volume of the sandalwood being the second lowest after Khaya senegalensis. It is clearly evident that this decline in sandalwood growth was not due to tree height or canopy. Cedrela odorata had grown to an average height of 5.98 m compared to Khaya senegalensis which had grown to an average height of 11.95 m.

There were differences in the performance between the Leguminoseae family treatments used in this trial, both as host species and interaction with the sandalwood. These differences were masked by the successful establishment and growth of the primary host, Acacia trachycarpa, for the first two years of the trial. Whilst differences were appearing between the growth performance of the secondary host treatments, this was not reflected in the sandalwood survival and growth. Even after three years of growth, no survival or growth differences between the sandalwood with these legume species could be detected.

It was only when the trial was assessed in its ninth year, differences between the legume secondary hosts treatments on sandalwood growth were apparent. Sandalwood survival was significantly better with Dalbergia and Cathormium compared to Pongamia and Pterocarpus whilst overall growth per tree was significantly better with Dalbergia and Pongamia with Pterocarpus lagging significantly behind.

The confusing factor in this trial is the uneven establishment of the hosts and sandalwood so that the ratio between the species has not remained constant in each plot. The Dalbergia plots are presently at a ratio of sandalwood to host of 1:0.6, which is far lower than the other legume species (1:0.9 for Cathormium and Pterocarpus, and 1:1.2 for Pongamia). The satellite picture of this trial (Figure 1) highlights the high tree canopy density that the Pongamia plots are presently planted at compared to the Dalbergia, Cathormium and Pterocarpus plots.

The present analysis suggests that the present proportion of secondary hosts in the treatments other than Dalbergia will become too high and shade the sandalwood and stunt growth. Indications of this trend are the rate of breast height diameter growth of Dalbergia compared to the other secondary host species tested.

Understanding the importance of each of these different legume species at tree survival and growth level of analysis may not be possible. Perhaps, as has been done with the primary hosts (Radomiljac, 1998), studying the movement and concentration of the nitrogenous components between the hemi- parasite and the hosts may be more elucidating. Of economic significance is the ability each of these secondary hosts may have to support or stimulate the production of the santalol.

The collation and analysis of the data over the past 9 years has highlighted the importance of this trial to provide key information to developing the Tropical sandalwood industry in the ORIS and other plantation projects in the world. This project has shown the importance of the primary host and the consequences of selection of a secondary host to maintain the growth and survival of the sandalwood. The need to continue to manage and assess this trial in the next few years is highlighted by the questions still to be answered.

Implications

Tropical Sandalwood is becoming a major industry in the ORD and community of Kununurra. It is part of the State-wide interest in making Western Australia the world-leader in plantation-grown sandalwood. The rapid increase in the past five years places this crop in a new light. To maintain this rapid industry growth, further research is needed to understand the plant /host relationship to sustain sandalwood growth. Confidence is lacking in the present sandalwood and secondary host planting designs currently being used in plantations. Forest Products Commission, together with the expertise at UWA, has provided a rare opportunity to add to the knowledge base from which the industry can draw for their decision-making.

This project offered the following:

Economic Two secondary hosts were identified that are able to sustain sandalwood growth through to 9 years of age with trends indicating that this growth will continue.

The first tree, Dalbergia latifolia, is from the Rosewood genus which are known for their strong and heavy timber, taking an excellent polish and being suitable for flooring, furniture, turnery, musical instruments, billiard cues, and chess sets (the black pieces). In general, supplies are poor through overexploitation and thus the potential to add value by the addition of this species to the sandalwood plantation mix has great economic potential.

Pongamia (or Millettia) pinnata was the second tree identified which is having a resurgence of interest due to the bio-diesel potential of the seed. Whilst the wood may only have value in a bio-energy market, there are many other interesting compounds produced by this tree that could be further investigated.

Environmental The parasitic nature of sandalwood and the need for multiple hosts lends the plantation system to greater biodiversity than agriculture and other plantation systems. The reliance on leguminose plants as hosts adds a nitrogen-fixation element to the system, which both enriches and adds to the soil flora. This project confirmed the need of two leguminose hosts, primary and secondary, to sustain sandalwood growth.

Social benefits The Tropical sandalwood project in Kununurra has not completed its first rotation. The sustainability of the industry will be influenced by the success of this first generation of plantings as well as visible improvements that are being made to ensure continuous improvement. This project proved that Tropical sandalwood can be grown in plantations with a proven silviculture and host system to produce sandalwood trees of an expected wood production. The continuing expanding industry will provide employment and add to the diversity of crops and services in the region.

Recommendations

Of the six secondary host species tested in this trial, three of the leguminose hosts, Dalbergia latifolia, Pongamia pinnata and Cathormium umbellatum can provide continued sandalwood growth once the primary host has died.

The two examples from the meliaceae did not support continued sandalwood growth and it suggested that this was due to their non-nitrogen fixing capability. They initially provided structural and shade requirements but as the sandalwood trees aged, there was an increasing demand for nitrogenous compounds which this family of trees could not provide.

Not all leguminose plants were good hosts and further investigation, carrying on from the work of Radomiljac (late 1990’s), is required to understand these differences. Whether the plantation system can be sustained from a continuous nitrogen source that is not a tree-based was not investigated in this trial. It was however clear that support and shade were required for the sandalwood in the early years from the host. It is recommended that further trials be established to look at this aspect of leguminose plants and their host role with sandalwood.

The most important question of oil production differences between the different secondary hosts is still yet to be measured and this will be undertaken in for the next RIRDC report when the trees are older and will provide more meaningful results.

It is also recommended that the trial be thinned so that the host ratios are even within the trial. This will help clarify whether the spatial arrangement or species is having the most dominant influence on sandalwood growth. This will be undertaken prior to the next measurement for the next RIRDC report.

References

Iyengar, A.V.V. (1960) The relation of soil nutrients to the incidence of spike disease in sandalwood (Santalum album Linn.). Indian Forester, 86, 220-230.

Nagaveni, H.C. & Vijayalakshmi, G. (2003) Growth performance of sandal (Santalum album L.) with different host species. Sandalwood Research Newsletter, 18, 1-4.

Nagaveni, H.C. & Srimathi, R.A. (1985) A note on haustoria-less sandal plants. Indian Forester, 111, 615-618.

Radomilja, A.M. & McComb, J.A. (1998a) Alternathera nana R.Br. Nursery sowing time influences Santalum album L. growth following field planting. In, Sandal and its Products, ACIAR proceedings No. 84. Eds, Radomiljac, A.M., Ananthapadmanbho, H.S., Welbourn, R.M. & Satyanarayan Rao, K. ACIAR, Canberra.

Radomilja, A.M. & McComb, J.A. (1998b) Nitrogen-fixing and non-nitrogen fixing woody host influences on the growth of the root hemi-parasite Santalum album L. In, Sandal and its Products, ACIAR proceedings No. 84. Eds, Radomiljac, A.M., Ananthapadmanbho, H.S., Welbourn, R.M. & Satyanarayan Rao, K. ACIAR, Canberra.

Radomiljac, A.M., McComb, J.A., Pate, J.S. & Tennakoon, K.U. (1998) Xylem transfer of organic solutes in Santalum album L. (Indian sandalwood) in association with legume and non-legume hosts. Annals of Botany, 82, 675-682.

Rao, R (1904) Notes on Sandal. Indian Forester, 30, 248-251.

Rural Industries Research and Development Corporation (RIRDC) (2006) Australia’s sandalwood industry - An overview and analysis of research needs. Publication No. 06/131, RIRDC, Canberra.

Sceenivasan Rao, Y.V. (1933) Contributions to the physiology of sandal (Santalum album L.). Influence of the host plants on the nitrogen metabolism of sandal. Journal of the Indian Instituted of Science, 16, 164-184.

Srimathi, R.A., Babu, D.R. & Sreenivasaya, M, (1961) Influence of host plants on amino acide make up of Santalum album Linn. Current Science, 30, 417.

25 Analysis of Plant-Host Relationships in Tropical Sandalwood (Santalum album) RIRDC Publication No. INSERT PUB NO. HERE RIRDC Publication No. 08/138

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