United States 

Department of Short-Rotation Management of Agriculture 

Forest Service Eucalyptus: Guidelines for 

Pacific Southwest 

Research Station Plantations in Hawaii 

General Technical 

Report PSW-GTR-137 Craig D. Whitesell Dean S. DeBell Thomas H. Schubert 

Robert F. Strand Thomas B. Crabb 
Whitesell, Craig D.; DeBell, Dean S.; Schubert, Thomas H.; Strand, Robert F.; Crabb, Thomas B. 1992. Short-rotation 

management of Eucalyptus: guidelines for plantations in Hawaii. Gen. Tech. Rep. PSW-GTR- 137. Albany, CA: 

Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture; 30 p. 

A 10-year research and development program was conducted by the BioEnergy Development Corporation, USDA Forest 

Service, and U.S. Department of Energy on the island of Hawaii, where nearly 230,000 acres are suitable for growing biomass in 

short-rotation Eucalyptus plantations. Successful techniques are described for seedling production, plantation establishment (site 

preparation, weed control, planting), maintenance (weed control, fertilization), biomass yield estimation, and harvest. Basic 

biological relationships are described to aid decisions on site selection, initial spacing, fertilizer schedules, and rotation length. 

Environmental issues likely to be faced by growers of Eucalyptus plantations are discussed, including soil erosion, nutrient 

depletion, and monocultures. Continuing programs for tree improvement, monitoring, and silviculture research are recommended. Production costs for biomass yields are estimated for three promising management regimes, representing pure 

Eucalyptus plantings at dense and wide spacings and a mixed species plantation where Albizia is used as a nurse crop to provide 

nitrogen needed for optimum Eucalyptus growth. This information will help prospective investors decide whether to invest in 

Eucalyptus plantations, and will help growers develop or choose among alternative management regimes. 

Retrieval Terms: Albizia admixtures, Eucalyptus biomass, Eucalyptus grandis plantations, Eucalyptus saligna plantations, 

Hawaii, short rotation silviculture 

The Authors 

Craig D. Whitesell is the project leader of the Pacific Southwest Research Station's American Pacific Islands Forestry Research 

Unit, and is stationed in Honolulu, Hawaii (Institute of Pacific Islands Forestry, 1151 Punchbowl St., Room 323, Honolulu, HI 

96813). Dean S. DeBell is team leader for the Pacific Northwest Research Station's research on the biology and silviculture of 

forests of the Douglas-fir region, with headquarters in Olympia, Washington. Thomas H. Schubert is a research silviculturist 

with the BioEnergy Development Corporation, Hilo, Hawaii. Robert F. Strand was formerly a soil scientist with the Pacific 

Southwest Research Station in Hilo, Hawaii. Thomas B. Crabb is vice president and manager of the BioEnergy Development 

Corporation, a subsidiary of C. Brewer Company, Hilo, Hawaii. 

Pen, and pencil Illustrations by Daniel H. Dizon, Pacific Southwest Research Station, Albany, California. 

Cover: Height of Eucalyptus saligna 6, 18, 36, and 54 months after outplanting. Along Hawaii's Hamakua Coast, height 

growth averages about 1 foot per month. 

Acknowledgments 

Many organizations and individuals have contributed significantly to this paper and the 10-year research program on which it 

is based. The research program was funded primarily by the Short-Rotation Woody Crops Program (now called the Biofuels 

Feedstock Development Program) of the U.S. Department of Energy. The work was performed under Subcontract No. 19X09061 C with Oak Ridge National Laboratory under Martin Marietta Energy Systems, Inc., Contract DE-AC05-840R21400 with the 

U.S. Department of Energy and under Interagency Agreement No. DE-A105-860R21661. Funds have also been provided by the 

Governor's Agricultural Coordinating Committee; the Department of Business and Economic Development—-Energy Division 

of the State of Hawaii; the University of Hawaii's Hawaii Natural Energy Institute; and the Hawaiian Sugar Planters Association. 

J. Warren Ranney, Lynn L. Wright, Judy Trimble, and Janet Cushman provided constructive guidance throughout the period of 

their agencies' involvement. Susan Miyasaka, University of Hawaii at Hilo, was formerly research agronomist for BioEnergy 

Development Corporation (BDC) and responsible for installation of many of the field trials. Thomas Cole, Pacific Southwest 

Research Station (PSW), USDA Forest Service, at Honolulu, performed many of the data analyses. Members of the technical 

staffs of the BDC and PSW provided much assistance in establishment, maintenance, and measurement of the field trials. 

Faculty of the University of Hawaii at Manoa participated- in several studies: Russell Yost assisted in several studies related to 

nutrition, and Samir El-Swaify and his students conducted the research on soil erosion. Several members of the North Central 

Forest Experiment Station's Harvesting Research Work Unit, Houghton, Michigan, provided guidance on harvesting aspects of 

the program. An earlier draft of the manuscript was reviewed by Russell Yost and Vie Phillips, University of Hawaii at Manna; 

Robert Curtis, Pacific Northwest Research Station, USDA Forest Service, Olympia, Washington; and Roger Skolmen (retired), 

Pacific Southwest Research Station, USDA Forest Service, Honolulu. We thank them all. 

Publisher: 

Pacific Southwest Research 

Station Albany, California 

(Mailing address: P.O. Box 245, Berkeley, California 94701-0245 

Telephone: 510 559-6300) 

November 1992 
Short-Rotation Management

of Eucalyptus: Guidelines 

for Plantations in Hawaii 

Craig D. Whitesell Dean S. DeBell Thomas H. Schubert 

Robert F. Strand Thomas B. Crabb 

Contents 

In Brief ...........................................................................................................................ii 

Introduction ................................................................................................................... 1

Background .................................................................................................................... 2

Availability of Suitable Lands ............................................................................... 2 

Environmental Setting for Short-Rotation Research Project .................................. 2 

Plantation Establishment .............................................................................................. 2

Species and Provenance Selection ......................................................................... 2 

Site Selection and Relative Productivity ................................................................ 7 

Planting Stock Production ...................................................................................... 7 

Site Preparation ...................................................................................................... 9 

Planting Procedures ............................................................................................. 10 

Initial Spacing ...................................................................................................... 11 

Initial Fertilizer Applications ............................................................................... 11 

Weed Control ....................................................................................................... 12 

Stand Development and Cultural Practices .............................................................. 14 

Influence of Growing Space ................................................................................. 14 

Fertilization .......................................................................................................... 14 

Mixed Plantings of Eucalyptus and Albizia ......................................................... 17 

Management Considerations ...................................................................................... 18 

Biomass Estimation ............................................................................................. 18 

Growth Patterns and Rotation Length .................................................................. 18 

General .......................................................................................................... 18 

Eucalyptus ..................................................................................................... 19 

Mixed Species Planting ................................................................................. 21 

Other Considerations in Rotation Length.............................................................. 22 

Harvesting ............................................................................................................ 22 

Regeneration ........................................................................................................ 23 

Diseases and Insects ............................................................................................. 23 

Environmental Issues ........................................................................................... 24 

Soil Erosion ................................................................................................... 24 

Nutrient Depletion ......................................................................................... 24 

Monocultures ................................................................................................. 25 

Tree Improvement ................................................................................................ 25 

Current Program ............................................................................................ 25 

Short-Term Improvement Program ............................................................... 25 

Long-Term Improvement Program ................................................................ 25 

Recommendations for Monitoring and Research ................................................. 26 

Production Economics ......................................................................................... 27 

References .................................................................................................................... 29

Conversions (English-metric) ..................................................................................... 30 
In Brief ... 

Whitesell, Craig D.; DeBell, Dean S.; Schubert, Thomas H.; 

Strand, Robert F.; Crabb, Thomas B. 1992. Short-rotation 

management of Eucalyptus: guidelines for plantations 

in Hawaii. Gen. Tech. Rep. PSW-GTR-137. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture; 30 p. 

Retrieval Terms: Albizia admixtures, Eucalyptus biomass, Eucalyptus grandis plantations, Eucalyptus saligna plantations, 

Hawaii, short rotation silviculture 

In 1978, the USDA Forest Service's Pacific Southwest 

Research Station and the C. Brewer Co. Ltd. started a joint 

study of establishing and managing short-rotation (5 to 8 

years) Eucalyptus plantations in Hawaii. Funded largely by the 

U.S. Department of Energy's Short Rotation Woody Crops 

Program, the study has sought to determine whether woody 

biomass is a suitable source of bioenergy. Test plots were 

located along the wet Hamakua Coast and in the drier Ka'u 

District on the island of Hawaii. Since the start of the study, 

results at periodic intervals have been reported. The guidelines 

offered here are based on results since the first plantings, 

spacing trials, fertilization tests, species comparisons, and 

provenance or progeny evaluations. 

• Species: The most promising species to date are Eucalyptus 

grandis and E. saligna. Specific provenances (place of seed 

origin in Australia) have been identified for these two species 

from which seed should be obtained for future planting. 

• Seedlings: Seedlings were raised in plastic dibble tubes, 

grown in a shadehouse for about a month and then moved into 

full sunlight for an additional 2 to 3 months. 

• Planting Sites: Suitable sites include ranch lands, abandoned lands, and sugarcane fields, from sea level to about 

3000 feet, totaling nearly 230,000 acres. Rainfall there ranges 

from 40 to 250 inches annually, usually well distributed or 

with an occasional dry season of no more than 3 months. 

Planting sites are cleared of brush, abandoned cane, and other 

vegetation by a combination of crawler tractor and harrow or 

crushing roller, and herbicides. Shallow and poorly drained 

soils should be avoided. 

• Tree Spacing: Initial spacing should allow at least 72 ft2

 of 

growing space per tree, to reach a minimum mean stand d.b.h. 

(diameter breast height, 4.5 ft above the ground) of 6 inches at 

5 years of age. This spacing is equivalent to a spacing of 8.5 ft 

between and within rows. A similar spacing of 7 ft by 10 ft 

would provide room for mowing machines and other equipment. 

Wider spacings, providing more initial growing space per tree, 

could also be used if larger tree sizes, longer rotation ages, or 

higher yields per acre at harvest are desired. 

• Planting: Planting and initial fertilization have been done 

manually but could be mechanized. Post-planting weed control is needed twice during the first 6 months and must be done 

carefully with manual backpack sprayers because young Eucalyptus seedlings are highly susceptible to herbicide damage. 

Mechanized mowing is an option where appropriate spacings 

are used. 

• Fertilization: A complete nitrogen, phosphorus, and potassium (N-P-K) fertilizer is applied at planting and again about 6 

months later. Subsequently, only N is needed on most sites. The 

total amount required depends on the N status of the topsoil and 

may range from 200 to 600 lb/acre in four to eight applications 

(depending on site quality and rotation length). Experiments 

with mixed plantations of Eucalyptus and Albizia falcataria, a 

nitrogen-fixing tree, showed that the need for N fertilizer after 

the first year can be eliminated along the Hamakua Coast by 

establishing appropriate admixtures of these two species. Further research on fertilizer types, rates, and timing and method 

of application is needed. 

• Harvesting: In limited harvesting trials, felling, chipping, 

and hauling represented more than 50 percent of the total delivered cost of wood chips from short-rotation plantations. Logistics as well as tree size are major determinants of the cost and 

productivity of harvesting operations. A balanced system in 

which all machines work close to capacity is needed. 

• Regeneration: Short-rotation plantations after harvest can 

be regenerated with seedlings or rooted cuttings for several 

generations as improved, higher-yielding stock is developed. 

A tree improvement effort should be started by using selected 

superior trees from the existing plantations, and by acquiring 

the best E. grandis and E. saligna provenances from Australia, 

and possibly material of E. urophylla for eventual hybridization with E. grandis. 

• Production Costs: Biomass yields and production costs are 

presented, based on three potential management regimes: (a) a 

5-year rotation with 620 trees/acre producing an average 6 in. 

d.b.h. tree, (b) a 6-year rotation with 360 trees/acre producing an 

average 8 in. d.b.h. tree, and (c) a mixed Eucalyptus/Albizia 

plantation with 218 Eucalyptus and 311 Albizia trees/acre producing an average 9 in. d.b.h. Eucalyptus tree on an 8-year 

rotation without supplementary N fertilization. Costs of chipped 

Eucalyptus biomass at the mill are estimated to be $54/dry ton 

for 45 ton/acre for the 5-year rotation, $45/dry ton for 50 ton/ 

acre for the 6-year rotation, and $35/dry ton for 80 ton/acre of 

Eucalyptus only for the 8-year rotation. 

A continuing program of monitoring and research is recommended to detect and respond to any problems in the 

plantations and to refine and improve fertilization and other 

management practices. 

ii USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 
Introduction 

The need for wood supplies in excess of amounts available 

from native forests has led to interest in establishing Eucalyptus 

plantations in many parts of the world, particularly in the tropics 

and subtropics. Many Eucalyptus species are noted for rapid 

growth, adaptability to a wide range of climates, relative freedom from pest damage, and suitability for a variety of purposes 

such as structural wood products, fiber, and fuel. Extensive 

plantations have been established in South Africa, Brazil, Chile, 

India, Spain, Portugal, and many other countries (FAO 1979, 

Florence 1986). Industrial plantations of Eucalyptus have also 

been established in Florida (Geary and others 1983), but on a 

much more modest scale. 

The first Eucalyptus plantations in Hawaii were established 

more than a century ago (LeBarron 1962). Those early plantings 

usually consisted of E. robusta and E. globulus. Between 1932 

and 1960, a total of 437,000 E. saligna seedlings were planted on 

the forest reserves (Skolmen 1963). These and more recent 

plantings of E. saligna have shown impressive yields (Pickford 

and LeBarron 1960, Walters 1980). 

During the energy crises of the early 1970's, Szego and 

Kemp (1973) suggested the concept of short-rotation, intensively cultured tree farms for fuel production. This concept had 

considerable appeal in Hawaii because the State depends on 

imported oil to meet 90 percent of its energy needs, and there 

was a long history of generating electrical power from bagasse 

(residue from sugarcane). Moreover, thousands of acres of 

underutilized agricultural land as well as commercial forest land 

seemed to be available for the culture of Eucalyptus. 

In 1978, BioEnergy Development Corporation, a whollyowned subsidiary of C. Brewer and Company Ltd., and the 

USDA Forest Service launched a joint research and development project to produce woody biomass for energy. The project 

was funded by the U.S. Department of Energy's Short-Rotation 

Woody Crops Program for 10 years, and resulted in the establishment of more than 700 acres of plantations containing both 

short-term and long-term studies (fig. 1). Information has been 

developed on many significant matters related to site selection, 

plantation establishment, stand culture, harvest, and other management considerations. Much of the data has been published in 

a variety of research papers. 

This paper summarizes and integrates data and observations from formal investigations, development efforts, and 

management experiences into guidelines for short-rotation culture of Eucalyptus. These guidelines are based primarily on work 

conducted on the island of Hawaii that was focused on 

maximizing production of biomass for energy, but the information should be useful—at least in principle—for establishing and managing short-rotation Eucalyptus plantations in 

other regions and for other end products. 

Figure 1—Aerial view of BioEnergy's Eucalyptus plantations at Kamae on the Hamakua Coast. 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 1 
Background 

Availability of Suitable Lands 

The State of Hawaii, with its year-round subtropical climate, 

provides an ideal environment for forest development. Growth 

rates for plantations of Eucalyptus saligna (Pickford and LeBarron 

1960) and Pinus taeda (DeBell and others 1989b) in Hawaii are 

among the highest reported for these species anywhere in the 

world. Of the various islands in the Hawaiian chain, the island of 

Hawaii (the Big Island) offers the greatest potential for production of short-rotation woody biomass. It has the largest land area 

suitable for biomass plantations and has primarily an agricultural economy. 

Commercial forest land on the island of Hawaii totals more 

than 600,000 acres (Metcalf and others 1978), but much of this 

land is unsuited to short-rotation intensive culture. The inventory of prime forest lands prepared by the Hawaii State Department of Lands and Natural Resources (1981) provides a good 

indication of locations and areas of suitable land. This survey 

identified land having the soil and site characteristics capable of 

providing good forest yields, regardless of current vegetative 

cover or use (excluding urban land use). The categories labeled 

Prime 1 and Prime 2 in the report (fig. 2) represent the areas 

most suitable for intensive culture of Eucalyptus and other fastgrowing tree species. More than 600,000 acres are included in 

these two categories, of which about 230,000 acres are now in 

brush, range, pasture, and sugarcane, or lie fallow (fig. 3). 

These 230,000 acres offer the best opportunity for shortrotation management. Nearly all of the remaining 370,000 

acres of prime lands are now in forest, portions of which may 

be suitable for such management. 

Regardless of growth capability of the land, there may be 

other significant factors that affect availability or suitability. 

Other agricultural enterprises may offer more profitable uses. 

Restrictions due to topography or soil conditions may preclude 

the use of machinery normally associated with production of 

woody biomass. Sociopolitical considerations, such as public 

desire to maintain or preserve significant portions of native 

forests, may prevent the conversion to short-rotation plantations. 

On the other hand, some lands may provide substantial economic advantages for woody biomass production because of 

their proximity to mill or conversion sites and because of existing road networks. In addition, many agricultural field records 

provide detailed information regarding soil quality, weather conditions, and comparative sugarcane yields that may be useful to 

managers of short-rotation woody crops. 

Environmental Setting for Short-Rotation Research Project 

Local records on the island of Hawaii showed that Eucalyptus 

saligna grew well in plantations at elevations ranging from 

1,750 to 6,600 ft with precipitation levels of 45 to 250 inches 

(Pickford and LeBarron 1960); planting recommendations by 

Carlson and Bryan (1959) extended this range to sea level. 

Our field trials were established at sites located along the 

Hamakua Coast and in the Ka'u District at elevations from 1,000 

to 2,000 ft (fig. 4). The Hamakua sites are very wet, receiving 

200 to 245 inches of rain annually. Soils are highly weathered 

silty clay loams developed on volcanic ash (Hydrandepts). 

Hydrandepts are known for high phosphorus retention and for 

low availability of nutrient cations (Yost and Fox 1981). The 

Ka'u sites receive much less rainfall (40-90 in/yr). They have 

rocky, organic soils (Tropofolists) that have low nutrient-retention capacity (Sato and others 1973). Soil test results for sites at 

Ka'u and Hamakua are presented in table 1. 

Total soil nitrogen (N) concentrations vary substantially within 

both areas, and these differences may be associated with past 

land use. Sites which have been under forest or grass generally 

have higher soil nitrogen concentrations. Prime caneland and 

more recently abandoned caneland generally have lower concentrations of soil nitrogen. The length of time the area was 

managed for sugarcane also influences soil properties, because 

the amounts of nitrogen and organic matter generally diminish 

with successive crops. 

The guidelines proposed in this report were developed from 

data collected at the above-mentioned sites. Some recommendations, such as seedling production and initial spacing, have 

general applicability to other areas. Other recommendations, 

including species or provenance selection and fertilizer treatments, are much more site specific and must be validated when 

applied to other localities. 

Plantation Establishment 

Species and Provenance Selection 

Previous work in Hawaii guided our species selections for 

short-rotation intensive culture of biomass plantations. Initial 

emphasis was placed on fast growing Eucalyptus saligna, and 

then on the closely related E. grandis. Desirable criteria for 

selection of these and other eucalypts include: 

• Fast growth and good stem form, providing high biomass 

production over a range of site conditions. 

• The ability to be asexually reproduced using vegetative 

propagation methods. 

• he ability to coppice readily. 

• Resistance to serious disease or insect attacks. 

• Have other uses besides biomass, for example pulp, lumber, 

or chemicals. 

The quickest and most efficient gains in a tree improvement 

program are obtained by identifying the best species and the best 

adapted provenances within a species (Zobel and Talbert 1984). 

Use of the best provenances (place of seed origin) can make a 

difference between profit and loss in a forestry enterprise. The 

relative performance of species or provenances of a given spe2 USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 
Figure 2—Island of Hawaii prime and unique forest land boundaries (Reprinted with permission of the Division of Forestry and Wildlife, Department of 

Land and Natural Resources, State of Hawaii) 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 3 
Figure 3—Typical caneland that could be converted to Eucalyptus plantations 

cies is evaluated in field trials, at relatively low cost, considering 

the potential gains in yields that may be obtained. 

Ten species trials were established between 1979 and 1984 

(Schubert and Whitesell 1985). The number of species appraised 

in each trial ranged from three to 15. In these trials a total of 30 

species, including 15 eucalypts, were screened to determine 

their potential (table 2). Eucalyptus saligna, E. grandis, E. 

urophylla, and E. robusta consistently outperformed the other 

species in height, diameter, and survival. Major exceptions to this 

generality were Acacia mangium and Albizia falcataria; the 

former outgrew the aforementioned eucalypts at one location, 

whereas Albizia ranked second or third to the eucalypts at three 

locations. 

The performance of E. saligna, planted in 10 species trials, 

was equal to or better than any other species on eight of 10 sites. 

However, E. grandis outgrew E. saligna in two of four species 

trials and also proved superior in four provenance trials. 

Eucalyptus urophylla grew well along the Hamakua Coast 

and at Ka'u. Of the six sites planted to E. urophylla, trees 

performed satisfactorily on five of them (table 2). This tropical 

eucalypt is native to Timor and several other Indonesian islands. 

Eucalyptus robusta growth was satisfactory in five of six 

species trials. However, it has not performed as well as E. 

grandis and E. saligna in our trials and is not a recommended 

species for biomass production in Hawaii. 

Twelve nitrogen-fixing species were tested. On Hamakua 

sites on well-drained soils, Albizia falcataria performed quite 

well and increased site fertility through the recycling of its 

nitrogen-rich foliage. However, on dry sites at Ka'u, its performance was unsatisfactory. Acacia mangium performed well on 

only two of seven sites. The dense foliage of this species contributes to breakage or blowdown in high winds. None of the other 

nitrogen-fixing species we tested (table 2) performed satisfactorily (Whitesell and others 1992a). 

Eucalyptus camaldulensis, which is planted world-wide, performed very poorly in a trial of eight Australian provenances 

planted at Kamae on the Hamakua Coast (Whitesell and others 

1992b). These provenances were collected from widely varying 

sites ranging from Lat. 17°S to 35°S. The best source, from the 

Emu River area in Queensland, yielded only 1.8 tons/acre/yr at 

age four. Apparently, this species is not suitable for biomass 

production on high rainfall areas on Hawaii Island. 

4 USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 
Figure 4—BioEnergy Development Corporation's Eucalyptus planting sites on the Island of Hawaii. 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 5
-----------------

Table 1—Soil nutrient and pH analyses for BioEnergy's planting sites, 

Island of Hawaii 

Site Depth Total N1 P K Ca M pH 

in. ------------------ppm 

Hamakua Coast 

Kamae 6 0.68 18 52 64 37 5.0 

18-24 47 10 43 40 13 5.1 

Chin Chuck 0-6 0.60 14 50 459 70 5.8 

18-24 47 10 43 181 33 5.7 

Akaka Falls 0-6 0.37 7 39 197 39 5.7 

18-24 40 7 50 810 83 6.0 

Pepeekeo 6 0.57 24 88 166 40 4.9 

18-24 42 12 38 96 27 5.1 

Onomea 6 0.54 8 27 93 47 5.3 

18-24 48 6 22 54 36 5.3 

Amauulu 6 0.67 6 48 103 112 4.8 

18-24 38 5 30 35 26 5.0 

Ka'u District 

Ninole 6 0.41 201 110 510 5.6 

(Kiloa soil) 18-24 0.36 140 91 696 156 5.7 

Ninole 6 0.65 104 112 792 201 5.7 

(Alapai soil) 18-24 0.34 77 57 894 208 5.9 

Kaunamano 6 1.07 27 142 1,366 800 5.4 

(Alapai soil) 18-24 0.86 6 104 1,669 804 5.5 

pct 

0-

0.

0.

0.

0-

0.

0-

0.

0-

0.

0- 156 

0-

0-

1

N - nitrogen, P-phosphorus, K- potassium, Ca-calcium, Mg-magnesium 

Four provenance trials of the Eucalyptus grandis/saligna 

complex were designed and installed by James D. King in 1979 

and 1981 (Skolmen 1986). These trials were located along the 

Hamakua Coast and at Ka'u. Twenty-two seed sources were 

appraised: 11 E. grandis and 10 E. saligna from Australia, and 

one local E. saligna provenance. At all four sites E. grandis 

provenances generally outperformed the E. saligna provenances. 

In diameter growth, for example, seven to nine of the top ten 

provenances were E. grandis. Future plantings of E. grandis and 

E. saligna should utilize seeds collected from selected provenances in Queensland and New South Wales, Australia, until 

better provenances are identified (table 3). 

A trial of four provenances of E. urophylla was established 

at Kamae in 1982. There were no significant differences in 

height and diameter growth, survival, or yield at age four 

years. However, the fastest growing seed source from Mt. 

Lewotobi, Flores Island, Indonesia, CSIRO Seedlot No. 12896 

(CSIRO = Commonwealth Scientific and Industrial Research 

Organization, Canberra, Australia) produced 8.6 dry tons/ 

acre/yr, 21 percent greater yield than the other sources (Whitesell 

and others 1992b). 

Ten hybrid Eucalyptus clones developed in Brazil by the 

Aracruz Florestal Company were outplanted at Pepeekeo in 

1985. These vegetatively propagated trees were selected in Brazil for fast growth, high yields, good coppicing ability, and 

resistance to diseases. One of the most important characteristics 

of these clones is their uniform growth, compared to eucalypts 

raised from seed. The best of these clones grew as well as the 

best E. saligna and E. grandis in our species trials at Pepeekeo 

Table 2—Species showing satisfactory and unsatisfactory growth in seven 

species trials on the Hamakua Coast and two in the Ka'u District, Island of 

Hawaii 

Satisfactory Growth1 

Hamakua Coast 

Kamae (trial 1) Amauulu 

Acacia mangium2 E. saligna 

Eucalyptus urophylla E. robusta 

E. grandis 

Pepeekeo 

Kamae (trial 2) E. grandis 

E. saligna E. urophylla 

Albizia falcataria2

 E. saligna 

E. robusta 

Onomea 

Kamae (trial 3) E. saligna 

E. saligna E. urophylla 

E. robusta A. falcataria2 

A. falcataria2

 E. robusta 

E. grandis 

Kamae (trial 5) 

E. saligna 

E. urophylla 

Ka'u District 

Ninole (Alapai) Kaunamano 

E. saligna E. saligna 

A. mangium2

 E. grandis 

E. urophylla 

Ninole (Kiloa) E. robusta 

E. saligna 

Unsatisfactory Growth 

Hamakua Coast 

E. alba Acacia koa2 

E. botryoides A. melanoxvlon2 

E. camaldulensis Casuarina equisetifolia2 

E. citriodora Copaifera langsdorfii 

E. dunnii Gmelina arborea 

E. globulus Leucaena leucocephala2 

E. maidenii Lippia toressi 

E. microcorys Mimosa scahrella2 

E. nitens Pinus elliottii 

E. tereticornis Sesbania grandiflora2 

E. viminalis S. seshan2 

Ka'u District 

E. camaldulensis Acacia auriculiforrnis2 

E. citriodora A. confusa2 

E. globulus Mimosa scabrel/a2 

E. miens 

E. tereticornis 

E. viminalis 

1

Satisfactory: mean annual growth increment equals or exceeds 3.3 ft height 

and 0.6 in. diameter; survival equals or exceeds 75 pct. 2

Nitrogen-fixing species. 

6 USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 
Table 3 —Best s eed sour ces of Eucalyptus grandis and E. saligna in 

provenance trials on the Island of Hawaii (Skolmen 1986) 

Species and 

CSIRO1 seedlot no. Seed source location Latitude Elevation 

E. grandis 

12423 Tinaroo Falls Dam, Qld.2 17°l1'S 

ft 

2,624 

12409 Ravenshoe, Qld. 17°42'S 3,083 

10774 E. of Gympie, Qld. 26°14'S 1,312 

7823 Coffs Harbor, NSW3 30°10'S 59 

7810 Bulahdelah, NSW 32°20'S 394 

E. saligna 

11025 W. of Rockhampton, Qld. 23°49'S 2,821 

12064 S. of Calliope, Qld. 24°23'S 2,624 

12145 Connondale, Qld. 26°44'S 1,968 

11756 Clifford, Qld. 28°30'S 787 

1

Commonwealth Scientific and Industrial Research Organization, Australia 2

QLD = Queensland, Australia 3

NSW = New South Wales, Australia

(68 ft in height and 5.0 in. in diameter after 6 years vs. 52 ft and 

5.3 in). If these clones continue to perform well, they could 

form a component of genetically improved material in future 

trials. 

Site Selection and Relative 

Productivity 

Productivity of Eucalyptus plantations along the Hamakua 

Coast is positively correlated with total soil N (nitrogen) and soil 

depth; it is negatively related to soil erosion and poor drainage 

(Strand and Cole 1992). Soil profile examinations and productivity determinations from 60 locations in Eucalyptus plantations showed that poorly to somewhat poorly drained soils produced low biomass yields, as did sites with shallow soils (<24 in. 

deep). Soils that had experienced substantial erosion also generally had low productivity. 

Low productivity related to low total soil N can be remedied 

with frequent applications of nitrogen fertilizer (Strand and others 1992). Low productivity associated with shallow or poorly 

drained soils or both, however, is unlikely to be substantially 

increased by fertilization. Trees should not be planted on these 

sites, unless the area is small or too intermingled with adjacent 

soil types for practical exclusion. 

Although no research on soil and site productivity was conducted at Ka'u, we expect that limitations on plantation growth 

would arise primarily from shallow soils and insufficient or 

poorly distributed rainfall. Annual rainfall at Ka'u varies from 

40 to 90 inches, and 4 or more dry months are common. A 

survey of world literature on E. saligna and E. grandis plantations suggested that minimum rainfall is 30 to 40 inches and that 

the dry season should be no more than 3 to 4 months (FAO 

1979). The lower rainfall limit for E. saligna stands sampled on 

the island of Hawaii by Pickford and LeBarron (1960) was 45 

inches per year. 

Wind damage may be an important consideration in certain 

locations. Plantations at Ninole valley in Ka'u were destroyed 

by windstorms in February 1982 and January 1985; however, 

stands at Kaunamano, a few miles south of Ninole, suffered little 

damage in either storm. The damage at Ninole appears to be 

associated with wind velocity caused by the funneling action of 

closely adjacent hills. Areas that may be subject to such wind 

funneling should not be planted. Some blowdown and broken 

tops also occurred at several Hamakua sites in February 1986, 

destroying one trial and slightly damaging another in two widely 

separated locations. Wind does not appear to be a serious concern for short-rotation plantations along the Hamakua Coast as it 

is in the Ka'u District. However, strong winds have caused 

losses in mature Eucalyptus stands along this coast. 

Planting Stock Production 

Our planting stock production is based on a containerized 

nursery system using plastic dibble tubes and racks. Most Eucalyptus plantation programs utilize container-raised stock (FAO 

1979), and the dibble-tube system has been shown to be more 

reliable and less costly than bare-root stock for Eucalyptus and 

other species in Hawaii (Walters 1981). BioEnergy Development Corporation's system, described below, was labor intensive because the size of the operation did not justify investment 

in an automated system. About 450,000 seedlings per year were 

produced in three 4-month cycles of 150,000 each. This time 

period could conceivably be shortened to 3 months, producing 

600,000 seedlings per year. Automated dibble-tube systems for 

larger scale reforestation programs in Hawaii have been described by Skolmen and others (1982) and by Walters (1983). 

BioEnergy's system was developed from previous experience with Eucalyptus in Hawaii, and by our nursery practice 

experiments carried out between 1979 and 1983. Our system 

used plastic dibble tubes called "Ray Leach Cone-tainer Pine 

Cells"1

 which have a volume of 4 in .

3 The tubes have interior ribs 

to prevent root spiraling and a hole in the bottom for drainage 

and air pruning of the roots. The tubes are placed in racks that 

hold 200 dibble tubes. 

The potting medium used is a 2:1 mix of vermiculite and peat 

moss. Two bales of vermiculite (3.2 ft3

/bale) are thoroughly 

mixed with one bale of peat moss (4 ft3

/bale). Osmocote1 (14-14-

14), dolomite, and Micromax1

 (micronutrients) are added at 37, 

25, and 7-oz. respectively, per batch (one batch fills about 5,400 

tubes). The mixture is moistened so that it will stick together in 

the tubes. Racks of tubes are filled manually, then jarred on a 

table to settle the mixture in the tubes. A plexiglas plate with 

protrusions for each tube is pressed on top of each rack of filled 

tubes to make an indentation for the seeds. Seeding is done 

manually with a mixture of seeds and chaff, the amount depending on germination tests of each seed lot. The seeds are then 

covered lightly with a layer of fine gravel. 

1

Trade names or commercial brands are mentioned solely for information. 

No endorsement by the U.S. Department of Agriculture is implied. 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 7 
Every other row of tubes is removed and placed in another 

rack to give a density of 100 tubes per rack. The racks are then 

moved to benches in a roofed shadehouse (fig. 5) and watered by 

an overhead automated sprinkler system several times a day, 

depending on weather conditions. Germination occurs within 5 

to 7 days. Thinning to one plant per tube is done manually when 

the seedlings have two pairs of true leaves, about 3 to 4 weeks 

after sowing. The extra seedlings are then used to fill tubes 

lacking seedlings. 

The seedlings are moved from the shadehouse to outside 

areas to harden off, under full sunlight (fig. 6), when they are 3 to 

4 in. tall, usually 4 to 6 weeks after sowing. Irrigation is provided 

as needed by an automated sprinkler system. The annual rainfall 

at BioEnergy's nursery is about 200 in.; therefore, it is not 

possible to harden (acclimatize) the seedlings by withholding 

water. The seedlings do, however, gradually lose their succulence and height growth slows, presumably because they use up 

the nutrients in the potting medium. They are ready for outplanting 

3.5 to 4 months after sowing, when they are 12 to 15 in. tall. 

Additional fertilization in the hardening area is not recommended so that the seedlings will harden-off, but small amounts 

of supplemental Osmocote are sometimes added if the foliage 

shows symptoms of nutrient deficiency. Top pruning is necessary when seedlings are to be held in the nursery longer than 4 

months. Several pairs of leaves must be left on the stem below 

the cut. 

An alternative method of producing planting stock is to use 

rooted cuttings from selected outstanding trees in existing 

plantations. This method was developed for Eucalyptus in 

Brazil by the Aracruz Florestal Company (Campinhos and 

Ikemori 1983). Our present system could be adapted to these 

techniques, but the cost per plant would be higher, and several 

years' lead time would be needed to build up clone banks of 

superior material. A substantial improvement in yield, however, may be obtained via selection and propagation of superior clones (Brandao and others 1984). 

There have been few problems with nursery diseases or 

insects in Hawaii. Damping off is only a problem when the 

seedlings are watered too frequently. Proper irrigation schedules and close monitoring of weather conditions will control 

damping off. Occasional attacks of aphids or rose beetles are 

handled by using an appropriate insecticide. Continuous monitoring of the nursery stock is the key to discovering and dealing 

with problems before they become serious. 

Problems caused by lack of or incompatible mycorrhizal 

species have not been reported for Eucalyptus grandis, E. saligna, 

and E. urophylla, the three species of major interest to us (FAO 

1979, Le Tacon and others 1988). No increased growth occurred 

in the field when we inoculated a portion of our nursery stock 

with spores from fruiting bodies collected from older established 

plantations in Hawaii. Presumably suitable mycorrhizae-formFigure 5—BioEnergy's shadehouses, with racks of seedlings being loaded on truck. 

8 USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 
Figure 6—Eucalyptus (on right) and Albizia (on left) seedlings in hardening area ready for outplanting. 

ing fungi are in Hawaiian soils as a result of more than 100 years 

of Eucalyptus culture, or because the native ohia (Metrosideros 

polymorpha) is in the same family as Eucalyptus and may harbor 

compatible mycorrhizal species. Wind-disseminated spores apparently provide adequate inoculation of container seedlings. 

Site Preparation

Most of our eucalypt plantations were planted on lands that 

can be placed into one of three categories: recently harvested 

caneland, abandoned caneland, or wasteland. On recently harvested caneland the crop had been cleared no longer than 2 to 3 

months before tree planting. Abandoned caneland had been out 

of crop production for periods ranging from 3 months to more 

than 25 years. Wasteland consisted of areas that had never been 

in cane production because of steep terrain, poor drainage, or 

rocky conditions. We also did some clearing and planting in 

secondary forest on land zoned for agriculture, but the costs for 

clearing the dense vegetation and building access roads for 

establishing plantations on such land are very high. 

On recently harvested caneland, the volunteer cane and 

weeds are allowed to regrow for 6 to 8 weeks. When the 

vegetation is no more than 2 feet tall and 50 percent or more of 

the soil is still bare, the area is sprayed with a mixture of one 

gallon of gyphosate

2

 and 2.5 lbs a.i. simazine2 per acre (a.i. = 

active ingredient). Glyphosate is a contact herbicide, whereas 

simazine is a pre-emergent herbicide. The herbicide is applied 

with a tractor-drawn spray rig, and application requires about 

0.2 hour per acre. 

On abandoned caneland and wasteland, a low ground-pressure D-6 tractor equipped with wide-gauge shoes is used to pull 

a heavy-duty off-set cutaway harrow (fig. 7). This requires about 

0.3 tractor hour/acre. On very rocky soils such as those at Ka'u, 

a heavy Krajewski roller is used to cut and crush the cane and 

other vegetation, which requires 2 hours/acre on rocky soils. If 

the area is covered with particularly heavy vegetation and brush, 

as when it has been abandoned for many years, a tractor equipped 

with a bulldozer blade is used. The blade is positioned about one 

2

This paper neither recommends the pesticide uses reported nor implies 

that the pesticides have been registered by the appropriate governmental 

agencies. Pesticides should be utilized in accordance with label instructions 

for their use. Surplus materials and containers should be disposed of properly. 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 9 
Figure 7—D-6 tractor pulling cutaway harrow to clear abandoned caneland. 

foot above the ground to knock down the brush so that the 

harrow or roller can then crush it. This requires about 3 tractor 

hours/acre. 

After clearing, the vegetation is allowed to regrow for 6 to 8 

weeks before spraying. If 50 percent or more bare soil is showing, the same glyphosate/simazine mixture is used for weed 

control. However, if the soil is mostly covered with a mulch of 

cut-up and crushed cane and other vegetation, only glyphosate is 

used, at 0.5 gallon/acre, because simazine is effective only when 

sprayed on bare soil. About 0.2 tractor hours/acre are required 

for this treatment. 

The Eucalyptus seedlings are planted from 3 to 4 weeks after 

the herbicide spraying. If simazine was used, care should be 

exercised during the planting operation to not disturb the soil any 

more than necessary. 

Planting Procedures 

Racks of seedlings in dibble tubes are transported to the field 

in enclosed trucks or trailers to avoid exposure to the wind. The 

racks are hand-carried to the planting site; the tubed seedlings 

are then transferred to planting bags and the seedling removed 

from the tube just before it is placed in the ground. Planting is 

done manually by a 2-person crew, with one worker opening 

holes with a metal dibble bar (fig. 8) and the other following 

behind to place a seedling in each hole and to stamp the soil 

around the hole to close and firm the soil around the root mass. 

About 600 seedlings can be planted per person-day under Hamakua 

site conditions, but only 300 per person-day in the rocky soils at 

Ka'u where more time is needed to open the planting hole and to 

scrape together enough soil to close the hole and to firm the soil 

around the roots. 

The empty dibble tubes are replaced in the racks and returned 

to the nursery where they are reused after washing and sterilizing 

with a solution of 1 part chlorine bleach to 9 parts water. The 

tubes (resistant to the effects of ultraviolet light) are good for 

about four cycles, and the racks are still usable after five years 

unless they are broken by careless handling. 

After initial fertilization, as discussed in a subsequent section, 

little further care is needed until the first weeding. The plantations should be monitored for areas needing replanting, but 

survival is usually at least 95 percent. Supplementary watering may 

be needed if an extended dry period occurs soon after planting. 

Our planting operations have not been mechanized because 

they have been of a relatively small scale. Manual planting has 

been efficient and, unlike a planting machine, a planting crew 

can work under quite adverse weather conditions. Tree-planting 

machines have been used, however, for planting other areas in 

Hawaii. Moreover, the local sugar companies are developing 

machines for planting cane plantlets instead of the traditional 

stem pieces. Such machines could easily be adapted for tubed 

tree seedlings if large scale operations make this desirable. 

10 USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 
Figure 8—Planting with dibble bar; tops of seedlings are sticking out of 

planting bag. 

Initial Spacing 

Spacing of trees in short-rotation plantations affects individual tree growth rates and stand productivity as well as the 

costs of management practices and utilization. Product quality 

may also be affected. A positive effect of higher planting densities is an increase in wood production at early ages because of 

the greater number of trees per acre. The corresponding negative 

effects are a decrease in individual tree growth rates and therefore tree size, and an increase in planting and harvesting costs. 

Choice of the optimum spacing therefore usually involves a 

balance between shortening the time to attain trees of some 

minimum desired size, maximizing production of biomass or 

wood, and minimizing the costs of management and utilization. 

Although numerous plantations of Eucalyptus saligna, E. 

grandis, and other eucalypt species had been established in 

Hawaii and elsewhere, information to guide decisions on tree 

spacing for short-rotation eucalypts was limited. Several trials 

were established to evaluate tree growth and stand development 

across a range of planting densities from 16 to 172 ft2

 of growing 

space per tree. Data from these trials have provided a general 

understanding of relationships between diameter and density, 

and effects of initial spacing on patterns of tree growth and stand 

development. 

Tentative relationships between quadratic mean stand diameter and stand density for E. saligna and the rationale for 

their development and use were described in an earlier paper 

(DeBell and Whitesell 1988). In essence, the upper maximum 

diameter density line in fig. 9 represents the maximum number 

of trees that can be grown to any given mean stand diameter. 

Severe competition occurs, however, before most stands attain 

this upper limit, resulting in significant numbers of unusable 

and dead trees. We have therefore defined an operating "maximum" line, which estimates the number of trees to establish 

for given target diameters (fig. 9). This line represents 70 

percent of the total number of trees that could attain a given 

mean diameter if the stand was allowed to attain the upper 

asymptote. Using this operating maximum line, we estimated 

the number of E. saligna trees to plant per acre and the 

effective square spacing for selected target diameters at harvest (table 4). These recommendations assume that no thinning will be done and that mortality due to causes other than 

competition is minimal. If such assumptions are not appropriate, planting density should be increased accordingly. 

Effects of initial stand density on patterns of tree growth and 

stand development are equally important in spacing decisions 

because they determine mean tree size and yield per acre at 

various harvest ages. Composited data from two spacing trials 

are displayed in fig. 10. Note that mean stand diameters exceeded 6 inches at 4, 5, or 6 years, depending on whether stands 

were initially planted at densities providing growing space per 

tree of 94, 72, or 65 ft2

. Although a similar mean diameter was 

reached under these three stand densities, estimated yields at 

harvest ranged from 28 to 46 tons/acre. 

Self-thinning was in progress at ages 5 and 6 years in the 

plots planted at densities providing 65 ft2

 of growing space per 

tree. Mortality averaged I1 percent in these plots; thus, effective 

growing space per surviving tree was about 72 ft2

, nearly identical to that indicated by the operating maximum line developed 

from diameter-density relationships (DeBell and Whitesell 1988). 

Initial Fertilizer Applications

Beneficial effects of nitrogen (N), phosphorus (P), and potassium (K) fertilization on tree growth during the first year have 

been demonstrated in field trials at Hamakua Coast locations 

(Strand and others 1992, Whitesell and others 1987, Yost and 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 11 
others 1987). Thus, Eucalyptus plantings on the BioEnergy 

project usually received two applications of commercial fertilizer during the first year. At planting or soon thereafter, 4 ounces 

of N-P-K (14-14-14) are buried in a dibble hole adjacent to each 

seedling (fig. 11). A second dose is applied in similar fashion 6 

months after planting. The fertilizer is buried rather than broadcast in young plantings on the Hamakua Coast in order to 

decrease the chance of it being washed away by frequent heavy 

rains, which often cause severe erosion of the bare silty-clay 

loam soils. At Ka'u early fertilizer applications are broadcast 

because the lower rainfall intensity causes less surface loss. 

Also, the extremely stony soil at Ka'u makes digging holes for 

the fertilizer difficult. 

Weed Control 

Post-planting weed control is done with manual backpack 

sprayers. The most critical time is 2 to 3 months after planting, 

when regrowth of the cane plants and other weeds is competing 

strongly with the tree seedlings. Glyphosate at a rate of one 

gallon/acre, with appropriate surfactant and antifoam agents, is 

used as a directed spray on the weeds. Special care is required to 

avoid spraying the tree seedlings, because Eucalyptus foliage is 

extremely susceptible to herbicide damage at this stage. About 6 

person-hours per acre are needed. 

The importance of keeping the young trees free from competition was demonstrated by an experiment comparing herbicide 

weed control with hand sickling (which provides immediate but 

very short-term release). After 18 months the trees weeded with 

Figure 9—Relationship between stand density and mean stand diameter for Eucalyptus saligna, Island of 

Hawaii (adapted from DeBell and Whitesell 1988). 

Table 4—Recommended planting densities and approximate growing space per tree to achieve mean target stand diameter for 

Eucalyptus saligna, Island of Hawaii 

Mean target Trees per Growing space Approximate 

stand diameter acre per tree spacing 

in. no. ft2 ft 

2 3,400 13 3.6 x 3.6 

4 1,130 39 6.2 x 6.2 

6 590 74 8.6 x 8.6 

8 370 117 10.8 x 10.8 

10 260 167 12.9 x 12.9 

12 200 223 14.9 x 14.9 

14 150 287 16.9 x 16.9 

12 USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 
herbicides were 70 percent larger in height and diameter than 

those weeded by hand sickling. 

If the first herbicide treatment is done carefully and is applied 

on schedule (2-3 months), many of the trees will have outgrown 

the weeds by the end of the first 6 months; the second fertilizer 

application at this time will maintain their growth rates (see 

cover illustration). There are always some problem areas, especially where the site preparation spraying was less effective or 

where vigorous cane regrowth has occurred. A second spot 

application of herbicide is therefore done 5 to 6 months after 

planting (fig. 12). Typically only about half of the area will need 

this spot application. The same formulation of glyphosate, surfactant, and antifoam agents is used. The work should take only 

about 3 person-hours per acre. The second fertilizer application 

follows the spraying; the advantage of this timing is that the area 

has been opened up by the passage of the backpack spray crew. 

Most of the plantations in which our weed control practices 

were developed were established at 5- by 5-ft or 6- by 6-ft 

spacings. At these densities herbicide spraying covers essentially the entire area, and crown closure by the eucalypts reduces 

the need for weeding after about one year. When wider spacings 

are used, the first spraying could be confined to circles around 

the trees large enough to keep them free of competition. The 

second spraying might need to be more intensive to control taller 

vegetation between the rows which could interfere with the trees 

as they grow larger. Additional spraying may be needed if crown 

closure occurs at a later age. Mechanized mowing, as in macadamia nut orchards, may be appropriate where spacings are wide. 

Competition for moisture between eucalypts and weeds is 

unlikely to be a problem in the Hamakua area because of the 

high rainfall. In the Ka'u District, where rank growth of grasses 

is a problem and spraying is often hampered by windy conditions, there may be some advantage to mowing the weedy 

vegetation and leaving it on the ground as a mulch to help 

conserve soil moisture, especially at lower elevations and during 

dry periods (fig. 13). 

Figure 10—Effects of growing space per tree on height (a), diameter at breast height (b), and biomass (c and d) for Eucalyptus grandis, Island of 

Hawaii. 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 13 
Figure 11—Initial application of fertilizer placed in dibble hole next to 

seedling. 

Stand Development 

and Cultural Practices 

Influence of Growing Space 

Increased growing space had little effect on height growth 

during the first two years. Greater growing space did, however, 

result in trees that were substantially taller in later years. Mean 

heights of trees planted at 130 ft2

 (10 ft by 13 ft) of growing 

space per tree were approximately one-third taller than mean 

heights of trees planted at 32 ft2

 (10 ft by 3.2 ft) at 6 years of age 

(fig. 10a). Diameter growth was more strongly affected than 

height growth by growing space, and positive effects were seen 

at younger ages. By age 6, diameters of trees planted at wide 

spacings were nearly 60 percent larger than those at narrower 

spacings (fig. 10b). The combined influence of both height and 

diameter leads to even greater differences in tree biomass. Trees 

planted with 130 ft2

 of growing space weighed about 2.5 times 

more than those with 32 ft2 (fig. 10c), but produced only threefourths as much biomass per acre (fig. 10d) at age 6 years. 

The continued acceleration of growth in the wider spacings 

and accompanying widening of differences in mean tree size and 

weight at ages 5 and 6 are important considerations in decisions 

regarding spacing and rotation length, especially if tree size is a 

significant factor in product value and costs of harvesting or 

conversion. 

No thinnings are envisioned in the short-rotation management of Eucalyptus in Hawaii, so no thinning trials were conducted. 

Fertilization 

Although a complete N-P-K fertilizer is recommended at the 

time of planting, subsequent fertilizer recommendations involve 

only N. Frequent applications of this element early in the rotation were beneficial; however, subsequent applications of P and 

K may also be required on sites that do not have a history of 

fertilization associated with sugarcane production (Strand and 

others 1992). 

Growth increases associated with increased N supply are 

clearly demonstrated by comparing the biomass production and 

soil nutrient content of two spacing studies, one at Kamae and 

the other at Pepeekeo. Both studies had identical establishment 

practices, spacing, and fertilization. Biomass production is significantly higher at Kamae than at Pepeekeo at most levels of 

growing space (table 5). Comparison of soil nutrient levels at 

time of establishment shows a significantly higher level of topsoil total N at Kamae than at Pepeekeo (table 6) although most 

other elements contributing to soil fertility are better at Pepeekeo 

than at Kamae. The lower productivity and lower topsoil N at 

Pepeekeo suggest that a higher rate of N fertilization is required 

to match the growth achieved at Kamae. 

A fertilizer study at Pepeekeo confines that higher application rates of N fertilizer could have increased biomass production in the spacing study. The highest rate in the fertilizer study is 

somewhat higher than that used in the spacing study (399 lb vs. 

343 lb elemental N/acre), and response throughout the range of 

application rates is essentially linear (fig. 14). Because the two 

spacing studies occur at about the same elevation, with approximately the same rainfall and on the same soil series, differences 

in N supply most likely account for the higher biomass productivity at Kamae. 

Results of our field research show that plantation growth is 

positively correlated with soil N content and that response to N 

fertilization is greatest on topsoils with the lowest N content 

(Strand and Cole 1992, Strand and others 1992). Rates and 

frequency of N fertilization needed to promote growth, therefore, should be linked to topsoil N status (total N concentration 

in the top 6 inches of soil). 

We propose the following three classes of topsoil N status as 

the basis for such specificity in fertilizer prescriptions: 

Good - >0.60 pct N 

Average - 0.45 to 0.60 pct N 

Poor - <0.45 pct N 

14 USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 
Figure 12—Spraying herbicide for weed control about 6 months after outplanting. 

Figure 13—Mowing for weed control in the Ka'u District. 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 15
------------------

----------------------

Table 5—Comparison of biomass production in two Eucalyptus grandis spacing studies at age 6 years, for identical 

spacings and fertilization, Hamakua coast, Island of Hawaii 

Location Initial growing space (ft

2

) 

32 65 100 130 

dry tons/acre/yr 

Kamae 11.7a1 8.8a 0a 3a 

Pepeekeo 8.2b 7.6a 7b 2b 

9. 8.

6. 6.

1

Means in a column not having the same letter are statistically different by Student's "t" test at 0.05 confidence level. 

Table 6—Comparison of soil analyses values for two spacing studies at Kamae and 

Pepeekeo, Island of Hawaii 

Sample Soil analyses

depth 

Location 

(study) Total N1 P Mg pH 

in. pct ------------------ ppm 

0-6 ae 0.67a2 10a 54.7a 10.0a 19.5a 4.2a 

0-6 keo 0.57b 24b 89.9b 174.3b 40.1a 4.9b 

18-24 Kamae 0.5 la 8a 43.0a 10.0a 34.0a 4.6a 

18-24 Pepeekeo 0.42a 12a 39.1a 134.3b 26.8a 5.1b 

K Ca 

Kam

Pepee

1

N-nitrogen, P-phosphorus, K-potassium, Ca-calcium, Mg-magnesium. 

2

Means in a column (by soil depth) not having the same letter differ significantly by 

Student's "t" test at the 0.05 confidence level. 

Table 7—First approximation of nitrogen fertilization regimes 

for Eucalyptus plantations on soils of different topsoil 

nitrogen (N) status classes, Hamakua Coast, Island of Hawaii 

Topsoil N status class M 1 onths after 

planting Poor Average Good 

------------------lb N/acre 

02 20 20 20 

62

 40 20 20 

122

 60 30 — 

18 100 100 100 

24 100 — 

30 — 100 100 

36 100 — — 

42 — 50 — 

48 100 — — 

Total applied: 520 320 240 

No. of applications: 

Manual 

3 3 2 

Aerial 4 3 2 

Total applications: 7 6 4 

1

N status classes (total N concentration in topsoil [0 - 6 in.]): 

Poor=<0.45pct; Average= 0.45 pct- 0.60 pct; Good=>0.60pct 2

Subsurface application of fertilizer 

Figure 14—Effect of nitrogen fertilizer treatments on biomass production of 6-year-old Eucalyptus grandis, Pepeekeo, Island of Hawaii. 

16 USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 
Fertilizer regime recommendations for each class (table 7) 

were developed from the results of six fertilizer, one admixture, 

and three spacing studies, nearly all of which were established 

on the Hamakua coast. A field trial at Akaka Falls indicated the 

need for higher amounts of initial N fertilization on poor sites 

(Whitesell and others 1987). This is reflected in table 7. 

Mixed Plantings of Eucalyptus

and Albizia 

Because many fertilizer studies in Hawaii and elsewhere 

(Cromer 1971, McIntyre and Pryor 1974) have demonstrated 

that Eucalyptus growth beyond the establishment phase is markedly enhanced by supplemental N applications, our project designed and evaluated cultural systems in which this supplemental N was supplied by nitrogen-fixing trees (DeBell and others 

1985). We found that the need for N fertilizer beyond the initial 

two applications during the first year could be eliminated on the 

Hamakua Coast by establishing mixed Eucalyptus/Albizia plantations. At Ka'u, however, Albizia falcataria grew poorly and 

provided no advantage on this much drier site (DeBell and 

others 1987). 

Our most comprehensive admixture trial was installed at 

Chin Chuck and has been evaluated for 7 years. A total of seven 

treatments was established on the basis of different admixtures 

of Eucalyptus saligna and Albizia falcataria (fig. 15). Besides 

pure Eucalyptus and Albizia treatments, the five mixed ratios 

were 11:89, 25:75, 34:66, 50:50, and 66:34 (Albizia to Eucalyptus percentages). All of the treatments received N-P-K initially, 

but only the pure Eucalyptus plots received additional N fertilization. All treatments had the same initial density of 1,012 

trees/acre (43 ft2

 of growing space per tree) and received supplemental applications of P and K. 

Figure 15—Mixed plantation of Eucalyptus and Albizia. 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 17 
Patterns of tree growth and stand development in the trial 

and adjacent plantings have been very dynamic. Survival and 

growth of both species through age 4 has been described in 

detail (DeBell and others 1989a). Additional data illustrating 

patterns of height and diameter growth through age 7 are 

displayed in fig. 16. 

As these stands develop over time, the combinations with 

Albizia look better and better. Height and diameter of the 

Eucalyptus in the 34 percent Albizia treatment are comparable 

to those Eucalyptus growing in the pure, fertilized plots. The 

Eucalyptus in the 50- and 66-percent Albizia treatments are 

substantially larger than those in the pure Eucalyptus plots, 

and so much larger than the admixed Albizia that a two-storied 

canopy has developed. The relative importance of improved N 

status versus increased growing space in these mixtures is 

unknown, but both factors are undoubtedly influential. Eucalyptus crowns in the 50- and 66-percent Albizia treatments 

occur in an environment similar to those with initial densities 

providing 86 and 130 ft2

 of growing space per tree. Regardless 

of the relative effect of these factors, these treatments demonstrate the growth potential of Eucalyptus at wider spacings and 

with enhanced N status (fig. 17). 

Management Considerations 

Biomass Estimation 

Production from short-rotation, intensively cultured plantations is usually expressed on an oven-dry weight basis as either 

stem-only or total above-ground biomass per unit of area. Actual 

weight can be determined only after harvest; thus estimates 

based on nondestructive measurements (d.b.h. and height) of 

standing trees are commonly used. Tree biomass is estimated 

from these measurements using regression equations developed 

by destructive sampling of trees from plantations over a range of 

ages, sites, and stocking conditions. Biomass in plantations is 

then estimated by measuring trees in sample plots, calculating 

the weight of each tree from the equations, and summing all the 

weights to obtain an estimate of biomass per unit area. This 

estimate is then multiplied by an approximate expansion factor 

to provide estimated yield per acre. 

Biomass equations were developed for seven of the species 

we planted (Schubert and others 1988, Whitesell and others 

1988). For three of these species—Eucalyptus grandis, E. saligna, 

and Albizia falcataria—the number of sample trees measured 

was large enough (n > 25) so that equations using both d.b.h. and 

height could be derived. For the other four species—Acacia 

melanoxylon, Eucalyptus globulus, E. robusta, and E. urophylla— 

fewer than 25 trees were sampled, and equations that use only 

diameter measurements were derived. Logarithmic equations 

were developed for both stem-only and for total above-ground 

dry biomass (table 8). Diameter and height measurements for 

these equations are in the metric system, and biomass is expressed in kilograms; this value should be multiplied by 2.2 to 

convert to dry pounds. 

The large sample size for E. saligna (n = 286), from 2- to 6-

year-old stands, made it possible to derive two sets of equations 

for this species (table 9). One set is for trees less than 4 years old; 

the other set is for trees 4 years old and older. 

Growth Patterns and Rotation Length 

General 

A classical concept in forest management holds that the 

optimal biological rotation age for any given forest crop is 

attained when mean annual increment of the desired product 

Figure 16—Average diameter (a) and height (b) of Eucalyptus 

saligna trees grown in pure stands with nitrogen fertilizer and those 

grown in various mixtures with Albizia falcateria and without 

nitrogen fertilizer. 

18 USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 
Table 8—Biomass equations for six species developed from 2- to 6-

year-old plantations located on the Island of Hawaii and recommended for prediction of stem-only and total above-ground dry 

biomass per tree1 

Species tions2 

Acacia melanoxylon Ys = 0.087366 * (D2.3778) 

Yt = 0.150484 * (D2.2310) 

Albizia falcataria Ys = 0.017945 * (D2.2026) * (H0.6660) 

Yt = 0.036207 * (D2.3146) * (H0.3600

) 

Eucalyptus globulus Ys = 0.076621 * (D2.5000) 

Yt = 0.082582 * (D2.5120) 

Eucalyptus grandis Ys = 0.026084 * (D1.7178) * (H0.9824) 

Yt = 0.069413 * (D2.1472) * (H0.3129

) 

Eucalyptus robusta Ys = 0.111171 * (D2.2670) 

Yt = 0.119339 * (D2.3200) 

Eucalyptus urophylla Ys = 0.075360 * (D2.4950) 

Yt = 0.119931 * (D2.3610) 

Equa

1

Schubert and others 1988 2

Ys= predicted stem-only dry weight in kilograms 

Yt = predicted total above-ground dry weight in kilograms 

D = diameter at breast height (1.3 in) in centimeters 

H = total tree height in meters 

Figure 17—Eucalyptus saligna at 10 years showing potential for enhanced growth with wide spacing and regular fertilization. 

Table 9—Biomass equations for Eucalyptus saligna plantations 

on the Island of Hawaii developed from two data bases and 

recommended, for prediction of stem-only and total aboveground dry biomass per tree1 

Data base (age) Equations

2 

Younger (<4 years) 

Diameter and height model 

Ys = 0.05501 * (D1.8942) * (H0.5408) 

Yt = 0.12022 * (D2.1448) * (H0.1352) 

Older (4 to 6 years) Ys = 0.01444 * (D1.7210) * (H1.2347) 

Yt = 0.01996 * (D1.9144) * (H0.9976) 

Diameter-only model 

Younger (<4 years) Ys = 0.08990 * (D2.2494) 

Yt = 0.13580 * (D2.2336) 

Older (4 to 6 years) Ys = 0.06352 * (D2.5412) 

Yt = 0.06594 * (D2.5772) 

1

Whitesell and others 1988 2

Ys = predicted stem-only dry weight in kilograms 

Yt = predicted total above-ground dry weight in kilograms 

D = diameter at breast height (1.3 in) in centimeters 

H = total height in meters

culminates. The culmination time is defined as the age at which 

the curve of current annual increment plotted over time crosses 

that of mean annual increment. Our work on short-rotation 

management of Eucalyptus indicates that peak mean annual 

increment will not occur before the onset of significant competition-related mortality, somewhat beyond the stage at which 

stands managed under any short-rotation intensive culture regime are likely to be harvested. Thus, classical theories about 

stand growth and optimum rotation age developed for more 

conventionally managed, longer rotation forests have limited 

application in short-rotation management. In this section, we 

will discuss general ideas that apply to short-rotation management and may help with decisions regarding optimum spacing 

and rotation length. These ideas will be illustrated with data on 

tree and stand characteristics from some plantings established 

and maintained under conditions approximating those recommended in this report. 

Eucalyptus 

Data from treatments in two spacing trials and one fertilization trial are presented in table 10. The spacing trials were 

located on average to good sites, and were fertilized regularly. 

The fertilizer trial was located on an average site, and the treatments included three levels of N application. 

The data describes tree and stand characteristics at the end 

of the year when competition-related mortality became significant (arbitrarily set at approximately 10 percent of initial 

stem density). Yields in the spacing trials averaged over 9 dry 

tons/acre/yr. In general, the denser spacings have the higher 

mean annual production. Although stands planted at densities 

of 16 ft2

 and 32 ft2 per tree have the highest production, on the 

average the trees are small and have not attained the minimum 

acceptable mean diameter of 6 inches required for cost-effective harvesting (Kluender 1980). Data from the fertilizer trial 

at Pepeekeo show the effect of increasing amounts of N fertilUSDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 19 
izer (fig. 14 and table 10). At the same spacing, tree growth 

and mortality were generally greater, and yields increased 

linearly with increasing levels of fertilizer. It therefore seems 

likely that mean annual productivity in the wider spacings of 

the studies at Kamae and Pepeekeo may be enhanced through 

additional applications of N fertilizer. 

Further evidence to support this conjecture can be seen in 

data on Eucalyptus trees from three treatments in the mixed 

species trial at Chin Chuck (fig. 18). The fertilized Eucalyptus 

was planted at a density of 43 ft2

 per tree. Eucalyptus trees in two 

of the mixed species treatments, 50 and 66 percent Albizia, were 

established at densities equivalent to 86 and 130 ft2

 per tree, 

respectively. The spacings of Eucalyptus ignore the presence of 

Albizia trees because Eucalyptus trees in the wider spacings 

average 33 ft taller than the Albizia. It is presumed that in recent 

years the Albizia trees in these treatments have offered little 

competition for light, that water was not limiting, and that 

nitrogen levels have been raised to near optimum levels. 

The rate at which biomass is being accumulated at Chin 

Chuck is strongly correlated with the effective spacing. 

Eucalypts planted at the widest spacing, 130 ft2

 per tree, are 

growing 99 to 110 lb/yr per tree (since age 4), while trees at 

the closest spacing, 43 ft2

 per tree, are growing only about 33 

lb/yr per tree. Such differences in growth rate are causing the 

gap in total production among treatments to close rapidly for 

both total and mean annual biomass per acre (fig. 18). These 

trends suggest that yields in the wider spacings will eventually 

equal (and may even surpass) those of the denser spacings, 

provided that rotation length is long enough. 

A more conservative view on which to base management 

decisions would be that if biomass yields at densities from 65 

to 130 ft2

 per tree are more or less equal at the onset of 

competition-related mortality, then the initial spacing will be 

Table 10—Tree and stand characteristics at onset of competition-related mortality in three studies. Island of Hawaii 

Growing 

space Mean Dry biomass per 

Study per tree Age urvival d.b.h.1 height tree acre 

ft2 yr pct in. ft lb --- tons ---

Kamae 3 90 3.8 50.2 60 36 12 

(spacing) 65 4 90 5.4 59.4 124 37 9 

100 4 88 6.7 72.2 207 41 10 

130 4 86 7.2 74.8 240 35 9 

Pepeekeo 4 83 3.0 41.0 40 45 11 

(spacing) 32 4 86 3.7 46.6 60 34 9 

Pepeekeo 

(fertilizer) 

(30)2 39 89 4.2 53.1 77 38 6 

(40) 39 6 91 4.5 58.4 88 46 8 

(50) 39 6 84 5.0 62.3 108 51 9 

S acre/yr 

32 

16 

6 

1

d.b.h. = diameter at breast height 2

N fertilization rate in parenthesis (g/tree). 

Figure 18—Biomass yields for 4- to 6-year-old Eucalyptus saligna as 

influenced by growing space per tree. 

20 USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 
-----

determined by the desired tree diameter at harvest. To achieve 

a minimum mean acceptable tree d.b.h. of 6 inches, tree spacing must be at least 8.5 by 8.5 ft per tree or a density of 72 ft2 

per tree. Choices among alternative wider spacings and associated rotation lengths can be based primarily on other considerations (discussed in next section). 

Mixed Species Planting 

In terms of producing large quantities of biomass from 

trees meeting minimum size limits, certain Eucalyptus/Albizia 

mixtures at Chin Chuck appear promising. Total yields of dry 

biomass and mean annual increments at ages 5 through 7 are 

given in table 11. 

These mixed species plantings are in a very dynamic state. 

Biomass growth is still accelerating, with current annual increments between 6 and 7 years ranging from 10 tons/acre in the 11 

percent Albizia treatment to 15 and 18 tons/acre in the 50 and 66 

percent Albizia treatments, respectively. Mean annual increments range from 9.3 to 13.4 tons/acre. 

An interesting trend has developed in relative production of 

the two species. The relative contribution of Albizia to total yield 

has increased over time in the 11 percent Albizia plots (from 15 

to 20 percent). Conversely, in the 66 percent Albizia plots, the 

relative contribution has decreased from 33 to 26 percent (table 

11). Presumably this trend results from the capacity of the 

Eucalyptus trees to grow more rapidly than the Albizia, using the 

greater amount of nitrogen-rich mulch provided by the increasing numbers of Albizia trees (Dunkin 1989). 

From an operational standpoint, it may not be efficient to 

completely intermix the two species as done in our research 

design. We suggest that the two species be planted in alternating 

rows spaced 10 ft apart. Within rows, Albizia could be planted 7 

ft apart and Eucalyptus 10 ft apart. This would provide the 

Albizia trees with an initial growing space of 70 ft2

 (311 trees/ 

acre) and the Eucalyptus 100 ft2

 (218 trees/acre) for a total of 529 

trees/acre. Of this number, about 58 percent would be Albizia. 

Eucalyptus growth has been so rapid under such density and 

composition regimes that their yields (9.9 tons/acre/yr in the 50 

and 66 percent Albizia treatments) approach those of pure Eucalyptus (11.3 tons/acre/yr) that received heavy, periodic applications of fertilizer. No N fertilizers are recommended beyond the 

first year in the mixed plantings, and additional applications of P 

and K are probably not necessary. Because the Eucalyptus trees 

were so large (which lowers harvesting costs), mixed treatments 

may be more economical than pure Eucalyptus stands, even if 

the Albizia trees are not utilized. 

Table 11—Total yield and mean annual increment (MAI) of dry biomass at ages 5 

through 7 years for various combinations of Eucalyptus and Albizia, Island of 

Hawaii 

Dry biomass at age (yr) 

Mean annual biomass 

Species increment at age (yr)

combination (pet) 5 6 7 5 6 7 

-------- tons/acre------- -------- tons/acre/yr 

Eucalyptus (100) 55 66 79 11.0 11.0 11.3 

Eucalyptus (89) 39 46 52 7.8 7.7 7.4 

Albizia (11) 7 9 13 1.4 1.5 1.9 

Total 46 55 65 9.2 9.2 9.3 

Eucalyptus (75) 32 41 52 6.4 6.8 7.5 

Albizia (25) 16 17 19 3.1 2.9 2.7 

Total 48 58 71 9.5 9.7 10.2 

Eucalyptus (66) 38 47 55 7.6 7.8 7.9 

Albizia (34) 19 22 26 3.8 3.6 3.7 

Total 57 69 81 11.4 11.4 11.6 

Eucalyptus (50) 45 56 70 9.0 9.4 9.9 

Albizia (50) 16 18 19 3.2 3.0 2.8 

Total 61 74 89 12.2 12.4 12.7 

Eucalyptus (34) 41 54 70 8.1 9.1 9.9 

Albizia (66) 20 22 24 4.0 3.6 3.5 

Total 61 76 94 12.1 12.7 13.4 

Albizia (100) 50 58 70 9.9 9.7 9.9 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 21 
Other Considerations 

in Rotation Length 

Aside from the physical growth patterns of the species under 

management, a number of other considerations can affect decisions on rotation length. These include economic factors, product characteristics and values, nutritional effects, and environmental and esthetic impacts. 

Economic factors can have a profound effect on rotation 

length. Optimum financial rotations shorten with increasing interest rates. Site preparation, regeneration, and other costs incurred at the beginning of the rotation are, in theory, carried with 

interest to the processing phase. On the other hand, stand establishment costs occur more frequently with short rotations, and 

this would somewhat modify effects of interest in determining 

the optimum rotation length. Costs of stand harvest constitute a 

major portion of total production costs, and may have effects as 

important as those of stand establishment costs. 

Product characteristics and value, if related to tree size or tree 

age, can affect rotation length. Utilization of total biomass as 

fuel does not particularly constrain rotation length because bark 

and leaves have little adverse effect on this product. Separation 

and removal of these components as well as limbs are required, 

however, for production of high quality pulp. Bark, limbs, and 

foliage could be tolerated in lower quality pulpwood, but chemical costs will increase and total mill production capacity may 

decrease with increasing quantities of these components (Schmidt 

and DeBell 1973). Bark and foliage increase as a percentage of 

the biomass harvest as rotation length decreases, so utilization 

for high quality pulpwood would tend to increase rotation length 

of short-rotation plantations. 

Nutrient relationships also are affected by rotation length. 

Shorter rotations result in more frequent and greater removal of 

nutrients from the site, especially if small branches and foliage 

are harvested. Furthermore, eucalypts appear to have efficient 

internal nutrient cycling mechanisms (Florence 1986). With 

longer rotations this mechanism may assist in husbanding nutrient resources and reducing nutrient drain. Nitrogen, the major 

limiting factor for eucalypt plantations on the Hamakua Coast, is 

the element of primary interest. The use of N-fixing species in 

mixture with eucalypts to supply nitrogen may influence rotation length. Since it takes time for the N-fixers to build up the 

soil nitrogen, a longer rotation may be required than for regimes 

with commercial fertilizer applications. If the management strategy is for the N-fixers to be over-topped and suppressed by the 

eucalypts—the final harvest product—then an even longer rotation may be appropriate. 

Frequency of harvest and regeneration activity as determined 

by rotation length will affect environmental and esthetic considerations. Clearing vegetation in a high-intensity rainfall area 

increases the probability of significant soil erosion. The more 

frequently the vegetative cover is removed, the greater the risk 

of soil erosion and site deterioration. A related productivity 

concern is the compaction and movement of the soil by harvesting and site preparation equipment. These problems increase in 

severity as rotation length decreases because the site is disturbed 

more often. Moreover, such disturbances may be esthetically 

displeasing to some segments of the public, especially since 

clearcutting is the normal harvesting method. However, sugar 

plantations on the Hamakua Coast presently harvest down to 

bare soil on a 2-year cycle, and soil loss can equal or exceed 1 to 

2 inches per rotation. Thus, longer cutting cycles and reduced 

soil exposure involved in biomass plantations should be more 

acceptable to most local residents than sugarcane culture. 

Harvesting 

The financial success of short-rotation, intensive culture systems for most species, particularly those of the temperate zone, 

hinges on the development of suitable harvesting technology for 

small stems. In subtropical Hawaii, rapid tree growth may permit use of conventional pulpwood harvesting systems with only 

minor modifications. Another advantage of short-rotation, intensive culture systems is that equipment and knowledge for sugarcane production can be adapted to develop tree harvesting systems suitable for soil and weather conditions in Hawaii. This 

situation in Hawaii does not diminish the importance of improving the efficiency of harvesting systems. Harvesting is the largest single cost item in short-rotation, intensively cultured tree 

crops, and may represent more than 50 percent of the total 

delivered cost. Several trials were established to analyze and 

evaluate approaches to harvesting (Crabb and Schubert 1989; 

Schubert and others 1992). 

One of the first systems we studied was cable yarding. The 

main advantage of this system is that little damage is done to the 

site or residual stumps. In our test the trees were felled manually 

with chain saws, with the butts aligned toward the roadside for 

easy hookup to the yarding equipment. Extraction was with a 

highline cable system using two boom trucks with winches and 

cables attached to spar trees within the area. The main problem 

encountered was that the yarding equipment was undersized and 

underpowered so that the extractive process was slow and inefficient. Inexperience with cable logging was also a factor. 

A second trial in the same area used mechanized equipment, 

including wheeled Morbark Mark IV1

 and tracked Caterpillar 

Model 2271

 feller-bunchers, a Timberjack1 clambunk skidder, 

and a Morbark Model 301

 whole tree chipper. A third trial used 

the same mechanized equipment to harvest three stands on 22 

acres. The conventional logging machines were able to handle 

our trees without difficulty. The tracked Caterpillar Model 227 

(fig. 19) was designed for considerably larger tree sizes, but 

seemed to be the best type of machine tested for our conditions. 

The shearing action of the felling heads caused extensive damage to the stumps, as did the rubber tires of the wheeled machines. This would be a problem only if coppice regeneration is 

relied upon. The wheeled machines also tended to get bogged 

down during wet weather. A large capital expenditure is necessary to purchase this type of specialized equipment, and depreciation costs add greatly to the total harvesting costs. 

These experiences revealed that logistics as well as tree size 

are major determinants of the productivity and cost of harvest 

operations. A balanced system in which all machines work close 

to capacity, with limited idle time due to delays in other parts of 

the system, is needed. Smaller, less expensive equipment, a good 

22 USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 
preventive maintenance system, and an adequate stock of critical 

spare parts would also help to bring down costs. 

Early during the life of the project it was suggested that 

modification of existing tracked sugarcane harvesting equipment for felling, bunching, and forwarding offered a promising 

opportunity to conduct harvesting research trials. Unfortunately, 

financial constraints prevented following up on this suggestion 

at the time, but it is still a concept that would be worth pursuing. 

There are also a number of new machines designed for pulpwood harvesting in Australia, North America, and Europe, which 

might be suited to our conditions. 

Regeneration 

There are three means of regenerating short-rotation intensive culture stands after harvest: natural regeneration, artificial regeneration, and coppice growth (resprouting of stumps). 

Natural regeneration by seedfall is not practical for our short 

6- to 8-year rotations. Eucalyptus grandis requires 4 to 5 years 

for its first flower production (FAO 1979), whereas E. saligna 

requires 7 to 8 years (Hillis and Brown 1978). In addition, 

with natural regeneration there is no control over spacing, and 

risk of establishment failure would be high compared to coppice or planted seedlings. 

Artificial regeneration with nursery-grown planting stock 

requires operations similar to those described earlier for plantation establishment. Planting stock could be either seedlings 

or rooted cuttings. Herbaceous weeds and stump sprouts must 

be controlled, probably with herbicides applied before or soon 

after planting. 

Adequate stand regeneration by coppice has been unsuccessful for E. saligna in our trials on the Hamakua Coast because of 

poor resprouting (Bowersox and others 1990). Increased success 

of coppice regeneration may be possible in the future if the 

selection of improved, higher yielding stock is based on coppicing 

ability as well as the potential for higher biomass production 

rates. Furthermore, any tree improvement program would initially emphasize the planting of superior stock. This would 

reduce the necessity for coppice regeneration until trees with 

inherently better coppicing ability are in place. 

Diseases and Insects 

A stem canker (Cryphonectria cubensis [Bruner] Hodges) is 

the only disease of eucalypts found to date in Hawaii. On Kauai, 

two adjacent Eucalyptus saligna plantations heavily infested 

with this canker were found more than 10 years ago, but it has 

not been observed on the other Hawaiian islands. Eucalyptus 

Figure 19—Harvesting using Caterpillar 227 fitted with feller-buncher head. 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 23 
saligna was rated as highly susceptible to this disease, E. grandis 

as moderately susceptible, and E. urophylla as highly resistant. 

Variation in susceptibility was considerable among different 

provenances of E. grandis (Hodges and others 1979). 

The Australian longhorn beetle (Phoracantha semipunctata 

Fabr.) has been found on Eucalyptus on Kauai, Oahu, and Maui, 

but not on Hawaii Island. A guava moth caterpillar (Anua 

indiscriminata Hampson) was observed feeding on E. saligna 

foliage at Amauulu on Hawaii Island. Neither of these insects 

was considered a serious threat to the plantations by local entomologists. Ambrosia beetles (Xylosandrus crassisuculus 

Motschulsky) attacked fresh stumps of Eucalyptus on the Hamakua 

Coast just as coppice was beginning to form (Schubert and 

Markin 1987). Although probably not the primary cause of 

failure, the attacks seemed to lower the ability of the stumps to 

coppice. Accidental importation of additional diseases or insects is always a possibility, which must be guarded against by 

strict observance of plant quarantine regulations and close monitoring of plantations. Over time, however, adaptation of native 

insects and diseases to exotic plantations is a distinct possibility. 

The "absolute rule" of Zobel and Talbert (1984) states: "exotic 

plantations will be attacked by one pest or another." 

Environmental Issues 

Questions regarding environmental effects of land management practices are being raised with increasing frequency by 

various interest groups and the general public. It is therefore 

probable that similar questions will arise regarding short-rotation management of Eucalyptus. Because most Eucalyptus plantations will likely be established on abandoned sugarcane lands, 

conflicts are unlikely to be as polarized and volatile as those 

occurring when native forests are cut and land is converted to 

intensive agricultural or forestry use. Still, some concerns will 

surface, and those most likely to be voiced in Hawaii will 

probably center around soil erosion, nutrient depletion, and use 

of eucalypt monocultures. 

At the outset, it should be recognized that the potentially 

negative impacts of production plantations of Eucalyptus, even 

with rotations as short as six years, will be substantially smaller 

in magnitude and will occur less frequently than impacts associated with most agricultural crops. The detrimental effects associated with site preparation, applications of fertilizers and herbicides, and harvesting will be considerably less than those from 

sugarcane production. In addition, increased establishment of 

forest cover has beneficial effects, including conservation and 

improvement of soils, increased habitat diversity for other plants 

and wildlife, and greater scenic variety throughout the landscape. 

Soil Erosion 

Site preparation and harvesting activities could increase 

erosion and thus adversely affect soil productivity. For this 

reason a cooperative study to evaluate such effects was initiated in 1981 with soil scientists in the Department of Agronomy 

and Soil Science at the University of Hawaii (Schultz 1988). 

The study was located at Amauulu on a Kaiwiki silty clay 

loam soil that receives more than 200 inches of rain annually. 

Twelve run-off plots were established—with six left bare as 

control plots, and six planted with Eucalyptus seedlings. Litter 

was periodically removed from half of the Eucalyptus plots 

after cover was established. The trees were cut after 6 years, 

and regenerated by coppice. Three post-harvest treatments 

were imposed: minimal disturbance, periodic litter removal, 

and establishment of a cover crop. 

Despite the high rainfall, soil erosion was minimal (Schultz 

1988). Annual pre-harvest soil loss on plots where litter was not 

removed was close to zero after 6 years. Soil loss from plots 

where the litter was removed periodically by raking was 13 

times higher than that from the bare control plots. Apparently 

water dripping from the tree canopy is more erosive than incident rainfall. Post-harvest soil losses from plots with minimal 

soil disturbance or with a cover crop were less than 165 lb/acre 

during the 18 months after cutting. Removing the litter caused 

more erosion, 251 lb/acre of soil. The worst losses were from 

those plots that were raked clean both before and after harvest, 

with 510 lb/acre of soil lost during the 18-month period. 

These soil losses are far below the designated maximum 

tolerable limit of 4.9 tons/acre/yr (Wischmeier and Smith 1978), 

even when the litter layer was removed under a tall canopy. 

Along the Hamakua Coast, the litter layer is far more important 

than the tree canopy in preventing soil losses. Management 

practices should be designed to develop and preserve this protective cover. 

Nutrient Depletion 

Questions are frequently asked about nutrient depletion by 

intensive cropping systems. All of our work has indicated that 

total N levels in Hamakua Coast soils are inadequate for good 

growth of Eucalyptus. Presumably the decades of intensive 

sugarcane cropping on the Hamakua Coast and the high temperatures and rainfall increased mineralization and leaching 

loss of N in the soil. Continuous cropping has also prevented 

the accumulation of organic matter and recharge of N reserves. There is no doubt that supplemental N will be needed 

for acceptable growth of Eucalyptus plantations established 

along the Hamakua Coast, and possibly also in the Ka'u 

District. However, this N deficiency can be overcome with 

applications of N fertilizer, at substantially lower rates than 

those used for sugarcane. 

There are factors that suggest that N deficiency may be less of 

a problem when the trees become older, both during the initial 

rotation and in subsequent rotations: 

• Nitrogen concentrations in soils appear related to length of 

time the land was devoted to cane, and to the length of the fallow 

period. Total soil N levels in long abandoned canelands and in 

forest land tend to be higher. Soil N levels after 4 years in one of 

our most productive Eucalyptus plantings were equal to or higher 

than those when the trees were planted, despite considerable N 

accumulation in the biomass (DeBell and others 1989a). 

• At Chin Chuck, no fertilizer was applied to the pure Eucalyptus plots after age 5 years, but yields continued to increase 

through age 7. Other work also has indicated that Eucalyptus is 

very efficient at internal recycling of nutrients (Florence 1986). 

24 USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 
If so, there are two nutrient-related reasons to consider rotations 

longer than those originally envisioned: (1) to capitalize on 

internal recycling, and (2) to lower nutrient drain per unit of 

biomass removed. 

• The planting of Albizia/Eucalyptus mixtures provides opportunities to enhance productivity by improving N levels and 

other soil properties. Although our work dealt with Albizia 

mixtures, potential benefits from use of other nitrogen-fixing 

plants (herbs, shrubs, and trees) and other cultural systems, 

including crop rotation, should be evaluated. 

In addition to rotation length, whole tree or stem-only removal, and use of nitrogen-fixing plants, nutrient management 

considerations should include protection of the litter layer during 

harvesting. Such protection not only preserves nutrients contained in the litter, it also reduces erosion of fertile topsoil. 

Finally, growth and nutrient status of trees should be monitored, 

and nutrients added as needed. 

Monocultures 

The desirability of planting large areas with monocultures of 

single species is often questioned, especially when clonal monocultures are involved. Concerns usually focus on increased 

susceptibility to insect and disease attacks, diminished habitat 

diversity for animals and other plants, and esthetics. 

Our plantings in Hawaii to date have not encountered any 

insect or disease pests of consequence. Such problems could 

appear in the future, and may warrant attention in selecting 

management regimes and in tree improvement programs. Effects of Eucalyptus plantings on biological and visual diversity 

depend on the setting; in general, the plantings have added 

diversity to a landscape that has been dominated by another 

clonal monoculture, sugarcane. 

A study of the ecological effects of eucalypts sponsored by 

the FAO (Poore and Fries 1985) concluded that plantations of 

these species do not appear to use significantly more water than 

plantations of other vigorously growing hardwood species. There 

was no evidence that eucalypt forests caused soil deterioration or 

irreversible site damage, but short-rotation plantations could 

lead to nutrient depletion, especially if the whole biomass is 

harvested. This is true of any rapidly growing, highly productive 

crop, and can be overcome by appropriate fertilizer treatments 

and by leaving the nutrient-rich organic material on the site after 

harvesting. The effects of eucalypts on ground vegetation depend greatly on climate, mostly because of competition for 

water, and ground vegetation in dry conditions may be greatly 

reduced. Habitat diversity is obviously less in eucalypt plantations than in native vegetation, but greater than in sugarcane 

plantations. Diversity can be increased to some extent by leaving 

patches or corridors of indigenous vegetation. 

It should also be recognized that highly productive species or 

clonal monocultures will require less land to produce wood for 

current needs, such as the increasing demand for fuelwood in the 

tropics (Davidson 1987), and thus more land can be managed or 

preserved in order to provide other needs and values. 

Tree Improvement 

A substantial increase in biomass yields can be expected from 

tree improvement programs for Eucalyptus in Hawaii. A tree 

improvement strategy for this purpose has been proposed by F. 

Thomas Ledig, USDA Forest Service, and is outlined below. 

Current Program 

The immediate goal is to obtain superior Eucalyptus grandis 

and E. saligna seeds for planting stock utilizing the following 

strategies: 

• Import Eucalyptus grandis and E. saligna seed from Australian provenances that performed well in field trials described 

by Skolmen (1986). 

• Convert provenance trials to seed production areas, removing inferior provenances and poorest phenotypes within the best 

provenances. 

• Collect seed from superior phenotypes in the project's 

field plantations. 

• Inspect all seed, discarding approximately the smallest 20 

percent, to decrease self-pollinated seed. 

• Upgrade the planting stock by culling the low vigor seedlings. 

Short-Term Improvement Program 

Select about 120 superior trees from project plantations on 

the basis of volume, biomass production, including wood density, and tree stem form. About 40 selections of these should be 

E. grandis from the best performing provenances in the trials 

reported by Skolmen (1986). Scions of selected trees should be 

collected and grafted into a clone bank to ensure against loss; 

then selected trees will be semi-girdled to induce epicormic 

sprouts from their base. Sprouts will be used for rooting. As a 

last resort, selected trees will be felled to promote sprouting. If 

stumps fail to sprout, it should be possible to take cuttings off the 

grafts and root them because grafting rejuvenates the scion. 

Scion material for rooting should be treated using techniques 

of Campinhos and Ikemori (1983). Successfully rooted clones 

will be multiplied by successive cycles of cutting and rooting 

until there are sufficient clones with economic rooting potential 

(at least 70 percent take) for testing over a range of planting sites. 

At the same time a cutting orchard should be established to 

multiply selected clones for commercial planting. After 2 years 

the best 10 to 20 clones should be selected for commercial 

plantings. 

Long-Term Improvement Program 

Although 10 to 20 clones may be adequate for a short-term 

planting program, they are insufficient for a breeding program. 

The genetic base must be expanded to allow greater scope in 

selection. 

The first step in the long-term tree improvement program is 

to verify the results of our provenance trials to determine whether 

the major effort should be placed on Eucalyptus grandis or E. 

saligna or on both. The verification will consist of establishing 

outplanting trials consisting of the best E. grandis provenances, 

the best E. saligna provenances, the best of the Aracruz clones, 

and a Hawaiian seed source of E. saligna. These outplanting 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 25 
trials should cover a full range of anticipated future planting sites 

and should emphasize different locations. 

Another collection of provenances of Eucalyptus grandis 

from Australia should be made to expand the base population for 

a long-term (5- to 20-year) tree improvement program. Seeds 

should be kept separate by mother tree to allow for establishment 

of combined provenance-progeny tests on anticipated planting 

sites in Hawaii. Selection and cloning could begin 3 years after 

out-planting. The larger the tests, the more gain that will be 

made by selection. 

Selected clones and seed from selected Eucalyptus grandis 

clones should be obtained wherever possible and planting stock 

from these sources tested under Hawaiian site conditions. 

Additional trials of E. urophylla should be conducted. Seeds 

should be acquired from the best available individuals in Timor 

and Flores, and in other areas where its introduction has been 

successful. These new test plantations would serve as a base 

population for future selection and hybridization. 

Another Eucalyptus species to consider in a Hawaiian tree 

improvement program is E. globulus. This species, more adapted 

to drier sites than either E. grandis or E. saligna, grows rapidly, 

with wood characteristics very suitable for fuel or for pulpwood. 

It has been widely planted at 2,500- to 5,000-ft elevation in 

Hawaii. The Forest Service has made seed collections from 

superior phenotypes in 60- to 70-year-old plantations along the 

Hamakua Coast. Seedlings were produced and outplanted at 

Chin Chuck, but all grew poorly at this high-rainfall, lowelevation site. Progeny trials for E. globulus should be initiated 

on drier sites, such as Ka'u, using these seed collections, and 

seeds from selected trees in Florida, California, and Portugal. 

Recommendations for Monitoring and

Research 

In short-rotation management of plantation forests, stand 

growth is rapid, and changes develop rapidly in nutrient status 

and competition for growing space. These changes can be detected by periodic measurements of d.b.h. and height in permanent sample plots. Growth rates of Eucalyptus saligna in Hawaii 

are positively correlated with foliar N, and critical levels for 

foliar N have been established (table 12). Therefore, concurrent 

measurement of growth and sampling for foliar nutrient levels 

can help identify N deficiency and suggest its degree of severity. 

Abnormal concentrations of other elements can also alert the 

plantation manager to emerging problems. Periodic adjustments 

can be made in fertilization regimes based on information obtained in stand monitoring. Frequency of monitoring should be 

every 6 months through the first two years with another appraisal 

at 4 years. Size and survival estimates should be obtained from 

tree and plot measurements at each monitoring examination. 

Foliar samples should be taken routinely during the first three 

monitoring periods when collections are easier and nutrient 

concentrations are changing rapidly. Foliar N concentrations 

should be determined on all samples, whereas levels of other 

major and minor elements should be determined in subsamples. 

Subsequent samples should be taken at locations where tree 

measurements indicate marked declines in growth rate. The 

concentration of other nutrient elements should be determined 

for these samples. 

The existence of monitoring trees and plots spread throughout the plantation types permits selection of matching trees and 

plots in small areas to compare alternative silvicultural treatments. This provides a convenient and low cost method to 

develop and evaluate new plantation management practices. 

Existence of the monitoring plot system also tends to build a data 

base of growth rates, foliar analyses concentrations, and results 

of research evaluations. This data base would be extremely 

useful for the continuing development of management practices. 

Additional research is needed on a number of points concerning short-rotation management of eucalypts on the island of 

Hawaii. The most cost-effective rates and frequencies of N 

fertilization for planting sites with different soil N status need to 

be determined. Experiments to contrast good versus poor sites 

should be established, testing varying amounts and frequencies 

of fertilizer applications, including an accelerated schedule with 

the total amount applied within the first three years. 

Tied in with fertilizer research is the question of nitrogenfixing species useful for admixture plantings. Further work is 

needed on optimum mixtures and rotation length. An alternative 

species with fast growth, dense wood, and a single stem would 

be useful for Hamakua Coast conditions to replace Albizia 

falcataria. Trials of an N-fixing species with such desirable 

properties which will grow successfully and enhance the growth 

of eucalypts are also needed for the drier site conditions at Ka'u. 

Continuing research on improved species and provenances in 

general should be an ongoing component of any large-scale 

plantation project. 

Research should be considered on reliable methods of coppice regeneration. Coppice is an attractive method of regenerating short-rotation tree crops if low mortality and high growth 

rates can be obtained. Coppice rates in our harvest cuts of 

eucalypts have been too low and unreliable for regeneration 

Table 12—Levels of foliar nutrients in Eucalyptus saligna trees from 

BioEnergy's plantations with biomass yields in the upper 25 percent of all 

plantings, Island of Hawaii 

Age (months) 

Nutrient 12 18 24 30 36 

------------------------------ pct ---------------------------

Nitrogen (N) (2.2)

1

 2.16 2.08 1.96 1.84 (1.8) 

Phosphorus (P) (0.2) 0.19 0.18 (0.2) 0.18 (0.2) 

Potassium (K) (1.2) 1.12 1.08 (1.2) 0.98 1.18 

Calcium (Ca) (0.6) 0.45 (0.5) 0.43 0.38 0.44 

Magnesium (Mg) (0.2) 0.25 0.24 (0.3) 0.27 (0.3) 

Sulfur (S) (0.2) 0.16 0.17 (0.2) 0.16 0.17 

-------------------------------- ppm --------------------------

Copper (Cu) (15) 11 11 11 8 7 

Zinc (Zn) (30) 27 27 (25) 22 25 

Iron (Fe) (100) 100 103 98 84 (95) 

Manganese (Mn) (300) (250) (250) (200) (180) (180) 

1

Values in parentheses are less reliable than those without parenthesis and 

were adjusted slightly from the averages upon inspection of the plots of biomass 

versus nutrient concentrations. 

26 USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 

48 
purposes (Bowersox and others 1990). Although we have 

alternative regeneration methods, the low cost and fast growth 

of coppice may be worth the cost of research to improve the 

frequency and reliability of stump sprouting. However, this 

must be balanced against possible higher harvesting costs 

because of the need to avoid stump damage, and to handle the 

two or three smaller diameter stems that remain on coppiced 

stumps at harvest. 

Production Economics 

Costs of production are a major factor in decisions regarding 

investment in short-rotation Eucalyptus plantations and in choices 

among alternative management regimes. Some costs and returns, of course, are specific to the objectives and situations of 

individual organizations and projects, i.e., land, taxes, administration, insurance, interest rates, and product values. Other costs 

tend to be relatively similar to all; these include costs related to 

plantation establishment, maintenance, and harvesting. 

We have not performed a financial analysis for inclusion in 

this paper. Rather we provide estimates of biomass yield and 

general production costs associated with three management regimes, each of which we believe has potential for use in shortrotation Eucalyptus plantations. Also, we provide some of the 

assumptions underlying the estimated costs, all of which are 

based on experience in this BioEnergy Development Corporation project. Prospective growers and others involved in decisions on short-rotation Eucalyptus plantations can use these 

data, making adjustments as desired to conduct economic analyses appropriate to their situation and needs. 

Regimes listed in table 13 include three of the most promising alternatives, based on current knowledge. Regime A represents the shortest rotation (5 years) in which minimum acceptable mean tree size (6 inches d.b.h.) is balanced with high 

productivity. Total biomass yield is estimated at 45 dry tons 

per acre or 9 tons per acre per year. Periodic fertilization is 

required on most former sugarcane land to attain this production level. Conceivably, this total yield could be attained in 

fewer years with genetically improved planting stock or higher 

fertilizer dosages. 

Regime B represents a slightly longer rotation (6 years) and 

produces a larger average stem size (8 inches d.b.h.). Larger 

trees may have advantages in quality for some products and 

generally can be harvested and processed at lower costs. Total 

biomass yield is estimated at 50 dry tons per acre or 8.3 tons 

per acre per year. The possibilities for enhancing growth rate 

and achieving higher productivity with genetic improvement 

and increased fertilization may be better than with Regime A 

because growing space is considerably greater (70 percent 

more space per tree). 

Regime C is an alternative developed from our experience 

with mixed Eucalyptus-Albizia planting on the Hamakua Coast. 

The planting pattern has been described previously in this 

paper; although the pattern has not been tested specifically, 

the ratio of Eucalyptus to Albizia and the density of trees per 

acre are identical to those in one of our experimental treatments. The main advantages of this 8-year rotation include 

larger tree size and reduction in costs of and dependence on 

synthetic nitrogen fertilizer. The biomass yield of Eucalyptus 

alone is 80 dry tons per acre or 10 tons per acre per year; even 

when excluding the Albizia, it is the most productive treatment 

we have observed. If harvested and utilized, Albizia trees 

might provide another 25 tons per acre, and thus increase 

annual productivity to 12 or more tons per acre. 

Assumptions underlying estimates of production costs are 

listed in table 14. We encountered considerable variation in 

some of these, such as site preparation, weeding, and harvesting costs. For example, costs of plantation establishment at 

Ka'u are substantially higher than those on the Hamakua 

Coast. Tree planting alone costs twice as much in the rocky 

soils of Ka'u. Existing and competing vegetation also creates 

changes in clearing and maintenance costs at both locations. 

Table 13—Selected management regimes for short-rotation Eucalyptus plantations, Island of Hawaii 

Rotation Biomass yield 

Regime Description length Fertilization schedule Stem Total 

yr mo. dosage/acre --------ton/acre -----

A Dense planting, pure Eucalyptus 5 0, 6 20 lb N,P,K 38 45 

Spacing: 7 ft by 10 ft (620 trees/acre) 12 30 lb N 

Mean tree size: 6 inches d.b.h. 18, 30 100 lb N 

42 50 lb N 

B Wide planting, pure Eucalyptus 6 0, 6 13 lb N,P,K 42 50 

Spacing: 10 ft by 12 ft (360 trees/acre) 12 30 lb N 

Mean tree size: 8 inches d.b.h. 18, 30, 42 100 lb N 

54 50 lb N 

C Mixed planting, Eucalyptus/Albizia 8 0, 6 18.5 lb N,P,K 

Species in alternate rows (10 ft apart) 

Eucalyptus: 10 ft within rows (218 trees/acre) 68 80 

Mean tree size: 9 inches d.b.h. 

Albizia: 7 feet within rows (311 trees/acre) 25 

Mean tree size: 4.5 inches d.b.h. 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 27 
Harvesting costs vary with average tree size, decreasing by 

one-third as tree size increases from 6 inches d.b.h. to 12 

inches d.b.h. Such differences in harvesting costs are taken 

into account in the production cost estimates given in table 15 

because they are predictable and are directly associated with 

the regimes. Variation in other costs, however, is not directly 

related to either tree size or management regimes; thus, costs 

are based on average values as listed in table 14. 

Cost estimates in table 15 indicate considerable differences 

among the three regimes. Total accumulated costs per dry ton 

of chipped Eucalyptus biomass at the mill range from $54 for 

Table 14—Assumptions underlying cost estimates for short-rotation Eucalyptus Plantations. Island of Hawaii 

Task Cost (in 1990 $) 

-Land clearing 2 hr/acre at $75/hr 

(range: 0.3 to 3.0 hr) 

-Herbicide application 

(applied before planting) 

0.2 hr/acre at $40/hr (tractor) 

(plus $70/acre for chemicals) 

-Planting stock $0.05/tree 

-Hand planting $0.13/tree on Hamakua coast 

$0.26/tree on Ka'u District 

-Replanting 5 pct of original planting cost 

-Herbicide application 

(applied after planting) 

2-3 month period 6 hr/acre at $8.33/hr (hand labor) 

(plus $70/acre for chemicals) 

5-6 month period 4 hr/acre at $8.33/hr (hand labor) 

(plus $32/acre for chemicals) 

-Mowing between rows 

(10-ft spacing) 

$19/acre 

(once at 6 me. or twice at 3 and 6 mo.) 

-Fertilizer application 

(N-P-K1

 applied by hand) 

1.2 hr/acre at $8.33 hr 

(plus $0.04/tree for fertilizer) 

-Subsequent fertilization 

(applied by aircraft) 

$10/acre + $0.31/lb N 

(or $0.14/lb urea) 

-Harvesting operations 

Felling and skidding $22/dry ton (stands averaging 6 in. d.b.h.) 

$16/dry ton (stands averaging 8 in. d.b.h.) 

$15/dry ton (stands averaging 9 in. d.b.h.) 

Chipping $10/dry ton (stands averaging 6 in. d.b.h.) 

$ 9/dry ton (stands averaging 8 in. d.b.h.) 

$ 8/dry ton (stands averaging 9 in. d.b.h.) 

Hauling $0.24/dry ton/round trip mile. 

1

N - nitrogen, P - phosphorus, K - potassium 

the shortest rotation (Regime A) to $35 for the longest rotation 

involving Albizia (Regime C). If Albizia were utilized, total 

biomass produced per acre would increase by about 25 percent, but delivered cost per ton would slightly increase because harvesting cost per ton for the smaller-sized Albizia (4 

1/2 inches d.b.h.) would be nearly 50 percent greater than the 

total production cost per ton incurred with utilization of Eucalyptus alone. The costs and returns in the three regimes occur 

at different times; thus, a financial analysis is needed to compare their relative profitability. 

Table 15—Production costs associated with selected management regimes 

for short-rotation Eucalyptus plantations, Island of Hawaii 

Regime 

Task A B C 

Cost (in 1990 $) 

Establishment (per acre) 

Land clearing 150 150 150 

Herbicide application 78 78 78 

Planting stock 31 18 26 

Hand planting 81 47 69 

Replanting 3 5 

Maintenance (per acre) 

Herbicide application 186 186 186 

Mowing 38 19 

Fertilizer application 201 224 65 

Establishment and maintenance costs (per acre) 

752 744 598 

Harvesting (per dry ton) 

Felling and skidding 22 16 15 

Chipping 10 9 8 

Hauling 5 5 

Harvesting cost (per dry ton) 37 30 28 

Establishment and maintenance costs 

(per dry ton)1 17 15 7 

Total cost (per dry ton) 54 45 35 

6 

19 

5

1

Assuming a yield/acre of 45-, 50-, and 80-dry ton/acre for regime A, B, 

and C, respectively (from table 13). 

28 USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 
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Conversions 

(English to Metric) 

Length 

-inches to millimeters -----------------------English × 25.40 

-inches to centimeters------------------------English × 2.540 

-feet to meters---------------------------------English × 0.305 

-miles to kilometers -------------------------English × 1.609 

Area 

-square inches to square centimeters English × 6.452 

-square feet to square meters ---------------English × 0.093 

-acres to hectares ----------------------------English × 0.405 

Weight 

-ounces to grams ----------------------------English × 28.350 

-pounds to kilograms ------------------------English × 0.454 

-tons to tonnes ------------------------------- English × 0.907 

Weight as applied to area 

-pounds/acre to kilograms/hectare --------- English × 1.121 

-ton/acre to tonne/hectare ------------------- English × 2.242 

Volume 

-cubic inches to cubic centimeters --------English × 16.387 

-gallons to liters ------------------------------ English × 3.785 

30 USDA Forest Service Gen. Tech. Rep. PSW-GTR-137. 1992. 
The Forest Service, U.S. Department of Agriculture, is responsible for Federal leadership in forestry. 

It carries out this role through four main activities: 

• Protection and management of resources on 191 million acres of National Forest System lands 

• Cooperation with State and local governments, forest industries, and private landowners to help 

protect and manage non-Federal forest and associated range and watershed lands 

• Participation with other agencies in human resource and community assistance programs to 

improve living conditions in rural areas 

• Research on all aspects of forestry, rangeland management, and forest resources utilization. 

The Pacific Southwest Research Station 

• Represents the research branch of the Forest Service in California, Hawaii, American Samoa 

and the western Pacific. 

Persons of any race, color, national origin, sex, age, religion, or 

with any handicapping conditions are welcome to use and enjoy 

all facilities, programs, and services of the U.S. Department of 

Agriculture. Discrimination in any form is strictly against agency 

policy, and should be reported to the Secretary of Agriculture, 

Washington, DC 20250. 
United States 

Department of Short-Rotation Management of Eucalyptus: GuideAgriculture for Plantations in Hawaii Forest Service Pacific Southwest 

Research Station 

General Technical Report 

PSW-GTR-137