Eucalyptus and Corymbia Species for Mulchwood, Pulpwood, Energywood, Bioproducts, Windbreaks, and/or Phytoremediation

Introduction

In Florida, Eucalyptus species grow faster than our native tree species. E. grandis (EG), E. grandis x E. urophylla (EH), E. benthamii (EB), and E. amplifolia (EA), in particular, are fast-growing trees that, when planted on suitable sites and managed properly, produce commercial products such as mulchwood, pulpwood, energywood, and bioproducts. Eucalyptus can also phytoremediate, i.e., remediate environmental problems (Table 1). Eucalyptus species are not invasive, having been planted commercially in Florida since the 1960s without spreading from managed plantations. EG and EA, along with Corymbia torelliana (CT), also may be used as windbreaks for citrus and vegetables. This circular describes potential applications and presents planting guidelines for these species.

Applications

Applications for EG, EH, EB, EA, and CT in Florida ranging from traditional and innovative forest products to phytoremediation systems and windbreaks are demonstrated in various locations (Table 1).

Forest Products. Commercial markets for Eucalyptus wood currently exist for landscape mulch and pulpwood and may be developed for oriented strand board, specialty pulp, and medium-density fiberboard. The color, texture, and durability of mulch produced from EG and EA compare very favorably to those of cypress mulch. EG and EH in southern Florida and EB and EA in northern Florida may be harvested for landscape mulch. About 50,000 acres of Eucalyptus plantations could perpetually supply the feedstock needs of the Florida mulch industry.

Considerable Eucalyptus pulp is imported into the United States. Florida-grown EG, EH, EB, and EA have very acceptable properties for pulp and paper making, and hardwood pulpwood demand and price are strong in the Southeast. Still, Eucalyptus plantations grown for pulpwood need to be in close proximity to existing pulpmills in northern Florida. EG used for specialty pulp could be greater distances from pulpmills.

Energy and Bioproducts. Trees can be bioenergy and bioproduct feedstocks. Energywood may be utilized for electricity generation by many utilities in Florida by cofiring with coal, for example. Some utilities in Florida currently use woody biomass to produce electricity and steam. Woody biomass also has numerous other energy-related applications including direct combustion, thermo-chemical gasification, methane, alcohol, and other bioproducts including biochar, diesel fuel, and graphene. Trees grown for energy applications may qualify for tax credits. EA and CT flowers are attractive to honeybees.

Windbreaks. The rapid growth and evergreen nature of EG, EA, and CT make them ideal for quickly establishing effective windbreaks around citrus and vegetables. With a wind-slowing effect extending approximately 10 times tree height, after six years these species can easily provide wind and disease protection for crops up to 600 feet downwind from the windbreak. EA and EG windbreaks tend to open at the bottom as the trees grow and lower branches self-prune; CT windbreaks typically stay full as the trees grow. Mixed species and coppicing can maximize early and continuous windbreak effectiveness.

Phytoremediation Systems. The rapid year-round growth of EG and EA is advantageous for phytoremediation applications such as a) effluent from sewage treatment facilities, b) stormwater in urban and industrial areas, and c) agricultural irrigation water. Water and nutrient uptakes by EG and EA depend on climatic limits, tree age and vigor, and the timing and extent of the wastewater applications. The upper limit on annual water uptake is approximately 65 inches. Annual nutrient accumulations by vigorous EG may reach 190, 35, 95, 80, and 25 pounds/acre of N, P, K, Ca, and Mg, respectively. In phytoremediation systems, Eucalyptus should be managed to reach full canopy development as rapidly as possible and to maintain active growth. They should be harvested as soon as productivity diminishes; they regenerate through vigorous coppicing (sprouting from the stump). At the accelerated growth rates EA and EG can achieve in phytoremediation applications, plantings as small as two acres could be commercially harvested in three to four years. Eucalyptus production combined with wastewater recycling thus has many mutual advantages, such as increasing tree growth, recycling nutrients, and renovating wastewater while at the same time producing mulch, pulpwood, biochar, or energywood.

Planting Guidelines

Successful establishment and management of EG, EH, EB, EA, and CT have several aspects (Table 2):

Growing Region. No single species is the most productive in all regions of Florida nor most suitable for all applications. Species choice by region (Figure 1) reflects freeze hardiness differences, particularly in northern Florida. Improved EB and EA are freeze hardy enough for all of Florida. The limited hardiness of EG restricts use of improved seedlings to southern and central Florida, but EG cultivars may also be used in northern Florida. EH and CT have freeze tolerance appropriate for central and southern Florida.

Site Requirements. EA, EB, EG, EH, and CT all grow best on agricultural lands. Lands recently in agricultural use or marginal for agricultural production are typically ideal. EA requires high quality land with relatively high pH. EG and CT have a wide site tolerance. EG and EH grow very well on sandy or organic soils and grow more rapidly than EA, EB, and CT on most sites.

All species may be grown on poorer sites if amendments are added to raise nutrient levels and/or pH. EG, for example, grows well on low-phosphorus sites when ground rock phosphate is applied. All these species are very responsive to fertilizer amendment. Some EG cultivars have acceptable flood tolerance.

Cultural Practices. On poorly drained flatwood sites or in phytoremediation applications involving flooding, bedding is essential. Beds should be at least one foot high and allowed to settle for about three months before the trees are planted.

All species survive and grow best when competing vegetation is well controlled during the first two years. The initial site preparation, if bedding is involved, is usually sufficient for vegetation control during the first growing season. Preemergent herbicides provide good first season wood control. With good tree growth during the first year, the trees typically dominate other vegetation for the rest of the rotation. Without adequate vegetation control during the first year, eucalypts will grow very slowly and are likely to fail.

Planting Stock. Superior genotypes have been identified within each species through two (CT and EA) and five (EG) generations of genetic testing and selection. These superior genotypes have far better growth and frost resilience than untested trees of the same species.

EA, EB, EG, EH, and CT can all be propagated as containerized trees. Superior EG seed is readily available, and EA and CT seed is increasingly available. EG is also currently available as vegetatively propagated cultivars G3, G4, and G5, but EB seedlings and EH cultivars are no longer commercially available. While the cultivars cost ~$.60 each compared to ~$.45 per seedling, their numerous attributes typically justify their higher cost.

EA, EG, and CT should be planted at the onset of the summer rainy season when soil moisture is ample. Use of water-absorbing gel can initiate or extend the planting season by about a month. Eucalypts planted too late will not reach a size that conveys some resistance to freeze damage.

Management. Management intensity and rotation length vary with species, site, and application. For example, through the 1980s, culture of EG for pulpwood on up to 15,000 acres of flatwoods sites in southern Florida had low intensity and consisted of 1) planting about 600 trees per acre, 2) basic application of ground rock phosphate and minimal weed control through bedding, 3) 8–10 year rotation, and 4) two to three rotations.

For the fastest-growing species grown for energywood, the time from planting to harvest may be two years or less if planted on a high-quality site or intensively managed at close spacing (for instance, EG planted on muck soils at 4,000 trees/acre). To maximize production, management may include intensive culture (environmentally safe site amendment with slow release organic fertilizer and biochar, irrigation, and weed control practices).

For mulchwood production, an intermediate planting density of about 1,000 trees/acre with a rotation of some six years could produce trees of suitable size. However, EG grown for mulchwood at Palmdale (Table 1) involves relatively low intensity culture of superior planting stock.

EA, EB, EG, EH, and CT all coppice (sprout from the stump) after harvest. In the coppice rotation, tree growth may exceed first rotation growth by some 20% and shorten the time to the second harvest by at least one year, but the time of harvest is critical to coppicing success. EA and EH coppice well throughout the year, while EG and CT harvests must be done during the winter to ensure good coppicing. Coppice cycles may be repeated up to six times. Windfall risk, e.g., from hurricanes, can be managed by a combination of genetics, site, culture, and rotation length options.

References

Abichou, T., J. Musagasa, L. Yuan, J. Chanton, K. Tawfiq, D. Rockwood, and L. Licht. 2012. Field performance of alternative landfill covers vegetated with cottonwood and eucalyptus trees. Internat. J. Phytoremediation 14(Supp 1): 47-60. https://www.tandfonline.com/doi/full/10.1080/15226514.2011.607869

Andreu, M. G., B. Tamang, M. H. Friedman, and D. L. Rockwood. 2008. The benefits of windbreaks for Florida growers. Florida Cooperative Extension Service Circular FOR192. 5p. https://edis.ifas.ufl.edu/publication/FR253

Brown, M. J., J. Nowak, and J. T. Vogt. 2017. Florida's forests, 2013. Resour. Bull. SRS–213. Asheville, NC, U.S. Department of Agriculture Forest Service, Southern Research Station. 94 p. https://www.srs.fs.usda.gov/pubs/55489

Castro, E., I. U. Nieves, M. T. Mullinnix, W. J. Sagues, R. W. Hoffman, M. T. Fernández-Sandoval, Z. Tian, D. L. Rockwood, B. Tamang, and L. O. Ingram. 2014. Optimization of dilute-phosphoric-acid steam pretreatment of Eucalyptus benthamii for biofuel production. Applied Energy 125: 76-83. https://www.sciencedirect.com/science/article/pii/S0306261914002785#!

Fabbro, K. W., and D. L. Rockwood. 2016. Optimal management and productivity of Eucalyptus grandis on former phosphate mined and citrus lands in central and southern Florida: Influence of genetics and spacing. In: Proceedings 18th. Biennial Southern Silvicultural Research Conference, March 2-5, 2015, Knoxville, TN. e-Gen. Tech. Rpt. SRS-212. p.510-517. http://www.srs.fs.usda.gov/pubs/gtr/gtr_srs212.pdf

Langholtz, M., D. Carter, J. Alavalapati, and D. Rockwood. 2007. The economic feasibility of reclaiming phosphate mined lands with short-rotation woody crops in Florida. J For Econ. 12(4): 237–249.

Langholtz, M., D. R. Carter, D. L. Rockwood, J. R. R. Alavalapati, and A. E. S. Green. 2005. Effect of dendroremediation incentives on the profitability of short-rotation woody cropping of Eucalyptus grandis. Forest Policy and Economics 7(5): 806–817.

Meskimen, G. F., D. L. Rockwood, and K. V. Reddy. 1987. Development of Eucalyptus clones for a summer rainfall environment with periodic severe frosts. New Forests 3: 197–205.

Minogue, P. J., M. Miwa, D. L. Rockwood, and C. L. Mackowiak. 2012. Removal of nitrogen and phosphorus by Eucalyptus and Populus at a tertiary treated municipal wastewater sprayfield. International Journal of Phytoremediation Volume 14, 2012 - Issue 10. https://www.tandfonline.com/doi/abs/10.1080/15226514.2011.649435

Nieves, I. U., M. T. Mullinnix, M. T. Fernández-Sandoval, Z. Tian, D. L. Rockwood, and L. O. Ingram. 2014. Evaluation of four different cultivars of Eucalyptus grandis for the production of ethanol in a liquefaction plus simultaneous saccharification and co-fermentation (L+SScF) process using ethanologenic bacteria Escherichia coli SY100. In Proc: Symposium on Biotechology for Fuels and Chemicals, April 28-May 1, 2014, Clearwater Beach, FL. (poster) https://sim.confex.com/sim/36th/webprogram/Paper26586.html

Osiecka, A., and P. Minogue. 2015. Herbicides for weed control in Eucalyptus culture. Florida Cooperative Extension Service Circular FOR 310. 7p. https://edis.ifas.ufl.edu/pdf/FR/FR37800.pdf

Rockwood, D. L. 2012. History and status of Eucalyptus improvement in Florida. International Journal of Forestry Research, Volume 2012 (2012), Article ID 607879, 10 pages. https://www.hindawi.com/journals/ijfr/2012/607879/abs/

Rockwood, D. L. 2013. Eucalyptus July 2013. In: New Plants for Florida 2013 Update. http://research.ifas.ufl.edu/files/2012plants/Eucalyptus.pdf

Rockwood, D. L., B. Becker, and M. Ozores-Hampton. 2012. Municipal solid waste compost benefits on short rotation woody crops. Compost Sci. Utilization 20(2):67-72. http://www.tandfonline.com/doi/abs/10.1080/1065657X.2012.10737027

Rockwood, D. L., and R. L. Bowman. 2017. Medically related products obtainable from Eucalyptus trees. International Biology Review 1(3) p. 1-10. https://esmed.org/MRA/ibr/article/view/1615/1559

Rockwood, D. L., D. R. Carter, M. H. Langholtz, and J. A. Stricker. 2006. Eucalyptus and Populus short rotation woody crops for phosphate mined lands in Florida USA. Biomass & Bioenergy 30 (8,9): 728–734. https://www.sciencedirect.com/science/article/abs/pii/S0961953406000675

Rockwood, D. L., D. R. Carter, and J. A. Stricker. 2008. Commercial tree crops on phosphate mined lands. Florida Institute of Phosphate Research. FIPR Publication #03-141-225. https://fipr.floridapoly.edu/wp-content/uploads/2014/12/03-141-225Final.pdf

Rockwood, D. L., R. J. Dinus, J. M. Kramer, T. J. McDonough, C. A. Raymond, J. V. Owen, and J. T. Devalerio. 1993. Genetic variation for rooting, growth, frost hardiness, and wood, fiber, and pulping properties in Florida-grown Eucalyptus amplifolia. In: Proc. 22nd. Southern For. Tree Improvement Conf., June 14–17, 1993, Atlanta, GA. p. 81–88. https://rngr.net/publications/tree-improvement-proceedings/southern/1993

Rockwood, D. L., M. F. Ellis, R. Liu, F. Zhao, P. Ji, Z. Zhu, K. W. Fabbro, Z. He, and R. D. Cave. 2019. Short rotation eucalypts: Opportunities for biochar. Forests 2019, 10, 314; https://www.mdpi.com/1999-4907/10/4/314/html

Rockwood, D. L., M. F. Ellis, R. Liu, F. Zhao, K. W Fabbro, Z. He, and D. R. Derbowka. 2020. Forest trees for biochar and carbon sequestration: Production and benefits. In: Applications of Biochar for Environmental Safety, (A Abdelhafez and M Abbas, Eds), IntechOpen, DOI: http://dx.doi.org/10.5772/intechopen.92377

Rockwood, D. L., J. G. Isebrands, and P. J. Minogue. 2013. Chapter 22. Phytoremediation trees for biofuel. In: Biofuel Crops, P. B. Singh (Editor), CABI, p. 474-490. https://www.cabi.org/bookshop/book/9781845938857

Rockwood, D. L., L. Q. Ma, G. R. Alker, C. Tu, and R. W. Cardellino. 2001. Phytoremediation of contaminated sites using wood biomass. Final Report to the Florida Center for Solid and Hazardous Waste Management, June 2001. 95p. https://ef9d653c-a2d3-4777-af7f-d32bf28d5b80.filesusr.com/ugd/054abf_44a4dc03f4cb4f4dbf0e8ad39bb5ee73.pdf

Rockwood, D. L., C. V. Naidu, D. R. Carter, M. Rahmani, T. Spriggs, C. Lin, G. R. Alker, J. G. Isebrands, and S. A. Segrest. 2004. Short-rotation woody crops and phytoremediation: Opportunities for agroforestry? In: New Vistas in Agroforestry, A Compendium for the 1st World Congress of Agroforestry 2004.

P. K. R. Nair, M. R. Rao, and L. E. Buck (Editors), Kluwer Academic Publishers, Dordrecht, The Netherlands. p. 51–63. https://www.researchgate.net/profile/Donald_Rockwood/publication/226436007_Short-Rotation_Woody_Crops_and_Phytoremediation_Opportunities_for_Agroforestry/links/5626d1bc08ae4d9e5c4d47dd.pdf

Rockwood, D. L., N. N. Pathak, and P. C. Satapathy. 1993. Woody biomass production systems for Florida. Biomass & Bioenergy 5(1): 23–34. https://www.sciencedirect.com/science/article/abs/pii/096195349390004N

Rockwood, D. L., G. F. Peter, M. H. Langholtz, B. Becker, A. Clark III, and J. Bryan. 2005. Genetically improved eucalypts for novel applications and sites in Florida. In: Proc. 28th South. For. Tree Improvement Conf., June 21–23, 2005, Raleigh, NC. p. 64–75. https://rngr.net/publications/tree-improvement-proceedings/southern/2005/genetically-improved-eucalypts-for-novel-applications-and-sites-in-florida

Rockwood, D. L., S. M. Pisano, and W. V. McConnell. 1996. Superior cottonwood and Eucalyptus clones for biomass production in wastewater bioremediation systems. Proc. Bioenergy 96, 7th National Bioenergy Conference, September 15–20, 1996, Nashville, TN. p. 254–261. https://www.osti.gov/biblio/478644

Rockwood, D. L., A. W. Rudie, S. A. Ralph, J. Zhu, and J. E. Winandy. 2008. Energy product options for Eucalyptus species grown as short rotation woody crops. Int. J. Mol. Sci. 9:1361–1378. https://www.mdpi.org/ijms/papers/i9081361.pdf

Rockwood, D. L., G. H. Snyder, and R. R. Sprinkle. 1994. Woody biomass production in waste recycling systems. Proc. Bioenergy 94, 6th National Bioenergy Conference, October 2–6, 1994, Reno/Sparks, NV. p. 351–358. https://www.osti.gov/search/semantic:rockwood%20snyder%20sprinkle

Rockwood, D. L., B. Tamang, M. Kirst, and J. Y. Zhu. 2012. Field performance and bioenergy characteristics of four commercial eucalyptus grandis cultivars in Florida. In: Butnor, John R., ed. 2012. Proceedings of the 16th biennial southern silvicultural research conference. e-Gen. Tech. Rep. SRS-156. Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station. 267-268. https://www.srs.fs.usda.gov/pubs/41458

Segrest, S. A., D. L. Rockwood, J. A. Stricker, and A. E. S. Green. 1998. Biomass cofiring with coal at Lakeland Utilities. Southeastern Regional Biomass Energy Program Publication No. 219287-1, TVA, Muscle Shoals, AL. 50p. https://www.researchgate.net/profile/Donald_Rockwood/publication/253733654_Biomass_Co-Firing_with_Coal_at_Lakeland_Utilities/links/5516c84d0cf2b5d6a0f0738d/Biomass-Co-Firing-with-Coal-at-Lakeland-Utilities.pdf

Tamang, B., M. G. Andreu, C. L. Staudhammer, D. L. Rockwood, and S. Jose. 2012. Equations for estimating above ground biomass of cadaghi (Corymbia torelliana) trees in farm windbreaks. Agroforestry Systems 86(2):255-66. https://link.springer.com/article/10.1007/s10457-012-9490-z

Tamang, B, D. Rockwood, M. Langholtz, E. Maehr, B. Becker, and S. Segrest. 2008. Fast-growing trees for cogongrass (Imperata cylindrica) suppression and enhanced colonization of understory plant species on a phosphate-mine clay settling area. Ecological Engineering 32:329–336. https://www.sciencedirect.com/science/article/abs/pii/S0925857408000153

Tamang, B., V. Steel, and M. Cunningham. Evaluation of Eucalyptus varieties for commercial applications in the southeastern United States. In: Proceedings 33rd. Southern Forest Tree Improvement Conference, June 8–11, 2015, Hot Springs, AR. p. 58. https://rngr.net/publications/tree-improvement-proceedings/southern/2015

Zalesny, R. S., Jr., M. W. Cunningham, R. B. Hall, J. Mirck, D. L. Rockwood, J. A. Stanturf, and T. A. Volk. 2011. Chapter 2. Woody Biomass from Short Rotation Energy Crops. In ACS Symposium Book: Sustainable Production of Fuels, Chemicals, and Fibers from Forest Biomass (Zhu, J., et al.). p. 27-63. https://pubs.acs.org/doi/abs/10.1021/bk-2011-1067.ch002