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AGROFORESTRY RESEARCH – THE JCU NELDER WHEEL
A Nelder wheel was established on JCU’s Townsville campus in August 1999, using Khaya senegalensis (African mahogany) supplied by North Queensland Afforestation Association. The trees are planted along the spokes of the wheel at increasing spacings – allowing study of tree growth at different densities (which relates to plantation management/thinning and yield) and growth of pasture along the shade gradient. The 16 replicated spokes allow a range of other studies to be made (e.g. response to fertiliser treatments, watering regimes, pruning techniques etc.)
Some close spaced blocks were also established for shading experiments, and to provide sacrificial trees for harvesting, to determine relationships between age, height, diameter and biomass and nutrient standing stocks.
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The JCU Nelder wheel in December 2004 - 5 year’s old |
The layout of the Nelder wheel -16 spokes with 10 trees along each, spaced at 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 and 5.5 m spacings. |
Previous Research
An initial purpose for these plantings was to provide a shade gradient for a study of shade-tolerance of pasture legumes, undertaken by Heath Addison and supported by RIRDC. Hence the close initial spacings. Introduction of legume cover crops into plantations can reduce erosion, shade the soil in the early establishment phase, increase soil organic matter and soil biological activity, improve soil structure and fertility, and increase the growth rate of trees (Jayasinghe 1991; Lal et al. 1979). The grazing of cattle under tree plantations can result in several benefits, including increased and diversified income, soil stabilisation, and higher plantation crop yield through better weed control and nutrient cycling, including nitrogen accretion (Shelton 1991).
Heath looked at growth of Clitoria ternatea (Butterfly Pea), Chamaecrista rotundifolia (Wynn Cassia) and 4 accessions of Arachis under the blocks, and the first 2 species, plus Centrosema brasilianum (cv. Ooloo, Centro) and Stylosanthes hamata (Caribbean Stylo) in the Wheel. As well as pot trials in the shade-house, he had other field trials at Clare and Babinda.
Heath found that several species still produced more than 60% of their maximum yields under 76% shade. Of 35 cultivars examined, 16 were potentially useful. The most promising species for the wet tropics were Desmodium intortum (Green-leaf Desmodium), Calopogonium mucunoides, Arachis pintoi, D. ovalifolium, D. canum, Centrosema acutifolium, Pueraria phaseoloides, D. heterophyllum, C. pubescens, D. uncinatum and C. macrocarpum. Clitoria ternatea, Arachis stenosperma, Macroptilium lathyroides (Phasey Bean), M. atropurpureum (Siratro) and Centrosema brasilianum were the most successful of the species suited for seasonally dry tropical regions. Chamaecrista rotundifolia was most suited to conditions where slashing was frequent and, as such, may prove useful in plantations that are frequently defoliated (slashing or grazing), or where understorey growth is kept low.
However, many of the species identified as shade tolerant, or being relatively productive under shaded conditions, have a climbing/twining habit that can cause concern in tree plantations, particularly in respect to potential smothering of small trees. When the climbing species are removed the remaining species recommended for the wet tropics are D. intortum, A. pintoi, D. ovalifolium, D. canum, D. heterophyllum and D. uncinatum, while A. stenosperma shows potential for the seasonally dry tropics. Nevertheless climbing species may still be useful beneath older plantations, or where a higher level of pasture management is acceptable in order to help prevent smothering of trees through controlling the frequency and intensity of grazing.
Current research
See Jacob Thomson’s project.
Related publications
Adams, F. (1995). Aspects of the Nutrition of Four Tropical Hardwood Species Grown in Three North Queensland Forest Soils. Honours thesis, James Cook University, Townsville.
Addison, H. (2005) Shade Tolerance Of Tropical Forage Legumes For Use In Agroforestry Systems. Ph.D. thesis, James Cook University, Townsville.
Addison, H., Congdon, R., Gardiner, C. & Holtum, J. (2000). Legumes for forestry systems. In: Snell A. & Vize S. (Eds) AFG2000 Proceedings of the Biennial Conference of the Australian Forest Growers, Cairns, September 2000, p. 231-234. Australian Forest Growers, Kingston, ACT.
Addison, H. & Congdon, R. (2001). Legumes for agroforestry systems. Proceedings of the 10th Australian Agronomy Conference, Hobart, 2001.
Addison, H. & Congdon, R. (2003). Identifying tropical pasture legumes for use in farm forestry. Agroforestry News 12(4), 18.
Amar, A. L. (1999) Edaphic Adaptation of a Range of Introduced Forage Legumes to Contrasting Conditions in Northern Queensland, Australia. Ph.D. thesis, James Cook University, Townsville.
Amar, A.L., Gardiner, C.P. and Congdon, R.A. (1996). Promising forage legumes for ruminants in shaded niches. Proceedings of the Small Ruminant Production: Recommendations for South East Asia Conference, 12-15 May 1996. pp. 225- 228. Parapat, Indonesia.
Amar, A.L., Congdon, R.A., Gardiner, C.P. & Coventry, R.J. Effects of shade on the performance of some tropical forage legumes.
Amar, A.L., Congdon, R.A., Coventry, R.J. & Gardiner, C.P. Responses of selected tropical forage legumes to imposed drought.
Arche, N. (1995). A Comparative Study on the Germination, Seedling Characteristics, Allelopathic and Competition Responses of Four Species of Albizia. M.Sc. thesis, James Cook University, Townsville.
Arche, N. (1995). Germination and seedling responses of some selected Albizia species to the allelopathic substances from Eucalyptus. The Philippine Scientist 32, 85-102.
Arche, N. C. (1997). Responses of selected Albizia species to the allelopathic substances from Eucalyptus at seedling stage under shade house conditions. In Zabala, N.Q. (Ed) International Workshop on Albizia and Paraserianthes Species. pp. 80-90. Winrock International, Arkansas, USA.
Claussen, J.W. (1996). Acclimation abilities of three tropical rainforest seedlings to an increase in light intensity. Forest Ecology and Management 80, 245-255.
Claussen, J. W. (2000). Tropical Rainforest Regeneration in North Queensland: Establishment, Survival, Growth and Nutrient Dynamics of Several Tropical Rainforest Tree Species During their Seedling and Sapling Stages. Ph.D. thesis, James Cook University, Townsville.
Congdon, R.A. & Addison, H. (2003). Optimising nutrition for productive and sustainable farm forestry systems - pasture legumes under shade. Publication No. 03/113, Rural Industries Research and Development Corporation, Barton, ACT. 99 pp. [pdf available]
Warburton, P. (1999). Growth Response of Cardwellia sublimis F. Muell. and Grevillea robusta A. Cunn. ex R.Br. to Differing Light and Available Phosphorus Regimes: Implications for Silviculture and Farm Forestry. Honours thesis, James Cook University, Townsville.
Content created by Bob Congdon
Updated on 4-February-2008