Kevin S Glencross

Silvicultural implications arising from a simple simulation model for Endospermum medullosum in Vanuatu

SUMMARY Whitewood (Endospermum medullosum) is a tree species that shows promise for plantation timber production in Vanuatu, but few growth data are available to inform yield forecasts. Three simple relationships summarizing stand dynamics, namely height-age, diameter-height-stocking, and mortality-basal area relationships, were calibrated with data from 15 plots to form the basis of a model for silvicultural and management decisions. Despite the simplicity of the model, it offers predictions consistent with independent data. The model suggests that the optimal silviculture involves planting 635 stems/ha, thinning at 20 and 26 years, and clearfelling at age 36 when trees have a diameter of 55 cm dbh. However, many options offer a net present value within 5% of this nominal optimum. The flexibility to vary the timing and intensity of harvests over a wide range while maintaining good financial returns, coupled with good growth and timber properties, suggests that whitewood warrants further domestication and promotion in Vanuatu.

Spacing Affects Stem form, early Growth and Branching in Young Whitewood (Endospermum medullosum) Plantations in Vanuatu

SUMMARY This paper investigates the early growth response, branching and stem quality of Endospermum medullosum (whitewood) at different spacings. Whitewood plantings were established at stockings of 400–833 trees per hectare and early growth, tree stem quality and branching were quantified up to age 3 years. Growth, number of live branches and branch size were negatively correlated with stocking. The stocking of trees of acceptable quality had high spatial variation. Initial spacing in whitewood plantations can be used to manipulate branch size, crown rise and stem size; all of which are important for development of pruning and thinning regimes to produce high quality logs. If unimproved whitewood stock is used, to ensure that there are 300 stems per hectare of acceptable quality to produce sawlogs, more than 600 trees per hectare should be established at planting.

A review of site-preparation, fertilizer and weeding practices for tropical plantation species with recommendations for whitewood (Endospermum medullosum) in Vanuatu

SUMMARY The development of plantations with a new species, such as is occurring with the endemic tree Endospermum medullosum (whitewood) in Vanuatu, requires the resolution of appropriate establishment techniques. Site preparation, fertilisation and weed control have a very large impact on plantation productivity and represent major risks to plantation success. Establishment techniques for tropical species are reviewed and preliminary site preparation and fertilisation trials for whitewood reported. Trials were established at a site on Espiritu Santo island using available general purpose fertiliser with and without micronutrients at two rates. There was no effect of fertiliser over various rates of complete fertiliser with and without micronutrients, designed to provide adequate phosphorus in volcanic ash soils. Ripping had no significant effect on growth, however insufficient hand clearing of vegetation resulted in lower growth due to competition and complete machine clearing of vines results in high temperatures and decreased survival. A serious issue for whitewood establishment in single species plantations is weed management, especially vine control (Merremia spp). The time needed for weed control is influenced by initial planting density and spacing. When inter-planted with mixed gardens of food crops, weed control is not an issue due to more regular tending.

Plantation-grown whitewood timber in Vanuatu: challenges and opportunities for export and domestic use

SUMMARY Whitewood (Endospermum medullosum) is a useful timber species, previously sourced from native forests and now available from plantations in Vanuatu. However, plantation-grown whitewood will have about 30% more knotty wood than previously experienced in logs from native forest. This will impact on the economics of growing and processing whitewood, and on potential uses of the timber. Opportunities to add value to knotty wood are to produce large section structural lumber, to recover short lengths of clear wood for furniture, and to treat heartwood with preservative chemicals to enable structural use in exposed and in-ground applications.

Constraints to whitewood (Endospermum medullosum) plantation development on Santo Island, Vanuatu

SUMMARY Valuable timber trees in accessible sites in Vanuatu have been mostly removed by logging. There are large areas where plantations would likely be successful. Yet plantation establishment among landholders in Vanuatu has been limited to date, even with considerable extension support. There has been little systematic investigation of why this has occurred. The purpose of this research was to identify constraints to whitewood (Endospermum medullosum) plantation development. A participatory social research approach was used on Espiritu Santo Island to look for trends in attitudes toward plantations. This was achieved through the use of mixed methods social research to survey 139 local landholders from 42 villages. Most landholders on Santo Island were not convinced that there are good reasons to plant whitewood, at least not in large extensions. Future efforts should be focused on the development of local capacity for plantation establishment, maintenance, processing and export marketing, at a variety of scales.

Agroecology and Sustainable Rural Livelihoods: A Conceptual Framework to Guide Development Projects in the Pacific Islands

This article reviews rural development literature in the areas of sustainable livelihoods and agroecology. Combining agroecological and sustainable livelihoods approaches enables interdisciplinary research that incorporates principles from sociology, economics, agronomy and ecology. The outcome of this literature analysis alongside participatory research in Vanuatu and Fiji in 2013–2014 was the development of the integrated Agroecology and Sustainable Rural Livelihoods Framework (ASRLF). The Pacific Island nations have a well-developed traditional economy, but appropriate rural economic development has been problematic. The ASRLF seeks to function in the local Pacific Island context while also having relevance to sustainable rural development projects elsewhere.

An ecologically and socially inclusive model of agritourism to support smallholder livelihoods in the South Pacific

ABSTRACT The neglect and marginalisation of smallholders in economic and development policy contributes to increasing vulnerability of rural communities. Underinvestment in agriculture, climate change impacts and growing competition for land and water places further pressure on smallholders. In this context, this paper examines the current focus in the South Pacific on strengthening the linkages between tourism and agriculture through agritourism. The paper seeks to merge multiple discourses, by firstly reviewing the development model that is driving tourism and linkages to agriculture in the South Pacific. Secondly, agritourism as it is conceptualised in the tourism literature and thirdly sustainable tourism discourse, to identify economic activities within agritourism that contribute to enhancing smallholders’ livelihoods in the South Pacific. An ecologically and socially inclusive model of agritourism is put forward based on principles of sustainable tourism and agroecology – referred to as agroecological tourism. Agroecological tourism strengthens the linkages between tourism and agriculture while fostering sustainability principles.

Species shade tolerance affects tree basal area growth behaviour in two eucalypt species in thinned and unthinned even-aged monoculture

ABSTRACT Individual tree and stand basal area growth were studied in a thinning experiment established over two sites in subtropical eastern Australia. The experiment compared the less shade tolerant species Eucalyptus dunnii with the more shade tolerant Corymbia citriodora var. variegata, both grown in plantation monoculture. Growth was compared over a 2½−3 year period that immediately followed thinning at 5½−7½ years of age. Towards the end of the growth period, tree crown depths and leaf mass per unit area were measured at one site. Crown depth and leaf mass per area of C. citriodora were greater than of E. dunnii, characteristics consistent with a more shade tolerant species. Gross stand basal area growth of E. dunnii was faster than that of C. citriodora. Individual-tree basal area growth behaviour was consistent with inter-tree competition involving asymmetric competition for light. Opening the stand by thinning reduced inter-tree competition to near zero. In unthinned control stands, smaller, more shaded trees of C. citriodora were better able to retain their basal area growth rates than those of E. dunnii in the face of competition. In consequence, the more shade tolerant C. citriodora developed a more evenly spread frequency distribution of tree diameters than less shade tolerant E. dunnii. This would have consequences for the assortment of log sizes that would be available ultimately from monocultures of the two species.

Difference in shade tolerance affects foliage–sapwood response to thinning by two eucalypts

In eucalypt plantations in subtropical Australia, Eucalyptus dunnii exhibits greater diameter increment after thinning than more shade-tolerant Corymbia citriodora. To elucidate the mechanism underlying this difference, we investigated relationships between tree leaf area and sapwood area following thinning in 11-year-old E. dunnii and C. citriodora plantations. There was no significant difference in specific leaf area (SLA) between thinned and unthinned stands in E. dunnii and C. citriodora, whereas crown zone significantly affected SLA in the two eucalypts. At the whole-tree level non-linear leaf area (Al)–sapwood area (As) relationships were measured in both eucalypts by thinning treatment. A significant increase in Al/As ratio was only observed at the upper crown in thinned E. dunnii. The present results suggested the plastic nature of response of leaf characteristics in both eucalypts grown in different light environments and the species-specific pattern of crown-zone leaf responses to thinning in the two species, i.e. the top of the canopy appears to be driving greater growth response to thinning in the less shade tolerant E. dunnii compared with the more shade-tolerant C. citriodora. It is concluded that different thinning regimes should be applied in shade-tolerant and shade-intolerant eucalypt forests.

Preliminary carbon sequestration modelling for the Australian macadamia industry

There is a need to accurately estimate the carbon sequestration potential of many of our agricultural and horticultural industries now that the Australian Government has introduced the Carbon Farming Initiative and is planning to introduce an emissions trading scheme in 2015. This study estimates that the carbon sequestration of macadamia plantations is around 3t CO2e/ha/yr, and provides a methodology to assess the carbon footprint of the Australian Macadamia Industry. This study attempts to estimate the growth rate, and subsequently the sequestration rate of plantation grown Macadamia spp. through regression analysis of stem characteristics of destructively sampled Macadamia integrifolia var. 344. A volume increment curve was also derived using three common genetic varieties (A4, A16 & A42). This curve is used to extrapolate a carbon sequestration rate for the national macadamia plantation estate. Once volume estimates and sequestration rates are determined, an economic benefit of the carbon sequestration can be estimated by auditing the amount of carbon produced by activities such as “on farm” fuel use, fuel used in transport, and energy used in producing the product. In this way, a life cycle carbon budget can be developed that will aid the sustainable development of the macadamia and horticultural industries in Australia through the production of carbon credits from the carbon stored in the trees.