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The planting of exotic tree species such as teak ( Tectona grandis L.f.) and mahogany ( Swietenia macrophylla King) in Solomon Islands was encouraged through various governmental and foreign aid programmes. While the programmes were very successful, resulting in thousands of individual woodlots or plantations throughout the country, lack of infrastructure to give access to export markets, reluctance to thin except for financial gain, poor land use planning and very little structural support has resulted in overstocked woodlots full of poor quality trees. The situation is made worse by the problems inherent in being a small island developing state. This study examines the problems facing smallholder growers who need to access international markets for their timber and the steps being taken to attain market access for growers. We also provide some recommendations to give the growers returns on their investment, thereby encouraging a sustainable timber industry in one of the poorest countries in the World. [ABSTRACT FROM AUTHOR]

Abstract: Mulching is used to conserve soil moisture during the establishment phase of hardwood plantations in subtropical Australia since further expansion of these plantations increasingly occurs in low rainfall areas (600–900mm rainfall annually), where water stress is a major factor affecting plantation establishment and productivity. We measured the stand leaf area index (LAI) and leaf-level physiological traits of two establishing hardwood plantations in subtropical Australia by using gas exchange and stable isotopic techniques. The blackbutt (Eucalyptus pilularis) plantation is located in Pechey (average rainfall of 851mm annually) and the spotted gum (Corymbia citriodora subsp. Variegata) plantation in Proston (average rainfall of 601mm annually), southeast Queensland, Australia. The distance between the two plantations is about 200km. The results showed that mulching had no impact on tree height, stand LAI and leaf-level physiological traits of blackbutt trees. Thus, the mulch treatment did not increase the amount of water used by the blackbutt plantation. In contrast, mulching decreased foliar carbon (δ 13C) and oxygen (δ 18O) isotope compositions in the lower canopy zone, but increased the stand LAI and tree height in the young spotted gum plantation, which suggests that mulching increased the amount of water used by the spotted gum plantation. The contrasting results indicate that mulching does not guarantee increased tree growth and improved leaf-level physiological traits of hardwood plantations during the establishment phase. Tree growth and physiological response of hardwood plantations to mulching depend on the eco-physiological traits of trees and environmental factors. [Copyright &y& Elsevier]

Nitrogen (N) is an essential element associated with crop yield and its availability is largely controlled by microbially-mediated processes. The abundance of microbial functional genes (MFG) involved in N transformations can be influenced by agricultural practices and soil amendments. Biochar may alter microbial functional gene abundances through changing soil properties, thereby affecting N cycling and its availability to crops. The objective of this study was to assess the effects of wood biochar application on N retention and MFG under field settings. This was achieved by characterising soil labile N and their stable isotope compositions and by quantifying the gene abundance of nifH (nitrogen fixation), narG (nitrate reduction), nirS , nirK (nitrite reduction), nosZ (nitrous oxide reduction), and bacterial and archeal amoA (ammonia oxidation). A wood-based biochar was applied to a macadamia orchard soil at rates of 10 t ha −1 (B10) and 30 t ha −1 (B30). The soil was sampled after 6 and 12 months. The abundance of narG in both B10 and B30 was lower than that of control at both sampling months. Canonical Correspondence Analysis showed that soil variables (including dissolved organic C, NO 3 − –N and NH 4 + –N) and sampling time influenced MFG, but biochar did not directly impact on MFG. Twelve months after biochar application, NH 4 + –N concentrations had significantly decreased in both B10 (4.74 μg g −1 ) and B30 (5.49 μg g −1 ) compared to C10 (13.9 μg g −1 ) and C30 (17.9 μg g −1 ), whereas NO 3 − –N concentrations increased significantly in B30 (24.7 μg g −1 ) compared to B10 (12.7 μg g −1 ) and control plots (6.18 μg g −1 and 7.97 μg g −1 in C10 and C30 respectively). At month 12, significant δ 15 N of NO 3 − –N depletion observed in B30 may have been caused by a marked increase in NO 3 − –N availability and retention in those plots. Hence, it is probable that the N retention in high rate biochar plots was mediated primarily by abiotic factors. [ABSTRACT FROM AUTHOR]