The role of forest productivity in defining the sustainability of plantation forests in New Zealand

New Zealand has signed an international agreement that commits it to report on progress towards sustainable forest management as measured by indicator s grouped within seven criteria. This paper evaluates the role of forest pr oductivity in defining the sustainability of plantation forests in New Zeal and. A key factor dictating the extent of the plantation forest industry in New Zealand is profitability. Therefore, forest productivity is an importa nt criterion of sustainability because of its important relationship with e conomics and profitability. Another important issue is whether plantations could be grown for an indefinite number of rotations without adversely affe cting the site's capacity for biomass production. Where management practice s lead to reductions in productivity, some form of amelioration is required and, as long as this is economically viable the practice is still sustaina ble. Forest productivity is not a good indicator of soil quality because of the confounding effects of plantation management. While improved modeling techniques may help to overcome this problem, measurement of soil- or tree- based indicators may provide a more sensitive measurement of soil quality. For a given soil type, if the effect of management practices on the soil in dicator and the effect of the soil indicator on forest productivity were kn own, then an assessment could be made of the impact of various management p ractices on productivity (or other sustainability criteria). This would all ow the establishment of management guidelines, constraints, and ameliorativ e requirements necessary to maintain or enhance soil quality. (C) 1999 Else vier Science B.V. All rights reserved.