Site assessment for farm forestry in Australia and its relationship to scale, productivity and sustainability

Trees are being established on substantial areas of Australian farmland, often extending into districts where forestry has not been previously practiced. Irrespective of purpose-wood production, increased water use, erosion control, habitat restoration, carbon sequestration or bio-energy production-the benefits of farm forestry depend on tree survival and adequate growth. Site assessment has been mainly used for the prediction of tree performance but it can be extended to form the basis for site-specific management. Site assessment needs to provide information on species and management inputs suitable to a site's inherent environmental attributes so that the aim of maximum profitability can be achieved while maintaining a sustainable use of resources. A new site concept for farm forestry is presented that reflects these factors. This new site concept is defined as the integrated effect of environmental factors that influence the potential growth of a particular tree genotype and affect the soil management of that stand of trees to produce a particular product or output. This concept of site is environment-based, independent of the presence of trees, and includes an explicit acknowledgement of a hierarchy of scale (both spatial and temporal) and how it affects what environmental factors need to be assessed. The goal for site assessment for farm forestry is to develop pragmatic, robust and quantitative interpretations from the measured data to aid multiple aspects of plantation management. A pragmatic approach to field survey is required, with data gathering (whether morphological, analytical or electronic) being based on demonstrated benefit rather than routine prescription, guess-work or tradition. Site assessment needs to be linked to well-designed species trials and permanent growth plots so continual evolution and improvement of edaphic and silvicultural relationships can be incorporated into future modifications