Effects of water, nutrients and their interactions on tree growth, and plantation forest management practices in Australasia: A review

Abstract

The amount and distribution of rainfall throughout the year is used to highlight climatic differences between Australia and New Zealand. Plantation forest growth is strongly influenced by both available moisture and nutrients. Practices such as cultivation and mounding (bedding) are used on wet sites, whereas cultivation, ripping, weed control, mulching andheavier thinning regimes are recommended for dry sites. Management of nutrients to improve growth includes some of the practices listed above which enhance moisture relationships. Nutrient conservation measures and the selection of planting stock with better root systems to explore the soil are suggested as methods to improve growth, along with the direct application of nutrients in fertiliser, sewage effluents and wastes. Responses to a questionnaire distributed to the major forestry enterprises in Australia showed that practices with very conspicuous benefits (e.g. weed control) had generally been accepted, but the lead-time for implementation of positive research and development was still excessive. A number of other promising practices (e.g. mycorrhizal inoculation of nurseries) had only received minimal or at best a moderate acceptance by managers. In reviewing the positive impact of recent past research on management practices, we suggest that more information on the interaction of moisture availability and nutrition along with detailed research on both positive and negative effects of cultivation is required. The potential benefits from the use of wastes and effluents within forests to supply both water and nutrients will ensure the development of this practice. Experiments should be designed to explore the interactions between genetically improved stock, sites and cultural treatments, as well as physiological processes determining growth.