Sustainable tree biomass production

Our understanding of forest production and forest growth is incomplete. Pre sent yield tables have not predicted the recent changes in boreal and tempe rate regions of Europe. We argue that we need to have a causal understandin g built upon a mechanistic knowledge of important processes. Using a carbon /nitrogen model as a framework, important components and processes of the f orest ecosystem are discussed and the new knowledge needed is identified. P resent soil chemistry may not be fully relevant in describing plant/soil re lationships, It has been shown that the near-root environment deviates from the conditions described by bulk chemistry. Modelling is discussed as an i mportant tool for increased understanding and prediction. Sustainability of forest production is usually treated from a long-term per spective. Long-term changes can lead to deficiency or even excess of minera l nutrients, which will affect the resistance of the tree or stand to droug ht, frost as well as attacks of insects and pathogens. Recent ideas of tree vigour or vitality in relation to insects and pathogens are reviewed as a component for understanding production stability in short- and long-term pe rspectives. (C) 2000 Elsevier Science B.V. All rights reserved.