Using mechanistic modeling within forest ecosystem restoration

In Europe, fast growing tree species such as Norway spruce and Scots pine were promoted in large areas typically covered with broadleaf or mixed species stands to increase commercial timber growth. Recent research suggests that such secondary coniferous stands may have an increased susceptibility to environmental stress factors because of soil nutrient depletion as well as retarded litter decomposition. One option to increase the resilience of such stands is to reintroduce broadleaf trees because one species may directly benefit from the presence of another. A method to assess such effects and how their impact may change over time is the adaptation of mechanistic models. Such models integrate the main biogeochemical and physiological processes and are specifically designed to describe the interaction between plants and the environment. The purpose of this study is to enhance the ecophysiological representation of single tree species within an existing mechanistic model, a pre-condition for assessing forest ecosystem restoration scenarios. We changed ecophysiological constants using published literature related to Norway spruce and common beech for a wide range of central European forests and evaluated model predictions using observations on stand transpiration, seasonal water balance, leaf area index, photoassimilation. tree volume. tree ring size, and soil and litter carbon and nitrogen content. A model validation, using an independent data set on tree volume, soil carbon and nitrogen content from a total 44 spruce and beech stands across the northern part of the Austrian Alps, exhibited no bias between model predictions and field observations. (C) 2002 Elsevier Science B.V. All rights reserved.