Determining the sustainable normal irregular condition: A provisional study on a transformed, irregular mixed species stand in Scotland
The aim of this study was to determine whether the sustainable irregular condition has been achieved in a rare example of a mixed-species irregular stand located in Faskally Forest, Scotland. The stand has been undergoing transformation over the past 60years and is now managed under the selection system. Comparisons of diameter distribution, stand increment and recruitment through natural regeneration were made in a 1ha permanent sample plot following two harvesting interventions separated by an interval of 6years. Results indicate that while the age-class distribution was approximately bimodal, the stem number/diameter distribution followed a negative exponential curve, a key characteristic of the balanced irregular state. The q-value, representing the diminution of stem numbers from one diameter class to the next, remained relatively stable between the first and second inventories (1.6 and 1.5, respectively) in spite of a reduction in overall stem numbers and basal area. Nevertheless, the stand appears to be in a state of flux, with a clear shift in species composition observed within the regeneration pool between inventories; the shade- and semi-shade-tolerant species being favoured at the expense of the shade-intolerant species. Recruitment through natural regeneration appears to have responded to the reduction in canopy and basal area in the harvesting intervention before the second inventory, although it is not clear whether this is sufficient to maintain the distribution in perpetuity. Alternative stem number/diameter distributions are considered in terms of biological and economic sustainability.
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Document Type: Research Article
Affiliations: Department of Forestry, School of Biological Sciences, University of Aberdeen, Aberdeen, UK
Publication date: 2007-01-01