Long regeneration periods, which result in two-layered or multilayered forest stands, are an important element of the close-to-nature forest management paradigm in central Europe. Such extended regeneration periods, however, may lead to undesirable development of advance regeneration, specifically in species such as Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) where root growth is strongly curtailed under competition. We hypothesized that root systems of naturally regenerated Douglas-fir that had grown under closed canopy for prolonged periods would be inhibited in their capacity to develop adequate structural root systems following release through removal of the canopy. Complete root systems of six approximately 25-year-old Douglas-fir that had grown for at least 12 years underneath a closed canopy before overstory removal were excavated using subterranean explosives. Root elongation, radial increment of primary lateral and vertical roots, and aboveground stem growth were investigated using retrospective analysis of growth rings. Structural roots of the previously suppressed Douglas-fir were capable of strongly responding to release from competition relative to growth prior to removal, but this response, particularly in the form of root elongation, was delayed. However, since the growth response of roots was not stronger than that above ground, an imbalanced root to shoot ratio, likely developed in trees when grown under the canopy, was not reverted. Generalizing interpretation of the derived findings of this study is limited because of the small sample size and the lack of freely grown control trees. Whether or not previously suppressed trees can develop the same physical stability as open-grown individuals therefore deserves further investigation.Résumé : De longues périodes de régénération qui produisent des peuplements forestiers biétagés ou multiétagés sont un élément important du paradigme de l'aménagement forestier proche de la nature en Europe centrale. Cependant, de telles pé-riodes prolongées de régénération peuvent entraîner le développement de régénération préétablie indésirable telle que le douglas vert (Pseudotsuga menziesii (Mirb.) Franco) dans les endroits où la croissance des racines est fortement limitée par la compétition. Nous avons formulé l'hypothèse que le système racinaire de la régénération naturelle de douglas vert qui s'était développée sous couvert fermé pendant de longues périodes inhiberait leur capacité à développer un système racinaire structural adéquat à la suite du dégagement causé par l'élimination de la canopée. Le système racinaire complet de six arbres de douglas vert âgés d'environ 25 ans qui s'étaient développés pendant au moins 12 ans sous un couvert fermé avant l'élimina-tion de l'étage dominant a été excavé à l'aide d'explosifs souterrains. L'élongation des racines, l'accroissement radial des racines primaires latérales et verticales, ainsi que l'accroissement de la tige au-dessus du niveau du sol ont été étudiés par l'analyse rétrospective des cernes annuels. Le...
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