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University of Idaho (1988)

Growth model for management of uneven-aged Cedrus atlantica stands in Morocco

Messat, Said

Titre : Growth model for management of uneven-aged Cedrus atlantica stands in Morocco

Auteur : Messat, Said

Université de soutenance : University of Idaho

Grade : Doctor of Philosophy (PhD) 1988

Résumé
A deterministic and dynamic growth model for stand projection of uneven-aged Atlantica cedar, Cedrus atlantica Manetti, was developed and applied to unregulated forest stands. Uneven-aged stands (536 hectares) in the Seheb Forest were chosen for this study. A transition matrix was built using data taken for diameter growth during the last 5, 10, and 15-year growth periods. To approach a desired target diameter-class structure, optimum harvest rates to be applied to each diameter class were determined for each growth period. Optimum harvest strategy developed for each growth period was determined from desired diameter distribution. Under optimum harvest rates, a steady state for the diameter distributions was defined for cutting cycles of 5, 10, and 15 years. Short term growth was also given. Using period by period projections, it was found that, at the optimum harvest, it would take approximately 155 years (31 growth periods), 190 years (19 growth periods), and 225 years (15 growth periods) for the diameter distribution to reach a steady state under cutting cycles of 5, 10, and 15 years, respectively. At steady state, the optimum harvest matrix, coupled with the observed transition rates overestimated the target structure by 13% for a 5-year cutting cycle and by 1% for a 10-year cutting cycle. It was underestimated by 6% under a cutting cycle of 15 years. In all cases, the inverse J-shape distribution characterizing uneven-aged stands was maintained. Changes in ingrowth function parameters and transition rates did not have a significant long-term effect on tree distribution, mortality and ingrowth. A cutting cycle of 10 years was shown to be the most appropriate management strategy. The projection matrix was shown to be a useful model for examining long-term results from the practice of different management strategies. Also, the approach used in this study can be applied to any unbalanced stand for which a target distribution of trees is desired.

Annonce (WorldCat)

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