Graduate Thesis Or Dissertation
 

A comparison of prediction models for cover type transitions and their effects on harvest schedules in coastal Oregon

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/x059c9836

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  • There is considerable uncertainty associated with stand establishment in coastal Oregon. Several species can gain control of the site depending on stand conditions as well as management practices. In this study, three cover type transition models were developed using data from the Siuslaw National Forest to predict stand establishment patterns in aggregate forest planning. Two discrete alternative probability models were analyzed. The full model included the cover type and age of the mature stand before harvest as well as vegetation management treatments. The reduced model included only the cover type of the mature stand. A third model, the naive model, consisted of assigning the old-stand cover type to the regenerated stand with probability one. Discrete alternative probability models constitute a challenge in evaluation and validation. A residualgenerating procedure developed in this study allowed graphic analysis of residual plots. Although specification bias in these models remains a potential concern, the full model gave the best fit of the models analyzed in this study. The different cover type transition models developed here resulted in substantially different forest plans in terms of harvest levels, financial return, and forest structure. The full model produced forest plans with lower harvest levels and financial returns, but greater biological diversity, than the other models investigated in this study. These results were achieved primarily through the typeconversion effects of vegetation management treatments. The attractiveness of vegetation management depended on minimum rotation age requirements as well as cover type conversion policies in the forest planning formulation. Vegetation management was most effective at short minimum rotation ages. Type conversion policies requiring either constant or non-decreasing biological diversity over time resulted in forest plans in which vegetation management was consistently a marginal or unprofitable investment. Given the substantial impact of different cover type transition models on forest plan results, and the indications of systematic bias in the models tested here, additional study on predicting cover type transition patterns is recommended. Recognition of the spatial configuration of hardwood seed sources surrounding the reforestation areas is likely to be an important area of research.
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