Evaluation of mixed-effects models for predicting Douglas-fir mortality

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• 作者：Jeremiah D. Groom ; ^{jgroom@odf.state.or.us} ; ^{jeremygroom@gmail.com} ; David W. Hann ^{david.hann@oregonstate.edu} ; Hailemariam Temesgen ^{hailemariam.temesgen@oregonstate.edu}
• 关键词：Generalized linear model ; Mixed model ; Douglas-fir ; Mortality
• 刊名：Forest Ecology and Management
• 出版年：2012
• 期刊代码：54_03781127
• 类别：abs
• 出版时间：15 July, 2012
• 卷：276
• 期：Complete
• 页码：139-145
• 文件大小：349 K

摘要

We examined the performance of several generalized linear fixed- and mixed-effects individual-tree mortality models for Douglas-fir stands in the Pacific Northwest. The mixed-effects models accounted for sampling and study design overdispersion. Inclusion of a random intercept term reduced model bias by 88%relative to the fixed-effects model; however, model discrimination did not substantially differ. An uninformed version of the mixed model that used only its fixed effects parameters produced predicted mortality values that exceeded the fixed-effects model bias by 31%. Overall, we did not find compelling evidence to suggest that the mixed models fit our data better than the fixed-effects model. In particular, the mixed models produced fixed-effects parameter estimates that predicted unreasonably high mortality rates for trees approaching 1 m in diameter at breast height.