| Summary: | Taiwania (Taiwania cryptomerioides Hayata) and red cypress (Chamaecyparis formosensis (Matsum.)) are two red-listed species found mostly in Taiwan. A better understanding of the mortality patterns is necessary for good forest management of taiwania and red cypress, which is critical given that they are vulnerable and threatened species, respectively. The data for this project come from thinning trials where high-density plantations were established and later thinned. Mortality due to thinning was not included in the analysis. The mortality data were fitted to an exponential function using a negative binomial distribution model under a finite mixed modeling framework with stand density measures as predictor variables. The negative binomial distribution was zero-inflated for red cypress. Maximum mortality rates were fitted to the same exponential function used to model the mean response. Generally, average and maximum mortality rates increased as stand density increased, with stocking and average tree basal area having a large influence on mortality. Mortality rates were higher for red cypress than for taiwania. The differences in mortality rates could be due to the species relative shade tolerance or their ability to withstand competition. The mortality models can be used for developing thinning prescriptions and managing these species for conservation.
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