Abstract
BackgroundTaiwania (Taiwania cryptomerioides Hayata) is a relict tree species found mainly in Taiwan, with smaller populations in China, Vietnam, and Myanmar. Taiwania is considered to be vulnerable to extinction. The objective of this research was to develop a model to predict the mortality of taiwania from climate and other mensurational variables.MethodsThe mensuration, mortality, and climate data came from permanent sample plots established as thinning experiments and a nearby climate station. The data were analysed using logistic regression with individual tree mortality as the response variable.ResultsThe important predictor variables of mortality were social status [defined as diameter at breast height (dbh) divided by average dbh] and annual precipitation in the year of death. The probability of mortality increased as social status decreased and as annual precipitation increased. The positive correlation between mortality and precipitation is likely a consequence of typhoons since precipitation and mortality caused by wind throw both result from typhoons.ConclusionsClimate change could increase the number and severity of typhoons occurring in Taiwan. This may increase the mortality rate of taiwania, which would detrimentally affect the viability of taiwania populations.
Highlights
Taiwania (Taiwania cryptomerioides Hayata) is a relict tree species found mainly in Taiwan, with smaller populations in China, Vietnam, and Myanmar
Self-thinning theory suggests that DENSITY would be an important predictor variable (Westoby 1984; Yoda et al 1963); the
High levels of precipitation due to typhoons at a research site in northern Taiwan resulted in the leaching of nutrients from the soil (Lin et al 2011), but the loss of nutrients due to leaching only lasted for a short time and slow decomposition rates of leaf litter at the site allows trees to take up most of the mineralised nutrients before they are leached away
Summary
Taiwania (Taiwania cryptomerioides Hayata) is a relict tree species found mainly in Taiwan, with smaller populations in China, Vietnam, and Myanmar. Broadleaf forests are generally found at lower elevations but Fourteen tree species are currently of conservation concern in Taiwan. One of these is taiwania (Taiwania cryptomerioides Hayata), which is a species considered vulnerable to extinction (Thomas and Farjon 2016; World Wildlife Fund 2017). Logging in national natural forests in Taiwan was prohibited in 1992 to protect forests from overexploitation and clearcutting, on mountain slopes, and to provide wildlife habitat (Shang 2013). Due to these conservation measures, the population of taiwania is currently stable vulnerable (Thomas and Farjon 2016). Commercial logging is done in plantations, and the annual harvest of all tree species is typically less than 50,000 m3 per year (Shang 2013)
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