Classification of Taiwan forest vegetation

Aim We identify the main forest vegetation types in Taiwan, provide their formal definitions and describe their species composition, habitat affinities and distribution. Location Taiwan. Methods A data set of 9822 vegetation plots with environmental characteristics recorded in the field or derived from digital maps in GIS was compiled from historical literature and an extensive field survey. Using expert knowledge, 6574 of these plots were used to build a classification into broad vegetation types. The units of the resulting classification were formally defined using a Cocktail determination key, which can be used for the automatic assignment of new vegetation plots to these vegetation types. Results Twelve vegetation types of zonal forests and nine types of azonal forests were distinguished. Zonal types in the subtropical region, from high mountains to foothills, are Juniperus subalpine coniferous woodland, Abies–Tsuga upper-montane coniferous forest, Chamaecyparis montane mixed cloud forest, Fagus montane deciduous broad-leaved cloud forest, Quercus montane evergreen broad-leaved cloud forest, Machilus–Castanopsis sub-montane evergreen broad-leaved forest, Phoebe–Machilus sub-montane evergreen broad-leaved forest and Ficus–Machilus semi-evergreen foothill forest. Zonal types in the tropical region, from high mountains to foothills, are Pasania–Elaeocarpus montane evergreen broad-leaved cloud forest, Drypetes–Helicia sub-montane evergreen broad-leaved forest, Dysoxylum–Machilus foothill evergreen broad-leaved forest and Aglaia–Ficus foothill evergreen broad-leaved forest. Azonal types are Illicium–Cyclobalanopsis tropical winter monsoon forest, Pyrenaria–Machilus subtropical winter monsoon forest, Diospyros–Champereia tropical rock-outcrop forest, Zelkova–Quercus subtropical rock-outcrop forest, Pinus successional woodland, Alnus successional woodland, Trema–Mallotus successional woodland, Scaevola–Hibiscus seashore woodland and Kandelia mangrove. Conclusions The diversity of forest vegetation in Taiwan is strongly structured by the temperature and moisture gradient. Along the temperature gradient, five altitudinal zones can be recognized. Azonal forest types develop at sites affected by the winter monsoon, on steep slopes, rocky soils, in seashore saline habitats and in places disturbed by fire, landslides and human activities. Zonal vegetation contains a higher ratio of endemic and Pacific species and occurs in wetter habitats, whereas azonal vegetation contains co-existing species from different regions and usually occurs in drier habitats.