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.
We examined the typhoon wind disturbance regime of the Fu‐Shan Experimental Forest in northeastern Taiwan. Mean number of typhoons passing within 200 kilometers of Taipei (40 kilometers from the site) was 1.4 per year. Category 4 and 5 typhoons, which are intense enough to uproot large numbers of trees, occurred every 8.3 and 12.5 years respectively, although it is likely that some category 4 and 5 typhoons did not produce extensive blowdowns at Fu‐Shan because the area of maximum winds missed the study site. Uprooting was more common than snapped boles; the most common damage to trees, however, was probably defoliation, although this damage was not quantified in the current study. Thirty‐five percent of wind‐damaged trees were associated with a gap. Six percent of the land area was in gaps. Canopy turnover time was calculated at 175 years when all gaps ≤ 9 years old were included in the calculation, but the time decreased when older gaps were excluded from the calculation. Turnover time was somewhat higher than calculated for other tropical forests. Because turnover time increases as the percent of land in gaps decreases, the short life span of gaps at Fu‐Shan probably contributed to our higher calculated time. Probability of being damaged was not related to tree species identity, and only a few species of trees were found regenerating in gaps. Principal Components Analysis indicated that damaged trees varied largely in treefall orientation and aspect; gaps varied primarily in aspect and in gap size.
The litterfall in a subtropical broadleaf forest within the Fushan Experimental Forest in northeastern Taiwan was monitored for 9 years. Mean annual litterfall was very sensitive to typhoon frequency and intensity, ranging from 3 to 11 Mg·ha -1 ·year -1 . Litterfall was significantly higher in years with strong typhoons than in years without typhoons, and the number of strong typhoons explained 82% of interannual variation in litterfall. Nutrient-use efficiency (dry mass/nutrients in litterfall) was high for N, but low for P compared with other tropical forests. This result supports the idea that the study forest is P limited but not N limited. Nutrient loss via litterfall represents a large percentage of aboveground biomass, especially during years with strong typhoons (e.g., 19%-41%, 15%-40%, 5%-12%, for N, P, and K, respectively). Forests that experience infrequent wind disturbance (e.g., temperate or boreal forests) can gradually regain any lost nutrients prior to the next disturbance; this is different from the situation observed in the Fushan Experimental Forest. At Fu-shan the pattern of not responding to typhoons with a flush of new growth appears to be an adaptation to the frequency with which there are multiple typhoons affecting the forest in a single year. Nutrient loss in litterfall caused by frequent typhoon disturbances appears to limit tree growth and contributes to the very low canopy height of the Fushan Experimental Forest.Résumé : La chute de litière dans une forêt décidue subtropicale située dans la forêt expérimentale de Fushan dans le Nord-Est de Taiwan a été suivie pendant 9 ans. La chute annuelle moyenne de litière était très sensible à l'intensité et la fréquence des typhons, variant de 3 à 11 Mg·ha -1 ·an -1 . La chute de litière était significativement plus élevée lors des années avec de violents typhons que lors des années sans typhons. Le nombre de typhons violents expliquait 82 % de la variation inter annuelle dans la chute de litière. L'efficacité d'utilisation des nutriments (masse sèche/nutriments dans la chute de litière) était élevée pour N mais faible pour P comparativement à d'autres forêts tropicales. Ce résultat supporte l'idée que P est un facteur limitant dans la forêt sous étude mais que N ne l'est pas. La perte de nutriments via la chute de litière représente un important pourcentage de la biomasse épigée, particulièrement lors des années avec de violents typhons (p. ex. respectivement 19-41 %, 15-40 % et 5-12 % pour N, P et K). Les forêts qui ne sont pas fré-quemment soumises à des perturbations par le vent (p. ex. les forêts tempérées ou boréales) peuvent graduellement retrouver les nutriments perdus avant que survienne une autre perturbation; cela est différent de la situation observée dans la forêt expérimentale de Fushan. À Fu-shan, le fait de ne pas produire de nouvelles pousses à la suite d'un typhon semble être une adaptation à la fréquence avec laquelle de multiples typhons affectent la forêt au cours d'une même année. La perte de nutriments causée par de fréqu...
Throughfall chemistry of a subtropical rain forest in Taiwan was examined for 3 yr to understand patterns of nutrient inputs to the forests of this region. Annual throughfall fluxes for NH+4, NO−3, and SO2−4 (89, 28, and 83 mmol/m2/yr, respectively) were close to the levels of the most polluted areas in the temperate region. The lack of major emission sources near the study site indicates that most of the pollutants were regional and/or international in origin. High rates of cation leaching from the forest canopy were evident and the pattern is similar to that seen in heavily polluted temperate forests. Typhoons played a central role in the hydrology of the study forest with eight typhoons contributing 26% of the total rainfall in 320 h over the three years monitored. This typhoon input represented 20% of the total precipitation flux of the ions found in seasalt aerosols but less than 10% of anthropogenically enriched ions. Canopy leaching was an important source of base cations in throughfall and NO−3 was retained in the canopy. Using the Na‐ratio method the contribution of dry deposition relative to precipitation input was estimated to be 40% in the summer and 10% in the winter. The contribution of dry deposition to total deposition is small relative to many temperate forests and might result from the lack of long dry periods between precipitation events. Net throughfall flux was negatively related to precipitation concentration for H+, NH+4, NO−3, and SO2−4, suggesting that passive movement was important in characterizing throughfall dynamics.
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