An Altitudinal Study on Vegetation of Tatachia Sub-alpine Ecosystem
The Experimental Forest, National Taiwan University,
12, Sec. 1, Chienshan Rd., Chushan 557, Nantou, Taiwan, ROC.
Tel: +886-49-642181 Fax: +886-49-641184
Three permanent plots, each for a major vegetation type, were established in Tatachia sub-alpine ecosystem. The grassland plot, one hectare in size, faces east and with slopes between 20 o and 30 o. Because of its thin soil layer and frequent fires, the dominant plant species are Yushan cane (Yushania niitakayamensis), Alpine silver grass (Miscanthus transmorrisonensis). Small shrubs like Rhododandron rubropilosum and Pieris taiwanensis are also found. The herbaceous layer mainly consists of Lycopodium multispicatum, Selaginella involvens, Pteridium aguilinum subsp. wightianum) and solidago virga-aurea var. leiocarpa. The Taiwan Hemlock (Tsuga chinensis var. formosana) plot is a one hectare, north facing, steep sloping (30o-50 o), and thick forest floor forest. The dominant species is Taiwan hemlock. Other canopy species are Taiwan red cypress (Charmaecyparis formensis), Taiwan armand pine (Pinus armandii var. mastersiana), and Trochodendron aralioides. The main species of the shrub layer are Rhododendron morii, Scheffera taiwaniana and Eurya spp. The understory is covered by a thick layer of Yushan cane. Probably due to past disturbances, the vegetation composition and physiognomy of this permanent plot significantly differ from other hemlock forests in Taiwan. The type and frequency and intensity of disturbances are remained to study. The Morrison spruce (Picea morrisonicola) Forest plot which is a two hectares, northwest facing, steep sloping (30 o -45 o) and deep soils ecosystem. The dominant species is Morrison spruce. Other canopy species are Taiwan hemlock, armand pine and Taiwan red cypress. Under canopy tree layer mainly consists of Litsea morrisonensis, Neolitsea acuminatissima, Daphniphyllum himalaense subsp. macropodum. Small shrubs are Pittosporum illicoides, Ligustrum microcarpus and Berberis kawakamii. The understory layer is rich in species and has a high diversity, with Ploystichum parvipinulum, Ctenitis transmorrisonensis, Peranema cyatheoides, Helictotrichon abitetorum, Ophiopogon formosanum and Calanthe caudatiabella etc. as the dominant species. Yushan cane is rarely seen within the plot.
The stand structure of the Morrison spruce forest showed that DBH of Morrison spruces within the plot range from 15 cm to 120 cm, with the majority of the DBH between 15 cm and 45 cm. Most of the Morrison spruces are between 80 to 90 years old, with the maximum age reaching 400 years old. Cluster analysis revealed that the structure of the stand has two main clusters, with significant differences in size and age between the clusters. The one formed by larger size Morrison spruces represents the mature patches of the stand, whereas the one formed by smaller size Morrison spruces and Taiwan hemlocks represents the establishing patches of the stand. Field observations suggest that Morrison spruce cannot regenerate in establishing toward mature patches of the stand. Seedlings and saplings of Morrison spruce can only be found in large gaps formed mainly by landslides and upstream gully erosion. Through a mosaic replacement among gaps, establishing and mature patches, the Morrison spruce forest within the research site is able to regenerate and maintain its dominant status.
Key words: Permanent plot, Tatachia sub-alpine ecosystem, Taiwan