Leaf demography and growth pattern of the tree fern Cyathea spinulosa in Yakushima Island
2007 年 16 巻 1 号 p. 47-57
詳細
2007 年 16 巻 1 号 p. 47-57
We studied the growth and leaf demography of tree fern Cyathea spinulosa Wall. ex Hook at a 40 m×100 m plot with 163 tree ferns in lowland of Yakushima Island, southern Kyushu to clarify its life history. The 70 healthy individuals were periodically observed (16 times) from March 1997 to March 2000. The numbers and lengths of leaves on a stem increased with stem length up to 20 leaves of a maximum of 3 m in length. Most sporophylls flushed in spring and most trophophylls flushed in summer, although a few leaves emerged continuously all year around. Leaf death followed the annual pattern of emergence with some delay. Leaf longevity was greater on leaves that emerged in summer than those in other seasons; the average leaf longevity was 7.1 months. The growth rate of the stem decreased gradually as stem length increased; the average annual growth in stem length was 8.9 cm/year. The lifespan of individual tree ferns in Yakushima Island were estimated less than 50 years. The pattern of continuous leaf emergence and the short leaf longevity may result from its pioneer habit in the successional stage.
