日時 8月25日(水) 18:00 -
場所 北大地球環境A棟309


宮本和樹 (北海道大学・地球環境)

 インドネシア・カリマンタン島には代表的な熱帯低地多雨林とともにヒース林(ケ ランガス林)とよばれる森林が発達している。ヒース林は硅砂質土壌という貧栄養環 境下に成立し,比較的低い樹高,均一な樹冠,小さく硬い葉などといった特徴をもち, 樹木の種多様性の高い熱帯林域にあって,最も識別が容易な森林群系であるといえる。 この特徴的な森林の構造と相関を決定づけている種々の要因に関する研究はまだ十分 にはなされていない。

 本研究は,ヒース林における生産量と空間構造を把握し,他の森林群系と比較する ことにより,この特徴的な森林の成立要因を解明することを目的として進められてい る。今回は推定された現存量といくつかの構成樹種の相対生長関係の比較について報 告する。

Elateriospermum tapos (Euphorbiaceae):
Spatial distribution, survival and growth
in a mixed dipterocarp forest

Herwint SIMBOLON (ボゴール植物標本館,インドネシア科学院生物学研究所植物学部門)

The second important family after Dipterocarpaceae, in a mixed dipterocarp forest (MDF) is Euphorbiaceae. Number of species and individuals of tree of Euphorbiaceae family per area was often found more than of Dipterocarpaceae. In a 1-ha plot at Gunung Berui, West Kalimantan, Suzuki et al, (1992) reported that number of species and individuals of Euphorbiaceae were 35 and 254, while those of Dipterocarpaceae were 22 and 193, respectively. Among Euphorbiaceae species, the most abundant and dominant in the study area was Elateriospermum tapos. This paper intends to examine the patterns of local distribution and the relationship among some in the plot. The paper also deals with the mortality and growth of the species in both closed forest and gap. The analysis was made based on the data collected from the plot between 1992 and 1998. Only 43.5% of produced seeds in a period of mass fruiting season could be escaped from predators and proceed to the next seedling stage. The escaped seedlings were drastically dropped on the following year of mass fruiting season and gradually increase in the next successive years. The species was well regenerated, has a stable population, and contagiously distributed in the study area. Mortality of shorter seedlings was higher than of taller seedlings, and the mortality of seedlings in the gap was consistently higher than of in closed forest either in first or in the second years. The mortality rate of seedlings were related linearly to the initial number of seedlings, but not to the total basal areas, density, canopy depth, canopy cover and relative light illuminant in the sub-plots. The growth strategy of the species as indicated by relationships among measured parameters drew a simple linear. The growth pattern of diameter, height and canopy in each individual plant of the species were increase proportionally, and closely dependent one to another. The RGR was tended to decrease in hyperbolic curve by increasing the height of seedlings and saplings. By the same patterns, the RGR of seedlings and saplings in the gap were consistently higher than of in the closed forest. The RGR of height on seedlings and saplings or the RGR of diameter on trees in the sub-plots was not significantly related to the total basal areas, density, canopy coverage and relative light illuminant in the sub-plot. For all individuals of tree categories, the RGR of dbh also tended to decrease as increasing of tree diameter class.


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