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Within the framework of a series of forest recovery researches of a subtropical evergreen broadleaved forest, this study was carried out to measure mortality rates of tree stumps changed by species diameter at breast height (DBH) based on the surveys of 62 woody species and 1,893 tree stems taller than 1.2m in four 20m X 10m plots were recorded in 1993. At\nan August 1998 tree census five years after clearcut, all sprouting stems higher than 1.0m were identified, and the statuses of all the residual stumps were checked. The investigation showed that 382 stumps were dead without any living sprouts whereas 1,511 stumps were survived with living sprouts. The further studies showed that the mortality rates of stumps did not vary with DBH of the stand, but vary with the species DBH remarkably. The mortality rates by stump DBH within species for these whose total stump numbers ≧10 stems in the study plots were divided into four patterns: (a) With the increasing DBH, the mortality rates increased, (b) Inversely, with the increasing DBH in a certain extent, the mortality rates decreased, (c) With an increasing DBH, the mortality rates decreased at first and then increased to some extent, (d) The mortality rates were independent of DBH. The above results suggested that different species might have different mortality patterns, and that different tree species might have different rational DBH ranges for sprout natural regeneration. This knowledge could be much useful for forest recovery forecasting when the severe forest disturbances occurred in subtropical regions., 本研究は、亜熱帯常緑広葉樹林の森林回復に関する研究の一環として、1993年に沖縄島北部の琉球大学農学部与那フィールドの林地に設置された試験地を対象に、皆伐施業5年後の1998年に根株の生育と毎木調査を実施した。今回は主として、根株の生育、とくに枯死状態について報告する。皆伐施業試験地では、設定された天然林当時の樹高1.2m以上の立木62樹種、1,893個体のうち、382個体の根株が枯死し、1,511個体の根株に萌芽が認められた。根株の枯死率は、全個体で胸高直径間には明確な差がなく、樹種別の胸高直径間に差がみられた。根株個体数が10個体以上の33樹種別および胸高直径別の根株枯死率は4型に類別された：(a)胸高直径の増加にともなって枯死率も増加した（カクレミノ､タイミンタチバナなど7種）；(b)胸高直径の増加にともない一定の直径範囲で枯死率が減少した（イヌガシ､イタジイなど9種）；(c)胸高直径の増加にともない枯死率は初め減少し、その後増加した（サクラツツジ、ヤブツバキなど4種）；(d)枯死率は胸高直径と関係がなかった（イジュ、ツゲモチなど13種）。萌芽力に対して、根株枯死率の類型別に異なることが示唆された。, 紀要論文

本研究は、亜熱帯沖縄における天然林の資源植物学的研究の一環として、亜熱帯・沖縄県の主要島嶼の沖縄島、宮古島、石垣島、西表島を対象に既応の著書・文献を用いて分布植物のデータベース化をはかるために森林植物を中心とした全ての在来植物の分布種及び外来種を明らかにするために行ったものである。琉球列島全体の分布植物は、琉球植物目録(FRSAI、1994)で238科、1688属、5,473種で最も多く、Flora of Okinawa and Southern Ryukyu Island (FOSRI、1976)で239科、1,061属、2,560種、琉球列島維管束植物集覧(FRSAI、1997)、200科、949属、2,275種、琉球植物誌(FR、1975)182科、863属、2,142種の順であった。全体的に総分布種は文献間に差異があり、その主な要因は外来種の分布の取り扱いによるものと思料される。在来植物の種の構成は沖縄島FR 1,451、FRSAI 1,445、CLVFR 1,404、宮古島FR 640、FRSAI 656、CLVFR 633、石垣島FR 1,099、FRSAI 1,132、CLVFR 1,119、西表島FR 1,151、FRSAI 1,139、CLVFR 1,142で各島嶼とも分布種に大きな差異はなかった。また、島嶼別の在来種は沖縄島>西表島>石垣島>宮古島の順であった。宮古島が最も少ないのは、同島の大部分が隆起サンゴ礁の石灰岩でおおわれ、平坦な島であるため、分布植物において山地性植物の森林植物が他島に比べて少ないものと思料される。島嶼別固有植物はいずれの文献も沖縄島に多くの固有植物が分布しVJOO 16種、FR 15種、CLVFR 33種であった。ついで西表島で多くVJOO 13種、FR 10種、CLVFR 9種、宮古島、石垣島では1～3種であった。, Within the frame work of a series of plant resource studies on the natural forests in the subtropical Okinawa, the present study was undertaken to clarify the distribution of forest plant for both indigenous and exotic species on the Ryukyu Islands, especially for the 4 main Islands, i.e. Okinawa, Miyako, Ishigaki and Iriomote Islands in the Ryukyus based on the database of the five reference books. The considerable difference was found for the total number of species among the references. The plants distributed in the entire Ryukyu Islands were 238 families, 1,688 genera and 5,473 species based on Flora of the Ryukyus, Southern of Amami Island (FRSAI), which had the highest number of species, while Flora of Okinawa and Southern Ryukyu Island (FOSRI, 1976) recorded 239 families, 1,061 genera and 2,560 species. According to Check List Vascular Flora of the Ryukyu Islands (CLVFR), 200 families, 949 genera and 2,275 species were present. Flora of the Ryukyus (FR) recorded the least species with a total of 182 families, 863 genera and 2,142 species. The methods of the handling of plant distribution to the exotic species may be responsible for the obvious differences in the main factor on the total number of species among these references. For the composition of the indigenous species, in Okinawa Island, 1,451 (FR), 1,445 (FRSAI) and 1,404 (CLVFR) species were recorded; 1,099 (FR), 1,132 (FRSAI) and 1,119 (CLVFR) species in Ishigaki Island; 1,151 (FR), 1,139 (FRSAI) and 1,142 (CLVFR) species in Iriomote Island. No obvious differences were found among the 3 references. Moreover, for the abovementioned indigenous species, the order of species number were Okinawa > Iriomote > Ishigaki > Miyako. As for the least value of indigenous species in Miyako Island, it is thought that the greater part of the Island is covered with the limestone of the upheaval coral reef, and the mountainous forest plant is less than other Islands because of its smooth landform on the Island. Each reference recorded a lot of endemic plants in the Okinawa Island, with 16 species recorded in VJOO, 15 species in FR, and 33 species in CLVFR, while Iriomote Island had the second highest value for endemic plants with 13 species recorded in VJOO, 10 species in FR and 9 species in CLVFR. In Miyako or Ishigaki Islands, few endemic plants were present with a range of 1-3 only., 紀要論文