Paleoenvironmental Analyses of the Buried Peat Deposit during the mid-Holocene at the Desaki Coast in Tamano City, Okayama Prefecture, Weatern Japan

The buried peat deposit was foud in the sand beach on the Desaki coast (Tamano City, Okayama Prefecture), the northeastern coast of Seto Inland Sea. In this study, we performed sulfur and diatom analyses of the deposit. The results were used along with 14C dates and the eruption age (7300 cal BP) of Kikai-Akahoya tephra (K-Ab) to derive sedimentary environments of the deposit. K-Ah was detected just below the peat deposit. At the culmination of the Jomon transgression, the peat deposit had been formed in brackish environments of salt marsh for about 300 years. In order to reconstruct local paleovegetation, we analyzed pollen, wood and plant fossils in the deposit. The results show vegetational transition from a deciduous broadleaved forest mainly of Ouercus subgen. Lepidobalanus to Pinus forest. In spite of the Holocene thermal optimum, the vegetation dominated by Ouercus subgen. Cyclobanopsis was not recognized at the Desaki site, as has been shown in many other regions of regions of western Japan. Ouercus sect. Prinus was replaced by Ouercus sect. Aegilops as the dominant section of Ouercus subgen. Lepidobalanus, suggesting early establishment of traditional rural vegetation of 'Satoyama' in Japan. However, no evidence for human agency has been obtained from the mid-Holocene archaeological sites around the Desaki site. Thus it is more likely that this vegetational transition resulted from the succession caused by natural forces such as ecological disturbance and climatic and/or endemic situations rather than by cultural deforestation

コモチシダの繁殖様式に及ぼす葉のサイズ及び根茎重量の影響

[論文

琉球列島奄美大島の絶滅危惧植物アマミヒイラギモチ（モチノキ科）の植物体サイズと葉の二型性

The tree Ilex dimorphophylla Koidz.（Aquifoliaceae）is a vulnerable species that is endemic to the summit of Mt. Yuwan on Amamioshima Island, Japan. This plant hows characteristic leaf dimorphism, which increases its horticultural value, and many individuals have been illegally removed from the natural habitat. We examined the umber of shoots, leaf morphology and plant size of the species in the natural habitat. Based on field observation for two years, we found 84 shoots, of which 32（38.1%）had entire mature leaves, whereas 52（61.9%）had only serrate juvenile leaves. Majority of the examined shoots surveyed fell into the smallest size classes : < 100 cm in eight（ca. 45%）and < 25 mm in diameter at the trunk base（ca. 60%）. Leaf dimorphism was clearly demarcated in trees at 130―210 cm in height and 15―27 mm in diameter at the trunk base.アマミヒイラギモチ（Ilex dimorphophylla Koidz.）は奄美大島の湯湾岳山頂付近に発達した風衝林内に生育するモチノキ科の樹木である。本種における樹木サイズと葉の二型性について自生地で調査した。84 シュートの生育を確認し，そのうちの32 シュートが全縁の成熟葉を，残りの52 シュートが鋭い鋸歯のある幼葉のみをもっていた。葉の二型性は樹木高で約130―210 cm，根元直径で15―27mm を境にして分かれていることが明らかになった