千葉県多古町における丸木舟の出土とその年代

The micro sea level changes in Late Holocene can be clarified in detail by means of the investigation near the shorelines of the coastal lakes. The coastal lakes have been linked with the sea in Late Holocene. So near the shorelines of these kinds of lakes, the geomorphological or sedimentological evidences tell of the former sea levels more clearly than in the general coastal lowlands. In other words, the rate of morphological reformations by the wave or tide are not so destructive in these kinds of lakes as happen in general coastal lowlands which face the open sea.In this paper, the author explain the lacustrine and sublacustrine microforms of Lake Saroma located on the coast of the Sea of Okhotsk, and obtained some sedimentological evidences that indicate several high water levels or low water levels after about 6, 000y. B. P.. The sea level changes in the Sea of Okhotsk in Late Holocene are presumed based on these data and the previous other reports.As shown in Figure 11, the water level (which means the sea level or the lake level) reached +2.5-+3.5m about 6, 000y. B. P. in the early Jomon period, and after that, the water level dropped down to below -0.5m about around 4, 500y. B. P. in the middle Jomon period. After that small transgression occurred at about 4, 000y. B. P. in late Jomon period. Then the another regression occurred during 2, 500-2, 000y. B. P. (called “Yayoi Regression”), and the water level rose again about 950y. B. P. in the middle or late Heian period. About 300y. B. P. in the early Edo period, the water level was below 0m a. s. l..Along the shoreline of Lake Saroma, we can see two Holocene lacustrine terraces at about 5m and 2-3m high, and widely developed littoral shelf in 2-3m depth. These lacustrine and sublacustrine microforms have been formed under the influences of the sea level changes, which consist of at least three high water levels and three low water levels in Late Holocene.The sand spits, which separate the Lake Saroma and the Sea of Okhotsk, are not all formed in Late Holocene. The Pleistocene terrace deposits are found in rather large area, some parts of which are covered by sand dunes. The Holocene deposits are small, and have been added inside the Pleistocene terrace deposits near the shoreline of the lake.

The Tasik Bera mire system represents deposition of peat and peaty sediments within a dendritic fluvial drainage basin in the humid tropics. Peaty sediments have been accumulating for at least 4,500 years in the lowest part of the basin, but accumulation rates and hence the thickness and lateral extent of the mire underwent a rapid increase and expansion beginning at about 660 years BP. In this preliminary study, pollen and diatom stratigraphy of two cores is related to some physical and chemical characteristics of the organic rich sediments. The sediments are highly variable, both vertically and laterally, the variations principally controlled by the type of vegetation dominant. Vegetation in turn is related to the degree of wetness of the site. Three environments of deposition contribute peat with distinctive palynological and physical characteristics. The limnetic environment, dominated by algae and easily degraded aquatic macrophytes, contributes very fine hemic peaty sediment with high fine silt content and a large algal component. The littoral environment is dominated by sedges and the woody shrub Pandanus, both of which have a large sub-aqueous biomass, and are quite resistant to degradation. Sediment from this environment is woody, hemic to coarse hemic, with a moderate to high very fine silt content and a much smaller algal element. Forest swamps, which occupy most of the mire area, contribute woody, fibric to hemic peaty sediments with low to moderate mineral matter content in the form of clays and very fine silt. Succession from both limnetic to forest swamp, and the reverse, is recorded in cores from different sites. No part of the mire yet studied is approaching oligotrophic conditions.

It has been indicated that littoral shelves are generally developed widely at the coastal lakes in Japan. The author takes notice that the littoral shelves are not a continuous flat plain but partly consist of two terraces, and considers that its formative processes have close relativity to the Holocene sea level changes. So, in this paper, the author investigated the southeast part of Lake Kasumigaura, which is the biggest coastal lake in Japan, where littoral shelves are developed in width of about 600m. Two transections of littoral shelves were obtained at Tennouzaki and Ukishima by using an echo-sounder (Fig. 4). Twelve surface deposit samples on the lake bottom were collected at two cases with a Ekman Birge sampler. Each sample was split to 200 g, sieved to the -2 to 4 phi fraction and analysed for particle sizes (Fig. 5). On the basis of these data, the detailed structure of the littoral shelves in Lake Kasumigaura was clarified and the origin of wide littoral shelves in the coastal lakes in Japan were considered as follows. (1) There are two kinds of littoral shelves in Lake Kasumigaura (Fig. 2). Littoral shelf I is developed along the shoreline continuously at the depth of 0.5_??_2.0m. On the other hand, littoral shelf II is found partly in the offing of littoral shelf I at the depth of 2.0_??_3.5 m. Littoral shelf I is considered to be a modern surface but the formation of littoral shelf II has high possibility to be a relict surface which was formed in the past at a low water level. That is to say, the wide littoral shelves in Lake Kasumigaura are made up of a modern surface (littoral shelf I) and a relict surface (littoral shelf II). And the former seems to be partially superposed on the latter. (2) At other main coastal lakes in Japan, for example, Lake Saroma, Lake Notoro, Lake Abashiri, Lake Ogawara, etc. (Table 2), we can also observe that littoral shelves are partly consist of two terraces. And these two terraces are correlative with the littoral shelf I and the littoral shelf II in Lake Kasumigaura respectively (Fig. 2). So the author assumes that the formation of the wide littoral shelves at the coastal lakes in Japan are also due to the superposition of littoral shelf I on littoral shelf II, and the low water level, when littoral shelf II was formed, is estimated to have appeared at almost the same time in those lakes, affected by the sea level changes in Late Holocene. It is known that the regression occurred at least three times in Late Holocene in Japan; middle Jomon period (about 5, 000_??_4, 000 y. B. P.), Yayoi period (about 3, 0002000 y. B. P.) and early Edo period (about 300 y. B. P.). The author supposes that littoral shelf II was formed during one of these periods, or during two or three periods with plural affections.

O-406 Pollen assemblage zone at the Jomon period in Central Sanin District, Southwest Japan

QuestionsDoes clear‐cutting intended to boost regeneration of abandoned secondary forests lead to an irreversible shift to non‐forest vegetation under high deer density?LocationWarm‐temperate forests in Boso Peninsula, Chiba Prefecture, Japan.MethodsWe designed a factorial experiment including two levels of forest canopy treatment (clear‐cutting or intact canopy) and two levels of herbivory control (presence or absence of deer) using 24 plots of 10 m × 10 m. Vegetation dynamics occurring under each experimental treatment were tracked for 7.5 years.ResultsGround vegetation under the closed canopy did not change significantly for 7.5 years both inside and outside the deer fences. However, plots were rapidly covered by early‐seral plants till 1.5 years after the cutting event. The quick growth of ground vegetation after clear‐cutting was supported by plants that are known to have soil seed banks, as suggested by their ubiquity immediately after clear‐cutting. Species richness of ground vegetation was maximized at that time and gradually decreased afterward, suggesting biological filtering. This filtering process worked differently inside and outside the deer fences, resulting in different types of vegetation. The clear‐cut‐and‐fence plots became dominated by tree recruits that will recover secondary forests in the future. Contrastingly, vegetation outside the fences lacked many species (e.g., common tree species) that were found inside the fences and became dominated by shrubs and plants unpalatable to deer. This post‐cutting vegetation outside the fences was not similar to that inside the deer fences at any seral stage. This means that the vegetation outside the fences could be tracking an alternative successional trajectory rather than a case of arrested succession.ConclusionsHere, abandoned secondary forests still seem to maintain a high regeneration potential that would be triggered by clear‐cutting, but reducing herbivory pressure by deer is necessary to avoid the risk of alternative successional trajectories.

This study attempts to reconstruct the vegetational and climatic history of the last 300 000 years for the Taranaki-Wanganui district, North Island, New Lignites in the cover beds of a wellpreserved sequence of marine terraces in South Wanganui Basin provide excellent material for pollen analysis from sequences that are chronologically constrained by the ages of the marine terraces and by the loessand tephrostratigraphy of their cover beds. Anthropogenic influences in New Zealand affect only the last c. 1000 years. Modern pollen samples from a variety of vegetation types from central-western North Island, together with previous modern pollen studies, indicate the palynological representation of taxa and allow the characterisation of the major vegetation types, although these data provide only a limited picture of the source vegetation. This information is used for helping to interpret the fossil pollen spectra. Two sites from the Waverley district, near Wanganui, which together cover the mid and late Holocene, provide an analogue of vegetation assemblages and their sequence of development in the area, for use in interpreting the Pleistocene pollen sequences. The vegetation history from these sites conforms to the known Holocene pattern from sites elsewhere. Polynesian deforestation at Lake Waiau Swamp is estimated to have occurred some time between 685 CAL B.P. and 210 years ago. Five sites from the Pleistocene marine terrace cover beds are pollen analysed in detail. The pollen assemblage zones are correlated with the established deep-sea oxygen isotope record. Combined with previous pollen studies from the terrace cover beds, the results provide a relatively continuous, detailed vegetation history dating from c. 400 ka ago to the present, for the fIrst time in New This record is closely linked to the marine terrace, loess-, and tephrostratigraphy of this region. Because the record is mostly from sequential rather than coeval sites, further work is required to corroborate certain details. The vegetation on the lowlands of Taranaki-Wanganui alternated from grass-shrubland communities during glacial periods, to podocarp-hardwood forest, dominated in the pollen assemblages by Dacrydium cupressinum, during the interglacial times. No particular period is uniquely characterised by its pollen assemblages. In interglacial pollen assemblages, generally some of the hardwood forest elements are severely underrepresented (e.g., Beilschmiedia tawa). The warmest, wettest, and mildest (with rare frosts and droughts) climates during interglacials are suggested by pollen assemblages matching those of the early to mid Holocene, with common Ascarina lucida and Dodonaea viscosa pollen in nearcoastal sites. Interstadial and stadial pollen assemblages are more diffIcult to characterise. In general, interstadial assemblages seem to be dominated by Prumnopitys taxifolia pollen, and· stadial assemblages seem to be dominated by Nothofagus fusca type or Libocedrus pollen, together with common shrub and grasS pollen. The vegetation for Some of the climatic stages, such as the Last and Penultimate Interglacials sensu stricto, are clearly demonstrated for the first time in New N. fusca type, N. menziesii, Libocedrus, Halocarpus, Phyllocladus, Empodisma minus, and Gleichenia are some taxa for which geographic range expansion. can be demonstrated when climates were cooler than present However, the vegetation history of the area generally agrees with the hypothesis that the flora of the Taranaki-W~ganui district has remained essentially the same through the Q\1aternary, although a few records of taxa well outside their present ranges require special explanation. Glacial period pollenrecords show that, while forest was probably largely excluded from the lowlands, it remained in the region during the coldest climatic periods and probably occupied sheltered areas. Broadly synchronous records from separate sites suggest that regional vegetational differences existed, probably due to local site and climate differences, analogous to the present pattern. Occasional natural fIres appear to have occurred throughout the periods studied, but there is no evidence that deforestation due to severe fIres occurred during the late Pleistocene. Palynology and radiocarbon dating of the Ohawe Beach Site, near Hawera, demonstrate that the marine terraces in this region have previously been mapped incorrectly, but in general the marine terrace mapping and chronology of B. J. Pillans (1983:. Upper Quaternary marine terrace chronology and deformation, south Taranaki, New Zealand. Geology 11: 292-297;) is upheld. Radiocarbon dating of separate organic fractions from degraded fossil wood samples at Ohawe Beach show that chemical contamination by young radiocarbon had occurred· and that the real age is beyond the radiocarbon range. This serves as· a warning against simple interpretation of radiOCarbon ages on wood from cover beds in the area. Pollen analyses also suggest that the Fordell Ash is younger than the Mt Curl Tephra, as opposed to previous interpretations . The extinct palynomorphs, Acacia· type andPeromonolites problematicus Couper, are identifIed from the cover beQ sediments, and their time ranges in New Zealand extended until c .. 11 0 ka ago and 90 ka ago, respectively. The implications of these fIndings are discussed. .

The Choshi Peninsula, located at the eastern margin of the Kanto tectonic basin, is composed of a series of late Pleistocene marine terraces except for a small older bedrock hill, Mt. Atago. Near Cape Inubo at the eastern tip of the peninsula, the last interglacial terrace is about 60m high, and the average rate of uplift is estimated to be 0.4m/1, 000 years. Holocene terraces are developed in the valley of the Tone River flowing eastward on the north side of the peninsula, and in the Takagami lowland in the Choshi Peninsula (Fig. 1).Excavations were carried out in these Holocene terraces in order to take systematic samples for reconstruction of environmental changes based on facies observation, 14C dates, and analysis of biological assemblages. Along the Tone River (Fig. 2), the Holocene terrace is well developed, and its upper limit of marine deposits ranges from 4.0 to 5.0m amsl. It is estimated that this surface emerged earlier than ca. 3, 500y.B.P. at the latest, judging from the presence of an archeological site of the late Jomon Period. Stratigraphic sections based upon excavation and bore hole are shown in Fig. 3.Takagami lowland, at an altitude of 9-10m amsl (Fig. 4), is overlain by a terrestrial peat bed up to 5m in thickness. The upper limit of the marine deposits, identified by facies observation and diatom analysis, is 4.8m amsl at the eastern margin of the lowland and is slightly lower northwestward (Figs. 5 and 6). In contrast with the unidirectional slope of the surface topography (Fig. 4), the basal topography beneath the Holocene marine deposits includes two buried valleys sloping in opposite directions (Fig. 5), and a former divide is found near Loc. 10. The eastward-sloping buried valley is called “Paleo Takagami Bay”. While the westward-sloping valley is filled with sandy deposits, Paleo Takagami Bay is filled with fine marine silt or clay deposited in a bay-head of a shallow drowned valley. 14C dates from Paleo Takagami Bay are 8, 380 and 10, 410y.B.P. for the basal marine deposits, 6, 520, 6, 960 and 5, 220y.B.P. for an analyzed marine clay, and six dates from the base of overlying peat deposit ranging from 6, 600 to 3, 580y.B.P. (Fig. 5 and Table 1). The transgression resulting in deposition of the marine sediments mentioned above is correlated with the post-glacial (Jomon) transgression. The emergence of Paleo Takagami Bay is considered to have taken place immediately prior to the deposition of the lowest part of the peat, that is, ca. 5, 000-5, 500y.B.P.Analysis of assemblages of molluscs, ostracods, diatoms and pollen from the longest core of Loc. 2 permits the reconstruction of the paleoecology of Paleo Takagami Bay during the Holocene (Fig. 7). Using molluscan assemblage as an example, a brackish water or shallow-marine assemblage from the intertidal zone is found in the lower part of the core. In the middle part of the core, an assemblage consisting of species common to a muddy bottom deeper than several meters predominates. The upper part of the core includes the shallow-marine assemblage characteristic of the base of the core as well as other assemblages characteristic of a shallow, sandy-bottom intertidal environment. Changes in water depth and environment deduced from the molluscan assemblages are concordant with those estimated from the analysis of diatoms, ostracods, and pollen. The upper limit of marine deposits obtained by different indices (Fig. 7) shows a good agreement, that is 3.3m amsl by facies observation, 2.3m by molluscan assemblages, 1.8m by ostracods, and 3.3m by diatoms.Three stages in the paleogeographic evolution of the Choshi Peninsula are depicted in paleogeographic maps in Fig. 8. Stage I is the early stage of the Jomon transgression.

Topography-specific emergence of fungal fruiting bodies in warm temperate evergreen broad-leaved forests on Yakushima Island, Japan

A thorough understanding of carbon storage patterns in forest ecosystems is crucial for forest management to slow the rate of climate change. Here, we explored fine-scale biomass spatial patterns in a secondary warm temperate deciduous broad-leaved forest in north China. A 20-ha plot was established and classified by topographic features into ridge, valley, gentle slope, and steep slope habitats. Total tree biomass varied from 103.8 Mg/ha on the gentle slope habitats to 117.4 Mg/ha on the ridge habitats, with an average biomass of 109.6 Mg/ha across the entire plot. A few species produced the majority of the biomass, with five species contributing 78.4% of the total tree biomass. These five species included Quercus mongolica Fisch. ex Ledeb (41.7 Mg/ha, 38.1%), Betula dahurica Pall. (19.8 Mg/ha, 18.0%), Acer mono Maxim. (12.6 Mg/ha, 11.5%), Betula platyphylla Suk. (7.0 Mg/ha, 6.4%), and Populus davidiana Dode. (4.8 Mg/ha, 4.4%). The five species were also associated with certain habitats; for example, Q. mongolica was positively associated with the ridge habitat and A. mono was positively associated with the valley habitat. Results from this work document the variability in forest biomass across a warm temperate forest ecosystem of north China, with implications for managing and accounting forest carbon.

Variation in foliar δ 15N among oriental oak ( Quercus variabilis) stands over eastern China: Patterns and interactions

<strong class="journal-contentHeaderColor">Abstract.</strong> Considered one of the most significant climate reorganizations of the Cenozoic period, the Eocene–Oligocene Transition (EOT; ca. 34.44–33.65) is characterized by global cooling and the first major glacial advance on Antarctica. In the southern high latitudes, the EOT cooling is primarily recorded in the marine realm, and its extent and effect on the terrestrial climate and vegetation are poorly documented. Here, we present new, well-dated, continuous, high-resolution palynological (sporomorph) data and quantitative sporomorph-based climate estimates recovered from the East Tasman Plateau (ODP Site 1172) to reconstruct climate and vegetation dynamics from the late Eocene (37.97 Ma) to the early Oligocene (33.06 Ma). Our results indicate three major climate transitions and four vegetation communities occupying Tasmania under different precipitation and temperature regimes: (i) a warm-temperate <i>Nothofagus</i>–Podocarpaceae-dominated rainforest with paratropical elements from 37.97 to 37.52 Ma; (ii) a cool-temperate <i>Nothofagus</i>-dominated rainforest with secondary Podocarpaceae rapidly expanding and taking over regions previously occupied by the warmer taxa between 37.306 and 35.60 Ma; (iii) fluctuation between warm-temperate–paratropical taxa and cool temperate forest from 35.50 to 34.49 Ma, followed by a cool phase across the EOT (34.30–33.82 Ma); and (iv) a post-EOT (earliest Oligocene) recovery characterized by a warm-temperate forest association from 33.55 to 33.06 Ma. Coincident with changes in the stratification of water masses and sequestration of carbon from surface water in the Southern Ocean, our sporomorph-based temperature estimates between 37.52 and 35.60 Ma (phase ii) showed 2–3 <span class="inline-formula">^∘</span>C terrestrial cooling. The unusual fluctuation between warm and cold temperate forest between 35.50 to 34.59 Ma is suggested to be linked to the initial deepening of the Tasmanian Gateway, allowing eastern Tasmania to come under the influence of warm water associated with the proto-Leeuwin Current (PLC). Further to the above, our terrestrial data show the mean annual temperature declining by about 2 <span class="inline-formula">^∘</span>C across the EOT before recovering in the earliest Oligocene. This phenomenon is synchronous with regional and global cooling during the EOT and linked to declining <span class="inline-formula"><i>p</i></span>CO<span class="inline-formula">₂</span>. However, the earliest Oligocene climate rebound along eastern Tasmania is linked to a transient recovery of atmospheric <span class="inline-formula"><i>p</i></span>CO<span class="inline-formula">₂</span> and sustained deepening of the Tasmanian Gateway, promoting PLC throughflow. The three main climate transitional events across the studied interval (late Eocene–earliest Oligocene) in the Tasmanian Gateway region suggest that changes in ocean circulation due to accelerated deepening of the Tasmanian Gateway may not have been solely responsible for the changes in terrestrial climate and vegetation dynamics; a series of regional and global events, including a change in the stratification of water masses, sequestration of carbon from surface waters, and changes in <span class="inline-formula"><i>p</i></span>CO<span class="inline-formula">₂</span>, may have also played vital roles.

The Upper Weichselian and Holocene layers of the 190 m thick peat sequence in the Philippi basin (NE Greece) are studied by means of their mineralogical and geochemical features. The ash contents range between 11.4 and 53.4% and inorganic carbon contents range between 0.5 and 5.7%. X-ray diffraction (XRD) analysis revealed that Mg-calcite, quartz, clay minerals, K-feldspars, plagioclases, and chlorites are the dominant minerals in the peat. Lime, pyrite, siderite, apatite, iron-oxides, weddellite, and basaluminite occur subordinately. During Upper Pleniglacial and Late Glacial times, clastic sedimentation prevailed in the palaeomire. Peat was enriched in Fe, K, Ti, As, Cr, Cu, Ni, Rb, Th, Y, Zn, and Zr. In Early Holocene, authigenic sedimentation of Ca-rich material dominated. Peat became enriched in As, Br, Se, Sr, and U. In Middle Holocene, fluctuations of the water table in the mire resulted in the deposition of both authigenic and clastic minerals. The Late Holocene peat is intensely damaged due to drainage and cultivation. The mineral matter features of the Upper Weichselian peat are identical to the features of many Greek lignites.

Multivariate, autocorrelation and spectral analyses of a pollen profile from Scotland and evidence for periodicity

Abstract. The biomisation method is used to reconstruct Latin American vegetation at 6000±500 and 18 000±1000 radiocarbon years before present (14C yr BP) from pollen data. Tests using modern pollen data from 381 samples derived from 287 locations broadly reproduce potential natural vegetation. The strong temperature gradient associated with the Andes is recorded by a transition from high altitude cool grass/shrubland and cool mixed forest to mid-altitude cool temperate rain forest, to tropical dry, seasonal and rain forest at low altitudes. Reconstructed biomes from a number of sites do not match the potential vegetation due to local factors such as human impact, methodological artefacts and mechanisms of pollen representivity of the parent vegetation. At 6000±500 14C yr BP 255 samples are analysed from 127 sites. Differences between the modern and the 6000±500 14C yr BP reconstruction are comparatively small; change relative to the modern reconstruction are mainly to biomes characteristic of drier climate in the north of the region with a slight more mesic shift in the south. Cool temperate rain forest remains dominant in western South America. In northwestern South America a number of sites record transitions from tropical seasonal forest to tropical dry forest and tropical rain forest to tropical seasonal forest. Sites in Central America show a change in biome assignment, but to more mesic vegetation, indicative of greater plant available moisture, e.g. on the Yucatán peninsula sites record warm evergreen forest, replacing tropical dry forest and warm mixed forest presently recorded. At 18 000±1000 14C yr BP 61 samples from 34 sites record vegetation reflecting a generally cool and dry environment. Cool grass/shrubland is prevalent in southeast Brazil whereas Amazonian sites record tropical dry forest, warm temperate rain forest and tropical seasonal forest. Southernmost South America is dominated by cool grass/shrubland, a single site retains cool temperate rain forest indicating that forest was present at some locations at the LGM. Some sites in Central Mexico and lowland Colombia remain unchanged in the biome assignments of warm mixed forest and tropical dry forest respectively, although the affinities that these sites have to different biomes do change between 18 000±1000 14C yr BP and present. The "unresponsive" nature of these sites results from their location and the impact of local edaphic influence.

Peat deposits in Greenland and Denmark were investigated to show that high-resolution dating of these archives of atmospheric deposition can be provided for the last 50 years by radiocarbon dating using the atmospheric bomb pulse. 14C was determined in macrofossils from sequential one cm slices using accelerator mass spectrometry (AMS). Values were calibrated with a general-purpose curve derived from annually averaged atmospheric 14CO2 values in the northernmost northern hemisphere (NNH, 30°–90°N). We present a thorough review of 14C bomb-pulse data from the NNH including our own measurements made in tree rings and seeds from Arizona as well as other previously published data. We show that our general-purpose calibration curve is valid for the whole NNH producing accurate dates within 1–2 years. In consequence, 14C AMS can precisely date individual points in recent peat deposits within the range of the bomb-pulse (from the mid-1950s on). Comparing the 14C AMS results with the customary dating method for recent peat profiles by 210Pb, we show that the use of 137Cs to validate and correct 210Pb dates proves to be more problematic than previously supposed.As a unique example of our technique, we show how this chronometer can be applied to identify temporal changes in Hg concentrations from Danish and Greenland peat cores.