Plant Macrofossil Analyses Research Articles

The late Holocene decline of Trapa natans L. in Northern Poland in the light of new palaeobotanical and geochemical data

Abstract Trapa natans (water chestnut) is an aquatic, thermophilic plant whose decline has been observed in many localities in central Europe during the last decades. In this paper, we present a description of two new T. natans subfossil sites located outside its present northern distribution in Poland. High-resolution analysis of plant macrofossils supported by geochemical analysis were undertaken to reconstruct the palaeoecological habitat and examine the cause of the late Holocene decline of T. natans that took place ca. 4000 calibrated years before AD 1950 (cal. yr BP) in a paleolake, presently the Bagno Kusowo bog. Its disappearance was a consequence of terrestrialisation and the development of peatland. In paleolake sediments covered by the peat layer in the Mechacz Wielki bog, T. natans macrofossils were found from before ca. 3300 cal. yr BP. The decline of T. natans could have resulted from the changes and development of other plant communities where the dominant role was played by Stratiotes aloides and Nymphaea sp. In our study sites, T. natans occurred together with Potamogeton crispus, Potamogeton obtusifolius, Nymphaea alba, and Nuphar sp. in eutrophic water dominated by Ca2+, Fe3+, and Al3+ ions. Our palaeobotanical and geochemical results align with the contemporary conditions of T. natans habitat.

To Dye or Not to Dye: Bioarchaeological Studies of Hala Sultan Tekke Site, Cyprus

Dated to the Late Bronze Age (Late Cypriot II: 1450–1200 BC and Late Cypriot III: 1200–1050 BC), the site of Hala Sultan Tekke brought to light interesting evidence of textile production and possible fabric dyeing. Finds of loom weights and spindle whorls together with remains of dyer’s croton (Chrozophora tinctoria), field gromwell (Buglossoides arvensis syn. Lithospermum arvense), and shells of murex allow opening a discussion over the methods and reasons for undertaking the time and cost-consuming procedure of dye production. The present article, through an examination of finds and an analysis of plant macrofossils and molluscs, tests a hypothesis of textile dyeing at the Late Cypriot city of Dromolaxia Vizatzia.

Late Holocene sea-level changes in eastern Québec and potential drivers

Late Holocene sea-level changes can be reconstructed from salt-marsh sediments with decimetre-scale precision and decadal-scale resolution. These records of relative sea-level changes comprise the net sea-level contributions from mechanisms that act across local, regional and global scales. Recent efforts help to constrain the relative significance of these mechanisms that include sediment dynamics and isostasy, which cause relative sea-level changes via vertical land motion, ocean-atmosphere processes that influence regional-scale ocean mass redistribution, and ocean-cryosphere and steric interactions that drive global scale ocean-volume changes. There remains a paucity of high-resolution Late Holocene sea-level data from eastern Canada. This precludes an interrogation of the mechanisms that define sea-level changes over recent centuries and millennia in a region sensitive to oceanic (Atlantic Multidecadal Variability, Atlantic Meridional Overturning Circulation), atmospheric (North Atlantic Oscillation, Arctic Oscillation) and cryospheric (ice-mass balance) changes. We present new relative sea-level data that span the past three millennia from Baie des Chaleurs in the Gulf of St. Lawrence generated using salt-marsh foraminifera supported with plant macrofossil analyses. The accompanying chronology is based on radiocarbon and radionuclide analyses, which are independently verified using trace metal and microcharcoal records. Relative sea level has risen at a mean rate of 0.93 ± 1.25 mm yr−1 over the past ∼1500 years. Residual structure within the reconstruction (‘internal variability’) has contributed up to an additional 0.61 ± 0.46 mm yr−1 of short-lived RSL rise prior to 1800 CE. Following a sea-level low stand during the Little Ice Age, acceleration in relative sea-level rise is identified between 1800 and 1900 CE within the estimates of internal variability and from 1950 CE to present in both the secular and residual trends. Phases of relative sea-level changes in the Gulf of St. Lawrence are concomitant with periods of glacier mass loss following the Little Ice Age, phase periods of the North Atlantic Oscillation and the Atlantic Meridional Overturning Circulation and Northern Hemisphere warming. Quantifying the individual effects of these different mechanisms is important for understanding how ocean-atmosphere processes redistribute ocean-mass upon larger scale background ocean-volume changes.

The impact of climate changes during the last 6000 years on a small peatland in North-Eastern Poland: A multi-proxy study

In this article, we focus on transformations of a small peatland, located in the remote area of north-eastern Poland, which originated through partial terrestrialisation of Lake Czarne during the last 6000 years. We investigated the changes in vegetation patterns and linked them to climate changes and a concurrent succession of forest in the surroundings of the basin. We applied pollen, non-pollen palynomorph (NPP), and plant macrofossil analysis, supplemented with geochemistry and 14C AMS dating. The transformation from poor fen to peat bog occurred within ca. 300 years (ca. 6000–5720 cal. BP). The hydrological changes on the peat bog, reconstructed qualitatively on the basis of selected NPPs (mostly HdV-10 and Archerella flavum), occur simultaneously to the widely recognised climatic events. During the cool and wet ‘5.2’ and ‘4.2’ climatic events the potential increases in the water table on the peat bog were identified. The subsequent period of dynamic fluctuations of the water table (ca. 3400 and 2350 cal. BP) was related to the gradual expansion of Betula on the mire. This period also partially overlapped with the ‘2.8’ event that was responsible for water level fluctuations across Europe. The ‘1750–1350’ cal. BP global cooling event also might have led to a potential wet shift ca. 1700–1600 cal. BP. Since ca. 1600 cal. BP the water level has significantly dropped and poor fen conditions were reestablished. This article shows the potential of NPPs in the qualitative detection of palaeohydrological events on the peat land. However, there is still a need to combine NPP data with quantitative reconstructions of water table changes to understand the complexity of relationships between climate changes and water table–vegetation responses.

Holocene vegetation dynamics and hydrological variability in forested peatlands of the Clay Belt, eastern Canada, reconstructed using a palaeoecological approach

Forested peatlands are widespread in boreal regions of Canada, and these ecosystems, which are major terrestrial carbon sinks, are undergoing significant transformations linked to climate change, fires and human activities. This study targets millennial‐scale vegetation dynamics and related hydrological variability in forested peatlands of the Clay Belt south of James Bay, eastern Canada, using palaeoecological data. Changes in peatland vegetation communities were reconstructed using plant macrofossil analyses, and variations in water‐table depths were inferred using testate amoeba analyses. High‐resolution analyses of macroscopic charcoal >0.5 mm were used to reconstruct local fire history. Our data showed two successional pathways towards the development of present‐day forested peatlands influenced by autogenic processes such as vertical peat growth and related drying, and allogenic factors such as the occurrence of local fires. The oldest documented peatland initiated in a wet rich fen around 8000 cal. a BP shortly after land emergence and transformed into a drier forested bog rapidly after peat inception that persisted over millennia. In the second site, peat started to accumulate from ~5200 cal. a BP over a mesic coniferous forest that shifted into a wet forested peatland following a fire that partially consumed the organic layer ~4600 cal. a BP. The charcoal records show that fires rarely occurred in these peatlands, but they have favoured the process of forest paludification and influenced successional trajectories over millennia. The macrofossil data suggest that Picea mariana (black spruce) persisted on the peatlands throughout their development, although there were periods of more open canopy due to local fires in some cases. This study brings new understanding on the natural variability of boreal forested peatlands which may help predict their response to future changes in climate, fire regimes and anthropogenic disturbances.

Holocene development of subarctic permafrost peatlands in Finnmark, northern Norway

Subarctic permafrost peatlands are important soil organic carbon pools, and improved knowledge about peat properties and peatland sensitivity to past climate change is essential when predicting future response to a warmer climate and associated feedback mechanisms. In this study, Holocene peatland development and permafrost dynamics of four subarctic peat plateaus in Finnmark, northern Norway have been investigated through detailed analyses of plant macrofossils and geochemical properties. Peatland inception occurred around 9800 cal. yr BP and 9200 cal. yr BP at the two continental sites Suossjavri and Iskoras. Younger basal peat ages were found at the two coastal locations Lakselv and Karlebotn, at least partly caused by the time lag between deglaciation and emergence of land by isostatic uplift. Here, peatland development started around 6150 cal. yr BP and 5150 cal. yr BP, respectively. All four peatlands developed as wet fens throughout most of the Holocene. Permafrost aggradation, causing frost heave and a shift in the vegetation assemblage from wet fen to dry bog species, probably did not occur until during the last millennium, ca. 950 cal. yr BP in Karlebotn and ca. 800 cal. yr BP in Iskoras, and before ca. 150 cal. yr BP in Lakselv and ca. 100 cal. yr BP in Suossjavri. In Karlebotn, there are indications of a possible earlier permafrost phase around 2200 cal. yr BP due to climatic cooling at the late Subboreal to early Subatlantic transition. The mean long-term Holocene carbon accumulation rate at all four sites was 12.3 ± 4.1 gC m−2 yr−1 (±SD) and the mean soil organic carbon storage was 97 ± 46 kgC m−2.

Palaeoecological evolution of a spring-fed fen in Pawłów (eastern Poland)

A continuous record of sedimentation in spring-fed fens makes them suitable for detailed palaeoenvironmental studies. A newly investigated cupola spring-fed fen (Pawłów site), located in the Lublin chalkland, eastern Poland, was the object of our study. This special karst region is characterised by the occurrence of Upper Cretaceous carbonate rocks in the substratum. Sedimentological observations indicated strong variability of biogenic-carbonate series in the deposits (=peat-tufa rhythmite), reflects changes of accumulation conditions (oxidising versus reducing), resulting from alternate occurrence of warmer and cooler periods. Difficulties in pollen analysis due to oxidising conditions necessitate a multidisciplinary approach for palaeoenvironmental reconstruction. We used a multidisciplinary approach (sedimentological, palaeobotanical, geochemical analyses and radiocarbon dating) to determine the main evolutionary stages of this unique fen ecosystem and to discuss the role of local or/and regional factors in its development. Pollen and plant macrofossil analyses, supported by radiocarbon dating, proved that the bottom part of the cores represents the Late Glacial–Early Holocene stages of the fen development. A comparative analysis of palaeoenvironmental data showed close resemblance between the Pawłów fen and the earlier studied fens in eastern Poland and Central-Eastern Europe, and the connection between their development and supraregional hydrological-climatic factors. The results indicated also the influence of the morphological position of such a type of ecosystem on the development of a continuous deposit succession. The occurrence of a river valley in close proximity of the Pawłów site resulted in the lack of tufa deposits from the Atlantic period, because of an erosional phase in the river valley.

The disturbance regime of an Early Holocene swamp forest in the Czech Republic, as revealed by dendroecological, pollen and macrofossil data

A unique remnant of forest dating back to the period 9733–7897 yr BC and consisting of hundreds of tree bases was discovered in the Czech Republic. We aimed to reveal the complex disturbance history of this (sub)fossil forest using dendrochronology, and to describe its detailed plant species composition changes using palaeobotanical techniques. Analysing such Early Holocene forest dynamics should help us understand the ability of the forest community to actively adapt to climate change and generally to understand the role of dynamic instability in ecosystem evolution.We anatomically identified woody species in 488 samples, and determined the ages, growth suppressions, releases and fire scars in 116 well preserved tree ring series using a modern boundary line approach. This image of the forest structure and dynamics was supplemented with analyses of pollen spectra and plant macrofossils in excavated profiles. In order to achieve accurate dating, we dated 87 samples using 14C and synchronized tree ring series, and compared them with an existing Pinus sylvestris chronology.The developmental trajectory of the forest was unique, and did not match the general trend of postglacial pine growth in central Europe. Palaeobotanical proxies indicated that during the circa 2000 years the forest persisted, this Early-Holocene ecosystem passed through several phases, reflected in the species composition of the vegetation as well as in habitat conditions. Nevertheless, the dominance of pine and the complex fine-scale disturbance regime were relatively robust and did not change fundamentally. Low-severity fires and short-term changes in soil moisture regime were crucial disturbance agents in the ecosystem. Stand-replacing disturbances were not found up to the gradual collapse of the forest around 8300 yr BC, replaced by a swamp community. The disturbance regime was relatively stable, suggesting a mitigating effect of changing climate due to the predominance of pine in the forest.

Vegetation and climate history of Quebec’s mixed boreal forest suggests greater abundance of temperate species during the early- and mid-Holocene

Today, scattered disjunct stands of two temperate species, yellow birch and white pine, are present north of their continuous distributional range in southern Quebec (Canada) at topographical locations that offer protection from severe fires. This study tested whether these species had populations more numerous and widespread millennia ago when the climate was presumably warmer. Specifically, this research involved the analyses of pollen, plant macrofossils, and charcoal fragments of two sites within the western part of Quebec’s balsam fir – paper birch bioclimatic domain: a forest humus deposit from a yellow birch stand (local scale), and a peatland (regional scale). Fossil data suggest that white pine was more abundant regionally between 7500 and 5000 cal. BP, before coming rare under subsequent cooler conditions. Likewise, yellow birch was more abundant regionally between 7700 and 1500 cal BP. Its subsequent decline and the local disappearance of white pine by ∼200 cal. BP may both be explained by the severe fires that occurred in recent centuries, as well as the rarity of suitable habitats for these species. The sustained presence of temperate species in mixed boreal forests is the result of the combined action of climate, natural disturbances and habitat characteristics.

Indicator value of oribatid mites in determining past permafrost dynamics in northern European sub‐Arctic peatlands

Permafrost dynamics play an important role in the surface hydrology and carbon balance of northern peatlands. Plant macrofossil analysis with radiocarbon dating has been widely used in detecting past permafrost dynamics in peatlands; however, there is a lack of permafrost‐specific plant indicator species, which makes it challenging to determine the exact timing of historical permafrost aggradation. We investigated the indicator value of oribatid mites in determining past permafrost dynamics in sub‐Arctic peatlands. Analyses of subfossil oribatid mite assemblages of Holocene peat profiles from two mires, one in northern Finland and one in northeastern European Russia, were carried out and interpreted using modern calibration data from the same study areas. The results were compared with previously published reconstructions of permafrost history based on plant macrofossil analyses from the same locations. The results suggest that the oribatid mites Carabodes labyrinthicus, Chamobates borealis and Neoribates aurantiacus are promising indicator species to detect past permafrost occurrence in peatlands. In addition, N. aurantiacus is clearly associated with the presence of lichens, which is particularly useful because lichen remains are rarely preserved in peat deposits. Results are in accordance with earlier studies showing that oribatid mites are useful indicators of past environmental change.

Impact of the Little Ice Age cooling and 20th century climate change on peatland vegetation dynamics in central and northern Alberta using a multi-proxy approach and high-resolution peat chronologies

Northern boreal peatlands are major terrestrial sinks of organic carbon and these ecosystems, which are highly sensitive to human activities and climate change, act as sensitive archives of past environmental change at various timescales. This study aims at understanding how the climate changes of the last 1000 years have affected peatland vegetation dynamics in the boreal region of Alberta in western Canada. Peat cores were collected from five bogs in the Fort McMurray region (56–57° N), at the southern limit of sporadic permafrost, and two in central Alberta (53° N and 55° N) outside the present-day limit of permafrost peatlands. The past changes in vegetation communities were reconstructed using detailed plant macrofossil analyses combined with high-resolution peat chronologies (14C, atmospheric bomb-pulse 14C, 210Pb and cryptotephras). Peat humification proxies (C/N, H/C, bulk density) and records of pH and ash content were also used to improve the interpretation of climate-related vegetation changes. Our study shows important changes in peatland vegetation and physical and chemical peat properties during the Little Ice Age (LIA) cooling period mainly from around 1700 CE and the subsequent climate warming of the 20th century. In some bogs, the plant macrofossils have recorded periods of permafrost aggradation during the LIA with drier surface conditions, increased peat humification and high abundance of ericaceous shrubs and black spruce (Picea mariana). The subsequent permafrost thaw was characterized by a short-term shift towards wetter conditions (Sphagnum sect. Cuspidata) and a decline in Picea mariana. Finally, a shift to a dominance of Sphagnum sect. Acutifolia (mainly Sphagnum fuscum) occurred in all the bogs during the second half of the 20th century, indicating the establishment of dry ombrotrophic conditions under the recent warmer and drier climate conditions.

Preliminary analysis of plant macrofossils from an Early Iron Age structure in Kærbøl, Denmark, with special emphasis on segetal and ruderal weeds

Abstract The paper presents results from an archaeobotanical analysis of samples from an Early Iron Age building in Kærbøl, Denmark, and brings to light an interesting correlation between crops and weeds which most probably characterised the majority of Early Iron Age societies in Denmark. It is suggested that the weed species were the primary plants stored for various reasons and that the crops only accompanied them. The authors discuss the plausibility of interpreting weed species as food plants during the Danish Iron Age, and the possible function of the sampled structure.

Plant use at the end of the Upper Palaeolithic: archaeobotanical remains from Cova de les Cendres (Teulada-Moraira, Alicante, Spain)

The use and consumption of plant resources by Palaeolithic hunter-gatherer societies has traditionally been overlooked by researchers. Nevertheless, recent studies have started to point out the significant role of these resources in hunter-gatherer economies. This paper presents the results of the plant macrofossil (carpological) analysis of two levels dated to the Middle and Upper Magdalenian at Cova de les Cendres, Teulada-Moraira, Alicante, Spain. The results have been combined with the charcoal (anthracological) analysis, in order to improve the interpretation of the assemblage. Thirty-seven different taxa, which provide information of plant food, basketry, wood and fuel, etc., have been identified among the plant remains. Moreover, the identified taxa allow us to complete the landscape reconstruction based on the charcoal remains. Some fruits and charcoals have been dated to 13,980 ± 50–14,590 ± 50 bp.

Middle to late Holocene flood activity estimated from loss on ignition of peat in the Ishikari lowland, northern Japan

Reconstruction of the magnitude and frequency of past floods is important for assessments of flood risk. However, there have been few reconstructions of past flood activity based on long-term continuous records from a single fluvial system and thus suitable for comparison with other paleoclimate proxies. Consequently, the influence of climate change on flood activity remains unclear. Floodplain peat beds can be preserved for long periods of geologic time; they also contain both clastic sediments from overbank flooding and organic material produced in situ, both of which are important inputs for geologic reconstructions. In this study, we examined 24 cores from the Ishikari lowland, northern Japan, to find out if temporal changes of loss on ignition (LOI) of peat can provide a record of flood magnitude and frequency and to investigate the influence of regional climate change on flood activity. Our plant macrofossil analyses, the distribution of characteristic LOI depth profiles, and sedimentary facies suggest that the LOI of peat increases when the magnitude and frequency of floods decreases, which in turn suggests that temporal changes of LOI in peat might be useful as a proxy for past flood activity. Our results indicate that increases in the LOI of peat deposited near the Ishikari River at ca. 5500–5000 and 4000–3500calBP may correspond to weakened activities of the East Asian summer monsoon (EASM) and El Niño–Southern Oscillation (ENSO). Furthermore, our analyses show that an increase in flood activity of the Ishikari River during 1400–1300calBP may be related to a decrease in ENSO activity. However, temporal changes of the LOI of peat formed near a tributary of the Ishikari River did not correlate with these climate changes. Our results suggest that the past flood activity of rivers with large watersheds reflects regional climate change, because the extensive precipitation that induces flooding of such rivers is generally associated with regional climate systems such as the EASM and ENSO, whereas this association is not necessarily the case for rivers with small watersheds.

Vegetation Succession, Carbon Accumulation and Hydrological Change in Subarctic Peatlands, Abisko, Northern Sweden

AbstractHigh‐resolution analyses of plant macrofossils, testate amoebae, pollen, mineral content, bulk density, and carbon and nitrogen were undertaken to examine the late Holocene dynamics of two permafrost peatlands in Abisko, Subarctic Sweden. The peat records were dated using tephrochronology, 14C and 210Pb. Local plant succession and hydrological changes in peatlands were synchronous with climatic shifts, although autogenous plant succession towards ombrotrophic status during peatland development was also apparent. The Marooned peatland experienced a shift ca. 2250 cal yr BP from rich to poor fen, as indicated by the appearance of Sphagnum fuscum. At Stordalen, a major shift to wetter conditions occurred between 500 and 250 cal yr BP, probably associated with climate change during the Little Ice Age. During the last few decades, the testate amoeba data suggest a deepening of the water table and an increase in shrub pollen, coinciding with recent climate warming and the associated expansion of shrub communities across the Arctic. Rates of carbon accumulation vary greatly between the sites, illustrating the importance of local vegetation communities, hydrology and permafrost dynamics. Multiproxy data elucidate the palaeoecology of S. lindbergii and show that it indicates wet conditions in peatlands. Copyright © 2017 John Wiley & Sons, Ltd.

The development pathways of two peatlands in South Africa over the last 6200 years: Implications for peat formation and palaeoclimatic research

For the first time, plant macrofossil analysis supported by detailed stratigraphic studies was used to reconstruct peatland development in South Africa. Two peat cores (4.69 and 1.5 m) from two coastal peatlands in KwaZulu-Natal were analysed for carpological macrofossils, wood and macrocharcoal. The first one, Matitimani, is an unchannelled valley bottom peatland (site VB), and the second one, KwaMazambane, an interdune depression peatland (site ID) further up in the same catchment. Radiocarbon dating reveals the peatland initiation at site VB at about 6260 cal. yr BP. Rising sea level and humid climatic conditions during that time coincide with the formation of organic gyttja (dominantly aquatic seeds like Nymphaea sp.). In ca. 4950 cal. yr BP, a change to drier condition took place, revealed by the formation of radicell peat from Cyperaceae, and an increase of fire frequency (macrocharcoal). After ca. 1200 cal. yr BP, peat swamp forest emerged, with Ficus trichopoda, Syzygium cordatum and Voacanga thouarsii forming wood peat. Site ID dates back to ca. 920 cal. yr BP. Its initiation is assumingly related to reduced drainage capacities of the catchment subsequently to the peat formation in Matitimani valley. A steady change from gyttja forming communities ( Nymphaea sp.– Eleocharis dulcis) to radicell peat-forming Cyperaceae communities took place. The long-term apparent rate of carbon accumulation (LORCA) is higher for site ID (89 gC m−2 yr−1) than for site VB (55 gC m−2 yr−1). Except for the peat swamp forest period, fire occurred frequently at both sites, however less in environments with frequent inundations.

Long-term environmental change and shifts in the aquatic plant community of Jones Creek, Thousand Islands National Park, Ontario, Canada based on plant macrofossil analysis

Plant macrofossils and pollen were analyzed from sediment cores to identify long-term changes in the aquatic plant community of Jones Creek, Thousand Islands National Park, Ontario, Canada. Six sediment cores were recovered from Jones Creek in February 2014. One complete core and five top/bottom samples were analyzed for plant macrofossil abundance and diversity. Sediment analysis and 210Pb dating confirmed a productive wetland throughout the core, dating back beyond 1883 AD. Jones Creek is currently dominated by thick stands of cattails, particularly the hybrid white cattail (Typha x glauca Godr). The relative abundance of Typha pollen began to increase in the late nineteenth and early twentieth century, reaching a relative abundance of nearly 40% in the modern day surface sediment. Common macrofossils recovered from the sediment record included seeds of Carex, Schoenoplectus, Najas, and Eleocharis. There is evidence that community composition, as recorded by the macrofossil record, has shifted in Jones Creek in response to human activities. In particular there has been a reduction in sedge species between historical and present day conditions as the wetland shifted from a sedge dominated wet-meadow wetland to a cattail dominated system. The results of our study indicate that future restoration efforts should be directed towards reintroducing native sedge species that were present prior to major changes in land-use that occurred in the St. Lawrence region throughout the nineteenth and twentieth centuries.

ДИНАМИКА РАСТИТЕЛЬНОСТИ НА ЮЖНОЙ ГРАНИЦЕ ЗОНЫ ШИРОКОЛИСТВЕННЫХ ЛЕСОВ ВОСТОЧНО-ЕВРОПЕЙСКОЙ РАВНИНЫ В СРЕДНЕМ И ПОЗДНЕМ ГОЛОЦЕНЕ

The paper presents new results of pollen and carpological analyses, as well as the plant macrofossil analysis and the radiocarbon dating of the peat profile of the Istochek peatland (the village of Yasnaya Polyana, Tula oblast). Based on these data, the reconstructions of vegetation dynamics on the north of the Middle Russian Upland during the Middle and Late Holocene were performed. The obtained data indicate that in the period 6500–4500 cal. years BP the study area was in the ecotone band between forest and steppe zones of the East European Plain. The boundary of the forest zone passed nearby the study area and was located in 50–70 km to the north in compare with its present position. Climate cooling and rise in moisture at 4500 cal. years BP led to increase of forested areas and shifted the forest boundary to the south. Human induced vegetation changes are traced in paleobotanical data from the Istochek peatland since 2000 cal. years BP, however dramatic environment deterioration when the natural vegetation was replaced by secondary forest stands and agricultural lands occurred during the last 300 years.

Macrofossils analysis of the peat to reconstruct holocene paleoecological conditions about Kansk forest-stepp zone (Yenisey Siberia)

В статье на примере болотного массива «Кускун», расположенного в пойме р.Есауловка (Канская лесостепь) приведены результаты изучения генезиса и эволюции болот северной лесостепи. На основании изучения макрофоссилий торфа, определения зольности и степени разложения, при применении экологических шкал Раменского и Элленберга были реконструированы палеоэкологические условия времени развития болот: дана оценка условий увлажнения за весь период торфонакопления, выделены фазы в развитии болота, описана свойственная им растительность.

Middle to late-Holocene decreased fluvial aggradation and widespread peat initiation in the Ishikari lowland (northern Japan)

This study investigated the influence of sea-level and climate changes on the decreased fluvial aggradation and subsequent widespread peat initiation in the middle to late-Holocene in the Ishikari lowland, which is a coastal floodplain formed in response to the postglacial sea-level change. By introducing a new approach to separately evaluate the rates of organic and clastic sediment input, we demonstrated that the peat began to form when the fluvial sedimentation rate was significantly decreased (less than 0.6 mm/yr), while plant macrofossil analysis suggested that lowering of water level is also important to the peat initiation. Such changes in sedimentary environment may be associated with the abrupt abandonment of crevasse splays. The concentrated ages of the peat initiation around 5600–5000, 4600–4300, and 4100–3600 cal. BP suggest that an allogenic control promoted the abandonment of crevasse splays, and different onset ages can be explained by different fluvial responses of the Ishikari River and its tributaries. The abandonment of crevasse splays could result from sea-level fall or decreased precipitation. While submillennial sea-level fluctuations coincident with the peat initiation have not been reported in coastal lowlands of Japan, the close comparison of the onset ages and decreased precipitation recorded in a stalagmite from China, which represents the strength of the East Asian summer monsoon (EASM), suggests that decrease in precipitation led to the abandonment of crevasse splays. Our results may indicate that similar fluvial responses might be common in other coastal floodplains affected by the EASM.