Paoay Lake,northern Luzon,the Philippines: a record of Holocene environmental change

The last 7000 years of environmental history for Paoay Lake and its surrounding landscape is examined through the analysis of pollen, diatoms, charcoal, mineral magnetics and AMS dating. Basal sediments contain shells of Cerithiidae and the saline‐tolerant diatom Diploneis indicating that this was an estuarine environment before becoming a freshwater lake after 6000 bp . Pollen analysis shows that submontane forests, characterized by Pinus pollen, underwent a major disturbance around 5000 years ago, recovering to previous levels by 1000 years ago. Charcoal as an indicator of fire is abundant throughout record, although the highest levels occur in the earlier part of the record, between 6500 and 5000 years ago. An aspect of the project was to examine whether there is evidence of land clearance and agricultural development in the region during the late Holocene. While a clear signal of human impact in the record remains equivocal, there appears to be a correspondence between submontane forest decline and mid‐Holocene ocean data that depict warmer and possibly drier conditions for the region. The study highlights the vulnerability of these montane forests to forecasts of a warmer and drier climate in the near future.     

Late glacial and Holocene environmental changes inferred from sediments in Lake Myklevatnet,Nordfjord, western Norway

Late Glacial and Holocene environmental changes were reconstructed using physical, chemical and biological proxies in Lake Myklevatnet, Allmenningen, (5º13′17″E, 61º55′13″N) located at the northern side of Nordfjorden at the coast of western Norway. Myklevatnet (123 m a.s.l.) lies above the Late Glacial marine limit and contains sediments back to approximately 14,300 years before a.d. 2000 (b2k). Because the lake is located ~48 km beyond the margin of the Younger Dryas (YD) fjord and valley glaciers further inland, and did not receive glacier meltwater from local glaciers during the YD, the lake record provides supplementary information to Lake Kråkenes that received glacial meltwater from a local YD glacier. Lake Myklevatnet has a small catchment and is sensitive to Late Glacial and Holocene climate and environmental changes in the coastal region of western Norway. The age-depth relationship was inferred from a radiocarbon- and tephra-based smoothing-spline model with correlated ages from oxygen isotope maxima and minima in the Late Glacial sequence of the NGRIP ice core (in years b2k) to refine the basal chronology in the Myklevatnet record. The results indicate a two-step YD warming, colder early YD temperatures than in the later part of the YD, and considerably more climate and environmental variability during the late Holocene in western Norway than recorded previously in the oxygen isotopes from Greenland ice cores. The Myklevatnet record is also compared with other Late Glacial and Holocene terrestrial and marine proxy reconstructions in the North Atlantic realm.     

Holocene vegetation history of the southern Levant based on a pollen record from Lake Kinneret (Sea of Galilee), Israel

Lake Kinneret, also known as the Sea of Galilee and Lake Tiberias, is located in the northeast of Israel. At a lake level of 211 m b.s.l. (below mean sea level), the central basin is 43 m deep. The maximum length of the lake is 21 km (N–S) and its maximum width is 12 km (W–E). Lake Kinneret’s surface area is 166 km². A new 17.8 m long sedimentary core was drilled in 2010. Here, we present the entire palynological record from it, which covers the last?~?9,000 years. Special emphasis is given to the natural and human-influenced vegetation history of Galilee in comparison to that of the more southerly Dead Sea region. Significant signs of human impact are the first Olea (olive) increase during the beginning of the Chalcolithic period between 7,000 and 6,500 years ago, as well as the prominent Olea phase during the Hellenistic/Roman/Byzantine period between 2,300 and 1,500 years ago. Mediterranean macchia and bathas scrub vegetation, as known in the area today, has developed in the southern Levant under human impact since the last ca. 1,500 years.     

Vegetation history of the SE section of the Zagros Mountains during the last five millennia; a pollen record from the Maharlou Lake, Fars Province, Iran

A pollen diagram was derived from a 150 cm core taken from the shallow hypersaline Lake Maharlou in the south-eastern part of the Zagros Mountains, SW Iran. The pollen record shows that Quercus brantii woodland and Pistacia–Amygdalus scrub dominated the area during the late Holocene. The record starts at around 5700 cal b.p. with a dry period during which both Pistacia–Amygdalus scrub and Quercus brantii woodland were at their minimum extent. This period was followed by the expansion of Pistacia–Amygdalus scrub in the area and the spread of Quercus brantii woodlands at higher altitudes. An important occupation phase, characterized by the appearance of several cultivated tree species such as Juglans, Olea, Vitis and Platanus, started at ca. 4300 cal b.p., coinciding with the onset of the Bronze Age civilization of Jiroft in Central Iran. Human activities become very clear after 3700 cal b.p. Around 2700 cal b.p., extensive stands of Pistacia–Amygdalus scrub became profoundly degraded, presumably under strong human pressure coinciding with the beginning of the Persian Empires. The maximum expansion of the Quercus brantii woodland occurred about 2100 to 1700 cal b.p. This woodland remained relatively stable until the end of the diagram at 400 cal b.p.     

The late Pleistocene climates of the Lake Zeribar region (Kurdistan,western Iran) deduced from the ecology and pollen production of nonarboreal vegetation

The concept of an arid pleniglacial in the Middle East depends primarily on the interpretation of pollen diagrams including those of Lake Zeribar in the Zagros Mountains of western Iran. It has been assumed that Lake Zeribar was surrounded by a Chenopodiaceae-Artemisia steppe and that the climate was therefore dry. Both assumptions are questioned. The environment of Pleistocene Lake Zeribar may have been similar to the tragacanthic or alpine zone of the modern Zagros Mountains. The dominance by pollen of Chenopodiaceae and Artemisia is explained by low pollen production of high-altitude vegetation, preferential incorporation of pollen of late-blooming plants into the sediments, and high production and long-distance transport of lowland pollen. In any case, high percentages of Chenopodiaceae and Artemisia pollen do not necessarily indicate low annual precipitation but a highly seasonal climate with cold winters and hot, dry summers. Such a climatic regime was in effect continuous except for a period beginning about 10600 B. P. during which summer rainfall or reduced summer drought occurred. This change in seasonality resulted in the dominance of Poaceae pollen and the initial increase in arboreal pollen. A moisture curve based on the ratio between Chenopodiaceae and Artemisia pollen indicates a pleniglacial climate with wet winters and a late-glacial and early-Holocene climate with periods of intense aridity. The climatic history presented here is compatible with non-palynological evidence of regional late Pleistocene climates and with seasonality changes suggested by climatic modelling based on orbital parameters.Abbreviations C/A Chenopodiaceae-Artemisia ratio     

Evidence for Late Glacial and Holocene environmental changes from subfossil assemblages in sediments of Lake Neuchâtel, Switzerland

Ostracod and diatom assemblages, mollusc remains, plus pollen and sediment stratigraphy from three cores taken at sites 40, 80 and 135 m deep in Lake Neuchâtel, Switzerland, show distinct changes since deglaciation. Shifts are interpreted in terms both of climatic change and major changes in the catchment input caused by the Aar River entering or bypassing Lake Neuchâtel. Three palaeoenvironmental phases are recognized: (1) the Late Glacial, with the inflow of the river before 10,000 yr B.P.; (2) the early to mid-Holocene, with temporary bypassing of the river between 10,000 and 4850 yr B.P.; and (3) the mid- to late Holocene, without river input after approx. 4850 yr B.P. During periods with river input, rhythmites were deposited. Ostracods indicate a well oxygenated hypolimnion, suggesting deep ventilation enhanced by the river inflow. The diatom assemblage indicates eutrophic to mesotrophic conditions and is dominated by generally well preserved periphytic species. The high number of unidentifiable pollen suggests oxidation during transport in the river. During periods without river input, a massive calcareous silt with abundant authigenic calcite was deposited, diatoms indicate a change to mesotrophic and oligotrophic conditions, and decreased sedimentation rates and higher alkalinity enhanced the dissolution of diatoms. Terrestrial and littoral molluscs as well as periphytic diatoms indicate erosion of the shore when the lake level rose or fell with onset or offset of the river inflow. Before 12,600 yr B.P., the patchy vegetation cover led to intensive soil erosion and high sedimentation rates. The lake was still frozen during the winter months. After approx. 12,600 yr B.P. the sediment changed from clastic rhythmites to thinly bedded, non-glacial rhythmites, the vegetation cover became denser, the abundance of ostracods increased, and molluscs started to colonize the profundal zone of the lake. The Younger Dryas (approx. 10,700–10,000 yr B.P.) displays maximum abundance of ostracods, indicating deep ventilation. The transition to the Holocene is characterized by a change in the ostracod assemblage and the river bypassed the lake between approximately 10,000 and 8900 yr B.P. When the river reentered the lake after approximately 8900 yr B.P., a new ostracod species appeared. After two short periods of river bypassing between approximately 7200 and 6950 yr B.P., diatoms indicate a higher trophic level about 6000–5000 yr B.P. associated with higher erosion rates and increased nutrient input due to Neolithic agricultural activities. After approximately 4850 yr B.P. the river bypassed the lake again and the trophic level decreased. In contrast to the early to mid-Holocene periods of decreased oxygen supply, the mid- to late Holocene is characterized by deep ventilation. This is attributed to the northward retreat of the polarfront and enhanced westerlies consequent to decreased insolation after 6000 yr B.P. The change of the river flow pattern correlates with glacier oscillations and may suggest a climatic control. The final cessation of the inflow is attributed to diversion of the river consequent to isostatic uplift and late Neolithic clearance activity.     

Human impact as registered in the pollen record: some results from the western Lake Constance region,Southern Germany

Pollen analytical results from a littoral profile taken in Lake Constance compared with pollen profiles from small kettle holes nearby form the basis for conclusions concerning human population density, the economy and environment from the Neolithic period to the Middle Ages. Early Neolithic human impact is implicated in a lime decline and also the expansion of beech. The late Neolithic lakeshore settlements caused a decline of elm, beech and lime and, by shifting cultivation, considerably changed the forest cover. The settlements were abandoned after less than 100 years. There were long periods without distinct human impact in the middle and towards the end of the late Neolithic period. Since at least the Late Bronze Age there has been permanent habitation in the region. Human impact was greatest in the High Medieval period and later, and was also substantial in the late La Tène and Roman periods. Distinct declines in human impact can be observed between the La Tène and Roman periods and in the Migration and Merovingian periods. In these intervals, open land and grazed oak forest were replaced by birch and later on by beech forests. The decreases in human impact are not of the same intensity in all diagrams.     

Holocene altitudinal shifts in vegetation belts and environmental changes in the Sierra Madre Occidental, Northwestern Mexico, based on modern and fossil pollen data

A modern pollen rain study was performed in a 300 km-long altitudinal transect (~ 28° N latitude) from 300 to 2300 m elevation. The higher elevation modern communities: epithermal oak–pines, pine–oak forest, pine forest, and mixed conifer forest were easy to distinguish from their pollen content. In contrast, lower elevation subtropical communities: thornscrub and tropical deciduous forest were difficult to separate, because they share many pollen taxa. Nevertheless we identify high frequencies of Bursera laxiflora as an important component of the tropical deciduous forest.Additionally, fossil pollen was analyzed at three sites located between 1700 and 1950 m altitude at ~ 28° latitude north in the Sierra Madre Occidental of northwestern Mexico. The sites were in pine–oak (Pinus–Quercus), pine, and mixed-conifer forests respectively. Shifts in the altitudinal distribution of vegetation belts were recorded for the last 12,849 cal yr BP, and climate changes were inferred. The lowest site (pine–oak forest) was surrounded by pine forest between 12,849 and 11,900 cal yr BP, suggesting a cold and relatively dry Younger Dryas period. The early Holocene was also cold but wetter, with mixed conifer forest with Abies (fir) growing at the same site, at 1700 m elevation, 300 m lower than today. After 9200 cal yr BP, a change to warmer/drier conditions caused fir migration to higher elevations and the expansion of Quercus at 1700 m. At 5600 cal yr BP Abies was growing above 1800 m and Picea (spruce) that is absent today, was recorded at 1950 m elevation. Fir and spruce disappeared from the 1950 m site and reached their present distribution (scattered, above 2000 m) after 1000 cal yr BP; we infer an episodic Holocene migration rate to higher elevations for Abies of 23.8 m/1000 cal yr and for Picea of 39.2 m/1000 cal yr. The late Holocene reflects frequent climate oscillations, with variations in the representation of forest trees. A tendency towards an openness of the forest is recorded for the last 2000 yrs, possibly reflecting human activities along with short-term climate change.     

Can molluscan assemblages give insights into Holocene environmental changes other than sea level rise? A case study from a macrotidal bay (Marennes–Oléron, France)

During the Late Holocene, the rate of sea level rise decreased and climate changes, hydrodynamic processes or anthropogenic impacts became predominant parameters governing the sedimentary infill of estuarine environments. The aim of this study is to describe the response of past benthic mollusc communities to these forcing factors. Mollusc skeletal remains were sampled from three 8000, 5500 and 2600 year-long sedimentary records in the Marennes–Oléron Bay (Atlantic Coast, France), where environmental changes have previously been identified thanks to a combination of very high resolution seismic profiles and sedimentological data. Molluscan assemblages successfully record environmental changes, even at the smallest temporal scale. They provide relevant information regarding bathymetry, salinity, hydrodynamics, oxygen content and sediment supply. In the 8000 year-long record, the transition from an upper to a lower intertidal mudflat community provides evidence of a transgressive phase that occurred between 8000 and 7600 years BP. In the 5500 year-long record, an oyster bank developed on the slopes of a tidal channel has been recovered. The composition of the fossil community and the careful examination of skeletal remains suggest that the channel was hydraulically inefficient, in response to the sediment infilling of its drainage area. In the 2600 year-long record, a soft-bottom, shallow-water, subtidal mollusc community, similar to that found nowadays in the Marennes–Oléron Bay, has been recovered from both lower mixed sand-mud and upper muddy units separated by a major regional unconformity dated to about 1000 years BP. This sharp transition is recorded by a few rare species, and was responsible for the local extinction of the bivalve Lepton squamosum. However, the abundance of the most common species and the quantity of fragmented shells remain stable, which may indicate that mud drape deposition was related to an increase in mud supply rather than a decrease in water energy. The level of detail of the palaeoenvironmental reconstructions varies, depending on the ecological requirements of the species. Stenotypic indicator species provide accurate, quantitative information, whereas eurytypic species add undesired variability to the assemblages. Since fossil molluscs are easy to collect and to identify and provide long-term, smoothed records of environment variations, this study suggests that they can be used prior to any other biological proxy, as a first step into reconstructions of Holocene coastal environments.     

Seven Millennia of human impact as reflected in a high resolution pollen profile from the profundal sediments of Litzelsee,Lake Constance region,Germany

A profundal core from Litzelsee, a small cirque lake in the western Lake Constance region, was investigated by pollen analysis and dated radiometrically. The upper part of the core, chronologically between 5000 cal bc and 1850 ad, was sampled continuously, resulting in a total of 449 samples, each with a sum of 1,000 arboreal pollen grains. Also in this huge data set, rare taxa, normally lacking or very scarce in pollen profiles, were registered. The ecological evaluation of these, with a focus on anthropogenic indicators, sheds light on environmental and human impact history from the Neolithic to Modern times. Further, the results are put in a regional context, together with seven other mostly unpublished pollen profiles studied in the same way.     

A 2700-year high resolution pollen record of climate change from varved Sugan Lake in the Qaidam Basin, northeastern Tibetan Plateau

A 2700-year high resolution pollen record from annually-varved Sugan Lake in the Qaidam Basin at 2793 m a.s.l was obtained to examine vegetation and climatic change on the NE Tibetan Plateau. Pollen data shows that Sugan Basin was constantly covered by open desert-steppe vegetation dominated by Chenopodiaceae, Artemisia, Poaceae and Ephedra. However, large variations in Artemisia/Chenopodiaceae (A/C) ratios suggest regional moisture fluctuations over the last 2700 years, including a dry and relatively stable climate prior to 300 AD, relatively wet climate from 300 to 1200 AD with variability during 1100-1200 AD, and unstable climate since 1200 AD with relatively moister climate during 1250-1400 AD and 1700-1800 AD. However, other proxies (varve thickness, Chironomid taxa, isotopes of oxygen in precipitated carbonate) show fresher water when regional moisture was lower inferred from A/C ratio. This inconsistency suggests the possible difference of in-lake lithology/environment and regional moisture change. Fresh water into the lake from ice melting on the surrounding mountains might have contributed to the in-lake lithology and environment variation. The effective moisture changes in the Basin are in opposite phases to snow accumulation records from Dunde ice core (5325 m a.s.l) and to the monsoon intensity inferred from Dongge Cave, suggesting that the regional topography might have played an important role in mediating moisture changes at regional scale. Pollen data from Sugan Lake shows the shift of moisture at 1200 AD, from stable to variable conditions. This event is well correlated with other paleoclimate proxies in China and other parts of the world; however, the mechanisms behind these patterns require further investigation.     

Vegetation history and climate changes in West Equatorial Africa during the Late Pleistocene and Holocene, based on a marine pollen diagram from the Congo fan

Palynological investigation of the marine core, GeoB 1008-3, from near the mouth of the Congo river (6°35.6S/10°19.1E), provides information about the changes in vegetation and climate in West Equatorial Africa during the last 190 ka. The pollen diagram is divided into zones 1–6 which are considered to correspond in time with the marine isotope stages 1–6. Oscillations in temperature and moisture are indicated during the cold stage 6. During stage 5, two cooler periods (5d and 5b) can be shown with an expansion of Podocarpus forests to lower elevations on the expense of lowland rain forest. Extended mangrove swamps existed along the coast in times of high sea level (stages 5 and 1).     

Climate-related changes during the Late Glacial and early Holocene in northern Poland, as derived from the sediments of Lake Sierzywk

Reconstruction of past climate change and ecosystem response is important to correctly assess the impacts of global warming. In this study, we provide a paleoenvironmental record of in-lake and catchment changes in northern Poland during the Late Glacial and early Holocene using various biotic proxies (pollen, macrofossils and Cladocera) preserved in the lake sedimentary record. Chronology was derived from palynological correlation with a well-dated pollen sequence from nearby-lying Lake Ostrowite and some well-dated events of vegetation history in Central Europe. Pollen analysis provided information on regional climate change affecting vegetation dynamics, whereas macrofossils supplied substantial information on the response of local flora and fauna to climatic, geomorphological and limnological changes. Data were supplemented by analysis of Cladocera remains, which are of special importance because of their quick response to changes in trophic conditions and climate (especially temperature). The bottom of the sediment core reflects an initial stage of the lake formed during the late Aller?d. The Younger Dryas cooling apparently resulted in forest recession and presence of cold tolerant Cladocera species. Due to amelioration of climate at the end of the Younger Dryas and melting of ice, the lake deepened. The beginning of the Holocene was characterised by forest shrinkage and induced clear changes in local flora and fauna communities. The regional vegetation development deduced from the lake’s core is generally consistent with the vegetation history of central Europe. Due to the location of the site near the seashore (oceanic climate and western wind), signals of warming came earlier than inland and in eastern Poland.     

Late-glacial and Holocene climate dynamics at the steppe/forest ecotone in southernmost Patagonia, Argentina: the pollen record from a fen near Brazo Sur, Lago Argentino

We present a pollen record from a fen at the eastern shore of Brazo Sur south of Lago Argentino, Argentina (core BRS 1/06, 50°34′54″S, 72°54′52″W, 198 m a.s.l.). The coring site is located in the transition zone from humid grass steppe to Andean Nothofagus forest. With the exception of a mid-Holocene sand layer, the record covers the interval between 13,350 and 1,700 cal b.p., indicating that there could have been no recurrence of Late-glacial conditions in Brazo Sur, as has been suggested in the literature as having been contemporary with the Younger Dryas interval in the northern hemisphere. The Late-glacial and early Holocene periods at Brazo Sur are characterized by fluctuations between humid grass-dominated steppe associations and drier ones dominated by Asteraceae and Ericaceae. At the start of the Holocene, the pollen influx increased. Nothofagus dominance began by 7,700 cal b.p. probably due to increasing moisture. Present-day closed Nothofagus forest developed around 2,500 cal b.p., related to a further increase in moisture.     

A late Holocene pollen diagram from the Megaris,Greece, giving possible evidence for cultivation of<Emphasis Type="Italic"> Ceratonia siliqua</Emphasis> L. during the last 2000 years

A late Holocene pollen profile from the Megaris on the eastern Gulf of Corinth shows a vegetation which was strongly influenced by human impact throughout. A Pistacia-Phillyrea maquis, which is reflected in the older parts of the profile, changed later to a more degraded vegetation type. In the uppermost part Pinus dominates the pollen spectrum. A continuous record of Ceratonia siliqua pollen older than cal a.d. 100 is of special interest.     

Centaurea rahiminejadii sp. nov. and a new record in the genus Centaurea (Asteraceae,Cardueae–Centaureinae) from Iran

A new species, Centaurea rahiminejadii Negaresh (Asteraceae) in C. sect. Cynaroides Boiss. ex Walp., is described and illustrated from the Kermanshah Province, west Iran. It is morphologically similar to Centaurea regia Boiss. subsp. regia. Diagnostic morphological of this and closely related taxa are discussed and presented. The ecology, habitat and conservation status of the new species are also described. In addition, Centaurea regia subsp. cynarocephala (Wagenitz) Wagenitz is reported as a new record to the flora of Iran. Finally, the geographic distribution of the new species and closely related species is presented and mapped.     

Recent changes in the fishery of a new tropical man-made lake, Lake Kamburu (Kenya)

Five years after inundation, two varieties of Cyprinus carpio —the common carp and the mirror carp, have appeared in the commercial fishery in Lake Kamburu. Species of Tilapia continue to remain the most abundant fish in the lake and their numbers are on the increase. The second most numerous species is Barbus while Labeo sp. seems to be declining. The numbers of Mormyrus have declined drastically. Species of the genera Tilapia, Barbus and Cyprinus are widely distributed within the lake; Labeo prefers the confluence of the rivers entering into the lake and Mormyrus has moved upriver.     

Ligand-induced conformational changes in the capping subdomain of a bacterial old yellow enzyme homologue and conserved sequence fingerprints provide new insights into substrate binding

We have recently reported that Shewanella oneidensis, a Gram-negative gamma-proteobacterium with a rich arsenal of redox proteins, possesses four old yellow enzyme (OYE) homologues. Here, we report a series of high resolution crystal structures for one of these OYEs, Shewanella yellow enzyme 1 (SYE1), in its oxidized form at 1.4A resolution, which binds a molecule of PEG 400 in the active site, and in its NADH-reduced and p-hydroxybenzaldehyde- and p-hydroxyacetophenone-bound forms at 1.7A resolution. Although the overall structure of SYE1 reveals a monomeric enzyme based on the alpha(8)beta(8) barrel scaffold observed for other OYEs, the active site exhibits a unique combination of features: a strongly butterfly-bent FMN cofactor both in the oxidized and NADH-reduced forms, a collapsed and narrow active site tunnel, and a novel combination of conserved residues involved in the binding of phenolic ligands. Furthermore, we identify a second p-hydroxybenzaldehyde-binding site in a hydrophobic cleft next to the entry of the active site tunnel in the capping subdomain, formed by a restructuring of Loop 3 to an "open" conformation. This constitutes the first evidence to date for the entire family of OYEs that Loop 3 may indeed play a dynamic role in ligand binding and thus provides insights into the elusive NADH complex and into substrate binding in general. Structure-based sequence alignments indicate that the novelties we observe in SYE1 are supported by conserved residues in a number of structurally uncharacterized OYEs from the beta- and gamma-proteobacteria, suggesting that SYE1 represents a new subfamily of bacterial OYEs.     

Palaeobotanical evidence for agricultural activities in the Eifel region during the Holocene: plant macro-remain and pollen analyses from sediments of three maar lakes in the Quaternary Westeifel Volcanic Field (Germany, Rheinland-Pfalz)

As a part of the ELSA-project (Eifel Laminated Sediment Archive) new pollen and plant macro-remain analyses have been carried out on a series of Holocene lacustrine sediments from three open maar lakes of the Quaternary Westeifel Volcanic Field. In combination with already existing pollen analyses, the archaeological record and written sources, the present study casts new light on settlement activities and henceforth the development of agriculture from the prehistoric to historic times in this region. While there are clues that wood pasturing was practised in the Eifel region from the Michelsberg Culture onwards (c. 4300 cal. b.c.), the Vulkaneifel is a remote area with relatively poor soils and a humid climate and was not constantly settled until the Late Neolithic/Early Bronze Age, when cereal pollen was found regularly in the deposits. Plant macro-remains (chaff), which give us direct evidence for arable agriculture in the surroundings of the maars, were also found in layers belonging to the Early Bronze Age (c. 1900 cal. b.c.). At the same time we can observe the massive spread of Fagus sylvatica (beech) in all pollen diagrams, which was most probably caused by a combination of climatic, anthropogenic and competitive factors. Later impacts of agriculture were an abundance of crop weeds and pollen in the following Middle Bronze Age. Nevertheless human impact remained discontinuous until the Urnfield Culture (1200–800 cal. b.c.). A layer of weeds dating at the end of the Urnfield Culture was found and also flax (Linum usitatissimum) cultivation first becomes apparent. However, the subsequent Iron Age and Roman Period reveal only crop weeds and cereal pollen in slightly higher concentrations, but the abundance of Poaceae pollen at this time is most probably consistent with grazing activities. There follows compelling evidence of the importance of flax cultivation and processing at the maars from the Merovingian Period (5th century a.d.) onwards. A detailed insight into the agriculture of the High Medieval comes from flash flood layers of the 14th century a.d., where remains of Secale cereale (rye) and crop weeds reflect winter-sown cultivation of rye. Cannabis sativa (hemp) was also cultivated and processed during the medieval. Finally we can trace the Prussian reforestation in the 19th century a.d., with an increase in Pinus sylvestris (pine) and Picea abies (fir), by both pollen and plant macro-remains.     

Understanding the human impact on Akita-sugi cedar (<Emphasis Type="Italic">Cryptomeria japonica</Emphasis>) forest in the late Holocene through pollen analysis of annually laminated sediments from Ichi-no-Megata,Akita, Japan

Akita-sugi (Cryptomeria japonica, Japanese cedar that is grown in Akita) forests are among the most important for commercially valuable timber in Japan. Historically, these forests have been severely exploited, although now some parts of them are conserved. It is important to know the detailed history of the forests in order to utilize them sustainably in the future. This study analyzes the pollen in an annually laminated lake sediment core from Ichi-no-Megata on the Oga peninsula, Akita, Japan, to understand the history of Akita-sugi cedar forests. An age-depth model was developed based on the results of an accelerator mass spectrometer dating of 13 plant macrofossils from the surface to 422 cm in depth, the Towada-a tephra and other well-known event layers. The dominant pollen taxa were Cryptomeria and Fagus crenata by ad 1000. The first increase of Cryptomeria was detected around 1700 bc. By the 1st century ad, Cryptomeria forest was established. At that time, Cryptomeria was mixed with deciduous trees, mainly F. crenata. The pollen analysis found evidence that the main loss of woodland occurred during the 11th century ad, when forest lands were cleared for agriculture. Substantial natural forests nevertheless remained until the 16th century, after which forest resources were exhausted. Conservation and plantation activities took place later, but human activity in response to severe famines prevented the recovery of the forests. After the famine periods, the remaining forests recovered to their previous condition, but after World War II, the natural forests shrank further and plantation forests without deciduous trees were established over large areas.