Early Holocene Climate Change Research Articles

Long-term ecological successions of vegetation around Lake Victoria (East Africa) in response to latest Pleistocene and Early Holocene climatic changes

Reconstructions of ecosystem dynamics in tropical East Africa during the latest Pleistocene and the Holocene provide important long-term ecological insights, but so far, only a few, sometimes incomplete terrestrial records exist. In this paper, we present a new high-resolution palynological record from the Lake Victoria basin, covering the period from 16,600 to 9000 cal yr BP, when Afromontane forests and tropical rainforests gradually replaced the savanna. We discuss this dataset in the context of published palaeoclimate data, TEX86 inferred temperature and δD leaf wax inferred precipitation records, to assess long-term ecological successions and their potential causes. By ca. 16,500 cal yr BP, the movement of the Afrotropical rainbelt, not only brought an increase in temperature and moisture into the Lake Victoria basin, but also promoted the spread of arboreal taxa, such as Celtis and Podocarpus, at the expense of the savanna. At that time, fires were prominent in the sparse Afromontane vegetation. Later from ca. 15,500–15,000 cal yr BP, temperature and humidity rose and Afromontane trees such as Olea and Macaranga spread slightly, while grasses were burning in the savanna. During the period from 13,250 to 10,700 cal yr BP, Afromontane vegetation dominated by Olea became more prominent and expanded towards the lowlands where the tropical rainforest or gallery forest established; however, the savanna only marginally retreated. An initial spread of tropical rainforests occurred from ca. 11,500–11,100 cal yr BP during the onset of the Holocene, when temperatures and moisture further increased. Subsequently, between 10,700 and 10,300 cal yr BP the tropical savanna was largely replaced by the tropical rainforest, while the Afromontane forest likely spread to higher elevations, similar to the patterns observed today. Our high-resolution record demonstrates the dynamic response of African tropical ecosystems to major temperature and humidity variations from 16,600 to 9000 cal yr BP, including some of the most important landscape transformations in East Africa in the past 20,000 years.

Early and Middle Holocene climate change inferred by Wayaogou Section in the Southeastern Mu Us Desert

Early and Middle Holocene climate change inferred by Wayaogou Section in the Southeastern Mu Us Desert

Multi-phased deglaciation of south and southeast Greenland controlled by climate and topographic setting

To put recent Greenland Ice Sheet (GrIS) ice loss into a longer-term context, we must understand its behavior during late-glacial and Early Holocene warming. Previous results seem to suggest that there is a large contrast in the timing of deglaciation between South and Southeast Greenland. However, because of lack of available data, in particular in Southeast Greenland, it is difficult to assess how the ice sheet responded to major late-glacial and Early Holocene climate changes. In this study, we use 41 new 10Be ages to constrain the deglaciation chronology in 12 new locations from the coast to the present ice margin in South and Southeast Greenland. We find that South Greenland (south of 61.5°N) deglaciated between ∼14.8 and 11.9 ka, whereas Southeast Greenland (61.5°N to 68.2°N) deglaciated between ∼11.4 and 11.3 ka. The deglaciation of the coastal, low-intermediate topography in South Greenland coincides with increased air surface temperatures during the Bølling-Allerød with fjords continuing to deglaciate into the Early Holocene. In contrast, the ice sheet persisted at the coast until the late-glacial and Early Holocene in Southeast Greenland, likely because of increased precipitation in the high alpine topography and fjord geometry and bathymetry (e.g. width of fjords and presence of sills). This multi-phased deglaciation demonstrates a contrasting response of the southern GrIS to changes in climate and variations in topographic setting, and that the spatial deglaciation of the GrIS was complex and likely did not respond to a single external climate forcing.

Speleothem and glacier records of latest Pleistocene–early Holocene climate change in the western North American interior

ABSTRACTRapid and high‐magnitude North Atlantic climate oscillations following the Last Glacial Maximum have been correlated to climate change events in western North America. However, the strength of teleconnections between the North Atlantic and the interior of western North America remains poorly understood. We present a U‐series calibrated speleothem record from Timpanogos Cave National Monument, located at 2040 m asl in the Wasatch Mountains of Utah, spanning 13.5–10.6 ka. Additionally, we carried out a climate reconstruction for a coeval glacier advance in the Wind River Range of Wyoming. Our results indicate that between 13.5 and 12.8 ka, the Wasatch was probably first cool and dry and then warmed. After 12.8 ka, our record suggests cool and/or wetter conditions followed by reduced moisture until 11.8 ka, followed by an early Holocene wet period. The Timpanogos record exhibits few similarities with those from the North Atlantic. Climate reconstructions of the Titcomb Basin glacier suggest modest temperature depressions relative to modern (<−3 °C) were necessary to sustain the glacier with a moderate increase in precipitation (>150%). The high‐altitude speleothem record presented here provides a valuable basis for understanding latest Pleistocene–early Holocene glacial episodes in western North America.

Late Pleistocene and Early Holocene climate changes and human habitation in the arctic Western Beringia based on revision of palaeobotanical data

Paleoenvironmental and paleoclimatic changes at the transition from the Late Pleistocene to the Early Holocene in the arctic Western Beringia (AWB) appear to be extremely important for human habitation record of the area. To estimate that we used multiple paleoenvironmental proxy-data collected from different locations (n = 30) and archaeological data from radiocarbon-dated sites (n = 36). Based on correlations between pollen records and their radiocarbon chronology we combined paleoenvironmental data into single generalized sequence for the entire AWB compared to global temperature trend and placed archaeological data on the same time scale. General trend of paleoclimatic changes in the second half of Late Pleistocene is explored, in which the sequence of major climate changes within Marine Isotope Stages 3 and 2, and in the beginning of the Holocene are revealed. Climate changes and landscape evolution play as a key governing factor for the human population of the area since its initial phase. Human habitation is documented starting ca. 50,000 BP. Since then, AWB remains human populated but witnessed a number of cultural changes and intrusions before the present-day map of ethnic groups became finally formed. Repeated arrival of new population into AWB finds strong correlation with major paleogeographic events, both cold and warm, such as Last Glacial Maximum, Younger Dryas, and the onset of the Holocene. It is shown that human habitation had been consistently driven by various abiotic and biotic factors, that is, by complex interpaly of development in plant and faunistic associations, landscape evolution, tree line change, and climate-driven changes in spatiotemporal patterns of population dynamics in megaherbivores, especially mammoth.

Diverse responses of common vole (Microtus arvalis) populations to Late Glacial and Early Holocene climate changes – Evidence from ancient DNA

The harsh climatic conditions during the Last Glacial Maximum (LGM) period have been considered the cause of local extinctions and major faunal reorganizations that took place at the end of the Pleistocene. Recent studies have shown, however, that in addition many of these ecological events were associated with abrupt climate changes during the so-called Late Glacial and the Pleistocene/Holocene transition. Here we used ancient DNA to investigate the impact of those changes on European populations of temperate vole species (Microtus arvalis). The genetic diversity of modern populations and the fossil record suggests that the species may have survived cold episodes, like LGM, not only in the traditional Mediterranean glacial refugia but also at higher latitudes in cryptic northern refugia located in Central France, the northern Alps as well as the Carpathians. However, the details of the post-glacial recoloni-zation and the impact of the Late Glacial and Early Holocene climate changes on the evolutionary history of the common vole remains unclear. To address this issue, we analysed mtDNA cytochrome b sequences from more than one hundred common vole specimens from 36 paleontological and archaeological sites scattered across Europe. Our data suggest that populations from the European mid-and high latitudes suffered a local population extinction and contraction as a result of Late Glacial and Early Holocene

Small headwater stream evolution in response to Lateglacial and Early Holocene climatic changes and geomorphological features in the Saint-Gond marshes (Paris Basin, France)

The study focuses on river dynamics and vegetation changes during the last Glacial-Interglacial transition from a headwater stream located in the eastern part of the Paris Basin. We adopt a spatial multiproxy approach combining image analyses, geophysical surveys, sedimentary and pollen record analyses to document the impact of Lateglacial climate changes and geomorphological features on vegetation and fluvial dynamics in the small Boitet catchment (ca. 20 km2). Our results show that the sedimentary record is organized into six successive alluvial sequences reflecting changes in discharge and channel morphology in response to short phases of climate oscillations during the Lateglacial and Early Holocene periods. The Boitet alluvial sequences present some similarities with other NW European rivers that are interpreted as large-scale fluvial system evolution to climate changes. However, some local differences have also been highlighted partly related to the upstream position of the catchment. Among them, two distinctive features of the Boitet catchment are 1) the preservation of the Oldest Dryas deposits, which have been rarely described in this area, and 2) the recognition of multichannel river dynamics during the Oldest Dryas and Younger Dryas. We demonstrate that the fluvial evolution is firstly triggered by climate changes and that land surface features may also influence specifically upstream areas revealing contrasting responses of the river system.

Late glacial and early Holocene climate and environmental changes in the eastern Baltic area inferred from sediment C/N ratio

We assessed the utility of using the sediment total organic carbon/total nitrogen (C/N) ratio as an indicator of paleoclimate changes in the eastern Baltic area during the late glacial and early Holocene. The C/N ratio in sediments from Lake Lielais Svētiņu, eastern Latvia, was compared with other sediment variables that are used as proxies of past climate and environment. Analysis revealed that although the organic matter (OM) content in late glacial sediments was extremely low, the C/N ratio captured information about OM origin, and fluctuations in the ratio tracked climate oscillations. The C/N ratio was significantly positively correlated with pollen-inferred mean summer temperature. Therefore, C/N ratio was lower under colder conditions, indicating a predominantly phytoplankton origin of OM, and was higher during warmer conditions, when there was more vegetation around the lake. A strong positive correlation between C/N ratio and the paleopigment beta carotene suggested that elevated phytoplankton production resulted from higher nutrient availability that was controlled largely by the input of terrestrial OM to the lake during warmer climate episodes. Thus, C/N ratio was a good indicator of paleoclimate changes, at least for the late glacial period, when generally cold conditions prevailed. This study also demonstrates the power of multi-proxy paleolimnological analyses for investigating past environmental changes in lakes and their watersheds.

Survival histories of marsupial carnivores on Australian continental shelf islands highlight climate change and Europeans as likely extirpation factors: implications for island predator restoration

Predators are critical components of ecosystems, but large marsupial carnivores have suffered major declines and extinctions in Australia. To inform predator restoration efforts on Kangaroo Island (South Australia) we examined the survival histories and potential extirpation factors of large marsupial carnivores that previously occurred on Kangaroo Island, King Island and Flinders Island, located off the southern coastline of the Australian mainland. Through a review of historical accounts and fossil evidence, we determined that the pattern of species persistence and extirpation on Kangaroo Island parallels that observed on King and Flinders Islands. Fossil data supports the terminal Pleistocene–early Holocene extinction of the thylacine (Thylacinus cynocephalus) from Kangaroo Island and the Tasmanian devil (Sarcophilus harrisii) from both Kangaroo and Flinders Islands. Though eastern quoll (Dasyurus viverrinus) fossils have been found on both Kangaroo and Flinders Islands, and western quoll (D. geoffroii) on Kangaroo Island, contemporary evidence for their post-European persistence is unclear. In contrast, fossil, museum and anecdotal data supports the presence of the spotted-tailed quoll (D. maculatus) on all three islands and, contrary to established knowledge, its post-European persistence on Kangaroo Island. The loss of T. cynocephalus, S. harrisii, D. geoffroii and D. viverrinus from these islands appears to be commensurate with late to terminal Pleistocene–early Holocene climate change and associated changes in vegetation communities. In contrast, anthropogenic persecution of D. maculatus appears to be the principal cause of its post-European extirpation. We recommend D. maculatus as a suitable candidate marsupial carnivore for reintroduction to Kangaroo Island.

Response of a land-terminating sector of the western Greenland Ice Sheet to early Holocene climate change: Evidence from 10Be dating in the Søndre Isortoq region

The prevalence of land-terminating Greenland Ice Sheet margins is expected to increase as tidewater glaciers retreat onto land, yet few studies have characterized the sensitivity of these slow-moving margins to climatic variability. The response of land-terminating ice sheet sectors to climate forcing can be assessed by examining records of paleo-ice margin positions preserved in ice sheet moraine systems. In western Greenland, the extensive Fjord Stade moraine system was deposited by minor readvances or stillstands of the Greenland Ice Sheet margin during early Holocene net recession. Here, we combine new moraine mapping and cosmogenic 10Be exposure dating to constrain the timing of Fjord Stade moraine deposition in the Søndre Isortoq region. We find that the Fjord Stade moraines are composed of a western stage and an eastern stage, which we constrain to 9.7 ± 0.7 ka (n = 7; 1 SD) and 9.0 ± 0.3 ka (n = 7; 1 SD), respectively. Synchronous deposition of the Fjord Stade moraine complex across at least 350 km of western Greenland implies a widespread response of the western Greenland Ice Sheet to the 9.3 ka event. Furthermore, these new moraine ages may correlate with Laurentide Ice Sheet-sourced freshwater pulses into the North Atlantic Ocean. We also show that the response of the western Greenland Ice Sheet to early Holocene freshwater forcing was not restricted to fast-flowing, marine-terminating outlet glaciers; the land-terminating margin in the Søndre Isortoq region halted or reversed its pattern of retreat in response to climatic change.

Patterns and dynamics of European vegetation change over the last 15,000 years

AbstractAimPalaeoecological reconstructions document past vegetation change, with estimates of fast shifts in species distributions. The resulting rates of plant spread are often not matched by model simulations of climate‐driven vegetation dynamics. Genetic surveys of extant plant populations document directions of the post‐glacial spread of trees, challenging traditional interpretations. Our aim is to examine an updated continental pollen data set from Europe in the light of the new ideas about vegetation dynamics emerging from genetic research and vegetation modelling studies.LocationEurope.MethodsWe use pollen data from the European Pollen Database (EPD) to construct interpolated maps of pollen percentages documenting changes in the distribution and abundance of major plant genera and the grass family in Europe over the last 15,000 years.ResultsOur analyses confirm high rates of post‐glacial spread with at least 1000 m year−1 for Corylus, Ulmus and Alnus and average rates of 400 m year−1 for Tilia, Quercus, Fagus and Carpinus. The late Holocene expansions of Picea and Fagus populations in many European regions cannot be explained by migrational lag. Both taxa shift their population centres towards the Atlantic coast suggesting that climate may have played a role in the timing of their expansions. The slowest rates of spread were reconstructed for Abies.Main conclusionsThe calculated rates of post‐glacial plant spread are higher in Europe than those from North America, which may be due to more rapid shifts in climate mediated by the Gulf Stream and westerly winds. Late Holocene anthropogenic land use practices in Europe had major effects on individual taxa, which in combination with climate change contributed to shifts in areas of abundance and dominance. The high rates of spread calculated from the European pollen data are consistent with rapid tracking of early Holocene climate change by common tree species, documenting that plants can spread fast tracing their climate space, regardless of their dispersal strategy.

Varved sediment responses to early Holocene climate and environmental changes in Lake Meerfelder Maar (Germany) obtained from multivariate analyses of micro X‐ray fluorescence core scanning data

ABSTRACTWe present an early Holocene record from Lake Meerfelder Maar in Germany for in‐depth interpretation of depositional changes in annually laminated lake sediments as proxies for climatic and local environmental changes. We characterized the compositional changes in the sediment record using Ward's clustering analyses of the micro X‐ray fluorescence core scanning data and linked these to microfacies descriptions. The down‐core distribution of the clusters allowed us to define boundaries that represent variations of a comprehensive element assemblage occurring at 11 555, 11 230, 10 650, 10 515 and 9670 varve a BP. Our main results show that during the Early Holocene the long‐term vegetation reorganization and evolution of the lake's catchment played a predominant role for sediment deposition. Abrupt shifts occurred at the Younger Dryas/Holocene and the Preboreal/Boreal biostratigraphical boundaries. We do not observe clear signals corresponding to known short‐term climatic oscillations described in the North Atlantic region such as the Preboreal Oscillation. A unique and intriguing episode in the history of the lake of predominantly organic deposition and very low amounts of allochthonous sediments occurred between 10 515 and 9670 varve a BP and is related to hydrological thresholds.

Lateglacial and early Holocene climatic fluctuations recorded in the diatom flora of Xiaolongwan maar lake, NE China

A palaeolimnological study of the annually laminated sediment sequence of Lake Xiaolongwan, a small maar lake in northeastern China, revealed distinct diatom responses to Lateglacial and early Holocene climate change between c. 19 700 and c. 10 700 a BP. In addition to analyses of diatom assemblage composition and of the biovolume accumulation rate of planktonic diatoms, geochemical (total nitrogen, total organic carbon) and physical (varve type and thickness) indicators were used to assess past environmental change. The diatom assemblages reveal a complex interplay between direct climate effects on the seasonal lake conditions (timing of ice cover break‐up, water column mixing and thermal stratification), catchment‐mediated effects on the concentrations of nutrients and dissolved organic carbon and, possibly, biotic interactions between the different algal groups present in the phytoplankton of Lake Xiaolongwan (diatoms, Chrysophyceae and Dinophyceae). The most remarkable changes in the aquatic system were: (i) a sharp increase in Asterionella formosa and the collapse of Handmannia balatonis at c. 14 780 a BP, corresponding with the onset of the Bølling – Allerød interstadial; (ii) a sharp rise in Stephanodiscus minutulus at c. 12 840 a BP, marking the start of the Younger Dryas event and (iii) when the lake phytoplankton became dominated by Dinophyceae instead of diatoms at c. 11 170 a BP, after the Pre‐Boreal oscillation. Two diatom assemblage zones characterize the Younger Dryas at Lake Xiaolongwan, suggesting a bipartite division of this stadial event as in several records from eastern Asia and Europe. The quasi‐synchronicity of these events with the oscillations described in the North Atlantic realm demonstrates that during the Lateglacial, North Atlantic dynamics at centennial and millennial time scales had a strong control upon the climate in northeastern China.

Insect faunal response to environmental changes during the last interglacial in Western Beringia

Reconstruction of the last interglacial (LI) environment could help us understand the mammoth faunal extinction and facilitate predictions of the effects of future on ecosystems. This work applied the fossil insect method to a number of interglacial sites in the Siberian Arctic (West Beringia). The main problem of the LI in Western Beringia is uncertain age determinations; many interesting sites are undated. Interpretation of “warming” signals is also problematic because of the special character of regional Pleistocene interglacial insect communities; these faunas are different from the modern ones. Investigation can clearly recognize interglacial faunas and, with additional stratigraphic evidence, correlate some units to the LI. Insect study helps shed light on the survival of large grazing mammals in Western Beringia during LI: 1) steppe-tundra areas remained in the forested regions; 2) climate change provided sufficient warmth to support the steppe-tundra environment in the north. Early Holocene climate change, in combination with marine transgression, progressively reduced suitable habitats for large mammals until a critical point was reached. Insect populations were also affected, but due to their small size, many steppe-tundra insect species remained as relicts in isolated patches of steppe-tundra.

South to north: Contrasting late-glacial and early-Holocene climate changes and vegetation responses between south and north Norway

Norway shows south–north climate and vegetation gradients today. Were there similar gradients during the late-glacial and early Holocene, 14,700–9000 years ago? A comparison was made along a south–north transect in Norway of plant-macrofossil reconstructions of past vegetation changes and independent summer temperature records derived from parallel chironomid data (C-Tjul). Three lake sites were selected with sediment cores with good chronological control. The importance of soil moisture is reflected by the reconstructed vegetation in relation to the temperature regime. Besides climate drivers, how important were intrinsic succession and competition in influencing vegetation patterns? Were migration delays significant, why and by how much? Oceanic climate in the late-glacial in south-west Norway resulted in snow-bed vegetation and glacier development in the Younger Dryas (YD). In contrast, the north was arid and continental, even into the early Holocene. Overall, temperatures were about 2°C colder than in the south. The YD impact differed markedly between south and north Norway. In the south, cooling at c. 12,700 cal. yr BP was swift and marked by strong responses. In the north, there was no impact at the chronological start of the YD, but cooling occurred later about 12,450 cal. yr BP together with increased aridity. During the early Holocene, temperature and oceanicity increased progressively northwards as the North Atlantic Current became established. Birch woodland developed in the south about 660 years after the start of the Holocene, after about 1000 years on Andøya, and after about 1450 years in northernmost Norway. However, the 590 year lag in the south after C-Tjul reached 11°C, the limiting temperature for tree-birch growth, decreased to 400 years in the north, as the birch tree-line kept pace with temperature rise. In the far north, a thermal maximum of 1°C above today’s mean July temperature and parallel vegetation development were recorded from 10,100 to 9370 cal. yr BP. On Andøya, temperatures exceeded present values by 1°C after 9700 cal. yr BP. There was no detectable period of above modern temperatures further south before 9000 cal. yr BP.

Long-term stabilization of deep soil carbon by fire and burial during early Holocene climate change

The Brady soil body was buried by loess deposits as a result of early Holocene climate change. Geochemical analyses suggest that large amounts of organic carbon were trapped in this soil as a result of fire activity and slow decomposition resulting from rapid burial.

Early Holocene environment at a key location of the northwest boundary of the Asian summer monsoon: a synthesis on chronologies of Zhuye Lake, Northwest China

The intensified monsoon increases summer rainfall and creates wet conditions in the Asian summer monsoon region during the early Holocene. Along with millennial-scale changes of the monsoon intensity, it is still unclear whether the boundary of the monsoon region changes according to monsoon variability. Investigations into the early Holocene environment in monsoon marginal zones are crucial for understanding the monsoon boundary changes. Zhuye Lake is located at the northwest edge of the Asian summer monsoon, the northern Qilian Mountains, which are less affected by modern summer monsoon water vapor. Previous studies have reached different conclusions regarding the early Holocene climatic and environmental changes based on different dating methods (14C and OSL (optically stimulated luminescence)) and materials (shells, carbonate, pollen concentrates and bulk organic carbon). In this study, we synthesized 102 14C dates and 35 OSL dates from ten Holocene sedimentary sections and ten paleo-shorelines in the lake basin. A comparison between ages from different dating methods and materials generally shows that carbon reservoir effects are relatively slight in Zhuye Lake while the disordered chronologies are mainly related to the erosion processes and reworking effects. In addition, proxy data, including lithology, pollen, total organic carbon and carbonate, were collected from different sites of Zhuye Lake. According to the new synthesis, the early Holocene environment was relatively humid, associated with high runoff and lake water levels. The result indicates that the monsoon boundary moves to the north during the period of the intensified monsoon. A typical arid-area lake was formed during the mid-Holocene when carbonate accumulation and high organic matter contents were the main features of this period. The lake retreated strongly during the late Holocene, showing a drought trend. Overall, the lake evolution is generally consistent with the Holocene Asian summer monsoon change, showing the monsoon influence to monsoon marginal zones.

Diatom and vegetation responses to Late Glacial and Early Holocene climate changes at Lake Estanya (Southern Pyrenees, NE Spain)

We investigate Lake Estanya's diatom and pollen records from the Late Glacial (LG) to the Early Holocene (EH), in order to compare limnological and vegetation responses to common climate forcing. The biotic changes recognized in this study largely agree with the hydrological evolution of the lake described previously for the same period. The diatom record shows high sensitivity to fluctuations in both lake level and salinity concentration as a consequence of climate shifts. In addition vegetation results indicate that the area could have played an important role as regional vegetation refuge. Shallow lake conditions during the Last Glacial Maximum (LGM) were punctuated by relatively deeper freshwaters between 19.3 and 18.6calkyr BP and at 18.0calkyr BP, as recorded by diatom shifts. A subsequent increasing aridity trend, coinciding with the Mystery Interval (MI), affected the diatom accumulation rates, which dropped to its minimum values between 17.2 and 14.7calkyr BP. Particularly dry and cold conditions during the LGM and MI are supported by the largest values of steppic pollen taxa of the whole sequence, which account for up to 40%. However, relatively high values of Betula during the Heinrich Event 1 suggest a plausible regional vegetation refuge. Abrupt cooling and warming episodes within the LG triggered remarkable ecological threshold crossings in the diatom communities, especially during the stadial/interstadial episodes. At this point, the vegetation reflects the onset of warm conditions during the Bølling/Allerød with the partial substitution of Betula by Marcescent and Evergreen Quercus, which probably indicates the arrival of temperate taxa to the area and the likely migration of birch to higher altitudes. The Younger Dryas Stadial shows a complex ecological response. Diatoms are very poorly preserved, but aquatic taxa reach their highest values. An increase in Marcescent Quercus during this cold stage lends further support to the hypothesis that this is a regional vegetation refuge. Low lake levels recorded during the EH affected the development and preservation of diatom communities. A delay in the onset of humid conditions for the EH is also supported by the vegetation composition, characterized by the maximum expansion of Juniperus.

Late Pleistocene and early Holocene climate and environmental changes in the Horton Plains, central Sri Lanka

Late Pleistocene and early Holocene climate and environmental changes in the Horton Plains, central Sri Lanka

Human used upper montane ecosystem in the Horton Plains, central Sri Lanka – a link to Lateglacial and early Holocene climate and environmental changes

This study utilizes radiocarbon-dated pollen, spores, Sphagnum spp. macrofossils and total organic carbon proxies to examine variability of past climate, environment and human activity in montane rainforest, grassland and wetland of the Horton Plains (HP), central Sri Lanka since the Last Glacial Maximum (LGM). The LGM is largely characterized by grasslands and xerophytic herbs dominated open habitats. Arid-LGM punctuated climatic ameliorations, which took place in short episodes. Humans appear to have reached the HP ecosystem after 18,000 cal yrs BP occasionally. The first Intertropical Convergence Zone (ITCZ) induced changes in South West Monsoon (SWM) rains occurred at low latitudes between 16,200 and 15,900 cal yrs BP suggesting an onset of monsoon rains. After this event, monsoon rains weakened for several millennia except the period 13,700–13,000 cal yrs BP, but human activity seems to have continued with biomass burning and clearances by slash and burn. Very large size grass pollen grains, which are morphologically similar to pollen from closer forms of Oryza nivara, were found after 13,800 cal yrs BP. Early Holocene extreme and abrupt climate changes seem to have promoted the forms of O. nivara populations in association with humans. New data from the HP would therefore be most interesting to investigate the dispersal and use of domesticated rice in South Asia.