The Tonica Depression (TD), a late Quaternary sediment-filled basin in northeastern Illinois, formed as a thermokarst lake as evidenced by a basal trash layer, its depositional history, and its occurrence on a late-Pleistocene permafrost landscape. Stratigraphy and radiocarbon ages reveal that a multiproxy paleoenvironmental record extends throughout the late Wisconsin. Burning of organically enriched sediments has abbreviated the Holocene sequence. The lowest stratum is a glacial diamicton that forms the basin's floor, and at a slightly higher elevation, the rim. Lithofacies 1, supraglacial and debris flow deposits, are draped by undated Peoria Silt (PS). PS yielded molluscs and Coleoptera indicative of spruce forest (Picea) in a cold and harsh climate. Lithofacies 2 (ca. 17 500-18 500 cal yr BP) is a "trash zone" with white spruce (Picea glauca) wood, cones and needles with pollen, Coleoptera, molluscs, and vertebrates, including an elk-moose. A "marl," Lithofacies 3 (ca. 14 600-17 400 cal yr BP), attests to the deepening of the lake (>2 m) as also reflected by the molluscs, coleoptera, and pollen. The environment was an open spruce forest, but the climate was warmer than the previous ones. The top of this zone is composed of a brick-red deposit with burned organic matter. Lithofacies 4 (ca. 14 600 cal yr BP) is composed of organic silt and lacustrine organic silt: a peaty silt loam. Finally, Middle Archaic artifacts on the rim of TD document human settlement around the depression during the dry and warm Middle Holocene (ca. 6747 cal BP). Tonica is the first well-studied thermokarst lake from temperate latitudes in the United States, and it provides an excellent paleoenvironmental record of the late Pleistocene of north central Illinois.

Pistia stratiotes L. (water lettuce) is a floating tropical macrophyte long identified and managed as a non-native species within the State of Florida and other areas of the southern United States. Macrofossil seeds from Lake Annie, Florida, however, indicate abundant presence of P. stratiotes intermixed with other locally native macrophytes from 13,500 to 12,000 calibrated years before present (cal yr BP). This was soon after the lake depression first began filling with water as the piezometric groundwater surface of the Florida peninsula rose in response to rising seas during the transition ( 18,000 to 11,000 cal yr BP) from the Last Glacial Maximum (LGM) to the Holocene interglacial. These macrofossil records join several other lines of evidence supporting native status of P. stratiotes in the Florida peninsula. While recent cryptic invasion of non-native Pistia genotypes into some of Florida’s freshwater ecosystems also appears likely, confirmed paleo-presence and contemporary persistence of native P. stratiotes subpopulations may have especially important management and conservation implications for Florida’s spring-fed streams. Palaeobotanical evidence of this type may be useful in further resolving the global biogeography of P. stratiotes and other cryptic aquatic plant species.

Avian populations can substantially influence lacustrine nutrient loading and biogeochemical cycling through guano deposition. Here, we examine the influence of climate-forced avian migration throughout the Holocene on Kettle Lake, North Dakota, using stable nitrogen and carbon isotope values (δ 15 N, δ 13 C) of lake sediment organic matter. Carbon content and δ 13 C values are negatively correlated with δ 15 N and appear to be driven by changes in charcoal abundance and watershed vegetation, respectively. We find enriched δ 15 N values when the guano mineral struvite is present in the lake sediment core in the early to Mid-Holocene. A strong δ 15 N-percent Nitrogen content relationship during periods with struvite, relative to periods without struvite, indicates that guano deposition from mass bird visitations altered past nitrogen cycle processes, likely through enhanced denitrification. These results attest to the ability of waterfowl to alter lacustrine N-cycling in a mid-continental North American lake, and indicate that paleo-N data in this particular lake are recording a unique history that does not necessarily represent regional paleoenvironmental conditions. However, a significant, positive relationship between δ 15 N and Ambrosia and Amaranthaceae pollen abundance suggests avian visitation and its impacts on the N-cycle occurred during periods of anomalously wet summers superimposed on the background conditions of early to Mid-Holocene drought.

Global vegetation over the past 18,000 years has been transformed first by the climate changes that accompanied the last deglaciation and again by increasing human pressures; however, the magnitude and patterns of rates of vegetation change are poorly understood globally. Using a compilation of 1181 fossil pollen sequences and newly developed statistical methods, we detect a worldwide acceleration in the rates of vegetation compositional change beginning between 4.6 and 2.9 thousand years ago that is globally unprecedented over the past 18,000 years in both magnitude and extent. Late Holocene rates of change equal or exceed the deglacial rates for all continents, which suggests that the scale of human effects on terrestrial ecosystems exceeds even the climate-driven transformations of the last deglaciation. The acceleration of biodiversity change demonstrated in ecological datasets from the past century began millennia ago.

Parker’s Pit is a cave located in the southern Black Hills of SW South Dakota, a mountainous area surrounded by short-grass prairies of the western Great Plains. The modern entrance is ~ 45 cm wide and 1 m long, with a 13.8 m vertical drop to the cave floor. Hence, the cave is a natural trap for animals, and a debris cone containing sediment and faunal remains has formed beneath the entrance. Over at least the past 15,000 years, runoff episodically poured into the pit and transported sediment and bones down a 6-m-long ramp to a flat area that is a depositional zone. Recent excavations to a depth of 1.5 m in the depositional zone revealed sheetwash consisting of laminated sandy and fine-grained sediment mostly derived from soils eroded off the landscape surrounding the cave. Hence, the package of sediment stored in the depositional zone is an archive of soil organic matter used here to reconstruct late-Quaternary bioclimatic change in the Black Hills. Based on the stable carbon isotope (δ13C) values of organic matter (OM) in the strata, the plant community of the Black Hills was strongly dominated by C3 vegetation before ca. 14,150 B.P. During that time, C4 vegetation contributed only 7-13% of the OM to sediments deposited in the cave, and the mean July temperature (MJT) ranged from 17.0 to 17.7° C. Between ca. 14,150 and 11,300 B.P., C3 vegetation continued to dominate the plant community (C4 grasses contributed only 20-41% of the OM), though warming was underway, with MJT steadily increasing from 18.3 to 20.3° C. A major shift in δ13C values occurred between ca. 11,300 and 8900 B.P. and continued until the late Holocene, with C4 grasses contributing 60 to 72% of the OC and MJT ranging from 21.7 to 23.3° C (the Altithermal). A C3-dominated plant community was reestablished after ca. 4350 B.P. and MJT declined (19.6-20.2° C). As a natural trap, Parker’s Pit provides a representative sample of animals that were small enough to fit through the narrow opening of the cave. Initial analysis and dating of the fauna suggests turnover that generally supports the nature of bioclimatic change inferred from the δ13C data. Further reconciliation of observed changes in the fauna in relation to δ13C changes observed in sediments presents an opportunity to integrate records of faunal change with independent climatic data for the late Quaternary of the southern Black Hills.

Large herbivores are keystone species on the Qinghai-Tibet Plateau (QTP), but their past population ecology is the product of a complex combination of climatic changes and human activities that span the Holocene. In this study we use the record of dung-residing fungal spores (Sporormiella) in the stratified lake sediments of Genggahai Lake in the northeastern QTP to track changes in large herbivore populations. We hypothesize that the abundance of Sporormiella spores would decrease with the reduction of herbivore populations with the retreat of the summer monsoon after the mid-Holocene and the resulting vegetation degradation which is indicated by the pollen record. However, our results reveal an increase in Sporormiella spores after 5.7 ka (1 ka = 1000 cal yr BP), suggesting an increase in herbivore populations. Combined with regional archeological evidence, we infer that hunter-gatherers may have influenced the regional herbivore ecology and that the early Tibetan people may have domesticated or managed yaks and other herbivores in the northeastern QTP since 5.7 ka. The records of Sporormiella spores are interpreted within a robust chrono-stratigraphic framework provided by numerous radiocarbon dates from regional archeological sites, and the representation of Sporormiella spores during the Tang Dynasty is tested by a comparison with historical records of the livestock population of the region. Our findings potentially improve understanding of early human adaptation to environmental changes and past herbivore-steppe ecology in the QTP during the Holocene. (C) 2020 Published by Elsevier B.V.

African ecosystems hold enormous ecological and economic value due to high biodiversity 1 and multiple valuable ecosystem services provided to urban and agrarian populations 2 .However, these services and biodiversity are vulnerable to climate change and land use 3 .Long paleoecological records from Africa provide iconic examples of abrupt ecosystem and environmental change, offering critical evidence for tipping points in the Earth system.Datasets in the region are notoriously difficult to access, with the African Pollen Database (APD), launched in 1996, largely unsupported for the last decade.Poor data accessibility has been a community complaint for over a decade.

A multiproxy study from Sweeton Pond, Ozark County, Missouri, USA, provides a high-resolution 1900-year-long history of vegetation and fire in the southern Missouri Ozarks, where the modern vegetation is oak-hickory (Quercus-Carya) forest. Pollen and charcoal data are compared with dendroecological data to assess how climate and fire shaped local vegetation history. Land use, particularly by the Osage tribe of Native Americans, is assessed from historical and archaeological records. Three cultural periods are superimposed on the paleoenvironmental history: (1) The Pre-Osage period, ending ~1500 CE, was characterized by open oak-hickory forest and frequent low-severity fires, suggesting interannual climate variability as a driver of vegetation and fire occurrence. At ~1360 CE, mesic tree species began to expand, while fire frequency remained low. (2) The Osage period (~1500–1820 CE) was characterized by the continued expansion of mesic, fire-sensitive species, especially elm (Ulmus), in conjunction with cool, effectively wet conditions in the southern Missouri Ozarks. Despite climate conditions less favorable for fire, Osage expansion in the region was accompanied by increased fire and fire-dependent shortleaf pine (Pinus echinata). The expansion of both fire-sensitive and fire-dependent taxa coincident with Osage occupation suggests that anthropogenic fire and land use was local in nature and increased landscape heterogeneity prior to Euro-American settlement. (3) The Euro-American period (since ~1820 CE) was characterized by increased disturbance pollen types (e.g. Ambrosia-type) at the expense of shortleaf pine pollen, resulting from increased settlement size and extensive agricultural and logging activities. During this period, forest clearance led to fuel fragmentation, reducing fire activity; after 1920 CE, fire was actively suppressed.

The grain size of lake sediments has been widely used to reconstruct environmental processes. However, the various components of lake sediments are influenced by different factors, and therefore the environmental significance of grain-size variations may be complex. For example, in situ authigenic biological siliceous components cannot be used to indicate variations in hydrodynamic conditions. Here we present a case study of the effects of diatoms on the grain size of the sediments of Lake Kanas in NW China. The analyses consist of measurements of bulk sediment grain size and biogenic silica, together with microscope observations. Based on both light and scanning electronic microscope observations, two large diatom species, Campylodiscus hibernicus Ehrenberg and Ellerbeckia arenaria (Moore) Crawford, were found to be abundant in sediment samples with a large bulk-sediment grain size, and they contributed substantially to the biogenic silica content and the measured bulk sediment grain size of the core. A quantitative assessment of the effects on grain size was made, and the study has a broad significance for evaluating the effects of diatoms on sediment grain-size distributions in other lakes. Because diatoms may deposit in situ or could be transported differently from other clastic material, the explanation of hydrodynamics could be misled if the influence of diatom has not been excluded. Therefore, we suggest BSi content should be tested to assess the diatom effect prior to grain-size analysis of lake sediments, together with microscope check of diatoms if BSi content is higher than 10%.

The Athabasca Oil Sands in Alberta, Canada, is one of the largest point sources emitters of NOx and SO2 in Canada, and there have been widespread concerns over potential ecosystem acidification owing to the acid sensitivity of the base-poor sandy soils in the region. In this study we compared soil and vegetation properties at a jack pine (Pinus banksiana Lamb) forest adjacent to one of the largest mines in the region with a jack pine stand located approximately 15 km from the mine. At the site closest to the mine, throughfall deposition of SO4-S and DIN (NO3 + NH4) exceeds 30 and 20 kg ha−1 y−1, respectively, compared with less than 9 kg ha−1 y−1 for SO4-S and less than 2 kg ha−1 y−1 DIN at the distant site. However, on an equivalence basis, base cation (Ca + Mg + Na) deposition in throughfall at both sites exceeded the combined S and N deposition. Total S and N as well as Ca and Mg concentrations in epiphytic lichens and tree bark were significantly higher at the site adjacent to the mine, reflecting the higher acidic and base cation throughfall deposition. The forest floor at the stand close to the mine had a significantly higher pH, exchangeable Ca, Mg, K and total S concentrations compared with the distant site. The chemistry of deeper mineral soil horizons was more consistent between the two sites. Foliar concentrations of S, Ca, Mg, Fe and Al in jack pine, Vaccinium vitis-idaea, Vaccinium myrtilloides and Arctostaphylos uva-ursi were also higher at the site close to the mine, but these differences were not always significant. Coincidental with differences in atmospheric deposition, herbaceous cover and biomass, especially A. uva-ursi, was significantly higher, and terricolous lichen cover was several fold lower at the site closest to the mine. This work indicates that despite high S and N emissions from oil sands activities, forest fertilization and alkalization may be of greater concern than acidification owing to large dust emissions from the mines and the Acid Deposition Management Framework for the region should be modified accordingly.

Tilia软件一直是微体古生物学特别是孢粉学科使用最为普遍的一款专业计算机程序.该软件主要将样品数据经统计计算分析,将每个样品化石科属类型含量以图谱的形式依据地层深度或时间顺序排列显示,使化石数据转换为地层图式.基于各科属特别是优势或建群类型含量上下层位变化特点和规律,划分生物组合带,以图的形式直观解读生物群落的地史演替和环境变化等科学问题.由于此软件一直在英文语境下运行,功能多样,操作较为复杂,往往令国内初学者难以入手和深入.本文将以新版Tilia 2.0.45软件为对象,基于先期积累的使用经验,结合我国学者的思维方式,通过简单的孢粉数据实例,图解步骤和过程,力求通俗易懂.为此,推出“基础版”和“高阶版”两种使用说明以满足不同层次的人员需求,前者针对初学者旨在短时间内快速入门掌握孢粉百分比图谱制作的基本技巧,后者面向有一定操作经验学者力求在浓度图谱、通量图谱及“深度-年代”模型和Neotoma全球生态数据库等方面拓展提高.

ABSTRACTThe Great Plains experienced extreme fluctuations in precipitation and temperature throughout the Holocene, but these fluctuations have been difficult to quantify systematically across the region. Pollen has long been used as a proxy for reconstructing climate changes, but its power is limited if a region is devoid of modern pollen samples to facilitate comparison with known climate conditions. Here, we present a set of pollen‐climate transfer functions developed using weighted‐averaging partial least squares to reconstruct mean annual precipitation (MAP), mean temperature of the coldest month (MTcold) and mean temperature of the warmest month (MTwarm). At the foundation of these transfer functions is a new set of 141 modern pollen samples that specifically cover the climate space of the Great Plains. These functions quantify the relationship between pollen assemblages and modern climate in this region (r = 0.928, 0.838 and 0.897 for MAP, MTcold and MTwarm, respectively). We applied these functions to three previously established pollen records taken from lacustrine sites in the region – Fox Lake, MN; Moon Lake, ND; and Kettle Lake, ND – to reconstruct precipitation and temperature at these sites throughout the Holocene. Annual precipitation reconstructed with these transfer functions at Moon Lake and Kettle Lake does not capture a severe, prolonged period of drought during the mid‐Holocene as seen in many other proxy records from these sites and from the region. Reconciliation of these results involves both the autecology of Ambrosia and the inability of any pollen surface samples to capture seasonal and short‐term variability in precipitation. Thus, the transfer functions correctly reconstruct periodic wet summers and a disturbance factor favouring Ambrosia, but miss the effects of reduced winter precipitation and increased frequency of severe drought. The problem revealed here may be more general to biomes with higher frequency disturbance regimes and more weedy species.

A comprehensive understanding of the regional vegetation responses to long-term climate change will help to forecast Earth system dynamics. Based on a new well-dated pollen data set from Kanas Lake and a review on the published pollen records in and around the Altai Mountains, the regional vegetation dynamics and forcing mechanisms are discussed. In the Altai Mountains, the forest optimum occurred during 10-7ka for the upper forest zone and the tree line decline and/or ecological shifts were caused by climatic cooling from around 7ka. In the lower forest zone, the forest reached an optimum in the middle Holocene, and then increased openness of the forest, possibly caused by both climate cooling and human activities, took place in the late Holocene. In the lower basins or plains around the Altai Mountains, the development of protograssland or forest benefited from increasing humidity in the middle to late Holocene. Plain Language Summary In the Altai Mountains and surrounding area of central Asia, the previous studies of the Holocene paleovegetation and paleoclimate studies did not discuss the different ecological limiting factors for the vegetation in high mountains and low-elevation areas due to limited data. With accumulating fossil pollen data and surface pollen data, it is possible to understand better the geomorphological effect on the vegetation and discrepancies of vegetation/forest responses to large-scale climate forcing, and it is also possible to get reliable quantitative reconstructions of climate. Here our new pollen data and review on the published fossil pollen data will help us to look into the past climate change and vertical evolution of vegetation in this important area of the Northern Hemisphere. Based on our study, it can be concluded that the growth of taiga forest in the wetter areas may be promoted under a future warmer climate, while the forest in the relatively dry areas is liable to decline, and the different vegetation dynamics will contribute to future high-resolution coupled vegetation-climate model for Earth system modelling.

We analyzed intestinal contents of two late-glacial mastodons preserved in lake sediments in Ohio (Burning Tree mastodon) and Michigan (Heisler mastodon). A multi-proxy suite of macrofossils and microfossils provided unique insights into what these individuals had eaten just before they died and added significantly to knowledge of mastodon diets. We reconstructed the mastodons' habitats with similar multi-proxy analyses of the embedding lake sediments. Non-pollen palynomorphs, especially spores of coprophilous fungi differentiated intestinal and environmental samples. The Burning Tree mastodon gut sample originates from the small intestine. The Heisler mastodon sample is part of the large intestine to which humans had added clastic material to anchor parts of the carcass under water to cache the meat. Both carcasses had been dismembered, suggesting that the mastodons had been hunted or scavenged, in line with other contemporaneous mastodon finds and the timing of early human incursion into the Midwest. Both mastodons lived in mixed coniferous-deciduous late-glacial forests. They browsed tree leaves and twigs, especially Picea. They also ate sedge-swamp plants and drank the lake water. Our multi-proxy estimates for a spring/summer season of death contrast with autumn estimates derived from prior tusk analyses. We document the recovered fossil remains with photographs.