A high-resolution paleolimnological study of climate and human impacts on Lac Noir, Québec, over the past 1000 yr

AbstractDiatom assemblages in lake sediments of Lac Noir, southwestern Québec, were studied at a resolution of 10 yr to determine principal drivers of primary producers for the past ~1000 yr. Generalized additive modeling revealed strong links between broadscale climate intervals of the late Holocene, forest composition, and diatom flora. During the Medieval Warm Period (~AD 1200) and onset of the Little Ice Age (~AD 1450), increases in Tabellaria flocculosa str. IIIp at the expense of Discostella stelligera reflected low lake productivity. At AD 1630, an abrupt shift to cooler temperatures and dry conditions triggered a decline in hemlock (Tsuga), replaced by disturbance and cool-adapted taxa. Greater nutrient availability and soil erosion in the catchment led to a corresponding and rapid increase in diatoms with higher optima for nitrogen, such as Asterionella formosa and Fragilaria crotonensis. After AD 1870, an increase in pollen of taxa associated with disturbances signaled the arrival of Euro-Canadians, and associated nutrient inputs to the lake triggered increases in Stephanodiscus minutulus and Achnanthidium minutissimum. Overall results of the study indicate that climate played an important underlying role in lake-ecosystem dynamics; however, disturbances affecting forest composition had more direct influences on the diatom communities of Lac Noir.

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Reconstructed high-resolution forest dynamics and human impacts of the past 2300 years of the Parc national de Mont-Orford, southeastern Québec, Canada

The Holocene ◽

10.1177/0959683621994642 ◽

2021 ◽

pp. 095968362199464

Author(s):

Claire E. O’Neill Sanger ◽

Jeannine-Marie St-Jacques ◽

Matthew C. Peros ◽

Kayden Avery Schwartz

Keyword(s):

High Resolution ◽

Forest Dynamics ◽

Sugar Maple ◽

Human Impacts ◽

Fagus Grandifolia ◽

Ice Age ◽

Forest Composition ◽

Pollen Record ◽

Landscape Modification ◽

The Past

We used a high-resolution lacustrine pollen record from Étang Fer-de-Lance (45°21′21.9′N, 72°13′35.3′W), southeastern Québec, Canada, together with microcharcoal, to infer forest dynamics and human impacts over the past 2300 years. The lake is located in the eastern sugar maple-basswood forest domain of the Northern Temperate Forest of eastern North America. We found that the pollen percentages and influxes of Fagus grandifolia (American beech) and Tsuga canadensis (eastern hemlock) significantly declined over the past 700 years. Over the last millennium, the pollen percentages and influxes of the Picea species ( P. glauca, P. mariana, P. rubens) (white, black, and red spruce), and Pinus strobus (eastern white pine) significantly increased. We showed that these shifts in forest composition are being driven by changes in regional climate. In addition to the pollen percentage changes, the Medieval Climate Anomaly (AD 800–1300) appeared as increased pollen influxes and the Dark Ages Cold Period (AD 400–700) and Little Ice Age (AD 1400–1800) appeared as decreased pollen influxes. The signal for human modification of the landscape first appeared at ~AD 1550–1650 as increases in Ambrosia (ragweed) and Poaceae (grasses) from possible Indigenous agriculture. The signal of European settler landscape modification appeared at ~AD 1770 as the beginning of a steep, “classic” Ambrosia rise. It intensified over the subsequent 250 years as further increases in non-arboreal pollen taxa and early successional Acer (maple) species. Microcharcoal analysis showed that fire was a re-occurring event in the sugar maple-basswood domain, but had little impact on forest composition.

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Climatic history of the northeastern United States during the past 3000 years

Climate of the Past ◽

10.5194/cp-13-1355-2017 ◽

2017 ◽

Vol 13 (10) ◽

pp. 1355-1379 ◽

Cited By ~ 18

Author(s):

Jennifer R. Marlon ◽

Neil Pederson ◽

Connor Nolan ◽

Simon Goring ◽

Bryan Shuman ◽

...

Keyword(s):

Ecosystem Dynamics ◽

Ice Age ◽

Extreme Weather Events ◽

Past Century ◽

Vegetation Growth ◽

The Past ◽

Weather Events ◽

Dry Conditions ◽

History Of ◽

Paleoclimate Records

Abstract. Many ecosystem processes that influence Earth system feedbacks – vegetation growth, water and nutrient cycling, disturbance regimes – are strongly influenced by multidecadal- to millennial-scale climate variations that cannot be directly observed. Paleoclimate records provide information about these variations, forming the basis of our understanding and modeling of them. Fossil pollen records are abundant in the NE US, but cannot simultaneously provide information about paleoclimate and past vegetation in a modeling context because this leads to circular logic. If pollen data are used to constrain past vegetation changes, then the remaining paleoclimate archives in the northeastern US (NE US) are quite limited. Nonetheless, a growing number of diverse reconstructions have been developed but have not yet been examined together. Here we conduct a systematic review, assessment, and comparison of paleotemperature and paleohydrological proxies from the NE US for the last 3000 years. Regional temperature reconstructions (primarily summer) show a long-term cooling trend (1000 BCE–1700 CE) consistent with hemispheric-scale reconstructions, while hydroclimate data show gradually wetter conditions through the present day. Multiple proxies suggest that a prolonged, widespread drought occurred between 550 and 750 CE. Dry conditions are also evident during the Medieval Climate Anomaly, which was warmer and drier than the Little Ice Age and drier than today. There is some evidence for an acceleration of the longer-term wetting trend in the NE US during the past century; coupled with an abrupt shift from decreasing to increasing temperatures in the past century, these changes could have wide-ranging implications for species distributions, ecosystem dynamics, and extreme weather events. More work is needed to gather paleoclimate data in the NE US to make inter-proxy comparisons and to improve estimates of uncertainty in reconstructions.

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Resilience of plant and testate amoeba communities after climatic and anthropogenic disturbances in a Baltic bog in Northern Poland: Implications for ecological restoration

The Holocene ◽

10.1177/0959683616652704 ◽

2016 ◽

Vol 27 (1) ◽

pp. 130-141 ◽

Cited By ~ 20

Author(s):

Mariusz Gałka ◽

Kazimierz Tobolski ◽

Aleksandra Górska ◽

Mariusz Lamentowicz

Keyword(s):

Human Impacts ◽

Testate Amoebae ◽

Ice Age ◽

Testate Amoeba ◽

Raised Bogs ◽

The Past ◽

Ombrotrophic Peatland ◽

History Of ◽

Climate Cooling

This study explores the history of the development of Sphagnum communities in an ombrotrophic peatland – Bagno Kusowo – over the past 650 years, based on high-resolution plant macrofossil and testate amoebae analysis. Our research provided information related to the length of peatland existence and the characteristics of its natural/pristine state before the most recent human impacts. Changes in the Sphagnum communities before human impact could have resulted from climate cooling during the ‘Little Ice Age’ (LIA). In this cold and unstable hydrological period, among vascular plants, Eriophorum vaginatum and Baeothryon caespitosum dominated in the peatland vegetation. Peat-forming Sphagnum communities survived the drainage conducted during the 20th century at the Bagno Kusowo bog. We provide three important messages through this study: (1) testate amoebae reflect similar hydrological trends in two peat cores despite considerable microhabitat variability, (2) average long-term water level 10 cm below the surface should be a target for active bog conservation and (3) sites like Bagno Kusowo are extremely important to preserve the remains of pristine biodiversity (including genetic diversity of plants and protists) that was completely removed from most of the raised bogs in Europe due to human activities, for example, drainage.

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African Biomes

Ecology ◽

10.1093/obo/9780199830060-0112 ◽

2014 ◽

Author(s):

Anthony R.E. Sinclair ◽

Rene L. Beyers

Keyword(s):

Protected Areas ◽

National Park ◽

Human Impacts ◽

Niche Partitioning ◽

Central Africa ◽

Ecosystem Dynamics ◽

Human Populations ◽

Vegetation Types ◽

North West ◽

The Past

Africa has a great diversity of environmental conditions. It is bisected by the equator so that the seasons are six months out of phase north and south of it. There are tropical forests on the west side as well as in the center of the continent. In roughly concentric rings out from the forest, there are progressively drier vegetation types from woodland, savanna, and grassland to desert. There are several major rivers flowing north, west, and east. Africa has also been the center of evolution of many large mammal groups. It has a high diversity of birds and insects. It is also the origin of the human species, and humans have influenced and modified the landscape for hundreds of thousands of years. Humans evolved there over the past four million years. The environment and the biomes that result from it in turn shaped the evolution of humans. Over the Pleistocene (past two million years), the environment swung from warm and wet to cool and dry several times, and consequently the biomes changed in extent from continuous forest (that stretched from the Atlantic to the Indian Ocean) to dry savanna and desert with only small patches of forest in West and Central Africa. These changes that were connected to the ice ages of temperate regions affected human populations. In the past millennium, human numbers have increased and migrations have moved peoples southward through the forests of Central Africa and into eastern and southern Africa. These movements have modified the biomes through grazing pressures on grasslands and agriculture in savanna. In the 20th century, forests were modified through deforestation. Wildlife conservation and ecotourism are prominent in Africa. There are several large protected areas especially in eastern and southern savanna Africa, with some less-known areas of forest reserves. Scientific studies on these protected areas over several decades describe the biology and ecosystem dynamics perhaps better than any other continent. There are scientific syntheses on the Kruger National Park, South Africa, and the Serengeti National Park, Tanzania. Both highlight how the whole ecosystem changes over time with climate change, human population increases, disease outbreaks, and other disturbances. The following sections first cover the vegetation types that are called Biomes; two abiotic environmental factors, climate and fire (Climate Variability and Patterns of Drought and Fire); prominent animal groups characteristic of Africa (Large Mammals, Primates, and Birds); dominant processes such as herbivory, predation, niche partitioning, facilitation, and migration (Herbivory, Predators and Predation, Niche Partitioning, Facilitation, and Migrations); and finally the expansion of human impacts on biomes and the related aspects of traditional livelihoods and conservation (Traditional Human Livelihoods and Conservation). Social and political history also modify human impacts but are not covered in this review.

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Diatom-inferred decline of macrophyte abundance in lakes of southern Quebec, Canada

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f2011-169 ◽

2012 ◽

Vol 69 (3) ◽

pp. 511-524 ◽

Cited By ~ 8

Author(s):

Jesse C. Vermaire ◽

Yves T. Prairie ◽

Irene Gregory-Eaves

Keyword(s):

Human Impacts ◽

Regression Tree ◽

Water Level Fluctuations ◽

Lake Ecosystem ◽

Nutrient Inputs ◽

Tree Model ◽

Lake Ecosystems ◽

Multivariate Regression Tree ◽

Modern Analogue ◽

Macrophyte Biomass

Submerged macrophytes play a central role in lake ecosystem functioning; however, their long-term dynamics are poorly understood. We have used the paleolimnological top–bottom approach to reconstruct changes in whole-lake macrophyte biomass between predisturbance and present-day conditions in 37 southern Quebec lakes. Estimates of whole-lake macrophyte biomass were produced using a diatom-based multivariate regression tree model (MRT) and modern analogue approach. Both approaches indicated an overall pattern of declining macrophyte abundance in the region. Based on MRT analysis, 80% of study lakes were classified as historically being in the macrophyte-dominated state, but now only 43% of the lakes are currently in this state. The lakes that shifted MRT group were found to have significantly (p = 0.03) greater building densities in their catchments compared with lakes that did not shift state. These results suggest that human impacts, primarily nutrient inputs and water level fluctuations, have played a role in reducing macrophyte abundance in southern Quebec lakes. Because submerged macrophyte beds help stabilize lake ecosystems and act as a phosphorus sink, a reduction in whole-lake macrophyte biomass could make lake ecosystems more susceptible to eutrophication.

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Climatic history of the northeastern United States during the past 3000 years

10.5194/cp-2016-104 ◽

2016 ◽

Author(s):

Jennifer R. Marlon ◽

Neil Pederson ◽

Connor Nolan ◽

Simon Goring ◽

Bryan Shuman ◽

...

Keyword(s):

Warming Trend ◽

Ecosystem Dynamics ◽

Ice Age ◽

Extreme Weather Events ◽

Past Century ◽

Climate Conditions ◽

Vegetation Growth ◽

The Past ◽

Tree Ring Data ◽

Cooling Trend

Abstract. Many ecosystem processes that influence Earth system feedbacks, including vegetation growth, water and nutrient cycling, and disturbance regimes, are strongly influenced by multi-decadal to millennial-scale variations in climate that cannot be captured by instrumental climate observations. Paleoclimate information is therefore essential for understanding contemporary ecosystems and their potential trajectories under a variety of future climate conditions. With the exception of fossil pollen records, there are a limited number of northeastern US (NE US) paleoclimate archives that can provide constraints on its temperature and hydroclimate history. Moreover, the records that do exist have not been considered together. Tree-ring data indicate that the 20th century was one of the wettest of the past 500 years in the eastern US (Pederson et al., 2014), and lake-level records suggest it was one of the wettest in the Holocene (Newby et al., 2014); how such results compare with other available data remains unclear, however. Here we conduct a systematic review, assessment, and comparison of paleotemperature and paleohydrological proxies from the NE US for the last 3000 years. Regional temperature reconstructions are consistent with the long-term cooling trend (1000 BCE–1700 CE) evident in hemispheric-scale reconstructions, but hydroclimate reconstructions reveal new information, including an abrupt transition from wet to dry conditions around 550–750 CE. NE US paleo data suggest that conditions during the Medieval Climate Anomaly were warmer and drier than during the Little Ice Age, and drier than today. There is some evidence for an acceleration over the past century of a longer-term wetting trend in the NE US, and coupled with the abrupt shift from a cooling trend to a warming trend from increased greenhouse gases, may have wide-ranging implications for species distributions, ecosystem dynamics, and extreme weather events. More work is needed to gather paleoclimate data in the NE US, make inter-proxy comparisons, and improve estimates of uncertainty in the reconstructions.

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An 8000-year record of vegetation, climate, and human disturbance from the Sierra de Apaneca, El Salvador

Quaternary Research ◽

10.1016/j.yqres.2004.01.002 ◽

2004 ◽

Vol 61 (2) ◽

pp. 159-167 ◽

Cited By ~ 30

Author(s):

Robert A. Dull

Keyword(s):

El Salvador ◽

Late Holocene ◽

Vegetation Change ◽

Human Impacts ◽

Cloud Forest ◽

Climatic Variability ◽

Forest Composition ◽

The Past ◽

Tropical Plant ◽

Drying Trend

An ∼8000-cal-yr stratigraphic record of vegetation change from the Sierra de Apaneca, El Salvador, documents a mid-Holocene warm phase, followed by late Holocene cooling. Pollen evidence reveals that during the mid-Holocene (∼8000–5500 cal yr B.P.) lowland tropical plant taxa were growing at elevations ∼200–250 m higher than at present, suggesting conditions about 1.0°C warmer than those prevailing today. Cloud forest genera (Liquidambar, Juglans, Alnus, Ulmus) were also more abundant in the mid-Holocene, indicating greater cloud cover during the dry season. A gradual cooling and drying trend began by ∼5500 cal yr B.P. culminating in the modern forest composition by ∼3500 cal yr B.P. A rise in pollen from weedy plant taxa associated with agriculture occurred ∼5000 cal yr B.P. and pollen from Zea first appeared in the record at ∼4440 cal yr B.P. Human impacts on local vegetation remained high throughout the late Holocene, but decreased abruptly following the Tierra Blanca Joven (TBJ) eruption of Volcán Ilopango at ∼1520 cal yr B.P. The past 1500 years are marked by higher lake levels and periodic depositions of exogenous inorganic sediments, perhaps indicating increased climatic variability.

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Evidence for a warmer period during the 12th and 13th centuries AD from chironomid assemblages in Southampton Island, Nunavut, Canada

Quaternary Research ◽

10.1016/j.yqres.2009.03.001 ◽

2009 ◽

Vol 72 (1) ◽

pp. 27-37 ◽

Cited By ~ 19

Author(s):

Nicolas Rolland ◽

Isabelle Larocque ◽

Pierre Francus ◽

Reinhard Pienitz ◽

Laurence Laperrière

Keyword(s):

Late Holocene ◽

Freshwater Ecosystems ◽

Ice Age ◽

Lake Ecosystem ◽

The Past ◽

New Information ◽

Higher Temperature ◽

Basin Region ◽

Entire Lake ◽

New Framework

AbstractThis study presents the Late-Holocene evolution of a northern Southampton Island (Nunavut, Canada) lake, using fossil chironomids supported by sedimentological evidences (XRF, grain size and CNS). All proxies revealed a relatively stable environment during the last millennium with short-lived events driving changes in the entire lake ecosystem. The chironomid-based paleotemperatures revealed variations of significant amplitude coincident with changes in the sediment density and chemical composition of the core. Higher temperature intervals were generally correlated to lower sediment density with higher chironomid concentration and diversity. Higher temperatures were recorded from cal yr AD 1160 to AD 1360, which may correspond to the Medieval Warm Period. Between cal yr AD 1360 and AD 1700, lower temperatures were probably related to a Little Ice Age event. This study presents new information on the timing of known climatic events which will refine our knowledge of the paleoclimate and climatic models of the Foxe Basin region. It also provides a new framework for the evolution of such freshwater ecosystems under the “Anthropocene” and underlines the importance of including sedimentological proxies when interpreting chironomid remains as this combined approach provides an extended overview of the past hydrological and geochemical changes and their impacts on lake biota.

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Variability of summer humidity during the past 800 years on the eastern Tibetan Plateau inferred from δ<sup>18</sup>O of tree-ring cellulose

Climate of the Past ◽

10.5194/cp-11-327-2015 ◽

2015 ◽

Vol 11 (2) ◽

pp. 327-337 ◽

Cited By ~ 42

Author(s):

J. Wernicke ◽

J. Grießinger ◽

P. Hochreuther ◽

A. Bräuning

Keyword(s):

Relative Humidity ◽

Tibetan Plateau ◽

Tree Ring ◽

Summer Season ◽

Ice Age ◽

Transfer Model ◽

The Tibetan Plateau ◽

The Past ◽

Dry Conditions ◽

Hydroclimatic Variables

Abstract. We present an 800-year δ18O chronology from the eastern part of the Tibetan Plateau (TP). The chronology dates back to AD 1193 and was sampled in AD 1996 from living Juniperus tibetica trees. This first long-term tree-ring-based δ18O chronology for eastern Tibet provides a reliable archive for hydroclimatic reconstructions. Highly significant correlations were obtained with hydroclimatic variables (relative humidity, vapour pressure, and precipitation) during the summer season. We applied a linear transfer model to reconstruct summer season relative humidity variations over the past 800 years. More moist conditions prevailed during the termination of the Medieval Warm Period while a systematic shift during the Little Ice Age is not detectable. A distinct trend towards more dry conditions since the 1870s is apparent. The moisture decline weakened around the 1950s but still shows a negative trend. The mid-19th century humidity decrease is in good accordance with several multiproxy hydroclimate reconstructions for south Tibet. However, the pronounced summer relative humidity decline is stronger on the central and eastern TP. Furthermore, the relative humidity at our study site is significantly linked to the relative humidity at large parts of the TP. Therefore, we deduce that the reconstructed relative humidity is mostly controlled by local and mesoscale climatic drivers, although significant connections to the higher troposphere of west-central Asia were observed.

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Urban Soils and Road Dust—Civilization Effects and Metal Pollution—A Review

Environments ◽

10.3390/environments7110098 ◽

2020 ◽

Vol 7 (11) ◽

pp. 98

Author(s):

Manfred Sager

Keyword(s):

Urban Soils ◽

Human Impacts ◽

Road Dust ◽

Platinum Group Metal ◽

Geochemical Background ◽

Nutrient Inputs ◽

Protection Measures ◽

The Past ◽

High Precipitation ◽

Hazardous Metal

Urban soils have been changed much by human impacts in terms of structure, composition and use. This review paper gives a general introduction into changes from compaction, mixing, water retention, nutrient inputs, sealing, gardening, and pollution. Because pollutions in particular have caused concerns in the past, metal pollutions and platinum group metal inputs have been treated in more detail. Though it is not possible to cover the entire literature done on this field, it has been tried to give examples from all continents, regarding geochemical background levels. Urban metal soil pollution depends on the age of the settlement, current emissions from traffic and industry, and washout. It seems that in regions of high precipitation, pollutants are swept away to the watershed, leaving the soils less polluted than in Europe. Health hazards, however, are caused by ingestion and inhalation, which are higher in 3rd world countries, and not by concentrations met in urban soils as such; these are not treated within this paper in detail. With respect to pollutants, this paper is focused on metals. Contrary to many reviews of the past, which mix all data into one column, like sampling depth, sieved grain sizes, digestion and determination methods, these have been considered, because this might lead to considerable interpretation changes. Because many datasets are not Gaussian distributed, medians and concentration ranges are given, wherever possible. Urban dust contains about two to three fold the hazardous metal concentrations met in urban soils. Some data about metal mobilities obtained from selective and sequential leaching procedures, are also added. Soil compaction, pollution, sealings and run-offs cause stress situations for green plants growing at roadside locations, which is discussed in the Section 5. Environmental protection measures have led to decrease metal pollutions within the last decade in many places.

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