scholarly journals Spatiotemporal patterns of tundra fires: late-Quaternary charcoal records from Alaska

2015 ◽  
Vol 12 (3) ◽  
pp. 3177-3209 ◽  
Author(s):  
M. L. Chipman ◽  
V. Hudspith ◽  
P. E. Higuera ◽  
P. A. Duffy ◽  
R. Kelly ◽  
...  
Keyword(s):  
Climate Change ◽  
Late Quaternary ◽  
Rotation Period ◽  
Arctic Tundra ◽  
Ecosystem Processes ◽  
Anthropogenic Climate Change ◽  
The Arctic ◽  
Spatial And Temporal Patterns ◽  
The Past ◽  
Tundra Ecosystem

Abstract. Anthropogenic climate change has altered many ecosystem processes in the Arctic tundra and may have resulted in unprecedented fire activity. Evaluating the significance of recent fires requires knowledge from the paleo-fire record because observational data in the Arctic span only several decades, much shorter than the natural fire rotation in Arctic tundra regions. Here we report results of charcoal analysis on lake sediments from four Alaskan lakes to infer the broad spatial and temporal patterns of tundra fire occurrence over the past 35 000 years. Background charcoal accumulation rates are low in all records (range = 0–0.05 pieces cm-2 year-1), suggesting minimal biomass burning across our study areas. Charcoal peak analysis reveals that the mean fire return interval (FRI; years between consecutive fire events) ranged from 1648 to 6045 years at our sites, and that the most recent fire events occurred from 882 to 7031 years ago, except for the CE 2007 Anaktuvuk River Fire. These mean FRI estimates are longer than the fire rotation periods estimated for the past 63 years in the areas surrounding three of the four study lakes. This result suggests that the frequency of tundra burning was higher over the recent past compared to the late Quaternary in some tundra regions. However, the ranges of FRI estimates from our paleo-fire records overlap with the expected values based on fire-rotation-period estimates from the observational fire data, and thus quantitative differences are not significant. Together with previous tundra-fire reconstructions, these data suggest that the rate of tundra burning was spatially variable and that fires were extremely rare in our study areas throughout the late Quaternary. Given the rarity of tundra burning over multiple millennia in our study areas and the pronounced effects of fire on tundra ecosystem processes such as carbon cycling, dramatic tundra ecosystem changes are expected if anthropogenic climate change leads to more frequent tundra fires.

scholarly journals Spatiotemporal patterns of tundra fires: late-Quaternary charcoal records from Alaska

2015 ◽  
Vol 12 (13) ◽  
pp. 4017-4027 ◽  
Author(s):  
M. L. Chipman ◽  
V. Hudspith ◽  
P. E. Higuera ◽  
P. A. Duffy ◽  
R. Kelly ◽  
...  
Keyword(s):  
Climate Change ◽  
Late Quaternary ◽  
Rotation Period ◽  
Arctic Tundra ◽  
Ecosystem Processes ◽  
Anthropogenic Climate Change ◽  
The Arctic ◽  
Spatial And Temporal Patterns ◽  
The Past ◽  
Tundra Ecosystem

Abstract. Anthropogenic climate change has altered many ecosystem processes in the Arctic tundra and may have resulted in unprecedented fire activity. Evaluating the significance of recent fires requires knowledge from the paleofire record because observational data in the Arctic span only several decades, much shorter than the natural fire rotation in Arctic tundra regions. Here we report results of charcoal analysis on lake sediments from four Alaskan lakes to infer the broad spatial and temporal patterns of tundra-fire occurrence over the past 35 000 years. Background charcoal accumulation rates are low in all records (range is 0–0.05 pieces cm−2 yr−1), suggesting minimal biomass burning across our study areas. Charcoal peak analysis reveals that the mean fire-return interval (FRI; years between consecutive fire events) ranged from ca. 1650 to 6050 years at our sites, and that the most recent fire events occurred from ca. 880 to 7030 years ago, except for the CE 2007 Anaktuvuk River Fire. These mean FRI estimates are longer than the fire rotation periods estimated for the past 63 years in the areas surrounding three of the four study lakes. This result suggests that the frequency of tundra burning was higher over the recent past compared to the late Quaternary in some tundra regions. However, the ranges of FRI estimates from our paleofire records overlap with the expected values based on fire-rotation-period estimates from the observational fire data, and the differences are statistically insignificant. Together with previous tundra-fire reconstructions, these data suggest that the rate of tundra burning was spatially variable and that fires were extremely rare in our study areas throughout the late Quaternary. Given the rarity of tundra burning over multiple millennia in our study areas and the pronounced effects of fire on tundra ecosystem processes such as carbon cycling, dramatic tundra ecosystem changes are expected if anthropogenic climate change leads to more frequent tundra fires.

The morphology of experimentally produced charcoal distinguishes fuel types in the Arctic tundra

The Holocene ◽  
2020 ◽  
Vol 30 (7) ◽  
pp. 1091-1096 ◽  
Author(s):  
Eleanor MB Pereboom ◽  
Richard S Vachula ◽  
Yongsong Huang ◽  
James Russell
Keyword(s):  
Arctic Tundra ◽  
Global Carbon Cycle ◽  
Fire Frequency ◽  
The Arctic ◽  
Fuel Type ◽  
The Past ◽  
Primary Means ◽  
Forested Ecosystems ◽  
Global Carbon ◽  
Tundra Ecosystems

Wildfires in the Arctic tundra have become increasingly frequent in recent years and have important implications for tundra ecosystems and for the global carbon cycle. Lake sediment–based records are the primary means of understanding the climatic influences on tundra fires. Sedimentary charcoal has been used to infer climate-driven changes in tundra fire frequency but thus far cannot differentiate characteristics of the vegetation burnt during fire events. In forested ecosystems, charcoal morphologies have been used to distinguish changes in fuel type consumed by wildfires of the past; however, no such approach has been developed for tundra ecosystems. We show experimentally that charcoal morphologies can be used to differentiate graminoid (mean = 6.77; standard deviation (SD) = 0.23) and shrub (mean = 2.42; SD = 1.86) biomass burnt in tundra fire records. This study is a first step needed to construct more nuanced tundra wildfire histories and to understand how wildfire will impact the region as vegetation and fire change in the future.

Ethics and politics in the Anthropocene

2020 ◽  
Vol 46 (10) ◽  
pp. 1167-1181 ◽  
Author(s):  
Maeve Cooke
Keyword(s):  
Climate Change ◽  
Human Activity ◽  
Land Degradation ◽  
Frankfurt School ◽  
Anthropogenic Climate Change ◽  
Considerable Evidence ◽  
The Past ◽  
Fundamental Challenge ◽  
Ecological Problems ◽  
Ethics And Politics

The most fundamental challenge facing humans today is the imminent destruction of the life-generating and life-sustaining ecosystems that constitute the planet Earth. There is considerable evidence that the strongest contemporary ecological threat is anthropogenic climate change resulting from the increasing warming of the atmosphere, caused by cumulative CO2 and other emissions as a result of collective human activity over the past few 100 years. This process of climate change is reinforced by further ecological problems such as pollution of land, air and sea, depletion of resources, land degradation and the loss of biodiversity. The name gaining currency for this emerging epoch of instability in the Earth’s eco-systems is the Anthropocene. Anthropogenic climate change calls for a categorical shift in thinking about the place of humanity in these systems and requires fundamental rethinking of ethics and politics. What would an appropriate ethical frame for politics in the Anthropocene look like? In response to this question, I sketch a proposal for an ethically non-anthropocentric ethics. I draw on early Frankfurt School Critical Theorists, and on Habermas, but move beyond these theorists in key respects.

scholarly journals Insights from mercury stable isotopes on terrestrial–atmosphere exchange of Hg(0) in the Arctic tundra

2019 ◽  
Vol 16 (20) ◽  
pp. 4051-4064 ◽  
Author(s):  
Martin Jiskra ◽  
Jeroen E. Sonke ◽  
Yannick Agnan ◽  
Detlev Helmig ◽  
Daniel Obrist
Keyword(s):  
Stable Isotope ◽  
Dominant Role ◽  
Arctic Tundra ◽  
Atmospheric Mercury ◽  
The Arctic ◽  
Night Time ◽  
Field Station ◽  
Terrestrial Atmosphere ◽  
Tundra Ecosystem ◽  
Flux Measurements

Abstract. The tundra plays a pivotal role in the Arctic mercury (Hg) cycle by storing atmospheric Hg deposition and shuttling it to the Arctic Ocean. A recent study revealed that 70 % of the atmospheric Hg deposition to the tundra occurs through gaseous elemental mercury (GEM or Hg(0)) uptake by vegetation and soils. Processes controlling land–atmosphere exchange of Hg(0) in the Arctic tundra are central, but remain understudied. Here, we combine Hg stable isotope analysis of Hg(0) in the atmosphere, interstitial snow air, and soil pore air, with Hg(0) flux measurements in a tundra ecosystem at Toolik Field Station in northern Alaska (USA). In the dark winter months, planetary boundary layer (PBL) conditions and Hg(0) concentrations were generally stable throughout the day and small Hg(0) net deposition occurred. In spring, halogen-induced atmospheric mercury depletion events (AMDEs) occurred, with the fast re-emission of Hg(0) after AMDEs resulting in net emission fluxes of Hg(0). During the short snow-free growing season in summer, vegetation uptake of atmospheric Hg(0) enhanced atmospheric Hg(0) net deposition to the Arctic tundra. At night, when PBL conditions were stable, ecosystem uptake of atmospheric Hg(0) led to a depletion of atmospheric Hg(0). The night-time decline of atmospheric Hg(0) was concomitant with a depletion of lighter Hg(0) isotopes in the atmospheric Hg pool. The enrichment factor, ε202Hgvegetationuptake=-4.2 ‰ (±1.0 ‰) was consistent with the preferential uptake of light Hg(0) isotopes by vegetation. Hg(0) flux measurements indicated a partial re-emission of Hg(0) during daytime, when solar radiation was strongest. Hg(0) concentrations in soil pore air were depleted relative to atmospheric Hg(0) concentrations, concomitant with an enrichment of lighter Hg(0) isotopes in the soil pore air, ε202Hgsoilair-atmosphere=-1.00 ‰ (±0.25 ‰) and E199Hgsoilair-atmosphere=0.07 ‰ (±0.04 ‰). These first Hg stable isotope measurements of Hg(0) in soil pore air are consistent with the fractionation previously observed during Hg(0) oxidation by natural humic acids, suggesting abiotic oxidation as a cause for observed soil Hg(0) uptake. The combination of Hg stable isotope fingerprints with Hg(0) flux measurements and PBL stability assessment confirmed a dominant role of Hg(0) uptake by vegetation in the terrestrial–atmosphere exchange of Hg(0) in the Arctic tundra.

scholarly journals Potential Arctic tundra vegetation shifts in response to changing temperature, precipitation and permafrost thaw

2016 ◽  
Vol 13 (22) ◽  
pp. 6229-6245 ◽  
Author(s):  
Henk-Jan van der Kolk ◽  
Monique M. P. D. Heijmans ◽  
Jacobus van Huissteden ◽  
Jeroen W. M. Pullens ◽  
Frank Berendse
Keyword(s):  
Climate Change ◽  
The Arctic ◽  
Soil Conditions ◽  
Climate Change Scenarios ◽  
Vegetation Shifts ◽  
Permafrost Thaw ◽  
Temperature And Precipitation ◽  
Tundra Vegetation ◽  
Tundra Ecosystem ◽  
Wide Range

Abstract. Over the past decades, vegetation and climate have changed significantly in the Arctic. Deciduous shrub cover is often assumed to expand in tundra landscapes, but more frequent abrupt permafrost thaw resulting in formation of thaw ponds could lead to vegetation shifts towards graminoid-dominated wetland. Which factors drive vegetation changes in the tundra ecosystem are still not sufficiently clear. In this study, the dynamic tundra vegetation model, NUCOM-tundra (NUtrient and COMpetition), was used to evaluate the consequences of climate change scenarios of warming and increasing precipitation for future tundra vegetation change. The model includes three plant functional types (moss, graminoids and shrubs), carbon and nitrogen cycling, water and permafrost dynamics and a simple thaw pond module. Climate scenario simulations were performed for 16 combinations of temperature and precipitation increases in five vegetation types representing a gradient from dry shrub-dominated to moist mixed and wet graminoid-dominated sites. Vegetation composition dynamics in currently mixed vegetation sites were dependent on both temperature and precipitation changes, with warming favouring shrub dominance and increased precipitation favouring graminoid abundance. Climate change simulations based on greenhouse gas emission scenarios in which temperature and precipitation increases were combined showed increases in biomass of both graminoids and shrubs, with graminoids increasing in abundance. The simulations suggest that shrub growth can be limited by very wet soil conditions and low nutrient supply, whereas graminoids have the advantage of being able to grow in a wide range of soil moisture conditions and have access to nutrients in deeper soil layers. Abrupt permafrost thaw initiating thaw pond formation led to complete domination of graminoids. However, due to increased drainage, shrubs could profit from such changes in adjacent areas. Both climate and thaw pond formation simulations suggest that a wetter tundra can be responsible for local shrub decline instead of shrub expansion.

Nitrogen fixation beyond leguminous plants: characterising overlooked plant-bacteria associations in the light of climate change

2020 ◽  
Author(s):  
Kathrin Rousk
Keyword(s):  
Climate Change ◽  
Nitrogen Fixation ◽  
Community Composition ◽  
Abiotic Factors ◽  
Arctic Tundra ◽  
The Arctic ◽  
Mean Annual Precipitation ◽  
Precipitation Gradient ◽  
Cyanobacterial Community ◽  
Moss Species

<p>Nitrogen (N<sub>2</sub>) fixation performed by moss-associated cyanobacteria is one of the main sources of new N in pristine, high latitude ecosystems like boreal forests and arctic tundra. Here, mosses and associated cyanobacteria can contribute more than 50% to total ecosystem N input. However, N<sub>2</sub> fixation in mosses is strongly influenced by abiotic factors, in particular moisture and temperature. Hence, climate change will significantly affect this key ecosystem process in pristine ecosystems. Here, I will present a synthesis of several field and laboratory assessments of moss-associated N<sub>2</sub> fixation in response to climate change by manipulating moisture and temperature in subarctic and arctic tundra.</p><p>Both in a long-term climate warming experiment in the arctic, and along a continental climate gradient, spanning arctic, subarctic and temperate ecosystems, increased temperatures (up to 30 °C) lead to either no effect or decreased N<sub>2</sub> fixation rates in different moss species. Yet, N<sub>2</sub> fixation rates were strongly dependent on moss-moisture, which seems to be a more important driver of N<sub>2</sub> fixation in mosses than temperature.</p><p>In another set of studies, two dominant moss species (Hylocomium splendens, Pleurozium schreberi) were collected from a steep precipitation gradient (400-1200 mm mean annual precipitation, MAP) in the Subarctic close to Abisko, Northern Sweden, and were incubated at different moisture and temperature levels in the laboratory. Nitrogen fixation, cyanobacterial abundance (via qPCR) and cyanobacterial community composition (via sequencing) on the mosses were assessed. Moisture and temperature interacted strongly to control moss-associated N<sub>2</sub> fixation rates, and the highest activity was found at the wet end of the precipitation gradient. Although cyanobacterial abundance was higher in one of the investigated mosses (H. splendens), translating into higher N<sub>2</sub> fixation rates, cyanobacterial community composition did not differ between the two moss species. Nostoc was the most common cyanobacterial genera on both mosses, and hardly any methanotrophic N<sub>2</sub> fixing bacteria were found on the mosses along the precipitation gradient. Increased temperatures lead to increased abundances of certain cyanobacterial genera (Cylindrospermum and Nostoc), while others declined in response to warming. Hence, cyanobacterial communities colonizing mosses will be dominated by a few cyanobacteria species in a warmer climate, and temperature and moisture interact strongly to affect their activity. Thus, these two major climate change factors should be considered in unison when estimating climate change effects on key ecosystem processes such as N<sub>2</sub> fixation. Further, host identity determines cyanobacterial abundance, and thereby, N<sub>2</sub> fixation rates.</p><p> </p><p> </p><p> </p>

Climate science and YouTube: deniers, memes, and Trojan horses

2020 ◽  
Author(s):  
Simon Clarke
Keyword(s):  
Climate Change ◽  
Search Engine ◽  
Science Communication ◽  
Primary Source ◽  
Climate Science ◽  
Anthropogenic Climate Change ◽  
Educational Video ◽  
Video Content ◽  
The Past ◽  
The World

<p>YouTube is the world's second largest search engine, and serves as a primary source of entertainment for billions of people around the world. Yet while science communication on the website is more popular than ever, discussion of climate science is dominated by - largely scientifically untrained - individuals who are skeptical of the overwhelming scientific consensus that anthropogenic climate change is real. Over the past ten years I have built up an extensive audience communicating science - and climate science in particular - on YouTube, attempting to place credible science in the forefront of the discussion. In this talk I will discuss my approach to making content for the website, dissect successful and less successful projects, review feedback from my audience, and break down my process of converting research into entertaining, educational video content.</p>

scholarly journals X-Ray Vision in the Arctic Tundra: Exploring How Redox Biogeochemistry Influences Ecosystem Processes

2020 ◽  
Author(s):  
Elizabeth Herndon ◽  
Lauren Kinsman-Costello ◽  
Alex Michaud ◽  
David Emerson ◽  
William Bowden
Keyword(s):  
Arctic Tundra ◽  
Ecosystem Processes ◽  
The Arctic ◽  
X Ray

Critical review of mercury fates and contamination in the arctic tundra ecosystem

2008 ◽  
Vol 400 (1-3) ◽  
pp. 173-211 ◽  
Author(s):  
Laurier Poissant ◽  
Hong H. Zhang ◽  
João Canário ◽  
Philippe Constant
Keyword(s):  
Critical Review ◽  
Arctic Tundra ◽  
The Arctic ◽  
Tundra Ecosystem

Yes, it is all about fetishism: A response to Daniel Cunha

2016 ◽  
Vol 3 (3) ◽  
pp. 205-207 ◽  
Author(s):  
Alf Hornborg ◽  
Andreas Malm
Keyword(s):  
Climate Change ◽  
Anthropogenic Climate Change ◽  
The Past ◽  
Number Of Publications ◽  
Deliberate Strategy

Daniel Cunha misreads us as suggesting that climate change has been a conscious and deliberate strategy of a global elite. This was very clearly not our suggestion. He proposes that the Marxian concept of fetishism is applicable to anthropogenic climate change, apparently unaware of our recurrent use of precisely this concept in a number of publications over the past decades. We thus fundamentally agree with his position, but find his critique of our own interpretation of the Anthropocene unfair and misdirected.

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