scholarly journals Response of vegetation and carbon fluxes to brown lemming herbivory in Northern Alaska

2021 ◽  
Author(s):  
Jessica Plein ◽  
Rulon W. Clark ◽  
Kyle A. Arndt ◽  
Walter C. Oechel ◽  
Douglas Stow ◽  
...  
Keyword(s):  
Carbon Fluxes ◽  
Arctic Tundra ◽  
The Arctic ◽  
Co2 Uptake ◽  
Co2 Fluxes ◽  
Environmental Controls ◽  
Global Rate ◽  
Tundra Ecosystem ◽  
The Impact ◽  
Tundra Ecosystems

Abstract. The Arctic is warming at double the average global rate, affecting the carbon cycle of tundra ecosystems. Most research on carbon fluxes from Arctic tundra ecosystems has focused on abiotic environmental controls (e.g. temperature, rainfall, or radiation). However, Arctic tundra vegetation, and therefore the carbon balance of these ecosystems, can be substantially impacted by herbivory. In this study we tested how vegetation consumption by brown lemmings (Lemmus trimucronatus) can impact carbon exchange of a wet-sedge tundra ecosystem near Utqiaġvik, Alaska during the summer, and the recovery of vegetation during a following summer. We placed brown lemmings in individual enclosure plots and tested the impact of lemmings’ herbivory on carbon dioxide (CO2) and methane (CH4) fluxes and the normalized difference vegetation index (NDVI) immediately after lemming removal and during the following growing season. During the first summer of the experiment, lemmings’ herbivory reduced plant biomass (as shown by the decrease in the NDVI) and decreased CO2 uptake, while not significantly impacting CH4 emissions. Methane emissions were likely not significantly affected due to CH4 being produced deeper in the soil and escaping from the stem bases of the vascular plants. The summer following the lemming treatments, NDVI and CO2 fluxes returned to magnitudes similar to those observed before the start of the experiment, suggesting recovery of the vegetation, and a transitory nature of the impact of lemming herbivory. Overall, lemming herbivory has short-term but substantial effects on carbon sequestration by vegetation and might contribute to the considerable interannual variability in CO2 fluxes from tundra ecosystems.

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.

scholarly journals Bulk partitioning the growing season net ecosystem exchange of CO<sub>2</sub> in Siberian tundra reveals the seasonality of its carbon sequestration strength

2012 ◽  
Vol 9 (10) ◽  
pp. 13713-13742 ◽  
Author(s):  
B. R. K. Runkle ◽  
T. Sachs ◽  
C. Wille ◽  
E.-M. Pfeiffer ◽  
L. Kutzbach
Keyword(s):  
Carbon Sink ◽  
Ecosystem Respiration ◽  
Growing Season ◽  
New Method ◽  
Apparent Temperature ◽  
The Arctic ◽  
Co2 Uptake ◽  
Night Time ◽  
Tundra Ecosystem ◽  
Co2 Sink

Abstract. This paper evaluates the relative contribution of light and temperature on net ecosystem CO2 uptake during the 2006 growing season in a~polygonal tundra ecosystem in the Lena River Delta in Northern Siberia (72°22´ N, 126°30´ E). We demonstrate that the timing of warm periods may be an important determinant of the magnitude of the ecosystem's carbon sink function, as they drive temperature-induced changes in respiration. Hot spells during the early portion of the growing season are shown to be more influential in creating mid-day surface-to-atmosphere net ecosystem CO2 exchange fluxes than those occurring later in the season. In this work we also develop and present a bulk flux partition model to better account for tundra plant physiology and the specific light conditions of the arctic region that preclude the successful use of traditional partition methods that derive a respiration-temperature relationship from all night-time data. Night-time, growing season measurements are rare during the arctic summer, however, so the new method allows for temporal variation in the parameters describing both ecosystem respiration and gross uptake by fitting both processes at the same time. Much of the apparent temperature sensitivity of respiration seen in the traditional partition method is revealed in the new method to reflect seasonal changes in basal respiration rates. Understanding and quantifying the flux partition is an essential precursor to describing links between assimilation and respiration at different time scales, as it allows a more confident evaluation of measured net exchange over a broader range of environmental conditions. The growing season CO2 sink estimated by this study is similar to those reported previously for this site, and is substantial enough to withstand the long, low-level respiratory CO2 release during the rest of the year to maintain the site's CO2 sink function on an annual basis.

scholarly journals Soil microbial biomass, activity and community composition along altitudinal gradients in the High Arctic (Billefjorden, Svalbard)

2018 ◽  
Vol 15 (6) ◽  
pp. 1879-1894 ◽  
Author(s):  
Petr Kotas ◽  
Hana Šantrůčková ◽  
Josef Elster ◽  
Eva Kaštovská
Keyword(s):  
Community Structure ◽  
Microbial Biomass ◽  
High Arctic ◽  
The Arctic ◽  
Soil Parameters ◽  
Organic Carbon Content ◽  
Soil Microbial ◽  
Environmental Controls ◽  
Arctic Soils ◽  
Tundra Ecosystem

Abstract. The unique and fragile High Arctic ecosystems are vulnerable to global climate warming. The elucidation of factors driving microbial distribution and activity in arctic soils is essential for a comprehensive understanding of ecosystem functioning and its response to environmental change. The goals of this study were to investigate microbial biomass and activity, microbial community structure (MCS), and their environmental controls in soils along three elevational transects in the coastal mountains of Billefjorden, central Svalbard. Soils from four different altitudes (25, 275, 525 and 765 m above sea level) were analyzed for a suite of characteristics including temperature regimes, organic matter content, base cation availability, moisture, pH, potential respiration, and microbial biomass and community structure using phospholipid fatty acids (PLFAs). We observed significant spatial heterogeneity of edaphic properties among transects, resulting in transect-specific effects of altitude on most soil parameters. We did not observe any clear elevation pattern in microbial biomass, and microbial activity revealed contrasting elevational patterns between transects. We found relatively large horizontal variability in MCS (i.e., between sites of corresponding elevation in different transects), mainly due to differences in the composition of bacterial PLFAs, but also a systematic altitudinal shift in MCS related to different habitat preferences of fungi and bacteria, which resulted in high fungi-to-bacteria ratios at the most elevated sites. The biological soil crusts on these most elevated, unvegetated sites can host microbial assemblages of a size and activity comparable to those of the arctic tundra ecosystem. The key environmental factors determining horizontal and vertical changes in soil microbial properties were soil pH, organic carbon content, soil moisture and Mg2+ availability.

scholarly journals Identifying multiscale zonation and assessing the relative importance of polygon geomorphology on carbon fluxes in an Arctic tundra ecosystem

2015 ◽  
Vol 120 (4) ◽  
pp. 788-808 ◽  
Author(s):  
Haruko M. Wainwright ◽  
Baptiste Dafflon ◽  
Lydia J. Smith ◽  
Melanie S. Hahn ◽  
John B. Curtis ◽  
...  
Keyword(s):  
Carbon Fluxes ◽  
Arctic Tundra ◽  
Relative Importance ◽  
Tundra Ecosystem

scholarly journals Partitioning net ecosystem exchange of CO<sub>2</sub> on the pedon scale in the Lena River Delta, Siberia

2019 ◽  
Vol 16 (7) ◽  
pp. 1543-1562 ◽  
Author(s):  
Tim Eckhardt ◽  
Christian Knoblauch ◽  
Lars Kutzbach ◽  
David Holl ◽  
Gillian Simpson ◽  
...  
Keyword(s):  
Growing Season ◽  
Arctic Tundra ◽  
River Delta ◽  
Environmental Drivers ◽  
Co2 Fluxes ◽  
Lena River ◽  
Hydrological Conditions ◽  
Tundra Ecosystem ◽  
Water Saturated ◽  
Lena River Delta

Abstract. Arctic tundra ecosystems are currently facing amplified rates of climate warming. Since these ecosystems store significant amounts of soil organic carbon, which can be mineralized to carbon dioxide (CO2) and methane (CH4), rising temperatures may cause increasing greenhouse gas fluxes to the atmosphere. To understand how net the ecosystem exchange (NEE) of CO2 will respond to changing climatic and environmental conditions, it is necessary to understand the individual responses of the processes contributing to NEE. Therefore, this study aimed to partition NEE at the soil–plant–atmosphere interface in an arctic tundra ecosystem and to identify the main environmental drivers of these fluxes. NEE was partitioned into gross primary productivity (GPP) and ecosystem respiration (Reco) and further into autotrophic (RA) and heterotrophic respiration (RH). The study examined CO2 flux data collected during the growing season in 2015 using closed-chamber measurements in a polygonal tundra landscape in the Lena River Delta, northeastern Siberia. To capture the influence of soil hydrology on CO2 fluxes, measurements were conducted at a water-saturated polygon center and a well-drained polygon rim. These chamber-measured fluxes were used to model NEE, GPP, Reco, RH, RA, and net primary production (NPP) at the pedon scale (1–10 m) and to determine cumulative growing season fluxes. Here, the response of in situ measured RA and RH fluxes from permafrost-affected soils of the polygonal tundra to hydrological conditions have been examined. Although changes in the water table depth at the polygon center sites did not affect CO2 fluxes from RH, rising water tables were linked to reduced CO2 fluxes from RA. Furthermore, this work found the polygonal tundra in the Lena River Delta to be a net sink for atmospheric CO2 during the growing season. The NEE at the wet, depressed polygon center was more than twice that at the drier polygon rim. These differences between the two sites were caused by higher GPP fluxes due to a higher vascular plant density and lower Reco fluxes due to oxygen limitation under water-saturated conditions at the polygon center in comparison to the rim. Hence, soil hydrological conditions were one of the key drivers for the different CO2 fluxes across this highly heterogeneous tundra landscape.

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 Delayed responses of an Arctic ecosystem to an extreme summer: impacts on net ecosystem exchange and vegetation functioning

2014 ◽  
Vol 11 (20) ◽  
pp. 5877-5888 ◽  
Author(s):  
D. Zona ◽  
D. A. Lipson ◽  
J. H. Richards ◽  
G. K. Phoenix ◽  
A. K. Liljedahl ◽  
...  
Keyword(s):  
Extreme Events ◽  
Extreme Event ◽  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Net Ecosystem Exchange ◽  
Co2 Uptake ◽  
Lag Effects ◽  
Tundra Ecosystem ◽  
Co2 Sink ◽  
The Impact

Abstract. The importance and consequences of extreme events on the global carbon budget are inadequately understood. This includes the differential impact of extreme events on various ecosystem components, lag effects, recovery times, and compensatory processes. In the summer of 2007 in Barrow, Arctic Alaska, there were unusually high air temperatures (the fifth warmest summer over a 65-year period) and record low precipitation (the lowest over a 65-year period). These abnormal conditions were associated with substantial desiccation of the Sphagnum layer and a reduced net Sphagnum CO2 sink but did not affect net ecosystem exchange (NEE) from this wet-sedge arctic tundra ecosystem. Microbial biomass, NH4+ availability, gross primary production (GPP), and ecosystem respiration (Reco) were generally greater during this extreme summer. The cumulative ecosystem CO2 sink in 2007 was similar to the previous summers, suggesting that vascular plants were able to compensate for Sphagnum CO2 uptake, despite the impact on other functions and structure such as desiccation of the Sphagnum layer. Surprisingly, the lowest ecosystem CO2 sink over a five summer record (2005–2009) was observed during the 2008 summer (~70% lower), directly following the unusually warm and dry summer, rather than during the extreme summer. This sink reduction cannot solely be attributed to the potential damage to mosses, which typically contribute ~40% of the entire ecosystem CO2 sink. Importantly, the return to a substantial cumulative CO2 sink occurred two summers after the extreme event, which suggests a substantial resilience of this tundra ecosystem to at least an isolated extreme event. Overall, these results show a complex response of the CO2 sink and its sub-components to atypically warm and dry conditions. The impact of multiple extreme events requires further investigation.

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.

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

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

2019 ◽  
Author(s):  
Martin Jiskra ◽  
Jeroen E. Sonke ◽  
Yannick Agnan ◽  
Detlev Helmig ◽  
Daniel Obrist
Keyword(s):  
Stable Isotope ◽  
Isotope Analysis ◽  
Elemental Mercury ◽  
Arctic Tundra ◽  
Atmospheric Mercury ◽  
The Arctic ◽  
Night Time ◽  
Field Station ◽  
Tundra Ecosystem ◽  
Flux Measurements

Abstract. The tundra plays a pivotal role in the Arctic mercury (Hg) cycling 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 by 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 therefore central, but remain understudied. Here, we combine Hg stable isotope analysis of Hg(0) in the atmosphere, interstitial snow and soil pore air, with Hg(0) flux measurements in a tundra ecosystem at Toolik field station in northern Alaska (USA). In 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 (AMDE's) occurred, with fast re-emission of Hg(0) after AMDE's 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, ε202Hg = −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.

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