scholarly journals The effect of a permafrost disturbance on growing-season carbon-dioxide fluxes in a high Arctic tundra ecosystem

2015 ◽  
Vol 12 (23) ◽  
pp. 19781-19817
Author(s):  
A. E. Cassidy ◽  
A. Christen ◽  
G. H. R. Henry
Keyword(s):  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Net Ecosystem Exchange ◽  
Growing Season ◽  
Arctic Tundra ◽  
High Arctic ◽  
Carbon Dioxide Fluxes ◽  
Tundra Ecosystem ◽  
Retrogressive Thaw Slump ◽  
Measurement Period

Abstract. Soil carbon stored in high-latitude permafrost landscapes is threatened by warming, and could contribute significant amounts of carbon to the atmosphere and hydrosphere as permafrost thaws. Permafrost disturbances, especially active layer detachments and retrogressive thaw slumps, have increased in frequency and magnitude across the Fosheim Peninsula, Ellesmere Island, Canada. To determine the effects of retrogressive thaw slumps on net ecosystem exchange (NEE) of CO2 in high Arctic tundra, we used two eddy covariance (EC) tower systems to simultaneously and continuously measure CO2 fluxes from a disturbed site and the surrounding undisturbed tundra. During the 32-day measurement period in the 2014 growing season the undisturbed tundra was a small net sink (NEE = −0.12 g C m−2 d−1); however, the disturbed terrain of the retrogressive thaw slump was a net source (NEE = +0.39 g C m−2 d−1). Over the measurement period, the undisturbed tundra sequestered 3.84 g C m−2, while the disturbed tundra released 12.48 g C m−2. Before full leaf out in early July, the undisturbed tundra was a small source of CO2, but shifted to a sink for the remainder of the sampling season (July), whereas the disturbed tundra remained a source of CO2 throughout the season. A static chamber system was also used to measure fluxes in the footprints of the two towers, in both disturbed and undisturbed tundra, and fluxes were partitioned into ecosystem respiration (Re) and gross primary production (GPP). Average GPP and Re found in disturbed tundra were smaller (+0.41 μmol m−2 s−1 and +0.50 μmol m−2 s−1, respectively) than those found in undisturbed tundra (+1.21 μmol m−2 s−1 and +1.00 μmol m−2 s−1, respectively). Our measurements indicated clearly that the permafrost disturbance changed the high Arctic tundra system from a sink to a source for CO2 during the growing season.

scholarly journals The effect of a permafrost disturbance on growing-season carbon-dioxide fluxes in a high Arctic tundra ecosystem

2016 ◽  
Vol 13 (8) ◽  
pp. 2291-2303 ◽  
Author(s):  
Alison E. Cassidy ◽  
Andreas Christen ◽  
Gregory H. R. Henry
Keyword(s):  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Net Ecosystem Exchange ◽  
Growing Season ◽  
Arctic Tundra ◽  
High Arctic ◽  
Carbon Dioxide Fluxes ◽  
Tundra Ecosystem ◽  
Retrogressive Thaw Slump ◽  
Measurement Period

Abstract. Soil carbon stored in high-latitude permafrost landscapes is threatened by warming and could contribute significant amounts of carbon to the atmosphere and hydrosphere as permafrost thaws. Thermokarst and permafrost disturbances, especially active layer detachments and retrogressive thaw slumps, are present across the Fosheim Peninsula, Ellesmere Island, Canada. To determine the effects of retrogressive thaw slumps on net ecosystem exchange (NEE) of CO2 in high Arctic tundra, we used two eddy covariance (EC) tower systems to simultaneously and continuously measure CO2 fluxes from a disturbed site and the surrounding undisturbed tundra. During the 32-day measurement period in the 2014 growing season, the undisturbed tundra was a small net sink (NEE  =  −0.1 g C m−2 d−1); however, the disturbed terrain of the retrogressive thaw slump was a net source (NEE  =  +0.4 g C m−2 d−1). Over the measurement period, the undisturbed tundra sequestered 3.8 g C m−2, while the disturbed tundra released 12.5 g C m−2. Before full leaf-out in early July, the undisturbed tundra was a small source of CO2 but shifted to a sink for the remainder of the sampling season (July), whereas the disturbed tundra remained a source of CO2 throughout the season. A static chamber system was also used to measure daytime fluxes in the footprints of the two towers, in both disturbed and undisturbed tundra, and fluxes were partitioned into ecosystem respiration (Re) and gross primary production (GPP). Average GPP and Re found in disturbed tundra were smaller (+0.40 µmol m−2 s−1 and +0.55 µmol m−2 s−1, respectively) than those found in undisturbed tundra (+1.19 µmol m−2 s−1 and +1.04 µmol m−2 s−1, respectively). Our measurements indicated clearly that the permafrost disturbance changed the high Arctic tundra system from a sink to a source for CO2 during the majority of the growing season (late June and July).

Long-term experimentally deepened snow decreases growing-season respiration in a low- and high-arctic tundra ecosystem

2016 ◽  
Vol 121 (5) ◽  
pp. 1236-1248 ◽  
Author(s):  
Philipp R. Semenchuk ◽  
Casper T. Christiansen ◽  
Paul Grogan ◽  
Bo Elberling ◽  
Elisabeth J. Cooper
Keyword(s):  
Growing Season ◽  
Arctic Tundra ◽  
High Arctic ◽  
Tundra Ecosystem

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 Impacts of active retrogressive thaw slumps on vegetation, soil, and net ecosystem exchange of carbon dioxide in the Canadian High Arctic

2017 ◽  
Vol 3 (2) ◽  
pp. 179-202 ◽  
Author(s):  
Alison E. Cassidy ◽  
Andreas Christen ◽  
Greg H.R. Henry
Keyword(s):  
Eddy Covariance ◽  
Ecosystem Respiration ◽  
Net Ecosystem Exchange ◽  
Growing Season ◽  
High Arctic ◽  
Vegetation Coverage ◽  
Soil Conditions ◽  
Soil Temperatures ◽  
The Impact ◽  
Chamber Measurements

Retrogressive thaw slumps (RTS) are permafrost disturbances common on the Fosheim Peninsula, Ellesmere Island, Canada. During the 2013 growing season, three different RTS were studied to investigate the impact on vegetation composition, soil, and growing season net ecosystem exchange (NEE) of CO2 by comparing to the adjacent undisturbed tundra. Eddy covariance and static chamber measurements were used to determine NEE and ecosystem respiration (Re), respectively. Vegetation cover was significantly lower in all active disturbances, relative to the surrounding tundra, and this affected the overall impact of disturbance on CO2 fluxes. Disturbances were characterized by greater Re compared to surrounding undisturbed tundra. Over the mid-growing season (34 days), eddy covariance NEE measurements indicated that there was greater net CO2 uptake in undisturbed versus disturbed tundra. At one site, the undisturbed tundra was a weak net sink (−0.05 ± 0.02 g C m−2 day−1), while the disturbed tundra acted as a weak net source (+0.07 ± 0.04 g C m−2 day−1). At the other site, the NEE of the undisturbed tundra was −0.20 ± 0.03 g C m−2 day−1 (sink), while the disturbed tundra still sequestered CO2, but less than the undisturbed tundra (NEE = −0.05 ± 0.04 g C m−2 day−1). Two of the RTS exhibited average soil temperatures that were greater compared to the surrounding undisturbed tundra. In one case, the opposite effect was observed. All RTS exhibited elevated soil moisture (+14%) and nutrient availability (specifically nitrogen) relative to the undisturbed tundra. We conclude that RTS, although limited in space, have profound environmental impacts by reducing vegetation coverage, increasing wet soil conditions, and altering NEE during the growing season in the High Arctic.

scholarly journals Microscale drivers of summer CO2 fluxes in the Svalbard High Arctic tundra

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Marta Magnani ◽  
Ilaria Baneschi ◽  
Mariasilvia Giamberini ◽  
Brunella Raco ◽  
Antonello Provenzale
Keyword(s):  
Ecosystem Respiration ◽  
Vegetation Type ◽  
Gross Primary Production ◽  
Arctic Tundra ◽  
High Arctic ◽  
The Arctic ◽  
Small Scale ◽  
Arctic Ecosystems ◽  
Additional Source ◽  
And Storage

AbstractHigh-Arctic ecosystems are strongly affected by climate change, and it is still unclear whether they will become a carbon source or sink in the next few decades. In turn, such knowledge gaps on the drivers and the processes controlling CO2 fluxes and storage make future projections of the Arctic carbon budget a challenging goal. During summer 2019, we extensively measured CO2 fluxes at the soil–vegetation–atmosphere interface, together with basic meteoclimatic variables and ecological characteristics in the Bayelva river basin near Ny Ålesund, Spitzbergen, Svalbard (NO). By means of multi-regression models, we identified the main small-scale drivers of CO2 emission (Ecosystem Respiration, ER), and uptake (Gross Primary Production, GPP) in this tundra biome, showing that (i) at point scale, the temporal variability of fluxes is controlled by the classical drivers, i.e. air temperature and solar irradiance respectively for ER and GPP, (ii) at site scale, the heterogeneity of fractional vegetation cover, soil moisture and vegetation type acted as additional source of variability for both CO2 emissions and uptake. The assessment of the relative importance of such drivers in the multi-regression model contributes to a better understanding of the terrestrial carbon dioxide exchanges and of Critical Zone processes in the Arctic tundra.

scholarly journals MODELING OF THE SEASONAL COURSE OF CARBON EXCHANGE IN WETLAND ECOSYSTEMS

2020 ◽  
Vol 1 (5) ◽  
pp. 56-61
Author(s):  
E. A. Dyukarev ◽  
◽  
Keyword(s):  
Carbon Dioxide ◽  
Western Siberia ◽  
Ecosystem Respiration ◽  
Net Ecosystem Exchange ◽  
Growing Season ◽  
Biological Productivity ◽  
Carbon Dioxide Fluxes ◽  
Wetland Ecosystems ◽  
Bog Ecosystems ◽  
Two Parameters

The paper summarizes the results of expeditionary studies to study biological productivity, carbon dioxide fluxes in the bog ecosystems of the Central Taiga of Western Siberia. The paper summarizes the results of expeditionary studies to study biological productivity, carbon dioxide fluxes in the bog ecosystems of the Central Taiga of Western Siberia. Measurements of carbon dioxide fluxes were carried out from July 7 to July 14, 2019 at six observation sites located on the territory of typical wetland ecosystems of eutrophic, mesotrophic and oligotrophic types, taking into account the diversity of microlandscapes. Automatic measurements of the CO2 fluxes were carried out using the Licor LI-8100A soil respiration system. To extend the obtained observation data to other periods and to calculate the annual carbon balance of the ecosystem, a net ecosystem exchange (NEE) model was proposed, and the net fluxes of greenhouse gases for the growing season were calculated. The model uses air temperature and incoming photosynthetically active radiation as explanatory factors for gross primary production and ecosystem respiration. The model was calibrated in accordance with field measurements of carbon dioxide fluxes. For each observation site, six parameters were determined: two parameters for the photosynthesis model, two parameters for the respiration model and two for the biomass growth model. As a result of calculations for the period from May to October 2019, time series of fluxes of carbon dioxide absorption by vegetation during photosynthesis, CO2 release during ecosystem respiration, and the resulting flux – net ecosystem exchange were obtained. In the annual course, an increase in the intensity of photosynthesis during the daytime is associated with both the annual course of solar radiation and the accumulation of plant biomass. It was found that the net ecosystem exchange varies more strongly than its components. The NEE for ecosystems without vegetation is always positive. NEE is negative for the hollow and the open transit mesotrophic fen on any day of the growing season. Other ecosystems show both positive and negative daily mean fluxes. Wetland ecosystems with large biomass storages have significant fluxes (more than 1500 g CO2 / m2 ) associated with photosynthesis, but they also have a large expenditure component of carbon exchange (750–2200 g / m2 ). As a result, it was found that the greatest total absorption of carbon dioxide is observed in the mesotrophic sedge- menyanthes fen (1062 g / m2 ) and in the low ryam, taking into account the tree layer (603 g / m2 ). Other wetlands accumulate 244–466 g / m2 from the atmosphere during the growing season.

scholarly journals Delayed responses of an Arctic ecosystem to an extremely dry summer: impacts on net ecosystem exchange and vegetation functioning

2013 ◽  
Vol 10 (12) ◽  
pp. 19189-19217 ◽  
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 ◽  
Vascular Plant ◽  
Net Ecosystem Exchange ◽  
Co2 Uptake ◽  
Tundra Ecosystem ◽  
Dry Conditions ◽  
The Impact

Abstract. The importance and mode of action 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. Summer 2007 in Barrow, Arctic Alaska, experienced unusually high air temperatures (fifth warmest over a 65 yr period) and record low precipitation (lowest over a 65 yr period). These abnormal conditions resulted in strongly reduced net Sphagnum CO2 uptake, but no effect neither on vascular plant development nor on net ecosystem exchange (NEE) from this arctic tundra ecosystem. Gross primary production (GPP) and ecosystem respiration (Reco) were both generally greater during most of this extreme summer. Cumulative ecosystem C uptake in 2007 was similar to the previous summers, showing the capacity of the ecosystem to compensate in its net ecosystem exchange (NEE) despite the impact on other functions and structure such as substantial necrosis of the Sphagnum layer. Surprisingly, the lowest ecosystem C uptake (2005–2009) was observed during the 2008 summer, i.e the year directly following the extremely summer. In 2008, cumulative C uptake was ∼70% lower than prior years. This reduction cannot solely be attributed to mosses, which typically contribute with ∼40% – of the entire ecosystem C uptake. The minimum summer cumulative C uptake in 2008 suggests that the entire ecosystem experienced difficulty readjusting to more typical weather after experiencing exceptionally warm and dry conditions. Importantly, the return to a substantial cumulative C uptake occurred two summers after the extreme event, which suggest a high resilience of this tundra ecosystem. Overall, these results show a highly complex response of the C uptake and its sub-components to atypically dry conditions. The impact of multiple extreme events still awaits further investigation.

scholarly journals Influence of Hudson Bay on the carbon dynamics of a Hudson Bay Lowlands coastal site

2016 ◽  
Vol 2 (3) ◽  
pp. 142-163 ◽  
Author(s):  
Kristina K. Delidjakova ◽  
Richard L. Bello ◽  
Kaz Higuchi ◽  
Bipin Pokharel
Keyword(s):  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Net Ecosystem Exchange ◽  
Growing Season ◽  
Offshore Wind ◽  
Hudson Bay ◽  
Air Masses ◽  
Hudson Bay Lowlands ◽  
N 93 ◽  
Wind Regimes

Eddy covariance (EC) estimates of net ecosystem exchange (NEE) and the surface energy balance were gathered from an elevated peat plateau within the Hudson Bay Lowlands near Churchill, Manitoba, Canada (58°43′46″N, 93°49′57″W) during the growing season of 2007. Data were segregated into onshore and offshore wind regimes to assess the advective influence of the generally cold and moist Hudson Bay air masses compared to generally warm and dry air masses of nonmarine origin. Monthly average NEE ranged from an uptake of 0.2 µmol·m−2·s−1 in September to 5.6 µmol·m−2·s−1 in July. Over the growing season, onshore winds from Hudson Bay contributed to an average 4.2 °C reduction in air temperature and an NEE increase of 27%. When normalized with respect to sunlight receipt, the ratio of gross primary production to photosynthetically active radiation (GPP/PAR) was 26% stronger for offshore regimes than for onshore, while the ratio of ecosystem respiration to PAR (ER/PAR) was 71% stronger for offshore regimes. It was concluded that GPP maintains the same strength for both wind regimes, while ER is significantly stronger for offshore regimes, resulting in reduced NEE capacity during periods when winds originate from inland.

Environmental Control of Inter-annual Variability of Net Ecosystem Exchange in Rice-rice Cropping System

2021 ◽  
Author(s):  
Chinmaya Kumar Swain ◽  
Amaresh Kumar Nayak ◽  
Dibyendu Chatterjee ◽  
Suchismita Pattanaik ◽  
Pratap Bhattacharyya ◽  
...  
Keyword(s):  
Environmental Control ◽  
Ecosystem Respiration ◽  
Net Ecosystem Exchange ◽  
Cropping System ◽  
Growing Season ◽  
Wet Season ◽  
Carbon Dioxide Fluxes ◽  
Ecosystem Responses ◽  
Annual Variability ◽  
Lower Temperature

Abstract Consecutive five-year long eddy covariance measurements in a lowland tropical rice-rice system were used to investigate the impacts of gross primary productivity (GPP), climate drivers and ecosystem responses (i.e. ecosystem respiration, RE) on the inter-annual variability (IAV) of the net ecosystem exchange (NEE), which is directly related to the agricultural productivity and climate change. The IAV of carbon dioxide fluxes in two crop growing phases i.e. dry and wet season along with fallow period were analysed. The respiratory fluxes build up during the non-growing season were lower by net uptake in growing season. Annual cumulative value of NEE was negative (sink) in both the crop growing season. The variability of climate drivers and changes in the ecosystem responses to drivers revealed a large intra-annual as well as inter-annual variability of net ecosystem fluxes. NEE was found to be strongly correlated with GPP and RE and also with other metrological variables such as photosynthetically active radiation (PAR), precipitation, air temperature and soil temperature. The anomalies of NEE, GPP and RE were observed to be less in 2017 and 2018 which may be due to lower temperature anomalies recorded in these years. Further understanding of biological mechanisms is needed which is involved in the variation of climatological variables to improve our ability to predict future IAV of NEE.

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