scholarly journals Response of hydrology and CO<sub>2</sub> flux to experimentally altered rainfall frequency in a temperate poor fen, southern Ontario, Canada

2018 ◽  
Vol 15 (13) ◽  
pp. 3937-3951
Author(s):  
Danielle D. Radu ◽  
Tim P. Duval
Keyword(s):  
Carbon Sink ◽  
Ecosystem Respiration ◽  
Moisture Regime ◽  
Co2 Uptake ◽  
Vegetation Types ◽  
Precipitation Frequency ◽  
Near Surface ◽  
Poor Fen ◽  
Rainfall Frequency ◽  
Strong Control

Abstract. Predicted changes to the precipitation regime in many parts of the world include intensifying the distribution into lower frequency, large magnitude events. The corresponding alterations to the soil moisture regime may affect plant growth and soil respiration, particularly in peatlands, where large stores of organic carbon are due to gross ecosystem productivity (GEP) exceeding ecosystem respiration (ER). This study uses lab monoliths corroborated with field measurements to examine the effect of changing rainfall frequency on peatland moisture controls on CO2 uptake in an undisturbed cool temperate poor fen. Lab monoliths and field plots containing mosses, sedges, or shrubs received either 2.3, 1, or 0.5 precipitation events per week, with total rainfall held constant. Decreasing rain frequency led to lower near-surface volumetric moisture content (VMC), water table (WT), and soil tension for all vegetation types, with minimal effect on evapotranspiration. The presence of sedges in particular led to soil tensions of ≥100 cm of water for a sizeable duration (37 %) of the experiment. Altered rainfall frequencies affected GEP but had little effect on ER; overall, low-frequency rain led to a reduced net CO2 uptake for all three vegetation types. VMC had a strong control on GEP and net ecosystem exchange (NEE) of the Sphagnum capillifolium monoliths, and decreasing rainfall frequency influenced these relationships. Overall, communities dominated by mosses became net sources of CO2 after 3 days without rain, whereas sedge communities remained net sinks for up to 14 days without rain. The results of this study demonstrate the hydrological controls of peatland CO2 exchange dynamics influenced by changing precipitation frequency; furthermore, they suggest these predicted changes in frequency will lead to increased sedge GEP but limit the carbon-sink function of peatlands.

scholarly journals Response of hydrology and CO<sub>2</sub> flux to experimentally-altered rainfall frequency in a temperate poor fen, southern Ontario, Canada

2017 ◽  
Author(s):  
Danielle D. Radu ◽  
Tim P. Duval
Keyword(s):  
Plant Growth ◽  
Ecosystem Respiration ◽  
Vascular Plant ◽  
Moisture Regime ◽  
Co2 Uptake ◽  
Vegetation Types ◽  
Near Surface ◽  
Poor Fen ◽  
Rainfall Frequency ◽  
Strong Control

Abstract. Predicted changes to the precipitation regime in many parts of the world include intensifying the distribution into lower frequency, large magnitude events. The corresponding alterations to the soil moisture regime may affect plant growth and soil respiration, particularly in peatlands, where large stores of organic carbon are due to gross ecosystem productivity (GEP) exceeding ecosystem respiration (ER). This study uses a combined lab and field approach to examine the effect of changing rainfall frequency on peatland moisture controls on CO2 uptake in an undisturbed cool temperate poor fen. Lab monoliths and field plots containing mosses, sedges, or shrubs received either 2.3, 1, or 0.5 events per week, with total rainfall held constant. Decreasing rain frequency led to lower near-surface volumetric moisture content (VMC), water table (WT), and soil tension for all vegetation types, with minimal effect on evapotranspiration. The presence of sedges in particular led to soil tensions > −100 cm of water of a sizeable duration (37 %) of the experiment. Altered rainfall frequencies affected GEP but had little effect on ER: overall low-frequency rain led to reduced net CO2 uptake for all three vegetation types. VMC had a strong control on GEP and net ecosystem exchange (NEE) of the Sphagnum capillifolium monoliths, and decreasing rainfall frequency influenced these relationships. Overall, communities dominated by mosses became net sources of CO2 after three days without rain, whereas sedge communities remained net sinks for up to 14 days without rain. Results of this study demonstrate the hydrological controls of peatland CO2 exchange dynamics influenced by changing precipitation frequency and suggest these predicted changes in frequency will lead to increased vascular plant growth and limit the carbon-sink function of peatlands.

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.

Impacts of long-term warming and enhanced nitrogen and sulfur deposition on carbon sink potential in a boreal peatland

2021 ◽  
Author(s):  
Tuula Larmola ◽  
Liisa Maanavilja ◽  
Heikki Kiheri ◽  
Mats Nilsson ◽  
Matthias Peichl
Keyword(s):  
Global Change ◽  
Wet Deposition ◽  
Carbon Sink ◽  
Ecosystem Respiration ◽  
N Deposition ◽  
Ecosystem Responses ◽  
Gross Photosynthesis ◽  
Poor Fen ◽  
The Individual

&lt;p&gt;In order to assess peatland carbon sink potential under multiple global change perturbations, we examined the individual and combined effects of long-term warming and enhanced nitrogen (N) and sulfur (S) deposition on ecosystem CO&lt;sub&gt;2 &lt;/sub&gt;exchange at one of the longest-running experiments on peatlands, Deger&amp;#246; Stormyr poor fen, Sweden. The site has been treated with NH&lt;sub&gt;4&lt;/sub&gt;NO&lt;sub&gt;3&lt;/sub&gt; (15 times ambient annual wet deposition), Na&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt; (6 times ambient annual wet deposition) and elevated temperature (air +3.6 C) for 23 years. Gross photosynthesis, ecosystem respiration and net CO&lt;sub&gt;2&lt;/sub&gt; exchange were measured weekly during June-August using chambers. After 23 years, two of the experimental perturbations: N addition and warming individually reduced net CO&lt;sub&gt;2&lt;/sub&gt; uptake potential down to 0.3-0.4 fold compared to the control mainly due to lower gross photosynthesis. Under S only treatment ecosystem CO&lt;sub&gt;2&lt;/sub&gt; fluxes were largely unaltered. In contrast, the combination of S and N deposition and warming led to a more pronounced effect and close to zero net CO&lt;sub&gt;2&lt;/sub&gt; uptake potential or net C source. Our study emphasizes the value of the long-term multifactor experiments in examining the ecosystem responses: simultaneous perturbations can have nonadditive interactions that cannot be predicted based on individual responses and thus, must be studied in combination when evaluating feedback mechanisms to ecosystem C sink potential under global change.&lt;/p&gt;

scholarly journals Can a bog drained for forestry be a stronger carbon sink than a natural bog forest?

2014 ◽  
Vol 11 (2) ◽  
pp. 2189-2226 ◽  
Author(s):  
J. Hommeltenberg ◽  
H. P. Schmid ◽  
M. Droesler ◽  
P. Werle
Keyword(s):  
Carbon Fixation ◽  
Carbon Sink ◽  
Ecosystem Respiration ◽  
Net Ecosystem Exchange ◽  
Weather Conditions ◽  
Co2 Exchange ◽  
Co2 Uptake ◽  
Spruce Forest ◽  
The Difference ◽  
Whole Life Cycle

Abstract. This study compares the CO2 exchange of a natural bog forest, and of a bog drained for forestry in the pre-alpine region of southern Germany. The sites are separated by only ten kilometers, they share the same formation history and are exposed to the same climate and weather conditions. In contrast, they differ in land use history: at the Schechenfilz site a natural bog-pine forest (Pinus mugo rotundata) grows on an undisturbed, about 5 m thick peat layer; at Mooseurach a planted spruce forest (Picea abies) grows on drained and degraded peat (3.4 m). The net ecosystem exchange of CO2 (NEE) at both sites has been investigated for two years (July 2010 to June 2012), using the eddy covariance technique. Our results indicate that the drained, forested bog at Mooseurach is a much stronger carbon dioxide sink (−130 ± 31 and −300 ± 66 g C m−2 a−1 in the first and second year respectively) than the natural bog forest at Schechenfilz (−53 ± 28 and −73±38 g C m−2 a−1). The strong net CO2 uptake can be explained by the high gross primary productivity of the spruces that over-compensates the two times stronger ecosystem respiration at the drained site. The larger productivity of the spruces can be clearly attributed to the larger LAI of the spruce site. However, even though current flux measurements indicate strong CO2 uptake of the drained spruce forest, the site is a strong net CO2 source, if the whole life-cycle, since forest planting is considered. We determined the difference between carbon fixation by the spruces and the carbon loss from the peat due to drainage since forest planting. The estimate resulted in a strong carbon release of +156 t C ha−1 within the last 44 yr, means the spruces would need to grow for another 100 yr, at the current rate, to compensate the peat loss of the former years. In contrast, the natural bog-pine ecosystem has likely been a small but consistent carbon sink for decades, which our results suggest is very robust regarding short-term changes of environmental factors.

scholarly journals Can a bog drained for forestry be a stronger carbon sink than a natural bog forest?

2014 ◽  
Vol 11 (13) ◽  
pp. 3477-3493 ◽  
Author(s):  
J. Hommeltenberg ◽  
H. P. Schmid ◽  
M. Drösler ◽  
P. Werle
Keyword(s):  
Carbon Fixation ◽  
Carbon Sink ◽  
Ecosystem Respiration ◽  
Soil Formation ◽  
Weather Conditions ◽  
Co2 Uptake ◽  
Spruce Forest ◽  
Area Index ◽  
Plant Area Index ◽  
Whole Life Cycle

Abstract. This study compares the CO2 exchange of a natural bog forest, and of a bog drained for forestry in the pre-Alpine region of southern Germany. The sites are separated by only 10 km, they share the same soil formation history and are exposed to the same climate and weather conditions. In contrast, they differ in land use history: at the Schechenfilz site a natural bog-pine forest (Pinus mugo ssp. rotundata) grows on an undisturbed, about 5 m thick peat layer; at Mooseurach a planted spruce forest (Picea abies) grows on drained and degraded peat (3.4 m). The net ecosystem exchange of CO2 (NEE) at both sites has been investigated for 2 years (July 2010–June 2012), using the eddy covariance technique. Our results indicate that the drained, forested bog at Mooseurach is a much stronger carbon dioxide sink (−130 ± 31 and −300 ± 66 g C m−2 a−1 in the first and second year, respectively) than the natural bog forest at Schechenfilz (−53 ± 28 and −73 ± 38 g C m−2 a−1). The strong net CO2 uptake can be explained by the high gross primary productivity of the 44-year old spruces that over-compensates the two-times stronger ecosystem respiration at the drained site. The larger productivity of the spruces can be clearly attributed to the larger plant area index (PAI) of the spruce site. However, even though current flux measurements indicate strong CO2 uptake of the drained spruce forest, the site is a strong net CO2 source when the whole life-cycle since forest planting is considered. It is important to access this result in terms of the long-term biome balance. To do so, we used historical data to estimate the difference between carbon fixation by the spruces and the carbon loss from the peat due to drainage since forest planting. This rough estimate indicates a strong carbon release of +134 t C ha−1 within the last 44 years. Thus, the spruces would need to grow for another 100 years at about the current rate, to compensate the potential peat loss of the former years. In contrast, the natural bog-pine ecosystem has likely been a small but stable carbon sink for decades, which our results suggest is very robust regarding short-term changes of environmental factors.

scholarly journals Drivers of long-term variability in CO<sub>2</sub> net ecosystem exchange in a temperate peatland

2014 ◽  
Vol 11 (10) ◽  
pp. 14981-15018 ◽  
Author(s):  
C. Helfter ◽  
C. Campbell ◽  
K. J. Dinsmore ◽  
J. Drewer ◽  
M. Coyle ◽  
...  
Keyword(s):  
Carbon Sink ◽  
Ecosystem Respiration ◽  
Net Ecosystem Exchange ◽  
Growing Season ◽  
Sink Strength ◽  
Co2 Uptake ◽  
Annual Variability ◽  
Dormant Season ◽  
Carbon Dioxide Co2

Abstract. Land–atmosphere exchange of carbon dioxide (CO2) in peatlands exhibits marked seasonal and inter-annual variability, which subsequently affects the carbon sink strength of catchments across multiple temporal scales. Long-term studies are needed to fully capture the natural variability and therefore identify the key hydrometeorological drivers in the net ecosystem exchange (NEE) of CO2. NEE has been measured continuously by eddy-covariance at Auchencorth Moss, a temperate lowland peatland in central Scotland, since 2002. Hence this is one of the longest peatland NEE studies to date. For 11 yr, the site was a consistent, yet variable, atmospheric CO2 sink ranging from −5.2 to −135.9 g CO2-C m−2 yr−1 (mean of −64.1 ± 33.6 g CO2-C m−2 yr−1). Inter-annual variability in NEE was positively correlated to the length of the growing season. Mean winter air temperature explained 87% of the inter-annual variability in the sink strength of the following summer, indicating a phenological memory-effect. Plant productivity exhibited a marked hysteresis with respect to photosynthetically active radiation (PAR) over the growing season, indicative of two separate growth regimes. Ecosystem respiration (Reco) and gross primary productivity (GPP) were closely correlated (ratio 0.74), suggesting that autotrophic processes were dominant. Whilst the site was wet most of the year (water table depth <5 cm) there were indications that heterotrophic respiration was enhanced by drought, which also depressed GPP. NEE was compared to 5 other peatland sites which have published long-term NEE records. The CO2 uptake rate during the growing season was comparable to 3 other European sites, however the emission rate during the dormant season was significantly higher.

scholarly journals Responses of Forest Carbon Cycle to Drought and Elevated CO2

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 212
Author(s):  
Jun-Lan Xiao ◽  
Feng Zeng ◽  
Qiu-Lan He ◽  
Yu-Xia Yao ◽  
Xiao Han ◽  
...  
Keyword(s):  
Water Stress ◽  
Elevated Co2 ◽  
Carbon Sink ◽  
Ecosystem Respiration ◽  
Co2 Exchange ◽  
Positive Influence ◽  
Research Field ◽  
Co2 Fertilization ◽  
Global Trends ◽  
Elevated Atmospheric Co2

Forests play a pivotal role in mitigating global warming as an important carbon sink. Recent global greening trends reflect a positive influence of elevated atmospheric CO2 on terrestrial carbon uptake. However, increasingly frequent and intense drought events endanger the carbon sequestration function of forests. This review integrates previous studies across scales to identify potential global trends in forest responses to drought and elevated CO2 as well as to identify data needs in this important research field. The inconsistent responses of ecosystem respiration to drought contributes to the change of forest net CO2 exchange, which depends on the balance of opposite effects of warming and water stress on respiration. Whether CO2 fertilization can offset the effects of drought remains controversial, however, we found a potential overestimation of global CO2 fertilization effects because of increasing water stress and other limitations such as light and nutrients (N, P) as well as the possibility of photosynthetic acclimation.

scholarly journals Distinct patterns in the diurnal and seasonal variability in four components of soil respiration in a temperate forest under free-air CO<sub>2</sub> enrichment

2011 ◽  
Vol 8 (10) ◽  
pp. 3077-3092 ◽  
Author(s):  
L. Taneva ◽  
M. A. Gonzalez-Meler
Keyword(s):  
Soil Respiration ◽  
Seasonal Variability ◽  
Ecosystem Respiration ◽  
Co2 Efflux ◽  
Diurnal Variability ◽  
Soil C ◽  
Free Air ◽  
C Cycle ◽  
Strong Control ◽  
Average Contribution

Abstract. Soil respiration (RS) is a major flux in the global carbon (C) cycle. Responses of RS to changing environmental conditions may exert a strong control on the residence time of C in terrestrial ecosystems and in turn influence the atmospheric concentration of greenhouse gases. Soil respiration consists of several components oxidizing soil C from different pools, age and chemistry. The mechanisms underlying the temporal variability of RS components are poorly understood. In this study, we used the long-term whole-ecosystem 13C tracer at the Duke Forest Free Air CO2 Enrichment site to separate forest RS into its autotrophic (RR) and heterotrophic components (RH). The contribution of RH to RS was further partitioned into litter decomposition (RL), and decomposition of soil organic matter (RSOM) of two age classes – up to 8 yr old and SOM older than 8 yr. Soil respiration was generally dominated by RSOM during the growing season (44% of daytime RS), especially at night. The contribution of heterotrophic respiration (RSOM and RL) to RS was not constant, indicating that the seasonal variability in RR alone cannot explain seasonal variation in RS. Although there was no diurnal variability in RS, there were significant compensatory differences in the contribution of individual RS components to daytime and nighttime rates. The average contribution of RSOM to RS was greater at night (54%) than during the day (44%). The average contribution of RR to total RS was ~30% during the day and ~34% during the night. In contrast, RL constituted 26% of RS during the day and only 12% at night. About 95% of the decomposition of soil C older than 8 yr (Rpre-tr) originated from RSOM and showed more pronounced and consistent diurnal variability than any other RS component; nighttime rates were on average 29% higher than daytime rates. In contrast, the decomposition of more recent, post-treatment C (Rpre-tr) did not vary diurnally. None of the diurnal variations in components of RH could be explained by only temperature and moisture variations. Our results indicate that the variation observed in the components of RS is the result of complex interaction between dominant biotic controls (e.g. plant activity, mineralization kinetics, competition for substrates) over abiotic controls (temperature, moisture). The interactions and controls among roots and other soil organisms that utilize C of different chemistry, accessibility and ages, results in the overall soil CO2 efflux. Therefore understanding the controls on the components of RS is necessary to elucidate the influence of ecosystem respiration on atmospheric C-pools at different time scales.

scholarly journals Daily and seasonal patterns of CO2 fluxes and evapotranspiration in maize-grass intercropping

2016 ◽  
Vol 20 (9) ◽  
pp. 777-782 ◽  
Author(s):  
Cássia B. Machado ◽  
José R. de S. Lima ◽  
Antonio C. D. Antonino ◽  
Eduardo S. de Souza ◽  
Rodolfo M. S. Souza ◽  
...  
Keyword(s):  
Soil Water ◽  
Climate Changes ◽  
Carbon Sink ◽  
Soil Water Storage ◽  
Co2 Uptake ◽  
Co2 Fluxes ◽  
Area Index ◽  
Available Energy ◽  
Atmospheric Carbon ◽  
Main Consumer

ABSTRACT Studies that investigate the relationships between CO2 fluxes and evapotranspiration (ET) are important for predicting how agricultural ecosystems will respond to climate changes. However, none was made on the maize-grass intercropping system in Brazil. The aim of this study was to determine the ET and CO2 fluxes in a signal grass pasture intercropped with maize, in São João, Pernambuco, Brazil, in a drought year. Furthermore, the soil water storage (SWS) and leaf area index (LAI) were determined. The latent heat flux was the main consumer of the available energy and the daily and seasonal ET and CO2 variations were mainly controlled by rainfall, through the changes in soil water content and consequently in SWS. The agroecosystem acted as an atmospheric carbon source, during drier periods and lower LAI, and as an atmospheric carbon sink, during wetter periods and higher LAI values. In a dry year, the intercropping sequestered 2.9 t C ha-1, which was equivalent to 8.0 kg C ha-1 d-1. This study showed strong seasonal fluctuations in maize-grass intercropping CO2 fluxes, due to seasonality of rainfall, and that this agroecosystem is vulnerable to low SWS, with significant reduction in CO2 uptake during these periods.

scholarly journals Shifting environmental controls on CH<sub>4</sub> fluxes in a sub-boreal peatland

2013 ◽  
Vol 10 (12) ◽  
pp. 7971-7981 ◽  
Author(s):  
T. G. Pypker ◽  
P. A. Moore ◽  
J. M. Waddington ◽  
J. A. Hribljan ◽  
R. C. Chimner
Keyword(s):  
Soil Temperature ◽  
Net Ecosystem Exchange ◽  
P Value ◽  
Co2 Uptake ◽  
Ch4 Flux ◽  
Environmental Controls ◽  
Poor Fen ◽  
Abiotic And Biotic Factors ◽  
The Relationship ◽  
Northern Michigan

Abstract. We monitored CO2 and CH4 fluxes using eddy covariance from 19 May to 27 September 2011 in a poor fen located in northern Michigan. The objectives of this paper are to: (1) quantify the flux of CH4 from a sub-boreal peatland, and (2) determine which abiotic and biotic factors were the most correlated to the flux of CH4 over the measurement period. Net daily CH4 fluxes increased from 70 mg CH4 m−2 d−1 to 220 mg CH4 m−2 d−1 from mid May to mid July. After July, CH4 losses steadily declined to approximately 50 mg CH4 m−2 d−1 in late September. During the study period, the peatland lost 17.4 g CH4 m−2. Both abiotic and biotic variables were correlated with CH4 fluxes. When the different variables were analyzed together, the preferred model included mean daily soil temperature at 20 cm, daily net ecosystem exchange (NEE) and the interaction between mean daily soil temperature at 20 cm and NEE (R2 = 0.47, p value < 0.001). The interaction was important because the relationship between daily NEE and mean daily soil temperature with CH4 flux changed when NEE was negative (CO2 uptake from the atmosphere) or positive (CO2 losses to the atmosphere). On days when daily NEE was negative, 25% of the CH4 flux could be explained by correlations with NEE, however on days when daily NEE was positive, there was no correlation between daily NEE and the CH4 flux. In contrast, daily mean soil temperature at 20 cm was poorly correlated to changes in CH4 when NEE was negative (17%), but the correlation increased to 34% when NEE was positive. The interaction between daily NEE and mean daily soil temperature at 20 cm indicates shifting environmental controls on the CH4 flux throughout the growing season.

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