scholarly journals Controls on autotrophic and heterotrophic respiration in an ombrotrophic bog

2021 ◽  
Author(s):  
Tracy Rankin ◽  
Nigel Roulet ◽  
Tim Moore
Keyword(s):  
Ecosystem Respiration ◽  
Heterotrophic Respiration ◽  
Sink Strength ◽  
Spatial And Temporal Variability ◽  
Turnover Rates ◽  
Symbiotic Relationships ◽  
Plant Parts ◽  
Ombrotrophic Bog ◽  
Soil Temperatures ◽  
Northern Peatlands

Abstract. Northern peatlands are globally significant carbon stores, but the sink strength may vary from year-to-year due to variations in environmental and biogeochemical conditions. This variation is mainly brought about by changes in primary production and ecosystem respiration. The processes that relate to variations in autotrophic respiration (AR; respiration by plant parts) are understood quite well, but heterotrophic respiration (HR; respiration by microbial bacteria in the soil, fungi, etc.) is crudely measured and modelled. This will lead to biased estimates if a change favours one form of respiration over another and alters allocations of carbon to labile pools with different turnover rates. HR has only recently been shown to be more intimately linked to vegetation dynamics than once thought, particularly in wetter, oligotrophic, sedge-dominated ecosystems. The objective of this study is to determine the factors that relate to the spatial and temporal variability in respiration and its autotrophic and heterotrophic components in an ombrotrophic bog (Mer Bleue) where woody shrubs are dominant, and to see if the more dynamic nature of HR in sedges also exists in this bog. Plot level measurements using manual chambers were used to partition respiration from both the dominant shrubs and the sparse sedges at the site, and the controls on respiration were explored by measuring a variety of environmental variables, such as air and soil temperatures (T) and water table (WT) depth. Results show that AR and HR correlate primarily with air and soil T, with WT depth playing an important role in some cases, and that a higher variability in respiration exists for the shrub plots than the sedge plots, especially when WT levels are more variable. Our findings also show that a plant’s response to changes in climate or land-use is related to different mechanisms of obtaining water resources and utilizing symbiotic relationships with other plants around them. These results will improve our understanding of peatland carbon cycling, as well as improve the conceptualization of HR.

Can management improve the lawn’s functioning in the conditions of multiple anthropogenic stressors?

2021 ◽  
Author(s):  
Olga Gavrichkova ◽  
Dario Liberati ◽  
Viktoriya Varyushkina ◽  
Kristina Ivashchenko ◽  
Paolo De Angelis ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Soil Respiration ◽  
Green Infrastructure ◽  
Urban Areas ◽  
Ecosystem Respiration ◽  
Heterotrophic Respiration ◽  
Sand Mixture ◽  
Anthropogenic Stressors ◽  
Unplanted Soil ◽  
The Impact

<p>Release of heavy metals, salts and other toxic agents in the environment is of increasing concern in urban areas. Contaminants not solely decline the quality of the local environment and affect the health of human population and urban ecosystems but are also spread through runoff and leaching into non-contaminated areas. Urban lawns are the most distributed green infrastructure in the cities. Management of lawn system may either exacerbate the negative effects of contaminants on lawn functioning either help to withstand the toxic effects and maintain the lawn ecosystem health and the efficient release of ecosystem services.  </p><p>The aim of this study was to evaluate the interactions between the lawn management, the lawn functioning, and the release into the soil of typical urban contaminants. For this purpose, <em>Festuca arundinacea</em> grass was planted in a turf-sand mixture with and without amendment addition (zeolite + vermicompost). To reproduce the impact of traffic-related contaminants in proximity of the road, pots were treated with a solution containing de-icing salt (NaCl) and 6 heavy metals (Zn, Cd, Pb, Cr, Cu, Ni), imitating road runoff solution. After contamination, half of pots was maintained at optimum soil water content (Smart irrigation), another half was left to periodical drying in order to simulate conditions with discontinuous watering (Periodical irrigation). The same experimental scheme was reproduced for unplanted soil. CO<sub>2</sub> net ecosystem exchange (NEE), soil and ecosystem respiration as well as flux from unplanted soil (heterotrophic respiration) were measured shortly after the treatment (short-term) and up 3 months since the treatment start (long-term).</p><p>Soil amendment stimulated plant productivity and increased the efficiency of the system in C uptake (+56% NEE). A relevant reduction of NEE was observed from 14 to 40 days after the application of traffic-related contaminants in both amended and non amended pots. During this period the contaminants had the greatest impact on lawn NEE subjected to Periodic irrigation (-49% and -66% in amended and non amended pots, respectively), while lawn under Smart irrigation was less affected (-35% and -26% in amended and non amended pots, respectively). Different respiration sources (ecosystem respiration, soil respiration, heterotrophic respiration) were characterized by different sensitivity to management and contamination. Heterotrophic flux was not sensitive to soil amending but declined with contamination with enhanced negative effect under Smart irrigation. Response of ecosystem respiration to contamination was less pronounced in confront to soil respiration suggesting leaf-level buffering.    </p><p>Three months later,  the effect of contaminants on lawn gas exchange ceased for all treated pots. Instead, the irrigation effect persisted depending on whether pots were amended or not. In non amended pots NEE was reduced by 18% under Periodic irrigation, while this effect was not present in amended pots. We conclude, that performance of such green infrastructure as lawns in terms of C sequestration under multiple anthropogenic stressors could be efficiently improved through soil amending and irrigation control.</p><p>Current research was financially supported by RFBR No. 19-29-05187 and RSF No. 19-77-30012.</p>

scholarly journals Assessment of model estimates of land-atmosphere CO<sub>2</sub> exchange across Northern Eurasia

2015 ◽  
Vol 12 (14) ◽  
pp. 4385-4405 ◽  
Author(s):  
M. A. Rawlins ◽  
A. D. McGuire ◽  
J. S. Kimball ◽  
P. Dass ◽  
D. Lawrence ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Soil Carbon ◽  
Residence Time ◽  
Primary Productivity ◽  
Ecosystem Respiration ◽  
Regional Scale ◽  
Northern Eurasia ◽  
Sink Strength ◽  
Vegetation Productivity ◽  
Co2 Sink

Abstract. A warming climate is altering land-atmosphere exchanges of carbon, with a potential for increased vegetation productivity as well as the mobilization of permafrost soil carbon stores. Here we investigate land-atmosphere carbon dioxide (CO2) cycling through analysis of net ecosystem productivity (NEP) and its component fluxes of gross primary productivity (GPP) and ecosystem respiration (ER) and soil carbon residence time, simulated by a set of land surface models (LSMs) over a region spanning the drainage basin of Northern Eurasia. The retrospective simulations cover the period 1960–2009 at 0.5° resolution, which is a scale common among many global carbon and climate model simulations. Model performance benchmarks were drawn from comparisons against both observed CO2 fluxes derived from site-based eddy covariance measurements as well as regional-scale GPP estimates based on satellite remote-sensing data. The site-based comparisons depict a tendency for overestimates in GPP and ER for several of the models, particularly at the two sites to the south. For several models the spatial pattern in GPP explains less than half the variance in the MODIS MOD17 GPP product. Across the models NEP increases by as little as 0.01 to as much as 0.79 g C m−2 yr−2, equivalent to 3 to 340 % of the respective model means, over the analysis period. For the multimodel average the increase is 135 % of the mean from the first to last 10 years of record (1960–1969 vs. 2000–2009), with a weakening CO2 sink over the latter decades. Vegetation net primary productivity increased by 8 to 30 % from the first to last 10 years, contributing to soil carbon storage gains. The range in regional mean NEP among the group is twice the multimodel mean, indicative of the uncertainty in CO2 sink strength. The models simulate that inputs to the soil carbon pool exceeded losses, resulting in a net soil carbon gain amid a decrease in residence time. Our analysis points to improvements in model elements controlling vegetation productivity and soil respiration as being needed for reducing uncertainty in land-atmosphere CO2 exchange. These advances will require collection of new field data on vegetation and soil dynamics, the development of benchmarking data sets from measurements and remote-sensing observations, and investments in future model development and intercomparison studies.

scholarly journals From sink to source: long-term (2002-2019) trends and anomalies in net ecosystem exchange of CO2 from a Scottish temperate peatland.

2020 ◽  
Author(s):  
Karen Hei-Laan Yeung ◽  
Carole Helfter ◽  
Neil Mullinger ◽  
Mhairi Coyle ◽  
Eiko Nemitz
Keyword(s):  
Water Table ◽  
Ecosystem Respiration ◽  
Net Ecosystem Exchange ◽  
Growing Season ◽  
Water Table Depth ◽  
Sink Strength ◽  
Summer Drought ◽  
C Cycle ◽  
Dry Spell

&lt;p&gt;Peatlands North of 45&amp;#730; represent one of the largest terrestrial carbon (C) stores. They play an important role in the global C-cycle, and their ability to sequester carbon is controlled by multiple, often competing, factors including precipitation, temperature and phenology. Land-atmosphere exchange of carbon dioxide (CO&lt;sub&gt;2&lt;/sub&gt;) is dynamic, and exhibits marked seasonal and inter-annual variations which can effect the overall carbon sink strength in both the short- and long-term.&lt;/p&gt;&lt;p&gt;Due to increased incidences of climate anomalies in recent years, long-term datasets are essential to disambiguate natural variability in Net Ecosystem Exchange (NEE) from shorter-term fluctuations. This is particularly important at high latitudes (&gt;45&amp;#730;N) where the majority of global peatlands are found. With increasing pressure from stressors such as climate and land-use change, it has been predicted that with a ca. 3&lt;sup&gt;o&lt;/sup&gt;C global temperature rise by 2100, UK peatlands could become a net source of C.&lt;/p&gt;&lt;p&gt;NEE of CO&lt;sub&gt;2&lt;/sub&gt; has been measured using the eddy-covariance (EC) method at Auchencorth Moss (55&amp;#176;47&amp;#8217;32 N, 3&amp;#176;14&amp;#8217;35 W, 267 m a.s.l.), a temperate, lowland, ombrotrophic peatland in central Scotland, continuously since 2002. Alongside EC data, we present a range of meteorological parameters measured at site including soil temperature, total solar and photosynthetically active radiation (PAR), rainfall, and, since April 2007, half-hourly water table depth readings. The length of record and range of measurements make this dataset an important resource as one of the longest term records of CO&lt;sub&gt;2&lt;/sub&gt; fluxes from a temperate peatland.&lt;/p&gt;&lt;p&gt;Although seasonal cycles of gross primary productivity (GPP) were highly variable between years, the site was a consistent CO&lt;sub&gt;2&lt;/sub&gt; sink for the period 2002-2012. However, net annual losses of CO&lt;sub&gt;2&lt;/sub&gt; have been recorded on several occasions since 2013. Whilst NEE tends to be positively correlated with the length of growing season, anomalies in winter weather also explain some of the variability in CO&lt;sub&gt;2&lt;/sub&gt; sink strength the following summer.&lt;/p&gt;&lt;p&gt;Additionally, water table depth (WTD) plays a crucial role, affecting both GPP and ecosystem respiration (R&lt;sub&gt;eco&lt;/sub&gt;). Relatively dry summers in recent years have contributed to shifting the balance between R&lt;sub&gt;eco&lt;/sub&gt; and GPP: prolonged periods of low WTD were typically accompanied by an increase in R&lt;sub&gt;eco&lt;/sub&gt;, and a decrease in GPP, hence weakening the overall CO&lt;sub&gt;2&lt;/sub&gt; sink strength. Extreme events such as drought periods and cold winter temperatures can have significant and complex effects on NEE, particularly when such meteorological anomalies co-occur. For example, a positive annual NEE occurred in 2003 when Europe experienced heatwave and summer drought. More recently, an unusually long spell of snow lasting until the end of March delayed the onset of the 2018 growing season by up to 1.5 months compared to previous years. This was followed by a prolonged dry spell in summer 2018, which weakened GPP, increased R&lt;sub&gt;eco&lt;/sub&gt; and led to a net annual loss of 47.4 ton CO&lt;sub&gt;2&lt;/sub&gt;-C km&lt;sup&gt;-2&lt;/sup&gt;. It is clear that the role of Northern peatlands within the carbon cycle is being modified, driven by changes in climate at both local and global scales.&lt;/p&gt;

Mismatch between the optimal ages for ecosystem productivity and net CO2 sequestration in Norway spruce forests

2021 ◽  
Author(s):  
Junbin Zhao ◽  
Holger Lange ◽  
Helge Meissner
Keyword(s):  
Climate Change ◽  
Primary Production ◽  
Norway Spruce ◽  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Economic Benefits ◽  
Sink Strength ◽  
Climate Change Scenarios ◽  
Ecosystem Productivity ◽  
Spruce Forests

&lt;p&gt;Forests have climate change mitigation potential since they sequester carbon. However, their carbon sink strength might depend on management. As a result of the balance between CO&lt;sub&gt;2&lt;/sub&gt; uptake and emission, forest net ecosystem exchange (NEE) reaches optimal values (maximum sink strength) at young stand ages, followed by a gradual NEE decline over many years. Traditionally, this peak of NEE is believed to be concurrent with the peak of primary production (e.g., gross primary production, GPP); however, in theory, this concurrence may potentially vary depending on tree species, site conditions and the patterns of ecosystem respiration (R&lt;sub&gt;eco&lt;/sub&gt;). In this study, we used eddy-covariance (EC)-based CO&lt;sub&gt;2&lt;/sub&gt; flux measurements from 8 forest sites that are dominated by Norway spruce (Picea abies L.) and built machine learning models to find the optimal age of ecosystem productivity and that of CO&lt;sub&gt;2&lt;/sub&gt; sequestration. We found that the net CO&lt;sub&gt;2&lt;/sub&gt; uptake of Norway spruce forests peaked at ages of 30-40 yrs. Surprisingly, this NEE peak did not overlap with the peak of GPP, which appeared later at ages of 60-90 yrs. The mismatch between NEE and GPP was a result of the R&lt;sub&gt;eco&lt;/sub&gt; increase that lagged behind the GPP increase associated with the tree growth at early age. Moreover, we also found that newly planted Norway spruce stands had a high probability (up to 90%) of being a C source in the first year, while, at an age as young as 5 yrs, they were likely to be a sink already. Further, using common climate change scenarios, our model results suggest that net CO&lt;sub&gt;2&lt;/sub&gt; uptake of Norway spruce forests will increase under the future climate with young stands in the high latitude areas being more beneficial. Overall, the results suggest that forest management practices should consider NEE and forest productivity separately and harvests should be performed only after the optimal ages of both the CO&lt;sub&gt;2&lt;/sub&gt; sequestration and productivity to gain full ecological and economic benefits.&lt;/p&gt;

scholarly journals Response of carbon dioxide emissions to sheep grazing and N application in an alpine grassland – Part 1: Effect of sheep grazing

2014 ◽  
Vol 11 (7) ◽  
pp. 1743-1750 ◽  
Author(s):  
Y. M. Gong ◽  
A. Mohammat ◽  
X. J. Liu ◽  
K. H. Li ◽  
P. Christie ◽  
...  
Keyword(s):  
Co2 Emissions ◽  
Carbon Dioxide Emissions ◽  
Ecosystem Respiration ◽  
Critical Role ◽  
Growing Season ◽  
Heterotrophic Respiration ◽  
Sheep Grazing ◽  
Alpine Grasslands ◽  
Soil Co2 Flux ◽  
Grazing Exclusion

Abstract. Previous work has failed to address fully the response of (autotrophic and heterotrophic) respiration to grazing in different ecosystems, particularly in alpine grasslands outside the growing season. From 2010 to 2011 a field experiment combined two methods (static closed chambers and a closed dynamic soil CO2 flux system) in alpine grasslands located in the Tianshan Mountains. We examined the effects of grazing regime on ecosystem respiration (Re) both outside (NGS) and during (GS) the growing season and determined the pattern of Re in relation to climate change. There was no significant change in CO2 emissions under grazing. Heterotrophic respiration (Rh) accounted for 78.5% of Re with short-term grazing exclusion and 93.2% of Re with long-term grazing exclusion. Re, Rh and autotrophic respiration (Ra) fluxes outside the growing season were equivalent to 12.9%, 14.1% and 11.4% of the respective CO2 fluxes during the growing season. In addition, our results indicate that soil water content played a critical role in Ra in the cold and arid environment. Both Rh and Re were sensitive to soil temperature. Moreover, our results suggest that grazing exerted no significant effect on CO2 emissions in these alpine grasslands.

scholarly journals Cushion bogs are stronger carbon dioxide net sinks than moss-dominated bogs as revealed by eddy covariance measurements on Tierra del Fuego, Argentina

2019 ◽  
Vol 16 (17) ◽  
pp. 3397-3423 ◽  
Author(s):  
David Holl ◽  
Verónica Pancotto ◽  
Adrian Heger ◽  
Sergio Jose Camargo ◽  
Lars Kutzbach
Keyword(s):  
Carbon Dioxide ◽  
Eddy Covariance ◽  
Ecosystem Respiration ◽  
Vascular Plant ◽  
Tierra Del Fuego ◽  
Peat Moss ◽  
High Temporal Resolution ◽  
Sink Strength ◽  
Bog Ecosystems ◽  
Annual Nee

Abstract. The near-pristine bog ecosystems of Tierra del Fuego in southernmost Patagonia have so far not been studied in terms of their current carbon dioxide (CO2) sink strength. CO2 flux data from Southern Hemisphere peatlands are scarce in general. In this study, we present CO2 net ecosystem exchange (NEE) fluxes from two Fuegian bog ecosystems with contrasting vegetation communities. One site is located in a glaciogenic valley and developed as a peat moss-dominated raised bog, and the other site is a vascular plant-dominated cushion bog located at the coast of the Beagle Channel. We measured NEE fluxes with two identical eddy covariance (EC) setups at both sites for more than 2 years. With the EC method, we were able to observe NEE fluxes on an ecosystem level and at high temporal resolution. Using a mechanistic modeling approach, we estimated daily NEE models to gap fill and partition the half-hourly net CO2 fluxes into components related to photosynthetic uptake (gross primary production, GPP) and to total ecosystem respiration (TER). We found a larger relative variability of annual NEE sums between both years at the moss-dominated site. A warm and dry first year led to comparably high TER sums. Photosynthesis was also promoted by warmer conditions but less strongly than TER with respect to absolute and relative GPP changes. The annual NEE carbon (C) uptake was more than 3 times smaller in the warm year. Close to the sea at the cushion bog site, the mean temperature difference between both observed years was less pronounced, and TER stayed on similar levels. A higher amount of available radiation in the second observed year led to an increase in GPP (5 %) and NEE (35 %) C uptake. The average annual NEE-C uptake of the cushion bog (-122±76 gm-2a-1, n=2) was more than 4 times larger than the average uptake of the moss-dominated bog (-27±28 gm-2a-1, n=2).

Fruit Set in Lupinus angustifolius Cv. Unicrop. II. Assimilate Flow During Flowering and Early Fruiting

1981 ◽  
Vol 8 (3) ◽  
pp. 307 ◽  
Author(s):  
JS Pate ◽  
P Farrington
Keyword(s):  
Lupinus Angustifolius ◽  
Main Stem ◽  
Carbon Dioxide Exchange ◽  
Sink Strength ◽  
Plant Parts ◽  
Single Leaf ◽  
Lateral Shoots ◽  
Using Data ◽  
A Minor ◽  
Stem Leaf

Assimilate distribution in Lupinus angustifolius was studied during 7 weeks after emergence of the main inflorescence by feeding [14C]urea to a single leaf or group of leaves on a plant and measuring 14C in plant parts 24 h after feeding. Nine times of feeding were involved, each with 14C treatments encompassing leaves of the main stem and first-order laterals. The inflorescence was a minor sink for assimilates compared with root, main stem and developing lateral shoots. During the first 4 weeks the inflorescence relied on main stem leaves, especially the upper leaves, but in the fifth week leaves of upper laterals became principal sources of assimilates. The transition occurred after four to six basal fruits had set, and just as upper flowers were commencing to abscise. Estimates were made of transfer of photosynthetically fixed carbon from the uppermost main stem leaf to the inflorescence, using data on carbon dioxide exchange and changes in carbon content of this leaf and its translocatory commitment to the inflorescence as determined by 14C feeding. Assimilate flow from leaves to flowers was confined largely to organs of the same or adjacent orthostichies (2/5 phyllotaxis), but these affinities became less definite during fruiting. Import of 14C by reproductive units was related to phenology, position on an inflorescence, and accumulation of dry matter. All flowers attracted assimilates strongly at the bud stage but lost sink strength progressively after opening. Upper flowers destined to abscise failed to import assimilates or to bleed from phloem for several days before being shed. Lower flowers which set fruits showed a rapid resurgence of sink strength once their corollas had senesced and the young fruits had commenced to elongate.

scholarly journals Physiological controls of the isotopic time lag between leaf assimilation and soil CO2 efflux

2014 ◽  
Vol 41 (8) ◽  
pp. 850 ◽  
Author(s):  
Yann Salmon ◽  
Romain L. Barnard ◽  
Nina Buchmann
Keyword(s):  
Environmental Changes ◽  
Ecosystem Respiration ◽  
Isotopic Signature ◽  
Sink Strength ◽  
Clear Understanding ◽  
Co2 Efflux ◽  
Carbon Isotopic ◽  
Environmental Controls ◽  
Carbon Transfer ◽  
Wide Range

Environmental factors and physiological controls on photosynthesis influence the carbon isotopic signature of ecosystem respiration. Many ecosystem studies have used stable carbon isotopes to investigate environmental controls on plant carbon transfer from above- to belowground. However, a clear understanding of the internal mechanisms underlying time-lagged responses of carbon isotopic signatures in ecosystem respiration to environmental changes is still lacking. This study addressed plant physiological controls on the transfer time of recently assimilated carbon from assimilation to respiration. We produced a set of six wheat plants with varying physiological characteristics, by growing them under a wide range of nitrogen supply and soil water content levels under standardised conditions. The plants were pulse-labelled with 13C-CO2, and the isotopic signature of CO2 respired in the dark by plants and soil was monitored continuously over two days. Stomatal conductance (gs) was strongly related to the rate of transfer of recently assimilated carbon belowground. The higher gs, the faster newly assimilated carbon was allocated belowground and the faster it was respired in the soil. Our results suggest that carbon sink strength of plant tissues may be a major driver of transfer velocity of recently assimilated carbon to plant respiratory tissues and soil respiration.

scholarly journals Moist moss tundra on Kapp Linne, Svalbard is a net source of CO<sub>2</sub> and CH<sub>4</sub> to the atmosphere

2021 ◽  
Author(s):  
Anders Lindroth ◽  
Norbert Pirk ◽  
Ingibjörg S. Jónsdóttir ◽  
Christian Stiegler ◽  
Leif Klemedtsson ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Air Temperature ◽  
Ecosystem Respiration ◽  
Net Ecosystem Exchange ◽  
Growing Season ◽  
Mean Value ◽  
The Arctic ◽  
Spatial And Temporal Variability ◽  
Annual Nee ◽  
Greenness Index

Abstract. We measured CO2 and CH4 fluxes using chambers and eddy covariance (only CO2) from a moist moss tundra in Svalbard. The average net ecosystem exchange (NEE) during the summer (June–August) was −0.40 g C m−2 day−1 or −37 g C m−2 for the whole summer. Including spring and autumn periods the NEE was reduced to −6.8 g C m−2 and the annual NEE became positive, 24.7 gC m−2 due to the losses during the winter. The CH4 flux during the summer period showed a large spatial and temporal variability. The mean value of all 214 samples was 0.000511 ± 0.000315 µmol m−2s−1 which corresponds to a growing season estimate of 0.04 to 0.16 g CH4 m−2. We find that this moss tundra emits about 94–100 g CO2-equivalents m−2 yr−1 of which CH4 is responsible for 3.5–9.3 % using GWP100 of 27.9 respectively GWP20. Air temperature, soil moisture and greenness index contributed significantly to explain the variation in ecosystem respiration (Reco) while active layer depth, soil moisture and greenness index were the variables that best explained CH4 emissions. Estimate of temperature sensitivity of Reco and gross primary productivity showed that a modest increase in air temperature of 1 degree did not significantly change the NEE during the growing season but that the annual NEE would be even more positive adding another 8.5 g C m−2 to the atmosphere. We tentatively suggest that the warming of the Arctic that has already taken place is partly responsible for the fact that the moist moss tundra now is a source of CO2 to the atmosphere.

scholarly journals Cushion bogs are stronger carbon dioxide net sinks than moss-dominated bogs as revealed by eddy covariance measurements on Tierra del Fuego, Argentina

2019 ◽  
Author(s):  
David Holl ◽  
Verónica Pancotto ◽  
Adrian Heger ◽  
Sergio Jose Camargo ◽  
Lars Kutzbach
Keyword(s):  
Carbon Dioxide ◽  
Eddy Covariance ◽  
Ecosystem Respiration ◽  
Vascular Plant ◽  
Tierra Del Fuego ◽  
Peat Moss ◽  
High Temporal Resolution ◽  
Sink Strength ◽  
Bog Ecosystems ◽  
Annual Nee

Abstract. The near-pristine bog ecosystems of Tierra del Fuego in southernmost Patagonia have so far not been studied in terms of their current carbon dioxide (CO2) sink strength. CO2 flux data from southern hemisphere peatlands is scarce in general. In this study, we present CO2 net ecosystem exchange (NEE) fluxes from two Fuegian bog ecosystems with contrasting vegetation communities. One site is located in a glaciogenic valley and developed as a peat moss-dominated raised bog, the other site is a vascular plant-dominated cushion bog located at the coast of the Beagle Channel. We measured NEE fluxes with two identical eddy covariance (EC) setups at both sites for more than two years. With the EC method, we were able to observe NEE fluxes on ecosystem level and at high temporal resolution. Using a mechanistic modeling approach, we estimated daily NEE models to gap-fill and partition the half-hourly net CO2 fluxes into components related to photosynthetic uptake (gross primary production, GPP) and to total ecosystem respiration (TER). We found a larger relative variability of annual NEE sums between both years at the moss-dominated site. A warm and dry first year led to comparably high TER sums. Photosynthesis was also promoted by warmer conditions but less strong than TER with respect to absolute and relative GPP changes. The annual NEE-C uptake was more than three times smaller in the warm year. Close to the sea at the cushion bog site, the mean temperature difference between both observed years was less pronounced, and TER stayed on similar levels. A higher amount of available radiation in the second observed year led to an increase of GPP (5 %) and NEE (35 %) carbon (C) uptake. The average annual NEE-C uptake of the cushion bog (−122 ± 76 g m−2 a−1, n = 2) was more than four times larger than the average uptake of the moss-dominated bog (−27 ± 28 g m−2 a−1, n = 2).

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