First application of low-cost eddy covariance for CO2 fluxes over agroforestry

2020 ◽  
Author(s):  
Justus van Ramshorst ◽  
Christian Markwitz ◽  
Timothy Hill ◽  
Robert Clement ◽  
Alexander Knohl ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Low Cost ◽  
Net Ecosystem Exchange ◽  
Agroforestry Systems ◽  
Agricultural System ◽  
Data Series ◽  
Custom Made ◽  
Flux Measurements ◽  
Eddy Covariance System ◽  
The Difference

<p>Agroforestry is a combination of monoculture agriculture and trees. Studies of net ecosystem exchange of CO<sub>2</sub> (NEE) of agroforestry systems are rare, in comparison to the extensive studies of NEE of agricultural systems (croplands and grasslands). Agroforestry has been shown to alter the microclimate, productivity, and nutrient and water usage – as compared to standard agricultural practise. The, potentially, higher carbon sequestration of agroforestry, relative to monoculture systems, provides an interesting option for mitigating climate change, highlighting the need for improved study of agroforestry systems. The current study, as part of the SIGNAL (sustainable intensification of agriculture through agroforestry) project, investigates NEE of agroforestry compared to that of monoculture agriculture. The study employs paired comparisons of flux measurements above agroforestry and monoculture agronomy, replicated at five locations across Germany. Fluxes are measured, using innovative low-cost CO<sub>2</sub> eddy covariance sensors (slow response Vaisala GMP343 IRGA with custom made housing), which have been successfully used in a study over grassland. Continuous data series from mid-summer until winter 2019 show that both systems acted as a sink with comparable fluxes during summer. The diurnal CO<sub>2</sub> cycle and the response to management activities are distinguishable and in autumn preliminary results suggest a small difference in fluxes between the two systems. The low-cost eddy covariance system is able to capture the turbulence and to measure the CO<sub>2</sub> flux over the agroforestry and monoculture agricultural system. We aim to further improve the quality of the CO<sub>2</sub> fluxes, by adapting post-processing software to better estimate the difference in carbon uptake between the agroforestry and monoculture systems.</p>

Evaluation of low-cost eddy covariance for CO2 fluxes over agroforestry and grassland

2021 ◽  
Author(s):  
Justus van Ramshorst ◽  
Christian Markwitz ◽  
Timothy Hill ◽  
Robert Clement ◽  
Alexander Knohl ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Low Cost ◽  
Arable Land ◽  
Agroforestry Systems ◽  
Post Processing ◽  
Flux Dynamics ◽  
Processing Scheme ◽  
Cost System ◽  
Custom Made ◽  
Significant Difference

<p>Agroforestry is an integration of trees in cropland or grassland and is discussed, within Germany and the EU, as a potential “Green Solution” for agriculture. Agroforestry alters the microclimate, productivity, biodiversity, and nutrient and water usage – as compared to standard agricultural practise. A potentially key benefit is the higher carbon sequestration of agroforestry, relative to monoculture systems, which could provide an interesting option for mitigating climate change, while still providing valuable arable land. Net ecosystem exchange studies of CO<sub>2</sub> (NEE) of agroforestry systems are rare, in comparison to the extensive studies of NEE of agricultural systems (croplands and grasslands). Therefore, the current study, as part of the SIGNAL (sustainable intensification of agriculture through agroforestry) project, investigates the NEE of agroforestry compared to that of monoculture agriculture.</p><p>At five locations across Germany, paired flux measurements above agroforestry and monoculture agronomy are performed using innovative low-cost CO<sub>2</sub> eddy covariance sensors (slow response Vaisala GMP343 IRGA, with custom made housing). During the summer of 2020 simultaneous measurements of the low-cost setup and a LI-COR 7200 are performed, above grassland at 3.5 m and adjacent agroforestry grassland at 10 m measurements height.</p><p>The low-cost eddy covariance system is able to capture the turbulent (diurnal) CO<sub>2</sub> flux dynamics and the response to management activities. After spectral corrections and applying quality control, the low-cost system at the agroforestry site (slope = 0.92, R<sup>2 </sup>= 0.88) performs better than the low-cost system at the grassland site (slope = 0.67, R<sup>2</sup> = 0.80), when compared to the LI-COR measurements. This is probably due to the difference in turbulence caused by different surface roughness and measurement height. The preliminary cumulative carbon flux during the four-month measurement campaign shows a significant difference between the grassland (source of (+) 16-38 gC/m<sup>2</sup>) and agroforestry grassland (sink of (-) 148-164 gC/m<sup>2</sup>), in favour of agroforestry. By applying post processing software, we aim to further optimize the frequency corrections for the low-cost system. In the future the obtained post processing scheme will be applied to the other low-cost eddy covariance systems within the project.</p>

scholarly journals Eddy-covariance flux measurements with a weight-shift microlight aircraft

2012 ◽  
Vol 5 (7) ◽  
pp. 1699-1717 ◽  
Author(s):  
S. Metzger ◽  
W. Junkermann ◽  
M. Mauder ◽  
F. Beyrich ◽  
K. Butterbach-Bahl ◽  
...  
Keyword(s):  
Heat Flux ◽  
Eddy Covariance ◽  
Low Cost ◽  
Sensible Heat Flux ◽  
Flux Measurement ◽  
Wind Measurement ◽  
Airborne Measurements ◽  
Weight Shift ◽  
Flux Measurements

Abstract. The objective of this study is to assess the feasibility and quality of eddy-covariance flux measurements from a weight-shift microlight aircraft (WSMA). Firstly, we investigate the precision of the wind measurement (σu,v ≤ 0.09 m s−1, σw = 0.04 m s−1), the lynchpin of flux calculations from aircraft. From here, the smallest resolvable changes in friction velocity (0.02 m s−1), and sensible- (5 W m−2) and latent (3 W m−2) heat flux are estimated. Secondly, a seven-day flight campaign was performed near Lindenberg (Germany). Here we compare measurements of wind, temperature, humidity and respective fluxes between a tall tower and the WSMA. The maximum likelihood functional relationship (MLFR) between tower and WSMA measurements considers the random error in the data, and shows very good agreement of the scalar averages. The MLFRs for standard deviations (SDs, 2–34%) and fluxes (17–21%) indicate higher estimates of the airborne measurements compared to the tower. Considering the 99.5% confidence intervals, the observed differences are not significant, with exception of the temperature SD. The comparison with a large-aperture scintillometer reveals lower sensible heat flux estimates at both tower (−40 to −25%) and WSMA (−25–0%). We relate the observed differences to (i) inconsistencies in the temperature and wind measurement at the tower and (ii) the measurement platforms' differing abilities to capture contributions from non-propagating eddies. These findings encourage the use of WSMA as a low cost and highly versatile flux measurement platform.

scholarly journals Ecosystem fluxes of hydrogen: a comparison of flux-gradient methods

2014 ◽  
Vol 7 (9) ◽  
pp. 2787-2805 ◽  
Author(s):  
L. K. Meredith ◽  
R. Commane ◽  
J. W. Munger ◽  
A. Dunn ◽  
J. Tang ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Forest Canopy ◽  
Trace Gases ◽  
Gradient Methods ◽  
Net Ecosystem Exchange ◽  
Heat Fluxes ◽  
Sensible Heat ◽  
Flux Gradient ◽  
Harvard Forest ◽  
Flux Measurements

Abstract. Our understanding of biosphere–atmosphere exchange has been considerably enhanced by eddy covariance measurements. However, there remain many trace gases, such as molecular hydrogen (H2), that lack suitable analytical methods to measure their fluxes by eddy covariance. In such cases, flux-gradient methods can be used to calculate ecosystem-scale fluxes from vertical concentration gradients. The budget of atmospheric H2 is poorly constrained by the limited available observations, and thus the ability to quantify and characterize the sources and sinks of H2 by flux-gradient methods in various ecosystems is important. We developed an approach to make nonintrusive, automated measurements of ecosystem-scale H2 fluxes both above and below the forest canopy at the Harvard Forest in Petersham, Massachusetts, for over a year. We used three flux-gradient methods to calculate the fluxes: two similarity methods that do not rely on a micrometeorological determination of the eddy diffusivity, K, based on (1) trace gases or (2) sensible heat, and one flux-gradient method that (3) parameterizes K. We quantitatively assessed the flux-gradient methods using CO2 and H2O by comparison to their simultaneous independent flux measurements via eddy covariance and soil chambers. All three flux-gradient methods performed well in certain locations, seasons, and times of day, and the best methods were trace gas similarity for above the canopy and K parameterization below it. Sensible heat similarity required several independent measurements, and the results were more variable, in part because those data were only available in the winter, when heat fluxes and temperature gradients were small and difficult to measure. Biases were often observed between flux-gradient methods and the independent flux measurements, and there was at least a 26% difference in nocturnal eddy-derived net ecosystem exchange (NEE) and chamber measurements. H2 fluxes calculated in a summer period agreed within their uncertainty and pointed to soil uptake as the main driver of H2 exchange at Harvard Forest, with H2 deposition velocities ranging from 0.04 to 0.10 cm s−1.

Surface energy flux measurements in a flooded and an aerobic rice field using a single eddy-covariance system

2014 ◽  
Vol 13 (4) ◽  
pp. 405-424 ◽  
Author(s):  
Daniele Masseroni ◽  
Arianna Facchi ◽  
Marco Romani ◽  
Enrico Antonio Chiaradia ◽  
Olfa Gharsallah ◽  
...  
Keyword(s):  
Surface Energy ◽  
Eddy Covariance ◽  
Energy Flux ◽  
Rice Field ◽  
Aerobic Rice ◽  
Surface Energy Flux ◽  
Flux Measurements ◽  
Eddy Covariance System

scholarly journals Design of the AmeriFlux Portable Eddy Covariance System and Uncertainty Analysis of Carbon Measurements

2007 ◽  
Vol 24 (8) ◽  
pp. 1389-1406 ◽  
Author(s):  
T. W. Ocheltree ◽  
H. W. Loescher
Keyword(s):  
Eddy Covariance ◽  
Spatial Scales ◽  
Flux Measurement ◽  
Field Measurements ◽  
Quality Control Laboratory ◽  
Flux Measurements ◽  
Eddy Covariance System ◽  
Uncertainty Analyses ◽  
Infrared Gas Analyzer ◽  
Ambient Co2

Abstract The AmeriFlux network continues to improve the understanding of carbon, water, and energy fluxes across temporal and spatial scales. The network includes ∼120 research sites that contribute to the understanding of processes within and among ecosystems. To improve the networks ability and confidence to synthesize data across multiple sites, the AmeriFlux quality assurance and quality control laboratory was established to reduce the within- and among-site uncertainties. This paper outlines the design of the portable eddy covariance system (PECS) and subsequent data processing procedures used for site comparisons. Because the PECS makes precision measurements of atmospheric CO2, the authors also present the results of uncertainty analyses in determining the polynomials for an infrared gas analyzer, estimating the CO2 in secondary standards, and estimating ambient CO2 in field measurements. Under field conditions, drift in the measurement of CO2 increased the uncertainty in flux measurements across 7 days by 5% and was not dependent on the magnitude or direction of the flux. The maximum relative flux measurement error for unstable conditions was 10.03 μmol CO2 m−2 s−1.

scholarly journals First eddy covariance flux measurements of gaseous elemental mercury (Hg<sup>0</sup>) over a grassland

2019 ◽  
Author(s):  
Stefan Osterwalder ◽  
Werner Eugster ◽  
Iris Feigenwinter ◽  
Martin Jiskra
Keyword(s):  
Detection Limit ◽  
Eddy Covariance ◽  
Net Ecosystem Exchange ◽  
Elemental Mercury ◽  
Terrestrial Ecosystems ◽  
Co2 Uptake ◽  
Gaseous Elemental Mercury ◽  
Flux Measurements ◽  
Net Co2 Uptake

Abstract. Direct measurements of the net ecosystem exchange (NEE) of gaseous elemental mercury (Hg0) are crucial to improve the understanding of global Hg cycling und ultimately human and wildlife Hg exposure. The lack of long-term, ecosystem-scale measurements causes large uncertainties in Hg0 flux estimates. Today it remains unclear whether terrestrial ecosystems are net sinks or sources of atmospheric Hg0. Here we show a detailed validation of the eddy covariance technique for direct Hg0 flux measurements (Eddy Mercury) based on a Lumex mercury monitor RA-915AM. The flux detection limit derived from a zero-flux experiment in the laboratory was 0.22 ng m−2 h−1 (maximum) with a 50 % cut-off at 0.074 ng m−2 h−1. The statistical estimate of the Hg0 flux detection limit under real-world outdoor conditions at the site was 5.9 ng m−2 h−1 (50 % cut-off). We present the first successful eddy covariance NEE measurements of Hg0 over a low-Hg level soil (41–75 ng Hg g−1 topsoil [0–10 cm]) in summer 2018 at a managed grassland at the Swiss FluxNet site in Chamau, Switzerland (CH-Cha). We measured a net summertime re-emission over a period of 34 days with a median Hg0 flux of 2.5 ng m−2 h−1 (−0.6 to 7.4 ng m−2 h−1, range between 25th and 75th percentiles). We observed a distinct diel cycle with higher median daytime fluxes (8.4 ng m−2 h−1) than nighttime fluxes (1.0 ng m−2 h−1). Drought stress during the measurement campaign in summer 2018 induced partial stomata closure of vegetation which led to a midday depression in CO2 uptake which did not recover during the afternoon. Thus, the cumulative net CO2 uptake was only 8 % of the net CO2 uptake during the same period in the previous year 2017. We suggest that partial stomata closure dampened Hg0 uptake by vegetation, resulting in a NEE of Hg0 dominated by soil re-emission. Finally, we give suggestions to further improve the precision and handling of the Eddy Mercury system in order to assure its suitability for long-term NEE measurements of Hg0 over natural background surfaces with low soil Hg concentrations (

scholarly journals Ecosystem fluxes of hydrogen: a comparison of flux-gradient methods

2014 ◽  
Vol 7 (3) ◽  
pp. 2879-2928 ◽  
Author(s):  
L. K. Meredith ◽  
R. Commane ◽  
J. W. Munger ◽  
A. Dunn ◽  
J. Tang ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Forest Canopy ◽  
Trace Gases ◽  
Gradient Methods ◽  
Net Ecosystem Exchange ◽  
Heat Fluxes ◽  
Sensible Heat ◽  
Flux Gradient ◽  
Harvard Forest ◽  
Flux Measurements

Abstract. Our understanding of biosphere-atmosphere exchange has been considerably enhanced by eddy-covariance measurements, however there remain many trace gases, such as molecular hydrogen (H2), for which there are no suitable analytical methods to measure their fluxes by eddy covariance. In such cases, flux-gradient methods can be used to calculate ecosystem-scale fluxes from vertical concentration gradients. The budget of atmospheric H2 is poorly constrained by the limited available observations, thus the ability to quantify and characterize the sources and sinks of H2 by flux-gradient methods in various ecosystems is important. We developed an approach to make nonintrusive, automated measurements of ecosystem-scale H2 fluxes both above and below the forest canopy at the Harvard Forest in Petersham, MA for over a year. We used three flux-gradient methods to calculate the fluxes: two similarity methods that do not rely on a micrometeorological determination of the eddy diffusivity, K, based on (1) trace gases or (2) sensible heat and one flux-gradient method that (3) parameterizes K. We quantitatively assessed the flux-gradient methods on CO2 and H2O by comparison to their simultaneous independent flux measurements via eddy covariance and chambers. All three flux-gradient methods performed well in certain locations, seasons, and times of day, and the best methods were trace gas similarity above and K parameterization below the canopy. Sensible heat similarity required several independent measurements and the results were more variable, in part because those data were only available in the winter when heat fluxes and temperature gradients were small and difficult to measure. Biases were often observed between flux-gradient methods and the independent flux measurements, including at least a 26% difference in nocturnal eddy-derived Net Ecosystem Exchange (NEE) and soil chamber measurements. All flux-gradient methods used to calculate above and below canopy H2 fluxes pointed to soil uptake as the main driver of H2 exchange at Harvard Forest. H2 fluxes calculated in a summer period agreed within their uncertainty and indicated that H2 deposition velocities ranged from 0.04 to 0.1 cm s−1.

scholarly journals Comparison between eddy covariance and automatic chamber techniques for measuring net ecosystem exchange of carbon dioxide in cotton and wheat fields

2013 ◽  
Vol 10 (5) ◽  
pp. 8467-8503 ◽  
Author(s):  
K. Wang ◽  
C. Liu ◽  
X. Zheng ◽  
M. Pihlatie ◽  
B. Li ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Eddy Covariance ◽  
Calcareous Soils ◽  
Net Ecosystem Exchange ◽  
Cotton Field ◽  
Wheat Field ◽  
Cropping Season ◽  
Flux Measurements ◽  
One Year ◽  
Carbon Dioxide Co2

Abstract. Static and transparent automatic chamber (AC) technique is a~necessary choice for measuring net ecosystem exchange (NEE) of carbon dioxide (CO2) in circumstances where eddy covariance (EC) technique is not applicable. However, a comparison of the two techniques for measurements on croplands has seldom been undertaken. We carried out NEE observations in a cotton field (for one year) and a winter wheat field (for one cropping season) using both AC and EC techniques, to (a) compare the NEE fluxes measured using each technique, and (b) test the NEE measurement performance of an automatic chamber system (AMEG), which was designed for simultaneous flux measurements of multiple gases. The half-hourly NEE fluxes measured with the two techniques were in approximate agreement, with the AC fluxes being 0.78 (cotton) and 1.06 (wheat) times those of the EC. When integrated to daily timescale, the fluxes of the two techniques were in better agreement, showing an average ratio of 0.94 and 1.00 for the cotton and wheat, respectively. During the periods with comparable field conditions and normal performance of both instruments, the cumulative NEE fluxes revealed small differences between the two techniques (–9.0 ~ 6.7%, with a mean of 0.1%). The measurements resulted in annual cumulative NEE of –40 g C m–2 yr–1 (EC) and –42 g C m–2 yr–1 (AC) in the cotton field and seasonal cumulative NEE of –251 g C m–2 (EC) and –205 g C m–2 (AC) in the wheat field. Our results indicate that, for cropland populated by short plants, the AMEG system and the data processing procedures applied in this study are able to provide NEE estimates comparable to those from EC measurements, although either technique may lead to an overestimation of the loss rate (or underestimation of the gain rate) of the soil organic carbon stock of an ecosystem, in particular with calcareous soils exposed to increasing atmospheric acid deposition.

scholarly journals Dynamics of net CO2 exchange in the wetland ecosystem recovering from a fire 

2021 ◽  
Author(s):  
Krzysztof Fortuniak ◽  
Włodzimierz Pawlak ◽  
Mariusz Siedlecki
Keyword(s):  
Eddy Covariance ◽  
National Park ◽  
Plant Cover ◽  
Net Ecosystem Exchange ◽  
Source Area ◽  
Co2 Exchange ◽  
Fire Event ◽  
North East ◽  
Flux Measurements ◽  
The Impact

&lt;p&gt;Wetlands, even if cover a relatively small fraction of Earth&amp;#8217;s surface, play an important role in global carbon cycle. They are the main terrestrial source of methane (CH&lt;sub&gt;4&lt;/sub&gt;), but due to anaerobic conditions they accumulate significant part of captured in photosynthesis carbon dioxide (CO&lt;sub&gt;2&lt;/sub&gt;). Due to the progressive climate change these ecosystems are exposed to different climate-inducted extreme events. One of them are fires that can significantly affect the carbon-storage potential of the wetlands.&lt;/p&gt;&lt;p&gt;In this study we analyze the impact of a great fire on one of the largest mid-European wetlands in Biebrza Valley (northeastern Poland) on the CO&lt;sub&gt;2&lt;/sub&gt; net ecosystem exchange (NEE). Over 5,500 ha of landscape of the Biebrza National Park burned down during this event in April 20-25, 2020. In the north-east edge of the core of this fire, there was an eddy-covariance measurement site, where greenhouse gas fluxes (CO&lt;sub&gt;2&lt;/sub&gt;, CH&lt;sub&gt;4&lt;/sub&gt;, H&lt;sub&gt;2&lt;/sub&gt;O) had been continuously recorded since 2013. The measurement system suffered to some extent, but flux measurements were resumed after repair works in approximately 2 weeks. Almost the entire source area of eddy-covariance system was affected by the fire. Thus, post-fire measurements show the dynamics of NEE for an ecosystem recovering from a fire.&lt;/p&gt;&lt;p&gt;In the flux measurements period (2013-2020) the studied ecosystem was affected not only by the above fire event but also by severe droughts in 2015 and 2018-2020. In consequence in non-fire years the annual totals of CO&lt;sub&gt;2&lt;/sub&gt; flux followed the mean ground water table level (WTL) and spanned from -990&amp;#160;gCO&lt;sub&gt;2&lt;/sub&gt;&amp;#8729;m&lt;sup&gt;-2&lt;/sup&gt;&amp;#8729;yr&lt;sup&gt;-1&lt;/sup&gt; (CO&lt;sub&gt;2&lt;/sub&gt; sink) in the wettest year to +1020&amp;#160;gCO&lt;sub&gt;2&lt;/sub&gt;&amp;#8729;m&lt;sup&gt;-2&lt;/sup&gt;&amp;#8729;yr&lt;sup&gt;-1&lt;/sup&gt; (CO&lt;sub&gt;2&lt;/sub&gt; source) in the driest year 2019. However, even taking into account the influence of WTL and temperature fluctuation we observed clear impact of the spring fire on CO&lt;sub&gt;2&lt;/sub&gt; exchange. Shortly after the fire, in May, the wetland was in average a source of CO&lt;sub&gt;2&lt;/sub&gt; (positive monthly total of NEE), which had not happened before even in the driest years. However, already in the second half of May, the absorption of CO&lt;sub&gt;2&lt;/sub&gt; began to predominate over the emissions. From the mid-June to the end of July we observed very intensive growth of plant cover and exceptionally strong absorption of CO&lt;sub&gt;2&lt;/sub&gt;, much higher than in other years with similar thermo-hydrological conditions. Consequently, the total CO&lt;sub&gt;2&lt;/sub&gt; flux in the post-fire period (May-December) was negative, while in remaining dry years the strong emission of CO&lt;sub&gt;2&lt;/sub&gt; was observed for the same part of year. &amp;#160;&lt;/p&gt;&lt;p&gt;Acknowledgements: Funding for this research was provided by the National Science Centre, Poland under project UMO-2020/37/B/ST10/01219. The authors thank the authorities of the Biebrza National Park for allowing the continuous measurements in the area of the Park.&lt;/p&gt;

scholarly journals Comparison between eddy covariance and automatic chamber techniques for measuring net ecosystem exchange of carbon dioxide in cotton and wheat fields

2013 ◽  
Vol 10 (11) ◽  
pp. 6865-6877 ◽  
Author(s):  
K. Wang ◽  
C. Liu ◽  
X. Zheng ◽  
M. Pihlatie ◽  
B. Li ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Eddy Covariance ◽  
Net Ecosystem Exchange ◽  
Cotton Field ◽  
Wheat Field ◽  
Cropping Season ◽  
Flux Measurements ◽  
One Year ◽  
Carbon Dioxide Co2 ◽  
B Test

Abstract. Static and transparent automatic chamber (AC) technique is a necessary choice for measuring net ecosystem exchange (NEE) of carbon dioxide (CO2) in circumstances where eddy covariance (EC) technique is not applicable. However, a comparison of the two techniques for measurements on croplands has seldom been undertaken. We carried out NEE observations in a cotton field (for one year) and a winter wheat field (for one cropping season) using both AC and EC techniques, to (a) compare the NEE fluxes measured using each technique, and (b) test the NEE measurement performance of an automatic chamber system (AMEG), which was designed for simultaneous flux measurements of multiple gases. The half-hourly NEE fluxes measured with the two techniques were in approximate agreement, with the AC fluxes being 0.78 (cotton) and 1.06 (wheat) times the size of the EC fluxes. When integrated to daily timescale, the fluxes of the two techniques were in better agreement, showing an average ratio of 0.94 and 1.00 for the cotton and wheat, respectively. During the periods with comparable field conditions and normal performance of both instruments, the cumulative NEE fluxes revealed small differences between the two techniques (−9.0% ~ 7%, with a mean of 0.1%). The measurements resulted in an annual cumulative NEE of −40 g C m−2 yr−1 (EC) and −42 g C m−2 yr−1 (AC) in the cotton field, and a seasonal cumulative NEE of −251 g C m−2 (EC) and −205 g C m−2 (AC) in the wheat field. Our results indicate that, for cropland populated by short plants, the AMEG system and the data processing procedures applied in this study are able to provide NEE estimates comparable to those from EC measurements.

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