Impact of cloudiness on net ecosystem exchange of carbon dioxide in different types of forest ecosystems in China

Abstract. Clouds can significantly affect carbon uptake of forest ecosystems by affecting incoming solar radiation on the ground, temperature and other environmental factors. In this study, we analyzed the effects of cloudiness on the net ecosystem exchange of carbon dioxide (NEE) of a temperate broad-leaved Korean pine mixed forest at Changbaishan (CBS) and a subtropical evergreen broad-leaved forest at Dinghushan (DHS) of ChinaFLUX, based on the flux data obtained during June–August from 2003 to 2006. The results showed that the response of the NEE of forest ecosystem to photosynthetically active radiation (PAR) was different under clear sky and cloudy sky conditions, and this difference was not consistent between CBS and DHS. Compared with clear skies, light-saturated maximum photosynthetic rate (Pec,max) of CBS during mid-growing season (from June to August) was respectively enhanced by 34%, 25%, 4% and 11% on cloudy skies in 2003, 2004, 2005 and 2006; however, Pec,max of DHS was higher under clear skies than under cloudy skies from 2004 to 2006. NEE of forests at CBS reached its maximum when the clearness index (kt) was between 0.4 and 0.6, and the NEE decreased obviously when kt exceeded 0.6. Compare with CBS, although NEE of forest at DHS tended to the maximum when kt varied between 0.4 and 0.6, the NEE did not decrease noticeably when kt exceeded 0.6. The results indicated that cloudy sky conditions were more beneficial to carbon uptake for the temperate forest ecosystem rather than for the subtropical forest ecosystem. This is due to the fact that the non-saturating light conditions and increase of diffuse radiation were more beneficial to photosynthesis, and the reduced temperature was more conducive to decreasing the ecosystem respiration in temperate forest ecosystems under cloudy sky conditions. This phenomenon is important to evaluate carbon uptake of temperate forests under climate change conditions.

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Impact of cloudiness on net ecosystem exchange of carbon dioxide in different types of forest ecosystems in China

Biogeosciences ◽

10.5194/bg-7-711-2010 ◽

2010 ◽

Vol 7 (2) ◽

pp. 711-722 ◽

Cited By ~ 31

Author(s):

M. Zhang ◽

G.-R. Yu ◽

L.-M. Zhang ◽

X.-M. Sun ◽

X.-F. Wen ◽

...

Keyword(s):

Carbon Dioxide ◽

Forest Ecosystem ◽

Temperate Forest ◽

Forest Ecosystems ◽

Ecosystem Respiration ◽

Net Ecosystem Exchange ◽

Subtropical Forest ◽

Strong Light ◽

Sky Conditions ◽

Temperate Forest Ecosystem

Abstract. Clouds can significantly affect carbon exchange process between forest ecosystems and the atmosphere by influencing the quantity and quality of solar radiation received by ecosystem's surface and other environmental factors. In this study, we analyzed the effects of cloudiness on net ecosystem exchange of carbon dioxide (NEE) in a temperate broad-leaved Korean pine mixed forest at Changbaishan (CBS) and a subtropical evergreen broad-leaved forest at Dinghushan (DHS), based on the flux data obtained during June–August from 2003 to 2006. The results showed that the response of NEE of forest ecosystems to photosynthetically active radiation (PAR) differed under clear skies and cloudy skies. Compared with clear skies, the light-saturated maximum photosynthetic rate (Pec,max) at CBS under cloudy skies during mid-growing season (from June to August) increased by 34%, 25%, 4% and 11% in 2003, 2004, 2005 and 2006, respectively. In contrast, Pec,max of the forest ecosystem at DHS was higher under clear skies than under cloudy skies from 2004 to 2006. When the clearness index (kt) ranged between 0.4 and 0.6, the NEE reached its maximum at both CBS and DHS. However, the NEE decreased more dramatically at CBS than at DHS when kt exceeded 0.6. The results indicate that cloudy sky conditions are beneficial to net carbon uptake in the temperate forest ecosystem and the subtropical forest ecosystem. Under clear skies, vapor pressure deficit (VPD) and air temperature increased due to strong light. These environmental conditions led to greater decrease in gross ecosystem photosynthesis (GEP) and greater increase in ecosystem respiration (Re) at CBS than at DHS. As a result, clear sky conditions caused more reduction of NEE in the temperate forest ecosystem than in the subtropical forest ecosystem. The response of NEE of different forest ecosystems to the changes in cloudiness is an important factor that should be included in evaluating regional carbon budgets under climate change conditions.

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Evaluating terrestrial CO2 flux diagnoses and uncertainties from a simple land surface model and its residuals

Biogeosciences ◽

10.5194/bg-11-217-2014 ◽

2014 ◽

Vol 11 (2) ◽

pp. 217-235 ◽

Cited By ~ 16

Author(s):

T. W. Hilton ◽

K. J. Davis ◽

K. Keller

Keyword(s):

Carbon Dioxide ◽

Parameter Estimation ◽

North American ◽

Land Surface ◽

Atmospheric Carbon Dioxide ◽

Ecosystem Respiration ◽

Land Surface Model ◽

Net Ecosystem Exchange ◽

Surface Model ◽

Considerable Uncertainty

Abstract. Global terrestrial atmosphere–ecosystem carbon dioxide fluxes are well constrained by the concentration and isotopic composition of atmospheric carbon dioxide. In contrast, considerable uncertainty persists surrounding regional contributions to the net global flux as well as the impacts of atmospheric and biological processes that drive the net flux. These uncertainties severely limit our ability to make confident predictions of future terrestrial biological carbon fluxes. Here we use a simple light-use efficiency land surface model (the Vegetation Photosynthesis Respiration Model, VPRM) driven by remotely sensed temperature, moisture, and phenology to diagnose North American gross ecosystem exchange (GEE), ecosystem respiration, and net ecosystem exchange (NEE) for the period 2001 to 2006. We optimize VPRM parameters to eddy covariance (EC) NEE observations from 65 North American FluxNet sites. We use a separate set of 27 cross-validation FluxNet sites to evaluate a range of spatial and temporal resolutions for parameter estimation. With these results we demonstrate that different spatial and temporal groupings of EC sites for parameter estimation achieve similar sum of squared residuals values through radically different spatial patterns of NEE. We also derive a regression model to estimate observed VPRM errors as a function of VPRM NEE, temperature, and precipitation. Because this estimate is based on model-observation residuals it is comprehensive of all the error sources present in modeled fluxes. We find that 1 km interannual variability in VPRM NEE is of similar magnitude to estimated 1 km VPRM NEE errors.

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Terrestrial CO2 Fluxes, Concentrations, Sources and Budget in Northeast China: Observational and Modeling Studies

10.5194/egusphere-egu2020-2317 ◽

2020 ◽

Author(s):

Xiaolan Li ◽

Xiao-Ming Hu ◽

Changjie Cai ◽

Qingyu Jia ◽

Yao Zhang ◽

...

Keyword(s):

Land Surface ◽

Northeast China ◽

Ecosystem Respiration ◽

Mixed Forest ◽

Net Ecosystem Exchange ◽

Growth Period ◽

Rice Paddy ◽

Light Use Efficiency ◽

Maximum Light ◽

Use Efficiency

CO2&#160;fluxes and concentrations are not well understood in Northeast China, where dominant land surface types are mixed forest and cropland. &#160;Here, we analyzed the CO2&#160;fluxes and concentrations using Eddy Covariance&#160;(EC)&#160;measurements, satellite observations, and the Weather Research and Forecasting model coupled with the Vegetation Photosynthesis and Respiration Model (WRF-VPRM). &#160;We also used WRF-VPRM outputs to examine CO2&#160;transport/dispersion, and to quantify the biogenic&#160;and anthropogenic contributions to atmospheric&#160;CO2&#160;concentrations. &#160;Finally, we investigated the uncertainties&#160;of simulating&#160;CO2&#160;fluxes&#160;related to&#160;four VPRM parameters (including&#160;maximum light use efficiency,&#160;photosynthetically active radiation half-saturation value, and two&#160;respiration parameters) using offline ensemble simulations with&#160;randomly selected&#160;parameter values.&#160;&#160;The results indicated that&#160;mixed forests&#160;acted as a larger CO2&#160;source&#160;and sink than rice paddies&#160;on average in 2016 due to a longer growth period and stronger ecosystem respiration, although the minimum EC-measured daily mean net ecosystem exchange (NEE) was smaller at rice paddy&#160;(-10 &#956;mol m-2&#160;s-1) than at mixed forest&#160;(-6.5 &#956;mol m-2&#160;s-1) during the growing season (May through September). &#160;The monthly&#160;fluctuation of column-averaged CO2&#160;concentrations (XCO2) exceeded 10 ppm&#160;in Northeast China during 2016. &#160;Biogenic contribution&#160;(large&#160;negative&#160;in summer&#160;and insignificant in other months)&#160;offset about 70% of anthropogenic contribution of XCO2&#160;in this region. &#160;WRF-VPRM modeling successfully captured seasonal&#160;and episodic variations of NEE and CO2&#160;concentrations, however, the NEE in mixed forest was overestimated during daytime, mainly due to the uncertainties of VPRM parameters,&#160;especially maximum light use efficiency.

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Evaluating terrestrial CO2 flux diagnoses and uncertainties from a simple land surface model and its residuals

Biogeosciences Discussions ◽

10.5194/bgd-10-13753-2013 ◽

2013 ◽

Vol 10 (8) ◽

pp. 13753-13802

Author(s):

T. W. Hilton ◽

K. J. Davis ◽

K. Keller

Keyword(s):

Carbon Dioxide ◽

Parameter Estimation ◽

North American ◽

Land Surface ◽

Atmospheric Carbon Dioxide ◽

Ecosystem Respiration ◽

Land Surface Model ◽

Net Ecosystem Exchange ◽

Surface Model ◽

Considerable Uncertainty

Abstract. Global terrestrial atmosphere-ecosystem carbon dioxide fluxes are well-constrained by the concentration and isotopic composition of atmospheric carbon dioxide. In contrast, considerable uncertainty persists surrounding regional contributions to the net global flux as well as the impacts of atmospheric and biological processes that drive the net flux. These uncertainties severely limit our ability to make confident predictions of future terrestrial biological carbon fluxes. Here we use a simple light-use efficiency ecosystem model (the Vegetation Photosynthesis Respiration Model, VPRM) driven by remotely-sensed temperature, moisture, and phenology to diagnose North American gross ecosystem exchange (GEE), ecosystem respiration, and net ecosystem exchange (NEE) for the period 2001 to 2006. We optimize VPRM parameters to eddy covariance (EC) NEE observations from 65 North American FluxNet sites. We use a separate set of 27 cross-validation FluxNet sites to evaluate a range of spatial and temporal resolutions for parameter estimation. With these results we demonstrate that different spatial and temporal groupings of EC sites for parameter estimation achieve similar sum of squared residuals values through radically different spatial patterns of NEE. We also derive a regression model to estimate observed VPRM errors as a function of VPRM NEE, temperature, and precipitation. Because this estimate is based on model-observation residuals it is comprehensive of all of the error sources present in modeled fluxes. We find that 1 km interannual variability in VPRM NEE is of similar magnitude to estimated 1 km VPRM NEE errors.

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Contrasting carbon dioxide fluxes between a drying shrub wetland in Northern Wisconsin, USA, and nearby forests

Biogeosciences ◽

10.5194/bg-6-1115-2009 ◽

2009 ◽

Vol 6 (6) ◽

pp. 1115-1126 ◽

Cited By ~ 84

Author(s):

B. N. Sulman ◽

A. R. Desai ◽

B. D. Cook ◽

N. Saliendra ◽

D. S. Mackay

Keyword(s):

Carbon Dioxide ◽

Water Table ◽

Climate Models ◽

Ecosystem Respiration ◽

Net Ecosystem Exchange ◽

Carbon Dioxide Exchange ◽

Co2 Fluxes ◽

Carbon Dioxide Fluxes ◽

Highly Correlated ◽

Shrub Wetland

Abstract. Wetland biogeochemistry is strongly influenced by water and temperature dynamics, and these interactions are currently poorly represented in ecosystem and climate models. A decline in water table of approximately 30 cm was observed at a wetland in Northern Wisconsin, USA over a period from 2001–2007, which was highly correlated with an increase in daily soil temperature variability. Eddy covariance measurements of carbon dioxide exchange were compared with measured CO2 fluxes at two nearby forests in order to distinguish wetland effects from regional trends. As wetland water table declined, both ecosystem respiration and ecosystem production increased by over 20% at the wetland, while forest CO2 fluxes had no significant trends. Net ecosystem exchange of carbon dioxide at the wetland was not correlated with water table, but wetland evapotranspiration decreased substantially as the water table declined. These results suggest that changes in hydrology may not have a large impact on shrub wetland carbon balance over inter-annual time scales due to opposing responses in both ecosystem respiration and productivity.

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Thermal adaptation of net ecosystem exchange

Biogeosciences Discussions ◽

10.5194/bgd-8-1109-2011 ◽

2011 ◽

Vol 8 (1) ◽

pp. 1109-1136 ◽

Cited By ~ 1

Author(s):

W. Yuan ◽

Y. Luo ◽

S. Liang ◽

G. Yu ◽

S. Niu ◽

...

Keyword(s):

Primary Production ◽

Air Temperature ◽

Ecosystem Respiration ◽

Thermal Adaptation ◽

Net Ecosystem Exchange ◽

Carbon Uptake ◽

Strongly Correlated ◽

Response Curves ◽

Mean Temperature ◽

Source To Sink

Abstract. Thermal adaptation of gross primary production and ecosystem respiration has been well documented over broad thermal gradients. However, no study has examined their interaction as a function of temperature, i.e. the thermal responses of net ecosystem exchange of carbon (NEE). In this study, we constructed temperature response curves of NEE against temperature using 380 site-years of eddy covariance data at 72 forest, grassland and shrubland ecosystems located at latitudes ranging from ~29° N to 64° N. The response curves were used to define two critical temperatures: transition temperature (Tb) at which ecosystem transferring from carbon source to sink and optimal temperature (To) at which carbon uptake is maximized. Tb was strongly correlated with annual mean air temperature. To was strongly correlated with mean temperature during the net carbon uptake period across the study ecosystems. Our results suggested that ecosystem CO2 flux switched from source to sink when air temperature reached annual mean temperature in spring and reached maximum uptake at mean temperature of the net carbon uptake period. Our results imply that the net ecosystem exchange of carbon adapt to the temperature across the geographical range due to intrinsic connections between vegetation primary production and ecosystem respiration.

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MODELING OF THE SEASONAL COURSE OF CARBON EXCHANGE IN WETLAND ECOSYSTEMS

Ecology Economy Informatics System analysis and mathematical modeling of ecological and economic systems ◽

10.23885/2500-395x-2020-1-5-56-61 ◽

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.

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Comparison of Regional Simulation of Biospheric CO2 Flux from the Updated Version of CarbonTracker Asia with FLUXCOM and Other Inversions over Asia

10.5194/egusphere-egu2020-4312 ◽

2020 ◽

Author(s):

Samuel Takele Kenea ◽

Lev Labzovskii ◽

Tae‐Young Goo ◽

Shanlan Li ◽

Young‐Suk Oh ◽

...

Keyword(s):

Interannual Variability ◽

Transport Model ◽

Southern Oscillation ◽

Carbon Sink ◽

Mixed Forest ◽

Net Ecosystem Exchange ◽

Co2 Flux ◽

Atmospheric Composition ◽

Carbon Uptake ◽

The Impact

There are still large uncertainties in the estimates of net ecosystem exchange of CO2 (NEE) with atmosphere in Asia, particularly in the boreal and eastern part of temperate Asia. To understand these uncertainties, we assessed the CarbonTracker Asia (CTA2017) estimates of the spatial and temporal distributions of NEE through a comparison with FLUXCOM and the global inversion models from the Copernicus Atmospheric Monitoring Service (CAMS), Monitoring Atmospheric Composition and Climate (MACC), and Jena CarboScope in Asia, as well as examining the impact of the nesting approach on the optimized NEE flux during the 2001&#8211;2013 period. The long&#8208;term mean carbon uptake is reduced in Asia, which is &#8722;0.32 &#177; 0.22 PgC yr&#8208;1, whereas &#8211;0.58 &#177; 0.26 PgC yr&#8208;1 is shown from CT2017 (CarbonTracker global). The domain aggregated mean carbon uptake from CTA2017 is found to be lower by 23.8%, 44.8%, and 60.5% than CAMS, MACC, and Jena CarboScope, respectively. For example, both CTA2017 and CT2017 models captured the interannual variability (IAV) of the NEE flux with a different magnitude and this leads to divergent annual aggregated results. Differences in the estimated interannual variability of NEE in response to El Ni&#241;o&#8211;Southern Oscillation (ENSO) may result from differences in the transport model resolutions. These inverse models&#8217; results have a substantial difference compared to FLUXCOM, which was found to be &#8211;5.54 PgC yr&#8208;1. On the one hand, we showed that the large NEE discrepancies between both inversion models and FLUXCOM stem mostly from the tropical forests. On the other hand, CTA2017 exhibits a slightly better correlation with FLUXCOM over grass/shrub, fields/woods/savanna, and mixed forest than CT2017. The land cover inconsistency between CTA2017 and FLUXCOM is therefore one driver of the discrepancy in the NEE estimates. The diurnal averaged NEE flux between CTA2017 and FLUXCOM exhibits better agreement during the carbon uptake period than the carbon release period. Both CTA2017 and CT2017 revealed that the overall spatial patterns of the carbon sink and source are similar, but the magnitude varied with seasons and ecosystem types, which is mainly attributed to differences in the transport model resolutions. Our findings indicate that substantial inconsistencies in the inversions and FLUXCOM mainly emerge during the carbon uptake period and over tropical forests. The main problems are underrepresentation of FLUXCOM NEE estimates by limited eddy covariance flux measurements, the role of CO2 emissions from land use change not accounted for by FLUXCOM, sparseness of surface observations of CO2 concentrations used by the assimilation systems, and land cover inconsistency. This suggested that further scrutiny on the FLUXCOM and inverse estimates is most likely required. Such efforts will reduce inconsistencies across various NEE estimates over Asia, thus mitigating ecosystem&#8208;driven errors that propagate the global carbon budget. Moreover, this work also recommends further investigation on how the changes/updates made in CarbonTracker affect the interannual variability of the aggregate and spatial pattern of NEE flux in response to the ENSO effect over the region of interest.

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Thermal adaptation of net ecosystem exchange

Biogeosciences ◽

10.5194/bg-8-1453-2011 ◽

2011 ◽

Vol 8 (6) ◽

pp. 1453-1463 ◽

Cited By ~ 18

Author(s):

W. Yuan ◽

Y. Luo ◽

S. Liang ◽

G. Yu ◽

S. Niu ◽

...

Keyword(s):

Primary Production ◽

Ecosystem Respiration ◽

Gross Primary Production ◽

Thermal Adaptation ◽

Temperature Response ◽

Net Ecosystem Exchange ◽

Carbon Uptake ◽

Strongly Correlated ◽

Response Curves ◽

Critical Temperatures

Abstract. Thermal adaptation of gross primary production and ecosystem respiration has been well documented over broad thermal gradients. However, no study has examined their interaction as a function of temperature, i.e. the thermal responses of net ecosystem exchange of carbon (NEE). In this study, we constructed temperature response curves of NEE against temperature using 380 site-years of eddy covariance data at 72 forest, grassland and shrubland ecosystems located at latitudes ranging from ~29° N to 64° N. The response curves were used to define two critical temperatures: transition temperature (Tb) at which ecosystem transfer from carbon source to sink and optimal temperature (To) at which carbon uptake is maximized. Tb was strongly correlated with annual mean air temperature. To was strongly correlated with mean temperature during the net carbon uptake period across the study ecosystems. Our results imply that the net ecosystem exchange of carbon adapts to the temperature across the geographical range due to intrinsic connections between vegetation primary production and ecosystem respiration.

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A top-down approach of surface carbonyl sulfide exchange by a Mediterranean oak forest ecosystem in Southern France

10.5194/acp-2016-525 ◽

2016 ◽

Author(s):

S. Belviso ◽

I. M. Reiter ◽

B. Loubet ◽

V. Gros ◽

J. Lathière ◽

...

Keyword(s):

Forest Ecosystem ◽

Time Window ◽

Ecosystem Respiration ◽

Gross Primary Production ◽

Carbonyl Sulfide ◽

Net Ecosystem Exchange ◽

Vertical Gradient ◽

Organic Carbon Content ◽

Top Down ◽

Southern France

Abstract. The role that soil, foliage and atmospheric dynamics have on surface carbonyl sulfide (OCS) exchange in a Mediterranean forest ecosystem in Southern France (the Oak Observatory at the Observatoire de Haute Provence, O3HP), was investigated in June of 2012 and 2013 with essentially a top-down approach. Atmospheric data demonstrate that the requirements are fulfilled as that OCS uptake can be used as a proxy of gross primary production. Firstly, OCS and carbon dioxide (CO2) diurnal variations and vertical gradients show no net exchange of OCS during the night when the carbon fluxes are dominated by ecosystem respiration. This contrasts with other oak woodland ecosystems of a Mediterranean climate, where nocturnal uptake of OCS by soil and/or vegetation has been observed. Since temperature, the water and organic carbon content of soil at the O3HP should favor the uptake of OCS, the lack of nocturnal net uptake would indicate that its gross consumption in soil is compensated by emission processes that remain to be characterized. Secondly, the uptake of OCS during the photosynthetic period was characterized in two different ways. We measured ozone (O3) deposition velocities and estimated the partitioning of O3 deposition between stomatal and non-stomatal pathways before the start of a joint survey of OCS and O3 surface concentrations. We observed an increasing trend in the relative importance of the stomatal pathway during the morning hours and synchronous steep drops of OCS (60–100 ppt) and O3 (15–30 ppb) after sunrise and before the break-up of the nocturnal boundary layer. The uptake of OCS by plants was characterized from vertical profiles too. However, the time window for calculation of the ecosystem relative uptake (ERU) of OCS, which is a useful tool to partition measured net ecosystem exchange, was limited in June 2012 to few hours after midday. This is due to the disruption of the vertical distribution of OCS by entrainment of OCS rich tropospheric air in the morning, and as the vertical gradient of CO2 reverses when it is still light. Moreover, polluted air masses (up to 700 ppt of OCS) produced dramatic variation in atmospheric OCS-to-CO2 ratios during daytime in June 2013, further reducing the time window for ERU calculation.

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Impact of cloudiness on net ecosystem exchange of carbon dioxide in different types of forest ecosystems in China