Comparison of carbon fluxes, growth and productivity of a winter wheat crop in three contrasting growing seasons

Dufranne, Delphine; Moureaux, Christine; Vancutsem, Françoise; Bodson, Bernard; Aubinet, Marc

doi:10.1016/j.agee.2011.02.023

Cited by 36 publications

(13 citation statements)

References 19 publications

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“…P max had positive correlations with LAI [9], [16], [18], [19], air temperature [17], [18] and SWC [9], [18] but negative correlation with VPD [9], [44]. A similar phenomenon was found in this study (Fig.…”

Section: Discussionsupporting

confidence: 89%

Biophysical Controls on Light Response of Net CO2 Exchange in a Winter Wheat Field in the North China Plain

Tong

et al. 2014

PLoS ONE

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To investigate the impacts of biophysical factors on light response of net ecosystem exchange (NEE), CO2 flux was measured using the eddy covariance technique in a winter wheat field in the North China Plain from 2003 to 2006. A rectangular hyperbolic function was used to describe NEE light response. Maximum photosynthetic capacity (P max) was 46.6±4.0 µmol CO2 m−2 s−1 and initial light use efficiency (α) 0.059±0.006 µmol µmol−1 in April−May, two or three times as high as those in March. Stepwise multiple linear regressions showed that P max increased with the increase in leaf area index (LAI), canopy conductance (g c) and air temperature (T a) but declined with increasing vapor pressure deficit (VPD) (P<0.001). The factors influencing P max were sorted as LAI, g c, T a and VPD. α was proportional to ln(LAI), g c, T a and VPD (P<0.001). The effects of LAI, g c and T a on α were larger than that of VPD. When T a>25°C or VPD>1.1−1.3 kPa, NEE residual increased with the increase in T a and VPD (P<0.001), indicating that temperature and water stress occurred. When g c was more than 14 mm s−1 in March and May and 26 mm s−1 in April, the NEE residuals decline disappeared, or even turned into an increase in g c (P<0.01), implying shifts from stomatal limitation to non-stomatal limitation on NEE. Although the differences between sunny and cloudy sky conditions were unremarkable for light response parameters, simulated net CO2 uptake under the same radiation intensity averaged 18% higher in cloudy days than in sunny days during the year 2003−2006. It is necessary to include these effects in relevant carbon cycle models to improve our estimation of carbon balance at regional and global scales.

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Section: Discussionsupporting

confidence: 89%

Biophysical Controls on Light Response of Net CO2 Exchange in a Winter Wheat Field in the North China Plain

Tong

et al. 2014

PLoS ONE

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“…A gradual decline in net carbon uptake started from July because GEP started to decline rapidly due to reduction in photosynthetic area, but ER did not decrease greatly (Fig. 6), most likely due to respiration from dead and senescence tissues (Dufranne et al, 2011). As a result, the ratio of ER to GEP increased and ultimately the ecosystem was a source of carbon.…”

Section: Discussionmentioning

confidence: 99%

Seasonal variability in net ecosystem carbon dioxide exchange over a young Switchgrass stand

Wagle

Kakani

2013

GCB Bioenergy

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Understanding carbon dynamics of switchgrass ecosystems is crucial as switchgrass (Panicum virgatum L.) acreage is expanding for cellulosic biofuels. We used eddy covariance system and examined seasonal changes in net ecosystem CO 2 exchange (NEE) and its components -gross ecosystem photosynthesis (GEP) and ecosystem respiration (ER) -in response to controlling factors during the second (2011) and third (2012) years of stand establishment in the southern Great Plains of the United States (Chickasha, OK). Larger vapor pressure deficit (VPD > 3 kPa) limited photosynthesis and caused asymmetrical diurnal NEE cycles (substantially higher NEE in the morning hours than in the afternoon at equal light levels). Consequently, rectangular hyperbolic lightresponse curve (NEE partitioning algorithm) consistently failed to provide good fits at high VPD. Modified rectangular hyperbolic light-VPD response model accounted for the limitation of VPD on photosynthesis and improved the model performance significantly. The maximum monthly average NEE reached up to À33.02 AE 1.96 lmol CO 2 m À2 s À1 and the highest daily integrated NEE was À35.89 g CO 2 m À2 during peak growth. Although large differences in cumulative seasonal GEP and ER were observed between two seasons, total seasonal ER accounted for about 75% of GEP regardless of the growing season lengths and differences in aboveground biomass production. It suggests that net ecosystem carbon uptake increases with increasing GEP. The ecosystem was a net sink of CO 2 during 5-6 months and total seasonal uptakes were À1128 AE 130 and À1796 AE 217 g CO 2 m À2 in 2011 and 2012, respectively. In conclusion, our findings suggest that the annual carbon status of a switchgrass ecosystem can be a small sink to small source in this region if carbon loss from biomass harvesting is considered. However, year-round measurements over several years are required to assess a long-term source-sink status of the ecosystem.

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“…Section 2.5) indicate an average leaf area index (LAI) of 4.0 (ranging from 3.3 to 5.4) and a vegetation height of 0.87 m (ranging from 0.84 to 0.9 m) during the measurement period. The observed winter wheat is in the stage of ripening (kernel formation completed) with the flag leaves being partly senescent, indicating that the bottom of the crop canopy is senescent [25] and that the plants are reaching maturity [26]. The underlying soil texture is classified as silt loam.…”

Section: Research Site and Vegetationmentioning

confidence: 99%

Diurnal Dynamics of Wheat Evapotranspiration Derived from Ground-Based Thermal Imagery

et al. 2014

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Abstract:The latent heat flux, one of the key components of the surface energy balance, can be inferred from remotely sensed thermal infrared data. However, discrepancies between modeled and observed evapotranspiration are large. Thermal cameras might provide a suitable tool for model evaluation under variable atmospheric conditions. Here, we evaluate the results from the Penman-Monteith, surface energy balance and Bowen ratio approaches, which estimate the diurnal course of latent heat fluxes at a ripe winter wheat stand using measured and modeled temperatures. Under overcast conditions, the models perform similarly, and radiometric image temperatures are linearly correlated with the inverted aerodynamic temperature. During clear sky conditions, the temperature of the wheat ear layer could be used to predict daytime turbulent fluxes (root mean squared error and mean absolute error: 20-35 W·m 9776Errors are dependent on the models' ability to simulate diurnal hysteresis effects and are largest during intermittent clouds, due to the discrepancy between the timing of image capture and the time needed for the leaf-air-temperature gradient to adapt to changes in solar radiation. During such periods, we suggest using modeled surface temperatures for temporal upscaling and the validation of image data.

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Comparison of carbon fluxes, growth and productivity of a winter wheat crop in three contrasting growing seasons

Cited by 36 publications

References 19 publications

Biophysical Controls on Light Response of Net CO2 Exchange in a Winter Wheat Field in the North China Plain

Biophysical Controls on Light Response of Net CO2 Exchange in a Winter Wheat Field in the North China Plain

Seasonal variability in net ecosystem carbon dioxide exchange over a young Switchgrass stand

Diurnal Dynamics of Wheat Evapotranspiration Derived from Ground-Based Thermal Imagery

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