Eddy covariance measurements of ozone flux above and below a southern subtropical forest canopy

2021 ◽  
pp. 148338
Author(s):  
Zan Liu ◽  
Yuepeng Pan ◽  
Tao Song ◽  
Bo Hu ◽  
Lili Wang ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Forest Canopy ◽  
Subtropical Forest ◽  
Ozone Flux ◽  
Eddy Covariance Measurements

scholarly journals Forest canopy mitigates soil N2O emission during hot moments

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Ülo Mander ◽  
Alisa Krasnova ◽  
Jordi Escuer-Gatius ◽  
Mikk Espenberg ◽  
Thomas Schindler ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Forest Canopy ◽  
Riparian Forest ◽  
Temporal Frequency ◽  
N2o Emission ◽  
Photochemical Reactions ◽  
Content Change ◽  
Reduction Mechanisms ◽  
Eddy Covariance Measurements ◽  
Soil Emissions

AbstractRiparian forests are known as hot spots of nitrogen cycling in landscapes. Climate warming speeds up the cycle. Here we present results from a multi-annual high temporal-frequency study of soil, stem, and ecosystem (eddy covariance) fluxes of N2O from a typical riparian forest in Europe. Hot moments (extreme events of N2O emission) lasted a quarter of the study period but contributed more than half of soil fluxes. We demonstrate that high soil emissions of N2O do not escape the ecosystem but are processed in the canopy. Rapid water content change across intermediate soil moisture was a major determinant of elevated soil emissions in spring. The freeze-thaw period is another hot moment. However, according to the eddy covariance measurements, the riparian forest is a modest source of N2O. We propose photochemical reactions and dissolution in canopy-space water as reduction mechanisms.

scholarly journals A comparison of CO<sub>2</sub> fluxes via eddy covariance measurements with model predictions in a dominant subtropical forest ecosystem

2009 ◽  
Vol 6 (2) ◽  
pp. 2913-2937 ◽  
Author(s):  
J.-H. Yan ◽  
G.-Y. Zhou ◽  
Y.-L. Li ◽  
D.-Q. Zhang ◽  
D. Otieno ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Forest Ecosystem ◽  
Ecosystem Respiration ◽  
Subtropical Forest ◽  
Co2 Fluxes ◽  
Canopy Layer ◽  
Model Predictions ◽  
Eddy Covariance Measurements ◽  
Annual Total ◽  
Biosphere Model

Abstract. CO2 fluxes were measured continuously for twelve months (2003) using eddy covariance technique at canopy layer in a dominant subtropical forest in South China. Our results showed that daytime maximum CO2 fluxes of the whole ecosystem varied from −15 to −20 μmol m−2 s−1. The peaks of CO2 fluxes appeared earlier than the peaks of solar radiation. Contribution of CO2 fluxes in a subtropical forest in the dry season was 53% of the annual total from the whole forest ecosystem. Daytime CO2 fluxes were very large in October, November and December, which was therefore an important stage for uptake of CO2 by the forest ecosystem from the atmosphere. Using the estimates of biomass, soil carbon and parameters of leaf photosynthesis from other studies at the same forest, we ran a process-based model, CBM (stands for CSIRO Biosphere Model) for this site, and compared the predicted fluxes of CO2 with measurements. We obtained reasonable agreement. The mean difference between the simulated and measured daytime CO2 fluxes from the year-round (8249 records) was −0.2 μmol m−2 s−1 and implied well within measurement accuracy. Based on estimates of forest ecosystem respiration, NEE was calculated −242 and −276 gCm−2 year−1 for measured and modelled, respectively. In previous study, NPP for this forest stand was 694 gCm−2 year−1 during 2003/04 and litterfall was 424 gCm−2 year−1. We therefore calculated NEE as −270 gCm−2 year−1 and very similar to the values obtained by measured and modelled CO2 fluxes in this study.

scholarly journals Preserving the variance in imputed eddy-covariance measurements: Alternative methods for defensible gap filling

2017 ◽  
Vol 232 ◽  
pp. 635-649 ◽  
Author(s):  
Sujit Kunwor ◽  
Gregory Starr ◽  
Henry W. Loescher ◽  
Christina L. Staudhammer
Keyword(s):  
Eddy Covariance ◽  
Alternative Methods ◽  
Gap Filling ◽  
Eddy Covariance Measurements

Application of an alternative method to derive reliable estimates of nighttime respiration from eddy covariance measurements in moderately complex topography

2008 ◽  
Vol 148 (6-7) ◽  
pp. 1174-1180 ◽  
Author(s):  
Eva van Gorsel ◽  
Ray Leuning ◽  
Helen A. Cleugh ◽  
Heather Keith ◽  
Miko U.F. Kirschbaum ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Complex Topography ◽  
Alternative Method ◽  
Eddy Covariance Measurements

Multi-year eddy covariance measurements of net ecosystem exchange in tropical dry deciduous forest of India

2021 ◽  
Vol 301-302 ◽  
pp. 108351
Author(s):  
Suraj Reddy Rodda ◽  
Kiran Chand Thumaty ◽  
MSS Praveen ◽  
Chandra Shekhar Jha ◽  
Vinay Kumar Dadhwal
Keyword(s):  
Eddy Covariance ◽  
Deciduous Forest ◽  
Net Ecosystem Exchange ◽  
Dry Deciduous Forest ◽  
Eddy Covariance Measurements

scholarly journals Estimating evaporation with thermal UAV data and two-source energy balance models

2016 ◽  
Vol 20 (2) ◽  
pp. 697-713 ◽  
Author(s):  
H. Hoffmann ◽  
H. Nieto ◽  
R. Jensen ◽  
R. Guzinski ◽  
P. Zarco-Tejada ◽  
...  
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
High Resolution ◽  
Eddy Covariance ◽  
Land Surface ◽  
Weather Conditions ◽  
Heat Fluxes ◽  
Thermal Camera ◽  
Model Input ◽  
Eddy Covariance Measurements

Abstract. Estimating evaporation is important when managing water resources and cultivating crops. Evaporation can be estimated using land surface heat flux models and remotely sensed land surface temperatures (LST), which have recently become obtainable in very high resolution using lightweight thermal cameras and Unmanned Aerial Vehicles (UAVs). In this study a thermal camera was mounted on a UAV and applied into the field of heat fluxes and hydrology by concatenating thermal images into mosaics of LST and using these as input for the two-source energy balance (TSEB) modelling scheme. Thermal images are obtained with a fixed-wing UAV overflying a barley field in western Denmark during the growing season of 2014 and a spatial resolution of 0.20 m is obtained in final LST mosaics. Two models are used: the original TSEB model (TSEB-PT) and a dual-temperature-difference (DTD) model. In contrast to the TSEB-PT model, the DTD model accounts for the bias that is likely present in remotely sensed LST. TSEB-PT and DTD have already been well tested, however only during sunny weather conditions and with satellite images serving as thermal input. The aim of this study is to assess whether a lightweight thermal camera mounted on a UAV is able to provide data of sufficient quality to constitute as model input and thus attain accurate and high spatial and temporal resolution surface energy heat fluxes, with special focus on latent heat flux (evaporation). Furthermore, this study evaluates the performance of the TSEB scheme during cloudy and overcast weather conditions, which is feasible due to the low data retrieval altitude (due to low UAV flying altitude) compared to satellite thermal data that are only available during clear-sky conditions. TSEB-PT and DTD fluxes are compared and validated against eddy covariance measurements and the comparison shows that both TSEB-PT and DTD simulations are in good agreement with eddy covariance measurements, with DTD obtaining the best results. The DTD model provides results comparable to studies estimating evaporation with similar experimental setups, but with LST retrieved from satellites instead of a UAV. Further, systematic irrigation patterns on the barley field provide confidence in the veracity of the spatially distributed evaporation revealed by model output maps. Lastly, this study outlines and discusses the thermal UAV image processing that results in mosaics suited for model input. This study shows that the UAV platform and the lightweight thermal camera provide high spatial and temporal resolution data valid for model input and for other potential applications requiring high-resolution and consistent LST.

Sign in / Sign up

Export Citation Format

Share Document