This title appears in the Scientific Report :
2016
Please use the identifier:
http://hdl.handle.net/2128/12559 in citations.
A high-resolution profile technique for CO$_{2}$ and H$_{2}$O at crop sites and implications for their flux source partitioning
A high-resolution profile technique for CO$_{2}$ and H$_{2}$O at crop sites and implications for their flux source partitioning
We present an elevator-based facility for measuring CO₂ and water vapour concentration profiles between the soil surface and the roughness sublayer above crops and similar plant canopies. The end of a tube connected to a closed-path gas analyser is continuously moving up and down over the profile he...
| Personal Name(s): | Ney, Patrizia |
|---|---|
| Graf, Alexander (Corresponding author) / Schmidt, Marius / Klosterhalfen, Anne / Vereecken, Harry | |
| Contributing Institute: |
Agrosphäre; IBG-3 |
| Imprint: |
2016
|
| Conference: | 2nd ICOS Science conference, Helsinki (Finland), 2016-09-27 - 2016-09-29 |
| Document Type: |
Poster |
| Research Program: |
Instrumental and Data-driven Approaches to Source-Partitioning of Greenhouse Gas Fluxes: Comparison, Combination, Advancement Terrestrial Systems: From Observation to Prediction |
| Link: |
OpenAccess OpenAccess |
| Publikationsportal JuSER |
|
We present an elevator-based facility for measuring CO₂ and water vapour concentration profiles between the soil surface and the roughness sublayer above crops and similar plant canopies. The end of a tube connected to a closed-path gas analyser is continuously moving up and down over the profile height (in our case, 2 m) while concentrations are logged at a frequency of 20 sˉ¹, collecting approximately 50 profiles during 30 minutes. Using campaign measurements in winter wheat during different stages of crop development and different times of the day, we demonstrate a simple approach to correct for time lags, and the resulting profiles of half-hourly mean concentrations and turbulent variances over height increments of 2.5 cm. During conditions favouring photosynthesis, a clear local minimum of CO₂ concentration in the canopy can be found. With more moderate effort and success, we also added measurements of temperature (based on a finewire thermocouple) and wind speed (based on hotwire anemometry). Post-harvest measurements over bare soil were analysed in the framework of Monin-Obukhov similarity theory to check the validity of the measurement and raw data processing approach, to derive CO₂ and latent heat fluxes, and to compare them to eddy-covariance and chamber measurements. We also tentatively apply an approach to derive source partitioning information for net fluxes of CO₂ (soil respiration vs. aboveground net primary production) and H₂O (evaporation vs. transpiration) from profiles measured across the green crop canopy, discuss its limitations and needed improvements. |