TEWL, Closed-Chamber Methods: AquaFlux and VapoMeter

2013 ◽  
pp. 345-352 ◽  
Author(s):  
Bob Imhof ◽  
Perry Xiao ◽  
Irena Angelova-Fischer
Keyword(s):  
Closed Chamber

scholarly journals CO<sub>2</sub> flux determination by closed-chamber methods can be seriously biased by inappropriate application of linear regression

2007 ◽  
Vol 4 (6) ◽  
pp. 1005-1025 ◽  
Author(s):  
L. Kutzbach ◽  
J. Schneider ◽  
T. Sachs ◽  
M. Giebels ◽  
H. Nykänen ◽  
...  
Keyword(s):  
Linear Regression ◽  
Nonlinear Regression ◽  
Co2 Flux ◽  
Exponential Model ◽  
Co2 Uptake ◽  
Co2 Fluxes ◽  
Closed Chamber ◽  
Exponential Regression ◽  
Closure Time ◽  
Over Time

Abstract. Closed (non-steady state) chambers are widely used for quantifying carbon dioxide (CO2) fluxes between soils or low-stature canopies and the atmosphere. It is well recognised that covering a soil or vegetation by a closed chamber inherently disturbs the natural CO2 fluxes by altering the concentration gradients between the soil, the vegetation and the overlying air. Thus, the driving factors of CO2 fluxes are not constant during the closed chamber experiment, and no linear increase or decrease of CO2 concentration over time within the chamber headspace can be expected. Nevertheless, linear regression has been applied for calculating CO2 fluxes in many recent, partly influential, studies. This approach has been justified by keeping the closure time short and assuming the concentration change over time to be in the linear range. Here, we test if the application of linear regression is really appropriate for estimating CO2 fluxes using closed chambers over short closure times and if the application of nonlinear regression is necessary. We developed a nonlinear exponential regression model from diffusion and photosynthesis theory. This exponential model was tested with four different datasets of CO2 flux measurements (total number: 1764) conducted at three peatlands sites in Finland and a tundra site in Siberia. Thorough analyses of residuals demonstrated that linear regression was frequently not appropriate for the determination of CO2 fluxes by closed-chamber methods, even if closure times were kept short. The developed exponential model was well suited for nonlinear regression of the concentration over time c(t) evolution in the chamber headspace and estimation of the initial CO2 fluxes at closure time for the majority of experiments. However, a rather large percentage of the exponential regression functions showed curvatures not consistent with the theoretical model which is considered to be caused by violations of the underlying model assumptions. Especially the effects of turbulence and pressure disturbances by the chamber deployment are suspected to have caused unexplainable curvatures. CO2 flux estimates by linear regression can be as low as 40% of the flux estimates of exponential regression for closure times of only two minutes. The degree of underestimation increased with increasing CO2 flux strength and was dependent on soil and vegetation conditions which can disturb not only the quantitative but also the qualitative evaluation of CO2 flux dynamics. The underestimation effect by linear regression was observed to be different for CO2 uptake and release situations which can lead to stronger bias in the daily, seasonal and annual CO2 balances than in the individual fluxes. To avoid serious bias of CO2 flux estimates based on closed chamber experiments, we suggest further tests using published datasets and recommend the use of nonlinear regression models for future closed chamber studies.

scholarly journals Pineapple Residue Ash Reduces Carbon Dioxide and Nitrous Oxide Emissions in Pineapple Cultivation on Tropical Peat Soils at Saratok, Malaysia

2021 ◽  
Vol 13 (3) ◽  
pp. 1014
Author(s):  
Liza Nuriati Lim Kim Choo ◽  
Osumanu Haruna Ahmed ◽  
Nik Muhamad Nik Majid ◽  
Zakry Fitri Abd Aziz
Keyword(s):  
Carbon Dioxide ◽  
Nitrous Oxide ◽  
Peat Soil ◽  
Nitrous Oxide Emissions ◽  
N2o Emissions ◽  
Peat Soils ◽  
Closed Chamber ◽  
Npk Fertilizers ◽  
Npk Fertilizer ◽  
Carbon Dioxide Co2

Burning pineapple residues on peat soils before pineapple replanting raises concerns on hazards of peat fires. A study was conducted to determine whether ash produced from pineapple residues could be used to minimize carbon dioxide (CO2) and nitrous oxide (N2O) emissions in cultivated tropical peatlands. The effects of pineapple residue ash fertilization on CO2 and N2O emissions from a peat soil grown with pineapple were determined using closed chamber method with the following treatments: (i) 25, 50, 70, and 100% of the suggested rate of pineapple residue ash + NPK fertilizer, (ii) NPK fertilizer, and (iii) peat soil only. Soils treated with pineapple residue ash (25%) decreased CO2 and N2O emissions relative to soils without ash due to adsorption of organic compounds, ammonium, and nitrate ions onto the charged surface of ash through hydrogen bonding. The ability of the ash to maintain higher soil pH during pineapple growth primarily contributed to low CO2 and N2O emissions. Co-application of pineapple residue ash and compound NPK fertilizer also improves soil ammonium and nitrate availability, and fruit quality of pineapples. Compound NPK fertilizers can be amended with pineapple residue ash to minimize CO2 and N2O emissions without reducing peat soil and pineapple productivity.

scholarly journals Evaluation of a plot-scale methane emission model using eddy covariance observations and footprint modelling

2014 ◽  
Vol 11 (17) ◽  
pp. 4651-4664 ◽  
Author(s):  
A. Budishchev ◽  
Y. Mi ◽  
J. van Huissteden ◽  
L. Belelli-Marchesini ◽  
G. Schaepman-Strub ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Methane Emission ◽  
Average Method ◽  
Temporal Dynamics ◽  
Weighted Average ◽  
Ambient Atmosphere ◽  
Emission Model ◽  
Closed Chamber ◽  
Weighted Average Method ◽  
Emission Models

Abstract. Most plot-scale methane emission models – of which many have been developed in the recent past – are validated using data collected with the closed-chamber technique. This method, however, suffers from a low spatial representativeness and a poor temporal resolution. Also, during a chamber-flux measurement the air within a chamber is separated from the ambient atmosphere, which negates the influence of wind on emissions. Additionally, some methane models are validated by upscaling fluxes based on the area-weighted averages of modelled fluxes, and by comparing those to the eddy covariance (EC) flux. This technique is rather inaccurate, as the area of upscaling might be different from the EC tower footprint, therefore introducing significant mismatch. In this study, we present an approach to validate plot-scale methane models with EC observations using the footprint-weighted average method. Our results show that the fluxes obtained by the footprint-weighted average method are of the same magnitude as the EC flux. More importantly, the temporal dynamics of the EC flux on a daily timescale are also captured (r2 = 0.7). In contrast, using the area-weighted average method yielded a low (r2 = 0.14) correlation with the EC measurements. This shows that the footprint-weighted average method is preferable when validating methane emission models with EC fluxes for areas with a heterogeneous and irregular vegetation pattern.

Controlling CO2 and CH4 Emission in a Degraded Peat Swamp Forest Related to Water Table and Peat Characteristics

2013 ◽  
Vol 391 ◽  
pp. 202-206
Author(s):  
Leila Kalsum ◽  
null Ngudiantoro ◽  
M. Faizal ◽  
A. Halim Pks
Keyword(s):  
Water Table ◽  
Forest Fires ◽  
Ash Content ◽  
Burned Area ◽  
Gas Temperature ◽  
Swamp Forest ◽  
Closed Chamber ◽  
Peat Swamp Forest ◽  
Peat Swamp

This study focuses on factors controlling CO2and CH4emission in a peat swamp forest related to water table and peat characteristics such as peat depth, C-organic, pH, ash content and N-total. This study was conducted in the dry season at a Merang peat swamp forest that has degraded due to logging activities, forest fires and canal opening. Emission of CO2and CH4was measured by using a closed chamber made by PVC material (60 cm x 60 cm x 40 cm). This close chamber was completed with a fan inside the chamber to stir the gas, a thermometer inside the chamber to measure the gas temperature and a syringe to sample gas. This study has shown that the highest CO2emission is at an average of 438.93 mg/m2/hr occurring in land cover type (1) ferns and grasses (open burned area) and the lowest is at average of 44.45 mg/m2/hr in thegelamandbelidang-dominated land. The emission of CH4is very low between 0.0018 to 0.0069 mg/m2/hr. the main controlling factor on CO2and CH4emission is concluded to be the water table. The emission of CO2will be greater if water table, pH and C-organic increase.

Phase-pure a-SiC:H films prepared by closed chamber CVD

2002 ◽  
Vol 299-302 ◽  
pp. 896-901
Author(s):  
Svetoslav Koynov ◽  
Marian Tzolov ◽  
Reinhard Schwarz
Keyword(s):  
Closed Chamber ◽  
Phase Pure
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