Small versus Large Chamber Surface Areas for Accurate Soil Gas Flux Estimates

INTRODUCTION

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Soil gas flux chambers are used for many applications, including estimating the effect of treatment types on flux, understanding and mapping spatial variability of flux, and monitoring temporal variability in flux over timescales ranging from minutes to years. Elements of the chamber design, including chamber geometry, pressure venting and chamber sealing, can have an impact on the measured gas flux if not accounted for correctly (Pumpanen et al., 2004).

Chamber geometry is often quite variable among studies and typically chamber size and shape is driven by requirements of the study (e.g. large plants need to be enclosed to measure NEE). Similarly, many researchers use large surface area chambers to try to adequately capture and integrate fluxes, especially for ecosystems or gases where spatial variability is high. These large surface area chambers are thought to be more likely to capture “hot spots” of gas production, while also providing spatially integrated flux values in areas of high spatial variability which may help avoiding false positives or negatives in treatment effect studies. But, there has been minimal systematic evaluation of the benefits and drawbacks of using large surface area chambers in the literature.

In this white paper, a numerical simulation of spatial variability is used in order to compare and contrast the benefits and drawbacks of chambers with small surface area versus those with large surface area. For two different chamber types, the mean and standard deviation is compared over a variety of different spatial variability simulations, and the performance of the two different chamber types in typical field scenarios is examined. Finally, the other aspects of chamber design and data interpretation will be discussed with reference to small and large chamber surface areas.

 

View the complete White Paper here Small versus Large Chamber Surface Areas for Accurate Soil Gas Flux Estimates