A cost-effective method for reducing soil disturbance-induced errors in static chamber measurement of wetland methane emissions

Abstract

Static chambers used for sampling methane (CH4) in wetlands are highly sensitive to soil disturbance. Temporary compression around chambers during sampling can inflate the initial chamber CH4 headspace concentration and/or lead to generation of non-linear, unreliable flux estimates that must be discarded. In this study, we tested an often-used rubber gasket (RG)-sealed static chamber against a water-filled gutter (WFG) seal design that could be set up and sampled from a distance of 2 m with a newly designed remote rod sampling system to reduce soil disturbance. Compared to conventional RG design, our remotely sampled static chambers reduced the chance of detecting inflated initial CH4 concentrations (>3.6 ppm) from 66 to 6 % and nearly doubled the proportion of robust linear regressions (r2 > 0.9) from 45 to 86 %. Importantly, the remote rod sampling system allows for more accurate and reliable CH4 sampling without costly boardwalk construction. This paper presents results demonstrating that the remote rod sampling system combined with WFG static chambers improves CH4 data reliability by reducing initial gas measurement variability due to chamber disturbance when tested on a mineral soil-restored wetland in Charles City County, Virginia, USA.