Final author response to ”Calculations of automatic chamber flux measurements of methane and carbon dioxide using short time series of concentrations”

The closed chamber technique is widely used to measure the exchange of methane (CH4) and carbon dioxide (CO2) from terrestrial ecosystems. There is, however, large uncertainty about which model should be used to calculate the gas flux from the measured gas concentrations. Due to experimental uncertainties the robust ::::: simple linear regression model (first order polynomial) is often applied, even though theoretical considerations of the 5 technique suggest the application of other, curvilinear models. High-resolution automatic chamber systems which sample gas concentrations several hundred times per flux measurement make it possible to resolve the curvilinear behavior and study the information imposed by the natural variability of the temporal concentration changes. We used more than 50000 such flux measurements of CH4 and CO2 from five field sites located in peat forming wetlands to calculate fluxes with :::::: ranging :::: from ::: 56 :: to ::::: 78°N :: to :::::::: quantify ::: the :::::: typical ::::::::: differences :::::::: between ::: flux 10 ::::::: estimates ::: of : different models. The flux differences from independent linear estimates :: In :::::::: addition, ::: we ::::: aimed :: to ::::: assess ::: the ::::::::::: curvilinearity ::: of ::: the ::::::::::: concentration :::: time ::::: series :::: and ::: test ::: the ::::::: general :::::::::: applicability :: of :::::::::: curvilinear :::::: models. :::::: Despite ::::::::: significant ::::::: episodic ::::::::: differences ::::::: between ::: the ::::::::: calculated ::: flux ::::::::: estimates, ::: the ::::: overall :::::::::: differences are generally found to be smaller than the local flux variability on the plot scale. The curvilinear behavior of the gas concentrations within the chamber is strongly influenced by wind driven chamber leakage, and less so by changing gas 15 concentration gradients in the soil during chamber closure. Such physical processes affect both gas species equally, which makes it possible to isolate biochemical processes affecting the gases differently, such as photosynthesis limitation by chamber headspace CO2 concentrations under high levels of incoming solar radiation. We assess the possibility to exploit this effect for a partitioning of the net CO2 flux into photosynthesis and ecosystem respiration and argue that:: as:: an:::::::: example :: of:::: how high-resolution au20 tomatic chamber measurements could be used for purposes beyond the estimation of the net gas flux. :::: This ::::: shows