Considering the short response time and short effective period of the pulse in biogenic gas fluxes, many peak fluxes might have been missed in previous studies, which frequently used only a few manual measurements (Joos et al., 2010; Maljanen et al., 2010). The lack of temporal sampling resolution may also influence the estimation of annual fluxes. In contrast, substantial rewetting effects have been frequently observed with automated chamber systems (Borken et al., 1999: 4−5 observation per a day), eddy covariance methods (Lee et al., 2004; Kim et al., 2010a) and automated measurements of soil CO2 profiles (Vargas et al., 2010b). Such continuous flux measurements during and after pulse events will help to calculate the temporal dynamics and the total contribution to the cumulative flux and annual flux (Maljanen et al., 2010; Vargas et al 2010a). When manual chamber methods have to be used, more frequent measurements (Smith and Dobbie, 2001; Parkin, 2008) or measurements coinciding with rewetting or thawing events (Beare et al., 2009; Kim et al., 2010b) should be considered.
Most studies have explored the effects of rewetting and thawing at small spatial scales (i.e., plot level). Thus, a critical issue is how to scale up to the ecosystem, landscape or continental scale. Rewetting and thawing pulses may be patchily distributed in space, and without measurements at multiple spatial and temporal scales (i.e., chambers, eddy covariance, upscaling through remote sensing) it is difficult to evaluate the impacts of these events across regions of the Earth. Although multi-spatial scale sampling is needed, we recognize that there is frequently a cost trade-off between temporal sampling and spatial sampling. But with improving technologies and the growth of continental and global networks (i.e., NEON, ICOS, FLUXNET) we hope multi-temporal and multi-scale experiments will be more common in the near future.
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