6. 4. Experimental settings

To test the effect of rewetting and thawing on biogenic soil gas flux, controlled experiments have been frequently conducted in fields and laboratories using, for example, rainfall exclusions (Borken et al., 2006; Davidson et al., 2008), snow removal (Groffman et al., 2006; Maljanen et al., 2007), and soil cores incubated in the lab (Panikov, 2000). However, these conditions may not be relevant to real field situations, (Henry, 2007). Future experiments might include: 1) simulate drying-rewetting and freezing-thawing based on historical or projected extreme events, the latter under multiple climate change scenarios (Jentsch et al., 2007); 2) collect soil samples in the appropriate season and include relevant surface factors such as plant litter in the fall or excess water in the spring (Henry, 2007); and 3) develop new methods for simulating field conditions more closely in the laboratory (Hu et al., 2006). Future studies could benefit from these approaches in combination with high-temporal frequency resolution using automated flux measurements.

An area of significant promise involves combining microbial community analyses (Kim et al., 2008; Smith et al., 2010; Sawicka et al., 2009) and/or stable isotope techniques (Wagner-Riddle et al., 2008; Goldberg et al., 2009; Gaudinski et al., 2009) with flux measurements. Whether performed in the lab or field, such experiments could improve our understanding of rewetting and thawing effect on biogenic gas fluxes, quantifying the relationship between the control factors and their impact.