2. Methodology

2. 1. Data collection


Data on changes in gas fluxes of CO2, CH4, N2O, NO and NH3 following rewetting and thawing were acquired by searching existing refereed literature published between 1950 and 2010 using Web of Science and Google Scholar with search terms such as “rewetting”, “thawing”, “peak flux”, “peak emission” and name of gases. Field observations of rewetting of dry soils include events caused by natural rainfall, simulated rainfall in natural ecosystems, and irrigation in agricultural lands. Similarly, thawing of frozen soils include field observations of natural thawing, simulated freezing-thawing events (i.e., thawing of simulated frozen by snow removal), and thawing of seasonal ice in temperate and high latitude regions. We included both field and laboratory studies, but did not include the longer-term effects of changing active layer depths in this review, as changes in gas fluxes in response to permafrost thaw is affected by both changing soil and plant successional processes (Turetsky et al., 2007). The resulting data set comprised 222 field and laboratory experiments focused on rewetting of dry soils, and 116 field studies and laboratory experiments focused on thawing of frozen soils.