Ninth International Conference on Permafrost ... - IARC Research

Ni n t h In t e r n at i o n a l Co n f e r e n c e o n Pe r m a f r o s tResultsA preliminary investigation of the relationships betweenvegetation and the presence or absence of permafrost wasundertaken using a dataset collected since 2002 of vegetationdescriptions and late-summer probing or temperature profilesin pits at more than 500 mountain sites. Observations weregrouped into three vegetation classes that exist in the studyareas: northern boreal forest, a shrub tundra zone of willowand birch above treeline, and alpine tundra or bare areas(combined) at the highest elevations.The percentage of pits exhibiting permafrost for eachvegetation type in each study area (organized by increasingprecipitation) is shown in Figure 1. The results suggest thatprecipitation totals may have an impact at the regional scale,but this apparent trend must be interpreted cautiously, as theprecipitation values come from low-elevation climatologicalstations located up to 80 km from the study areas. Organizingthe results by latitude (not shown) did not reveal any obvioustrends: three sites at virtually the same latitude (Wolf Creek,Johnson’s Crossing and Sa Dena Hes) exhibit significantvariation in the percentage of permafrost.Given the link between elevation and vegetation, it is notsurprising that the percentage of permafrost is generallyhigher for alpine tundra sites than for the other two classes.Reasons for the two exceptions (Faro for shrubs andJohnson’s Crossing for forest) require further investigationand more field sampling.The impact of vegetation in affecting the surface offsetand, hence, permafrost is best illustrated by the three studyareas where shrub sites have the smallest percentage ofpermafrost (lower than forested sites). This may indicate theimportance of trapping snow blown from the tundra above(e.g., Pomeroy et al. 2006) within the shrub zone and thesnow’s influence on reducing ground heat loss in winter.These field observations show that vegetation type is highlycorrelated with elevation, but this brief analysis indicatesFigure 1. Percent of ground truthing pits that contained permafrostfor each vegetation type in each study area. Numbers above thebars indicate the number of pits examined (groups with