Development of vegetation communities in a retrogressive thaw slump near Mayo, Yukon Territory: A 10-year assessment

The vegetation in a retrogressive thaw slump, first surveyed and documented in 1987, was revisited 10 years later to investigate its subsequent develo pment and to test a chronosequence-based successional model. The thaw slump stabilized in 1994, when the headwall became covered by organic and minera l debris. As a result, the meltwater supply from headwall ablation ceased. Alteration of environmental conditions due to stabilization of the headwall diverted the vegetation succession from the chronosequence determined in 1 987. Areas that were marshy in 1987 dried up, and an area dominated by Poly gonum alaskanum appeared close to the headwall. Much of the thaw slump was dominated by Salix spp. in 1997, rather than the Equisteum of 1987. However , the ground more than 200 m from the headwall, over a decade old in 1987, experienced less change in edaphic conditions, and the communities there co ntinued to develop a structure approaching the surrounding undisturbed fore st.