Permafrost thaw in boreal peatlands may be widespread as climate warms over
the next century. Thaw will lead to dramatic changes in vegetation, and an
understanding of the patterns and rates of succession following thaw is im
portant for assessing future ecosystem changes, such as carbon accumulation
and the likelihood of permafrost formation during climate warming. This pa
per describes the autogenic processes of peat accumulation and succession f
rom recently thawed, aquatic Sphagnum communities to lawn and hummock Sphag
num communities favorable for permafrost formation. Peat cores were used to
construct bulk density profiles in aquatic, lawn, and hummock habitats. So
il bulk density increased over time from the edges to the centers of thawed
bogs. These changes corresponded to changes from aquatic to lawn/hummock c
ommunities. Macrofossils from Pb-210-dated peat cores were used to document
historical changes to hummock communities. Succession to hummock communiti
es capable of forming permafrost was less than 80 years. Picea mariana seed
lings colonized emergent Sphagnum hummocks in collapse scars, which may lea
d to permafrost formation. However, permafrost formation in today's discont
inuous permafrost landscape is unlikely during future climate warming becau
se of limited tree establishment and shifting mean annual temperature isoth
erms.