Sphagnum Invasion beneath an Evergreen Forest Canopy in Southeastern Alaska

Noble, Mark; Lawrence, Donald; Streveler, Gregory

The first detailed observations of Sphagnumn colonization on the floor of a coniferous forest are used to evaluate the process of forest paludification. Theforest, which is dominated by Picea sitchensis, is situated on a neoglacial terminal morain near the mouth of Glacier Bay in southeastern Alaska. The observations span an period of 14 years and have shown that (a) Sphagnum girgensohnii is the first peat moss to colonize the thick moss carpet on the floor of this forest, (b) establishemnt occurs only where the moss carpet has been disturbed by tree falls, © the number of Sphagnum patches in this forest in increasing with time, and (d) the patches are enlarging in surface area about 2% per year. As these changes occur on the forest floor, S. mendocinum and S. squarrosum are invading wet depressions and ponds in this forest. jThese events seem to result from soil-forming processes that are causing the water table to rise. The rate of local paludification will be affected directly, rhgough the rise in the water table, as a water-tight seal forms within the stratified drift, and indirectly, as Sphagnum growth is stimulated by proximity to water. Investigations in this forest, at other places in Glacier Bay National Park, and elsewhere in southeastern Alaska suffest that colognization by Sphagnum takes place from 175 to 600 or ore years following the initiation of primary succession. The development of muskeg vegetation through autogenic processes may take from 800 to several thousand years, or possibly much less if allogenci factors contribute to the paludification process.

Sphagnum Invasion beneath an Evergreen Forest Canopy in Southeastern Alaska

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