摘要：The growth, longevity, and decay of mineral-cored palsas at an altitudinal treeline site in the southern Yukon all appear to be significantly affected by the activities of beaver ( Castor canadensis ). The palsas are composed of stratified, fine-grained, organic-rich, frost-susceptible deposits, which are interpreted as originating from sedimentation in beaver ponds. Peat development, which is a precondition for mound formation, takes place in the adjacent wetland, in part due to poor drainage because of dams. Palsa degradation over the past 55 yr preferentially followed flooding due to dam construction. Drainage of ponds by dam breach was succeeded by mound formation in aggrading permafrost. Unlike previous studies, therefore, it is impossible to infer a clear climate signal from palsa dynamics at this location.
