Calibrated Rhizocarpon spp. growth curve for the Mount Waddington area

A calibrated Rhizocarpon spp. lichen growth curve spanning the last 680 yr was developed for the Bella Coola and Mount Waddington areas, southern Coast Mountains of British Columbia (Canada). It is based on 18 control surfaces whose ages were determined using radiocarbon dates, tree-ring dated moraines, and ice front positions derived from historical air photographs. Population distribution statistics were used to assess the validity of each control lichen measurement. The relationship is characterized by logarithmic growth during the first 100 yr following surface stabilization, and is described as linear for the successive 600 yr. Application of the curve at Tiedemann Glacier revealed evidence for six periods of late-Neoglacial moraine formation in ca. AD 620, 925, 1118, 1392, 1575, and 1621. The study confirms the importance of incorporating a multisite approach and a lichen population dynamic assessment. Large samples sizes and replication are also noted as necessary in order to adequately assess any dating errors