Can Stem Strips Be Induced? An Experimental Investigation of Cliff‐Face Thuja occidentalis

Previous studies have suggested that strip‐bark growth in ancient Thuja occidentalis on cliffs in southern Ontario, Canada, may be initiated by root mortality following rockfall. We conducted a long‐term manipulative field study on 65 cliff‐face trees to test whether stem stripping could be experimentally induced by either severing or excavating part of the root system. Further evidence of the proposed mechanism was sought by monitoring the responses of individual branches on timescales ranging from hours to years, including gas exchange, growth, canopy condition, and mortality. The trees were harvested after 5–7 yr to identify and date any stem strips. The results showed that partial root excavation, but not severing, significantly increased the frequency of stem stripping. In two cut and four excavated trees, the treatments produced partial branch and cambial mortality, supporting the proposed mechanism in the long term. However, the majority of trees did not stem strip, despite major root loss, and sho...