THE FORMATION AND POSSIBLE ECOLOGICAL FUNCTION OF STEM STRIPS IN THUJA OCCIDENTALIS

The formation of stem strips through partial cambial dieback occurs in a number of long‐lived woody species and appears to be associated with old age, slow growth, and habitat adversity. The reason for this association is unknown, and investigations of the cause of stem stripping have been impeded by the strong correlation among the associated factors themselves. Hydraulic sectoring of the xylem is thought to be necessary for stem stripping to occur, and we hypothesize that loss of hydraulic conductance by permanent cavitation of tracheids in parts of the xylem is the first step in stem strip formation. The aim of this study was to identify characteristics of Thuja occidentalis that are directly associated with the presence of stem strips. We used a large data set of 842 T. occidentalis collected randomly from a favorable (cliff‐top plateau) and an unfavorable (cliff face) habitat to determine whether age, growth rate, and habitat were directly or indirectly related to the presence of stem strips. To dete...