The architectural significance of interfoliar branches in Pinus subsection Balfourianae

Abstract

In pines, branches of interfoliar origin (IFBs) often occur in response to injury. However, in all three species of Pinus subsection Balfourianae we observed in Utah, Nevada, and California, IFBs are common and of nontraumatic origin. They comprise 41 and 51% of the first-order branches in foxtail pine (Pinusbalfouriana Grev. & Balf.) and Great Basin bristlecone pine (P. longaeva D. K. Bailey), respectively. Second-order IFBs are frequent in Rocky Mountain bristlecone pine (P. aristata Engelm.) (45%) and Great Basin bristlecone pine (47%). All species of subsection Balfourianae produce exceptionally low numbers of long-shoot lateral branches (LSLBs). Growth and morphological data suggest that the IFBs function similarly to LSLBs.