Macroanatomy of compartmentalization in fire scars of three western conifers

Fire scars are visible evidence of compartmentalization and closure processes that contribute to tree survival after fire injury. Preliminary observations of dissected fire scars from trees injured within the last decade showed centripetal development of wound-initiated discoloration (WID) through 2-3 decades of former sapwood in Larix occidentalis and Pseudotsuga menziesii. Although the WID reached and was apparently confluent with the visually similar heartwood, WID lacked the decay and insect resistance characteristics of heartwood. In contrast, development of WID in Pinus ponderosa, was limited to fewer than 5 rings of former sapwood with healthy sapwood retained between the WID and heartwood. The healthy sapwood has the potential to actively resist the spread of infection and further loss of wood function. For wound closure, all three species produced wide rings of woundwood from the margin of the killed vascular cambium in the growing season following fire injury.