Pilgerodendron uviferum: The southernmost tree-ring fire recorder species

Abstract

This paper reports on the capability of the long-lived conifer Pilgerodendron uviferum in southwestern South America to record fire scars, making it the southernmost tree-ring fire recording species on Earth. We present detailed descriptions of the fire-scar morphology of this species and compare tree-ring fire-scar dates to independent sources of fire dates. The fire scars found on Pilgerodendron uviferum are morphologically similar to those found on conifers in western North America. All fire scars were crossdated on 80 out of 96 sampled cross-sections collected at 8 dispersed sites. Groups of micro-rings were the most common anatomical feature that impeded crossdating of fire-scar dates. A total of 597 fire-scar tips were successfully crossdated on these 80 cross-sections. The average number of fire scars per cross-section was 7.4, and the full collection of crossdated fire scars spanned from 1570 to 2004 AD. The crossdated fire-scar dates were highly synchronous within stands, and years of abundant scars matched years of widespread fire in documentary fire records from nearby areas. The high terpene content and mechanical properties of the wood of Pilgerodendron uviferum contribute to its resistance to decay and therefore long-term preservation of scars on both live and dead standing trees. The suitability of Pilgerodendron uviferum as a tree-ring fire recording species creates a significant opportunity to extend research on multi-century fire activity in relation to climate variability at mid to high latitudes (i.e., 43–55° s) in southwestern South America.