Sapstain and decay following fire in stands of Pinus elliottii var. elliottii near Beerburrum, south east Queensland

Abstract

In September and November, 1994, wildfires caused damage to 9 thousand hectares of slash pine (Pinus elliottii var. elliottii) in plantations near Beerburrum in south east Queensland. During the salvage operation sapstain and decay were monitored by periodically felling and sectioning trees in five plots in stands damaged by the November fire. Appreciable bluestain (affecting more than 10% of stem wood per plot) was first observed 10–13 weeks after the fire. Bluestain was associated with attack by the introduced bark beetle Ips grandicollis. and was initially greatest in plots where the earliest insect attack occurred. Bluestain was also dependant on moisture content and was significant where mean values fell below 100–110%, as drying occurred particularly in the outer sapwood. Trees with severe crown scorch dried more rapidly and developed substantial bluestain more quickly, except towards the base of the stem. Where less severely damaged, the sapwood of green-crowned trees dried gradually and developed bluestain more slowly, but even green-crowned trees attacked by I. grandicollis eventually became substantially bluestained. In a supplementary study in a plantation of slash pine on Bribie Island damaged in the November fire, bluestain was found only in association with attack by Ips grandicollis, which was a reliable indicator of the presence of stain in fire-damaged stands.

Isolations from the bluestained sapwood regularly yielded a species of Ophiostoma apparently introduced to the fire-damaged trees by Ips grandicollis. Sphaeropsis sapinea was not isolated from stems, but was present in dry branches and remains a potential agent of bluestain under suitable conditions. Signs of decay fungi were first detected 21 weeks after the fire, and decay was identified in 71% of the study trees sampled after 49 weeks. Stands appreciably damaged in early summer fires in south east Queensland should be salvaged within 3 months to avoid significant bluestain.