- Title:
-
Decline in the Temperate Overstorey Eucalypts in the Absence of Fire
- Date:
- September 2008
- Organisations
- Bushfire CRC
- Authors:
- D.C. Close, N.J. Davidson, B.M. Horton
- Location:
- Australia, TAS, Australia
Overview
The International Bushfire Research Conference 2008 - incorporating The 15th annual AFAC Conference, Adelaide, South Australia, Australia
Overstorey eucalypt decline may be developing in some temperate woodlands and forests. One hypothesis is that decline is linked to the long absence of fire. The objectives of this project were to survey overstorey tree decline, vegetation midstory, soil and tree nutrition, and tree foiar carbon isotope ratios (an indicator of water stress) in sites that have either a history of a long absence of fire or a history of relatively frequent fire.
Plant nutrient-availability following prescribed fire was also studied using seedlings as a bioassay and ion exchange resins buried in the soil. It is hypothesised that altered eucalypt water- and/or nutrient availability may underpin the decline. Experiments were replicated at the site level in Eucalyptus delegatensis forest (Tas) and E.gomphocephala woodland (WA).
Tree decline was elevated on long unburnt sites (Tas and WA). Trees had higher water use efficiency and were more water stressed in long unburnt sites (Tas and WA). The midstorey differed in composition and there was greater % cover of shrubs in long unburnt sites (Tas and WA). There was higher soil, but not leaf, nitrogen (N) in long unburnt sites (Tas and WA). In Tas foliar phosphorus (P) was deficient in long unburnt sites. In WA foliar copper (Cu) was deficient in long unburnt sites. In WA seedlings had higher foliar P and Cu on the burnt than the unburnt site and ion exchange resins captured significantly elevated levels of N,P,K and most micronutrients.
We conclude that the lng absence of fire leads to the development of midstorey and overstorey tree decline possibly via water stress and/or P deficiency (altered mycorrhizal relations?) in Tas and via water stress and/or Cu deficiency in WA. Prescribed fire may address tree water stress, though decreasing leaf area in the midstorey, and tree nutrient deficiency, through increased plant nutrient availability in ash.
