Few large tree hollows in an endangered peri-urban ecosystem highlights the need to restore suitable habitat for dependent woodland fauna
Michael J. M. Franklin, Christopher E. Gordon, Emma J. Gorrod, Zahra Emlaei, Jeremy Bendall, Dylan Bristol, Paul D. Rymer, Uffe N. NielsenContext
Tree hollows are essential habitat resources used by fauna in woody ecosystems globally. In addition to extensive historical and ongoing clearing, human use of woodlands has left remnants with structurally modified tree assemblages, including reductions in large hollow-bearing trees.
Aims
We aimed to assess tree hollow resources for dependent, arboreal vertebrates in fragmented, peri-urban woodlands. The objectives were to quantify the extant tree size distribution, estimate densities of hollow-bearing trees with different sized hollows, and determine the effect of tree size on both hollow occurrence and the number of hollows per tree.
Methods
The study was conducted in 100 plots located in remnant stands across the distribution of critically endangered Cumberland Plain Woodland, south-eastern Australia. Tree size was assessed using diameter at breast height (DBH). Hollows were classed as small, medium or large during systematic searches. Bayesian hurdle models were used to analyse effects of tree size on hollows.
Key results
There were 5566 live trees recorded (median DBH 10.2 cm), but only 105 were hollow-bearing. The mean density of trees bearing any size hollow was 15.6 per ha, but those bearing large hollows were scarce (3.1 per ha). Hollows were unlikely to occur in live trees with a DBH of <50 cm.
Conclusions
Overall hollow availability was diminished and comparable to other modified woodlands. Large hollow availability was disproportionately low.
Implications
Management of large, hollow-bearing trees in these systems should include the identification and protection of remaining individuals, actions to increase the number of individuals through time, and addition of artificial hollows.