Thermal Profiles of Chainsaw Hollows and Natural Hollows during Extreme Heat Events

Abstract

Loss of hollow-bearing trees threatens many hollow-dependent wildlife. To mitigate this process, artificial chainsaw-carved hollows (CHs) are often created in dead trees, yet little is known about their thermal profiles. We measured temperatures inside 13 natural hollows (8 live and 5 dead trees) and 45 CHs (5 live and 40 dead trees) in the central west of NSW, Australia, over the course of 2 summers. Maximum temperatures and daily temperature ranges within natural hollows and artificial hollows were similar in 2017–2018. Hollow temperatures were lower in thicker-walled hollows than in thinner-walled hollows. During the January 2019 heatwave, temperatures inside CHs in dead trees exceeded 35 °C—4 °C higher than the upper limit of the thermal neutral zone of sugar gliders—for 6.2 consecutive days (range 0–9 days). CHs in dead trees provided little buffering from thermal extremes; when air temperatures peaked at 44.6 °C, CHs in dead trees were on average 2.4 °C cooler than ambient (range: 5.5 °C cooler to 1.0 °C hotter than ambient). These results show that CHs created in dead trees may not provide suitable thermal conditions for hollow-dependent marsupials during summer heatwaves. Retention of large live trees, coupled with revegetation, is crucial for conserving hollow-dependent fauna in agricultural landscapes.

Structure and Function of Urban Forests and Green Spaces in a Changing World

“…In the west-central of New South Wales, Australia, the temperatures inside 13 natural hollows and 45 artificial chainsaw-carved hollows (CHs) were measured over the course of two summers, and it was found that CHs created in dead trees might not provide suitable thermal conditions for hollow-dependent marsupials during summer heatwaves. Therefore, the authors concluded that the retention of large live trees and revegetation was crucial for conserving hollow-dependent fauna in natural and urban landscapes [12].…”

Tree hollow decline in new forest reserves with a long history of logging

“…However, our results reveal that the historical silvicultural practice of ringbarking accounted for almost half of all dead trees. Dead hollow-bearing trees are a critical component of habitat provision (Thorn et al, 2020), but they have been shown to support four times fewer microhabitat types than living trees (Paillet et al, 2017) and their thermal properties differ from living trees which may limit their habitat suitability for some species (Griffiths et al, 2018;Callan et al, 2023). Further declines in hollow densities will occur in these forests due to the collapse of dead hollow-bearing trees (Lindenmayer et al, 2018).…”