Thermal buffering effect of alpine boulder field microhabitats in Australia: Implications for habitat management and conservation

Identifying and protecting microhabitats with conservation value is becoming a high priority for conservationists under projected climate change. Information on the buffering effects of microhabitats and its major drivers is a prerequisite to implementing effective conservation. We collected hourly temperature data from 70 alpine–subalpine sites nested within 9 boulder field clusters in an area measuring approximately 60 km × 30 km in New South Wales, Australia, over a period of more than 2 years. We studied the thermal buffering effect of the boulder fields and investigated the factors driving the effect using multilevel (i.e., sampling points nested within boulder field clusters) regression modeling. We found remarkable seasonal and spatial variations in the thermal buffering effect of boulder fields. Boulder fields buffered the surface temperature maxima by 2.91 °C at a depth of 50 cm and 4.39 °C at a depth of 100 cm, while they buffered the surface temperature minima by 0.54 °C at the depth of 50 cm and 1.36 °C at the depth of 100 cm, with temperature range reduced by 3.45 °C and 6.48 °C in warmer period and by 1.23 °C and 2.05 °C in colder period at two depths. We defined thermal buffering in temperature ranges as the thermal buffering capacity (TBC) as an exemplar for multilevel modeling. We found that vegetation cover and elevation affected the TBC at the point level, whereas the aspect and inclination of slopes affected the TBC at the cluster level. These findings are instructive for the protection of habitats, as high priority should be given to those habitats that offer effective TBC. Furthermore, the environmental factors identified to be driving TBC provide important input to the management of species habitats.