Feeling the cold in a warming climate: differential effects of low temperatures on co-occurring eucalypts

Abstract

Climate change is altering extreme temperature events, and is expected to drive changes in species composition as a result. To assess the potential for compositional shifts from low-temperature events, the effects of repeated events in 2010 and 2012 on three co-occurring eucalypts were determined in south-western Australia. To examine the climatic conditions that led to tree damage, and the long-term pattern of low-temperature events, temperatures were monitored on affected sites, and modelled from climate-station data. The three species varied considerably in their susceptibility to low temperatures. Corymbia calophylla K.D.Hill & L.A.S.Johnson was most affected (crown-damage index (CDI) = 47), followed by Eucalyptus marginata Sm. (CDI = 17) and E. wandoo Blakely (CDI = 3), which was comparatively tolerant. The temperatures leading to damage in 2010 and 2012 were –3.4°C and –2.1°C respectively. The frequency of low-temperature events (days below 0°C) have been steadily increasing in the study area since the mid-1990s. Because minimal tree mortality was observed, species composition is unlikely to change as a result of low temperatures in the short term. However, continued dieback from repeated events may disrupt regenerative processes, and cause long-term compositional shifts.