Topography influences the distribution of autumn frost damage on trees in a Mediterranean-type Eucalyptus forest

Abstract

Key messageExtreme temperatures are causing forest dieback in a Mediterranean-type forest. Topography and cold-air pooling explain the geographic distribution of frost dieback in susceptible tree species. AbstractAlterations to the frequency and intensity of extreme temperatures, predicted with climate change, pose a threat to the health of many forests. Some Mediterranean climate regions are experiencing higher temperature variability, including more extreme low and high temperature events. Following one such low-temperature event in autumn 2012, we conducted landscape-and site-level studies to examine the impact of frost on trees and the interaction between topography, temperature, and dieback in a forest ecosystem in the Mediterranean climate region of southwest Australia. Canopy damage was widespread across the survey area and occurred in distinct patches, with sizes ranging between 4.1 and 2,518.0 ha. In affected forest, Eucalyptus marginata and Corymbia calophylla experienced nearly complete crown dieback, while E. patens and E. wandoo were undamaged. Canopy damage was found more frequently in valleys and lower to mid-slope positions, and site-level studies confirmed that crown dieback generally increased with decreasing elevation. Low temperatures were strongly correlated with elevation along damaged forest transects and cold-air pooling explained the pattern of forest damage. By regressing temperatures from damaged sites against those collected from the nearest meteorological station, projected minimum air temperatures ranged from −0.1 to −2.7 °C at valley bottom when the dieback occurred. Insufficient tissue hardening is suspected to have predisposed trees to this autumn frost. The interaction between shifting temperature regimes with climate change and frost damage is discussed. With continued increases in temperature variability, we can expect to see more temperature-driven disturbance events and associated reductions in forest health.

Different ways to die in a changing world: Consequences of climate change for tree species performance and survival through an ecophysiological perspective

“…In a recent study, it was shown that a widespread mortality event in a tropical dry forest from Mexico was related to an unusual combination of duration, intensity, and timing of a frost event (Bojórquez, Álvarez‐Yépiz, Búrquez, & Martínez‐Yrízar, ). Similarly, dieback events related to frost injury were also reported for species from the Mediterranean region (Jalili et al, ; Matusick, Ruthrof, Brouwers, & Hardy, ). These examples illustrate well the impact of global warming on the vegetation, since its effects, especially the large temperature fluctuations, can significantly increase the vulnerability of forest species in virtually all biomes.…”

Variable tree establishment in bauxite mine restoration in south‐west Australia linked to rainfall distribution, seasonal temperatures and seed rain

“…A positive relationship with the only significant wet season temperature variable, the lowest daily minimum (Jarrah ES, 0.009 and Marri ES, 0.024), possibly relates to the damaging effects of frost (Matusick et al . ). Alternatively, lower wet season overnight temperatures are often associated with dry periods with clear night skies, suggesting an indirect effect of soil moisture availability.…”

Understanding and predicting frost‐induced tropical tree mortality patterns

“…Lowland vegetation is in general more prone to freezing damage when advective frosts occur in agreement with recent studies in savannas in South Africa and Brazil (Hoffmann et al, ; Muller et al, ; Whitecross et al, ). This finding can be explained by the strong influence of elevation on temperature distribution at the regional and landscape level (Florinsky, Kulagina, & Meshalkina, ; Hummer‐Miller, ; Matusick, Ruthrof, Brouwers, & Hardy, ), driving the movement of cold air masses downhill during an advective frost (Kalma, Laughlin, Caprio, & Hamer, ; Lindkvist & Lindqvist, ). Accordingly, the historic cold wave that caused the February 2011 severe frost entered our study area from the adjacent northeastern mountains and drained into the lowlands where cold air remained for at least three consecutive days, leading to the widespread frost‐induced tree mortality episode.…”