Landscape-scale assessment of tree crown dieback following extreme drought and heat in a Mediterranean eucalypt forest ecosystem

Abstract

Mediterranean regions are under increasing pressure from global climate changes. Many have experienced more frequent extreme weather events such as droughts and heatwaves, which have severe implications for the persistence of forest ecosystems. This study reports on a 5 landscape-scale assessment investigating potential associated factors of crown dieback in dominant tree species following an extreme dry and hot year/summer of 2010/11 in the Northern Jarrah Forest of Western Australia. Analyses focussed on the influence of (i) geology, (ii) topography, (iii) climate, and (iv) fire history. The results showed that trees on specific soils were more likely to show canopy dieback. Generally, trees on rocky soils with 10 low water holding capacity were found to be affected more frequently. Other explanatory factors identified that dieback occurred (i) on sites that were close to rock outcrops, (ii) in areas that received a slightly higher amount of annual rainfall compared to the surrounding landscape, (iii) on sites at high elevations and (vi) on steep slopes, and (v) in areas that were generally slightly warmer than their surroundings. These results expand our understanding of

Sudden forest canopy collapse corresponding with extreme drought and heat in a mediterranean-type eucalypt forest in southwestern Australia

“…This is especially evident in MTFs (Lloret et al 2004;Peñuelas et al 2000). Recent evidence suggests site factors influenced the occurrence of canopy collapse in the NJF (Brouwers et al 2013). Sites at elevated landscape positions, close to rock outcrops, low water-holding capacity soils were more likely to be affected (Brouwers et al 2013).…”

“…Recent evidence suggests site factors influenced the occurrence of canopy collapse in the NJF (Brouwers et al 2013). Sites at elevated landscape positions, close to rock outcrops, low water-holding capacity soils were more likely to be affected (Brouwers et al 2013). Factors related to variability in soil moisture, including soil depth and soil water storage capacity are known to predispose areas of forest to collapse in Mediterranean regions (Caspersen and Kobe 2011;Lloret et al 2004;Peñuelas et al 2000).…”

How drought-induced forest die-off alters microclimate and increases fuel loadings and fire potentials

“…There is a strong west-east rainfall gradient across the forest, ranging from >1100 mm year -1 on its western edge (Darling Scarp) to ~700 mm year -1 in the east and north (Gentilli 1989). Further details of the study region, climate events, sites and their selection are described in Matusick et al (2013) and Brouwers et al (2013).…”

Early Differential Responses of Co-dominant Canopy Species to Sudden and Severe Drought in a Mediterranean-climate Type Forest

“…The Northern Jarrah Forest (NJF), in the Southwest Botanical Province of Western Australia, covers an area of 1,127,600 ha [27] (see map in Brouwers et al [28]), and ranges in form from an open and dry sclerophyll forest in the north to a tall, closed forest in the south [29]. This study is focused on upland areas, which are dominated by Eucalyptus marginata (jarrah) and Corymbia calophylla (marri).…”