Temporal and spatial patterns in drought‐related tree dieback in Australian savanna

Fensham, R. J.; Holman, J. E.

doi:10.1046/j.1365-2664.1999.00460.x

Cited by 209 publications

(208 citation statements)

References 28 publications

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“…A recent review by Allen et al (2010) outlined 88 documented episodes of forest damage resulting from drought and/or heat events since the early 1970's, illustrating the vulnerability of forests to extreme climate conditions worldwide. Long periods of drought result in chronic stress, causing growth reductions (Barber et al 2000), crown dieback (Fensham and Holman 1999), and tree decline (Starkey et al 2004). For example, during five years of experimental drought conditions, the diameter increment of Quercus ilex L. was reduced by 41% (Ogaya and Peñuelas 2007).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2013

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Drought and heat-induced forest dieback and mortality are emerging global concerns.Although Mediterranean-type forest (MTF) ecosystems are considered to be resilient to drought and other disturbances, we observed a sudden and unprecedented forest collapse in a MTF in Western Australia corresponding with record dry and heat conditions in 2010/2011.An aerial survey and subsequent field investigation were undertaken to examine: the incidence and severity of canopy dieback and stem mortality, associations between canopy health and stand-related factors as well as tree species response. Canopy mortality was found to be concentrated in distinct patches, representing 1.5% of the aerial sample (1,350 ha).Within these patches, 74% of all measured stems (> 1cm DBHOB) had dying or recently killed crowns, leading to 26% stem mortality six months following the collapse. Patches of canopy collapse were more densely stocked with the dominant species, Eucalyptus marginata, and lacked the prominent midstorey species Banksia grandis, compared to the surrounding forest. A differential response to the disturbance was observed among cooccurring tree species, which suggests contrasting strategies for coping with extreme water stress. These results suggest that MTFs, once thought to be resilient to climate change, are susceptible to sudden and severe forest collapse when key thresholds have been reached.

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Section: Introductionmentioning

confidence: 99%

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

et al. 2013

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“…for September 1970 the running total is calculated from October 1967-September 1970) (Foley 1957). This provides a measure of sustained wet and dry periods, and has proved useful for relating rainfall patterns to tree dynamics in other studies (Fensham and Holman 1999). Gidgee seed germinates rapidly after seed-fall and does not accumulate in the seed-store (Reynolds et al 1992).…”

Section: Causes Of Change In Gidgee Structurementioning

confidence: 99%

“…4). There are historical records of this drought causing extensive tree dieback including gidgee (Fensham and Holman 1999):…”

Section: Causes Of Change In Gidgee Structurementioning

confidence: 99%

Preliminary assessment of gidgee (Acacia cambagei) woodland thickening in the Longreach district, Queensland

Fensham

Fairfax

2005

Rangel. J.

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Abstract. Gidgee (Acacia cambagei) forms woodlands and forests on moderately fertile clay soils throughout semi-arid areas of north-eastern Australia. Analysis of soil data from Queensland indicates that gidgee's environmental domain has a broad overlap with treeless Mitchell grassland although a preference for slightly coarser soils with higher phosphorus and lower potassium content. Mapping of woody cover change for an area of central Queensland suggests that gidgee thickening and spread has occurred between 1951 and 1994. However, this increase has been more than offset by loss of gidgee cover by clearing in other areas. Gidgee thickening and encroachment onto grassland is a problem for graziers because the trees suppress grass and are unpalatable except when very young. Landholder surveys and other information indicate that gidgee has recruited sporadically and that thickening occurred with a massive seedling recruitment in the 1950s with a smaller recruitment wave in the 1970s. These waves coincide with relatively wet times and the extreme rainfall abundance in the 1950s has a multi-century expected recurrence. There are historical records describing gidgee death during the extreme droughts in the first part of the 20th century. Young gidgee plants are fire sensitive but well-established gidgee stands are fire retardant, and the importance of fire for control of gidgee thickening is unknown. One scenario explaining gidgee dynamics emphasises the role of environment (mostly climate and soil), while another emphasises management (mostly fire). Research priorities are presented and may contribute to appropriate management of gidgee woodlands.

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“…There is considerable debate on how rainfall (Fensham and Holman 1999;FernandezGimenez and Allen-Diaz 1999;Fynn and O'Connor 2000) and grazing (Hulme et al 1999;Bokdam and Gleichman 2000;Sternberg et al 2000) should be taken into account in terms of management of shrub encroachment. The results of this study indicate that reductions in D. cinerea regeneration may occur when drought acts in concert with light grazing.…”

Section: Implications Of the Studymentioning

confidence: 99%

Interacting effects of grass height and herbivores on the establishment of an encroaching savanna shrub

Hagenah¹,

Munkert²,

Gerhardt³

et al. 2008

Herbaceous Plant Ecology

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Shrub encroachment is a widely observed problem in Southern African savannas.Although the effects of herbivory and grass height on woody species recruitment have been studied individually, little information exists about how these factors interact. In this study seeds and seedlings of the encroaching shrub Dichrostachys cinerea were planted in clipped and unclipped grass plots, with and without large herbivores present. Seed germination, seedling survival and seedling predation were monitored for 8 months. Germination started earlier in plots where herbivores were excluded. Overall, the earlier the seeds germinated, the longer the seedlings survived. Clipping positively affected the number of germinated seeds, seedling growth and survival but effects varied among herbivore exclusion treatments and sites. Invertebrates caused the majority of the seedling damage. We conclude the recruitment of D. cinerea is influenced by the interplay of grass height and herbivory. In this study, the presence of large herbivores early in the wet season, and the absence of simulated grazing later on, affected the regeneration of D. cinerea negatively. However, differences in effects among sites suggest that the mechanisms found here may work differently in other habitats.

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Temporal and spatial patterns in drought‐related tree dieback in Australian savanna

Cited by 209 publications

References 28 publications

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

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

Preliminary assessment of gidgee (Acacia cambagei) woodland thickening in the Longreach district, Queensland

Interacting effects of grass height and herbivores on the establishment of an encroaching savanna shrub

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