Lignotubers and burls— their structure, function and ecological significance in Mediterranean ecosystems

James, Susanne M.

doi:10.1007/bf02862633

Cited by 195 publications

(166 citation statements)

References 84 publications

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“…However, evidence of large-scale complete crown dieback and stem mortality from sudden and severe drought conditions have been rare in MTFs (Allen et al 2010). Trees in MTFs have evolved with frequent and extreme disturbance, including dramatic fluctuations in precipitation and temperature (Roberts et al 2001), which has resulted in unique adaptations and survival abilities (James 1984). For example, background annual mortality rates in E. marginata are low, ranging from 0.02% per year in the humid zone to 2.42% per year in the subhumid (Abbott and Loneragan, 1983).…”

Section: Discussionmentioning

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: Discussionmentioning

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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“…Despite the lignotuber being a specialized organ for underground starch storage in resprouter Erica species (James, 1984 ;Canadell & Lo! pez-Soria, 1998), we have considered root starch storage in this study as an estimate of underground storage to enable us to make comparisons between regeneration classes, since seeder Erica species lack a lignotuber (Ojeda, 1998).…”

Section: mentioning

confidence: 99%

“…Starch concentrations in above-ground parts collected in the current study proved to be variable and no significant differences were found between seeders and resprouters. The roles of starch stored in shoots are thought to be related to flowering and growth phenology (James, 1984 ;Chapin et al, 1990) and are highly likely to differ with species. Furthermore, the relevance of shoot starch to resprouting in Cape ericas is negligible since shoots are burnt down by fire.…”

Section: mentioning

confidence: 99%

Underground starch storage in Erica species of the Cape Floristic Region – differences between seeders and resprouters

1999

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Concentrations of starch in roots of seeder species of Erica from the Cape Floristic Region, South Africa were found to be considerably less than in resprouters. Shoot starch was highly variable but mean values were similar in both seeder and resprouter species of Erica. Three distinct patterns of starch storage in roots were recognized. All seeder species fell within definitions of Categories 1 (narrow major and minor parenchymatous rays, one to two cells wide with no inter-ray storage) or 2 (thick major rays up to seven cells wide and thin minor rays with small amounts of inter-ray storage) whereas resprouter species were consistently within Categories 2 or 3 (broad major and minor rays, up to eight cells wide and conspicuous inter-ray starch storage). Results are discussed in light of similar studies of the related Epacridaceae. ' Mixed ' species (i.e. with seeder or resprouter individuals present, often in distinct populations) were always classified as belonging to Category 2. Studies of populations of three ' mixed ' species confirmed that seeder forms had consistently lower amounts of root starch than resprouters. Rays of xylem parenchyma were the main sites for starch storage in roots of both seeders and resprouters and greater proportions of cross-sectional area of roots were consistently devoted to such storage tissues in resprouter forms of the three ' mixed ' species. Analyses of a number of seeder and resprouter Erica coccinea populations showed that differences in amounts of realised and potential root starch storage are best explained by the effect of regeneration behaviour rather than by among-population variability.

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“…Plants in ecosystems that are subjected to periodic and severe disturbances tend to store resources in the portion of the plant that will have the most stable environment from which to regenerate (Lacey 1974;James 1984). While any perennial portion of a plant can serve as a C reservoir, belowground tissue most consistently serves as the primary long-term storage organ (James 1984;Loescher et al 1990). Belowground organs are often better suited for storage because they can sustain an array of severe disturbances such as fire and extreme weather.…”

Section: Introductionmentioning

confidence: 99%

Extensive belowground carbon storage supports roots and mycorrhizae in regenerating scrub oaks

2002

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Portions of a regenerating scrub oak ecosystem were enclosed in open-top chambers and exposed to elevated C0 2 . The distinct 13 C signal of the supplemental C0 2 was used to trace the rate of C integration into various ecosystem components. Oak foliage, stems, roots and ectomycorrhizae were sampled over 3 years and were analyzed for 13 C composition. The aboveground tissue 13 C equilibrated to the novel 13 C signal in the first season, while the belowground components displayed extremely slow integration of the new C. Roots taken from ingrowth cores showed that 33% of the C in newly formed roots originated from a source other than recent photosynthesis inside the chamber. In this highly fireprone system, the oaks re-establish primarily by resprouting from large rhizomes, demobilization from belowground C stores may support fine roots and mycorrhizae for several years into stand re-establishment and, therefore, may explain why belowground tissues contain less of the new photosynthate than expected. Though it has been shown that long-term cycles of C storage are theoretically advantageous for plants in systems with frequent and severe disturbances, such patterns have not been previously examined in wild systems.

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Lignotubers and burls— their structure, function and ecological significance in Mediterranean ecosystems

Cited by 195 publications

References 84 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

Underground starch storage in Erica species of the Cape Floristic Region – differences between seeders and resprouters

Extensive belowground carbon storage supports roots and mycorrhizae in regenerating scrub oaks

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