Blow me down: A new perspective on Aloe dichotoma mortality from windthrow

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dc.contributor.authorJack, Samuel L
dc.contributor.authorHoffman, Michael T
dc.contributor.authorRohde, Rick F
dc.contributor.authorDurbach, Ian
dc.contributor.authorArchibald, Margaret
dc.date.accessioned2015-01-19T13:24:27Z
dc.date.available2015-01-19T13:24:27Z
dc.date.issued2014-03-18
dc.date.updated2015-01-15T17:52:51Z
dc.description.abstractBackground: Windthrow, the uprooting of trees during storms associated with strong winds, is a well-established cause of mortality in temperate regions of the world, often with large ecological consequences. However, this phenomenon has received little attention within arid regions and is not well documented in southern Africa. Slow rates of post-disturbance recovery and projected increases in extreme weather events in arid areas mean that windthrow could be more common and have bigger impacts on these ecosystems in the future. This is of concern due to slow rates of post-disturbance recovery in arid systems and projected increases in extreme weather events in these areas. This study investigated the spatial pattern, magnitude and likely causes of windthrown mortality in relation to other forms of mortality in Aloe dichotoma, an iconic arid-adapted arborescent succulent and southern Africa climate change indicator species. Results: We found that windthrown mortality was greatest within the equatorward summer rainfall zone (SRZ) of its distribution (mean = 31%, n = 11), and was derived almost exclusively from the larger adult age class. A logistic modelling exercise indicated that windthrown mortality was strongly associated with greater amounts of warm season (summer) rainfall in the SRZ, higher wind speeds, and leptosols. A statistically significant interaction term between higher summer rainfall and wind speeds further increased the odds of being windthrown. While these results would benefit from improvements in the resolution of wind and substrate data, they do support the hypothesised mechanism for windthrow in A. dichotoma. This involves powerful storm gusts associated with either the current or subsequent rainfall event, heavy convective rainfall, and an associated increase in soil malleability. Shallow rooting depths in gravel-rich soils and an inflexible, top-heavy canopy structure make individuals especially prone to windthrown mortality during storms. Conclusions: Results highlight the importance of this previously unrecognised form of mortality in A. dichotoma, especially since it seems to disproportionately affect reproductively mature adult individuals in an infrequently recruiting species. Smaller, more geographically isolated and adult dominated populations in the summer rainfall zone are likely to be more vulnerable to localised extinction due to windthrow events.en_ZA
dc.identifier.apacitationJack, S. L., Hoffman, M. T., Rohde, R. F., Durbach, I., & Archibald, M. (2014). Blow me down: A new perspective on Aloe dichotoma mortality from windthrow. <i>BMC Ecology</i>, http://hdl.handle.net/11427/12268en_ZA
dc.identifier.chicagocitationJack, Samuel L, Michael T Hoffman, Rick F Rohde, Ian Durbach, and Margaret Archibald "Blow me down: A new perspective on Aloe dichotoma mortality from windthrow." <i>BMC Ecology</i> (2014) http://hdl.handle.net/11427/12268en_ZA
dc.identifier.citationJack et al.: Blow me down: A new perspective on Aloe dichotoma mortality from windthrow. BMC Ecology 2014 14:7.en_ZA
dc.identifier.issn1472-6785en_ZA
dc.identifier.ris TY - Journal Article AU - Jack, Samuel L AU - Hoffman, Michael T AU - Rohde, Rick F AU - Durbach, Ian AU - Archibald, Margaret AB - Background: Windthrow, the uprooting of trees during storms associated with strong winds, is a well-established cause of mortality in temperate regions of the world, often with large ecological consequences. However, this phenomenon has received little attention within arid regions and is not well documented in southern Africa. Slow rates of post-disturbance recovery and projected increases in extreme weather events in arid areas mean that windthrow could be more common and have bigger impacts on these ecosystems in the future. This is of concern due to slow rates of post-disturbance recovery in arid systems and projected increases in extreme weather events in these areas. This study investigated the spatial pattern, magnitude and likely causes of windthrown mortality in relation to other forms of mortality in Aloe dichotoma, an iconic arid-adapted arborescent succulent and southern Africa climate change indicator species. Results: We found that windthrown mortality was greatest within the equatorward summer rainfall zone (SRZ) of its distribution (mean = 31%, n = 11), and was derived almost exclusively from the larger adult age class. A logistic modelling exercise indicated that windthrown mortality was strongly associated with greater amounts of warm season (summer) rainfall in the SRZ, higher wind speeds, and leptosols. A statistically significant interaction term between higher summer rainfall and wind speeds further increased the odds of being windthrown. While these results would benefit from improvements in the resolution of wind and substrate data, they do support the hypothesised mechanism for windthrow in A. dichotoma. This involves powerful storm gusts associated with either the current or subsequent rainfall event, heavy convective rainfall, and an associated increase in soil malleability. Shallow rooting depths in gravel-rich soils and an inflexible, top-heavy canopy structure make individuals especially prone to windthrown mortality during storms. Conclusions: Results highlight the importance of this previously unrecognised form of mortality in A. dichotoma, especially since it seems to disproportionately affect reproductively mature adult individuals in an infrequently recruiting species. Smaller, more geographically isolated and adult dominated populations in the summer rainfall zone are likely to be more vulnerable to localised extinction due to windthrow events. DA - 2014-03-18 DB - OpenUCT DO - 10.1186/1472-6785-14-7 DP - University of Cape Town J1 - BMC Ecology LK - https://open.uct.ac.za PB - University of Cape Town PY - 2014 SM - 1472-6785 T1 - Blow me down: A new perspective on Aloe dichotoma mortality from windthrow TI - Blow me down: A new perspective on Aloe dichotoma mortality from windthrow UR - http://hdl.handle.net/11427/12268 ER - en_ZA
dc.identifier.urihttp://dx.doi.org/10.1186/1472-6785-14-7
dc.identifier.urihttp://hdl.handle.net/11427/12268
dc.identifier.urihttp://hdl.handle.net/11427/12268
dc.identifier.urihttp://dx.doi.org/10.1186/1472-6785-14-7
dc.identifier.vancouvercitationJack SL, Hoffman MT, Rohde RF, Durbach I, Archibald M. Blow me down: A new perspective on Aloe dichotoma mortality from windthrow. BMC Ecology. 2014; http://hdl.handle.net/11427/12268.en_ZA
dc.languageengen_ZA
dc.language.rfc3066en
dc.publisherBioMed Centralen_ZA
dc.publisher.departmentPlant Conservation Unit (PCU)en_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.rightsCreative Commons Attribution 4.0 International (CC BY 4.0)*
dc.rights.holderJack et al.; licensee BioMed Central Ltd.
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en_ZA
dc.sourceBMC Ecologyen_ZA
dc.source.urihttp://www.biomedcentral.com/1472-6785
dc.titleBlow me down: A new perspective on Aloe dichotoma mortality from windthrowen_ZA
dc.typeJournal Articleen_ZA
uct.type.filetype
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceArticleen_ZA
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