Collapse of an iconic conifer: long-term changes in the demography of Widdringtonia cedarbergensis using repeat photography

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dc.contributor.authorWhite, J D M
dc.contributor.authorJack, S L
dc.contributor.authorHoffman, M T
dc.contributor.authorPuttick, J
dc.contributor.authorBonora, D
dc.contributor.authorVisser, V
dc.contributor.authorFebruary, E C
dc.date.accessioned2021-10-08T06:20:19Z
dc.date.available2021-10-08T06:20:19Z
dc.date.issued2016
dc.description.abstractBACKGROUND: Conifer populations appear disproportionately threatened by global change. Most examples are, however, drawn from the northern hemisphere and long-term rates of population decline are not well documented as historical data are often lacking. We use a large and long-term (1931-2013) repeat photography dataset together with environmental data and fire records to account for the decline of the critically endangered Widdringtonia cedarbergensis. Eighty-seven historical and repeat photo-pairs were analysed to establish 20th century changes in W. cedarbergensis demography. A generalized linear mixed-effects model was fitted to determine the relative importance of environmental factors and fire-return interval on mortality for the species. RESULTS: From an initial total of 1313 live trees in historical photographs, 74% had died and only 44 (3.4%) had recruited in the repeat photographs, leaving 387 live individuals. Juveniles (mature adults) had decreased (increased) from 27% (73%) to 8% (92%) over the intervening period. Our model demonstrates that mortality is related to greater fire frequency, higher temperatures, lower elevations, less rocky habitats and aspect (i.e. east-facing slopes had the least mortality). CONCLUSIONS: Our results show that W. cedarbergensis populations have declined significantly over the recorded period, with a pronounced decline in the last 30 years. Individuals that established in open habitats at lower, hotter elevations and experienced a greater fire frequency appear to be more vulnerable to mortality than individuals growing within protected, rocky environments at higher, cooler locations with less frequent fires. Climate models predict increasing temperatures for our study area (and likely increases in wildfires). If these predictions are realised, further declines in the species can be expected. Urgent management interventions, including seedling out-planting in fire-protected high elevation sites, reducing fire frequency in higher elevation populations, and assisted migration, should be considered.
dc.identifier.apacitationWhite, J. D. M., Jack, S. L., Hoffman, M. T., Puttick, J., Bonora, D., Visser, V., & February, E. C. (2016). Collapse of an iconic conifer: long-term changes in the demography of Widdringtonia cedarbergensis using repeat photography. <i>BMC Ecology</i>, 16(1), 174 - 177. http://hdl.handle.net/11427/34249en_ZA
dc.identifier.chicagocitationWhite, J D M, S L Jack, M T Hoffman, J Puttick, D Bonora, V Visser, and E C February "Collapse of an iconic conifer: long-term changes in the demography of Widdringtonia cedarbergensis using repeat photography." <i>BMC Ecology</i> 16, 1. (2016): 174 - 177. http://hdl.handle.net/11427/34249en_ZA
dc.identifier.citationWhite, J.D.M., Jack, S.L., Hoffman, M.T., Puttick, J., Bonora, D., Visser, V. & February, E.C. 2016. Collapse of an iconic conifer: long-term changes in the demography of Widdringtonia cedarbergensis using repeat photography. <i>BMC Ecology.</i> 16(1):174 - 177. http://hdl.handle.net/11427/34249en_ZA
dc.identifier.issn1472-6785
dc.identifier.ris TY - Journal Article AU - White, J D M AU - Jack, S L AU - Hoffman, M T AU - Puttick, J AU - Bonora, D AU - Visser, V AU - February, E C AB - BACKGROUND: Conifer populations appear disproportionately threatened by global change. Most examples are, however, drawn from the northern hemisphere and long-term rates of population decline are not well documented as historical data are often lacking. We use a large and long-term (1931-2013) repeat photography dataset together with environmental data and fire records to account for the decline of the critically endangered Widdringtonia cedarbergensis. Eighty-seven historical and repeat photo-pairs were analysed to establish 20th century changes in W. cedarbergensis demography. A generalized linear mixed-effects model was fitted to determine the relative importance of environmental factors and fire-return interval on mortality for the species. RESULTS: From an initial total of 1313 live trees in historical photographs, 74% had died and only 44 (3.4%) had recruited in the repeat photographs, leaving 387 live individuals. Juveniles (mature adults) had decreased (increased) from 27% (73%) to 8% (92%) over the intervening period. Our model demonstrates that mortality is related to greater fire frequency, higher temperatures, lower elevations, less rocky habitats and aspect (i.e. east-facing slopes had the least mortality). CONCLUSIONS: Our results show that W. cedarbergensis populations have declined significantly over the recorded period, with a pronounced decline in the last 30 years. Individuals that established in open habitats at lower, hotter elevations and experienced a greater fire frequency appear to be more vulnerable to mortality than individuals growing within protected, rocky environments at higher, cooler locations with less frequent fires. Climate models predict increasing temperatures for our study area (and likely increases in wildfires). If these predictions are realised, further declines in the species can be expected. Urgent management interventions, including seedling out-planting in fire-protected high elevation sites, reducing fire frequency in higher elevation populations, and assisted migration, should be considered. DA - 2016 DB - OpenUCT DP - University of Cape Town IS - 1 J1 - BMC Ecology LK - https://open.uct.ac.za PY - 2016 SM - 1472-6785 T1 - Collapse of an iconic conifer: long-term changes in the demography of Widdringtonia cedarbergensis using repeat photography TI - Collapse of an iconic conifer: long-term changes in the demography of Widdringtonia cedarbergensis using repeat photography UR - http://hdl.handle.net/11427/34249 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/34249
dc.identifier.vancouvercitationWhite JDM, Jack SL, Hoffman MT, Puttick J, Bonora D, Visser V, et al. Collapse of an iconic conifer: long-term changes in the demography of Widdringtonia cedarbergensis using repeat photography. BMC Ecology. 2016;16(1):174 - 177. http://hdl.handle.net/11427/34249.en_ZA
dc.language.isoeng
dc.publisher.departmentDepartment of Biological Sciences
dc.publisher.facultyFaculty of Science
dc.sourceBMC Ecology
dc.source.journalissue1
dc.source.journalvolume16
dc.source.pagination174 - 177
dc.source.urihttps://dx.doi.org/10.1186/s12898-016-0108-6
dc.subject.otherEcology
dc.subject.otherLife Sciences
dc.subject.othergeneral
dc.subject.otheraltitude
dc.subject.otherfire frequency
dc.subject.otherhabitats
dc.subject.otherrecords
dc.subject.otheradults
dc.subject.otherwildfires
dc.subject.otherdata collection
dc.subject.otherclimate models
dc.subject.othertrees
dc.subject.otherpopulation dynamics
dc.subject.otherjuveniles
dc.subject.otherconifers
dc.subject.otherphotographs
dc.subject.otherdemography
dc.subject.otherglobal change
dc.subject.otherprediction
dc.subject.othertemperature
dc.subject.othermortality
dc.subject.otherseedlings
dc.subject.otherphotography
dc.titleCollapse of an iconic conifer: long-term changes in the demography of Widdringtonia cedarbergensis using repeat photography
dc.typeJournal Article
uct.type.publicationResearch
uct.type.resourceJournal Article
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