Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
Pyrohydraulic traits: the role of hydraulic segmentation as a hydraulic fuse in resisting fires
Fire is known to kill trees, but the mechanisms underlying plant death and survival remain unclear. The central claim of the hydraulic death hypothesis (HDH) is that xylem embolism may kill plants by preventing tissues that survive fires from remaining hydrated and has been suggested to explain rapi...
Saved in:
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Language: | English |
| Published: |
Department of Biological Sciences
2022
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867613575227375616 |
|---|---|
| access_status_str | Open Access |
| author | Bloy, Shonese Thora |
| author2 | West, Adam G |
| author_browse | Bloy, Shonese Thora West, Adam G |
| author_facet | West, Adam G Bloy, Shonese Thora |
| author_sort | Bloy, Shonese Thora |
| collection | Thesis |
| description | Fire is known to kill trees, but the mechanisms underlying plant death and survival remain unclear. The central claim of the hydraulic death hypothesis (HDH) is that xylem embolism may kill plants by preventing tissues that survive fires from remaining hydrated and has been suggested to explain rapid post-fire mortality. A corollary of the HDH is that it would be beneficial for plants to invest in a suite of traits, ‘pyrohydraulic' traits, that may prevent embolism because this could aid post-fire survival. It was hypothesized that 1) the most distal parts along the branch of a fire-tolerant tree species, Eucalyptus cladocalyx, will act as a hydraulic fuse post-fire, in contrast to a fire sensitive species, Kiggelaria africana, where the hydraulic fuse post-fire would not be exhibited, and 2) the mechanism for this hydraulic fuse was vulnerability segmentation. A xylem conductance experiment post heat-plume (Chapter 2) and a vulnerability experiment (Chapter 3) were conducted on branches from both species. I predicted that 1) embolism would be localized to the distal parts of a branch for E. cladocalyx but not K. africana 2) non-suberized tissue of the distal tissue parts of E. cladocalyx branches will be more vulnerable to embolism than the suberized tissue, but K. africana would not exhibit this differentiation. Results indicate that embolism was localized to the most distal parts of a branch in E. cladocalyx, as well as that the non-suberized tissue was more vulnerable to embolism. E. cladocalyx suffered a 19% loss of conductance, while K. africana suffered a much greater 68% loss of conductance after heating. The P50 values of the non-suberized and suberized tissue sections were statistically similar in both species, but the P12 values differed between the sections for E. cladocalyx. E. cladocalyx was shown to be more vulnerable to embolism than K. africana. These results indicate that developing tissue of E. cladocalyx is more vulnerable to heat-plume induced embolism than developed stem tissue, consistent with the hypothesis that vulnerability segmentation is a pyrohydraulic trait. Therefore, the most distal parts of a E. cladocalyx branch acts as a hydraulic fuse and contributes to post-fire recovery. The phenomenon may be used by other fire-tolerant species as a strategy to survive post-fire, thereby enabling them to endure a fire and recover through protecting their hydraulic continuum. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/35640 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:38:19.666Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2022 |
| publishDateRange | 2022 |
| publishDateSort | 2022 |
| publisher | Department of Biological Sciences |
| publisherStr | Department of Biological Sciences |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/35640 Pyrohydraulic traits: the role of hydraulic segmentation as a hydraulic fuse in resisting fires Bloy, Shonese Thora West, Adam G Midgley, Jeremy J Skelton, Robert P Biological Sciences Fire is known to kill trees, but the mechanisms underlying plant death and survival remain unclear. The central claim of the hydraulic death hypothesis (HDH) is that xylem embolism may kill plants by preventing tissues that survive fires from remaining hydrated and has been suggested to explain rapid post-fire mortality. A corollary of the HDH is that it would be beneficial for plants to invest in a suite of traits, ‘pyrohydraulic' traits, that may prevent embolism because this could aid post-fire survival. It was hypothesized that 1) the most distal parts along the branch of a fire-tolerant tree species, Eucalyptus cladocalyx, will act as a hydraulic fuse post-fire, in contrast to a fire sensitive species, Kiggelaria africana, where the hydraulic fuse post-fire would not be exhibited, and 2) the mechanism for this hydraulic fuse was vulnerability segmentation. A xylem conductance experiment post heat-plume (Chapter 2) and a vulnerability experiment (Chapter 3) were conducted on branches from both species. I predicted that 1) embolism would be localized to the distal parts of a branch for E. cladocalyx but not K. africana 2) non-suberized tissue of the distal tissue parts of E. cladocalyx branches will be more vulnerable to embolism than the suberized tissue, but K. africana would not exhibit this differentiation. Results indicate that embolism was localized to the most distal parts of a branch in E. cladocalyx, as well as that the non-suberized tissue was more vulnerable to embolism. E. cladocalyx suffered a 19% loss of conductance, while K. africana suffered a much greater 68% loss of conductance after heating. The P50 values of the non-suberized and suberized tissue sections were statistically similar in both species, but the P12 values differed between the sections for E. cladocalyx. E. cladocalyx was shown to be more vulnerable to embolism than K. africana. These results indicate that developing tissue of E. cladocalyx is more vulnerable to heat-plume induced embolism than developed stem tissue, consistent with the hypothesis that vulnerability segmentation is a pyrohydraulic trait. Therefore, the most distal parts of a E. cladocalyx branch acts as a hydraulic fuse and contributes to post-fire recovery. The phenomenon may be used by other fire-tolerant species as a strategy to survive post-fire, thereby enabling them to endure a fire and recover through protecting their hydraulic continuum. 2022-02-03T10:21:02Z 2022-02-03T10:21:02Z 2021 2022-02-03T09:46:15Z Master Thesis Masters MSc http://hdl.handle.net/11427/35640 eng application/pdf Department of Biological Sciences Faculty of Science |
| spellingShingle | Biological Sciences Bloy, Shonese Thora Pyrohydraulic traits: the role of hydraulic segmentation as a hydraulic fuse in resisting fires |
| thesis_degree_str | Master's |
| title | Pyrohydraulic traits: the role of hydraulic segmentation as a hydraulic fuse in resisting fires |
| title_full | Pyrohydraulic traits: the role of hydraulic segmentation as a hydraulic fuse in resisting fires |
| title_fullStr | Pyrohydraulic traits: the role of hydraulic segmentation as a hydraulic fuse in resisting fires |
| title_full_unstemmed | Pyrohydraulic traits: the role of hydraulic segmentation as a hydraulic fuse in resisting fires |
| title_short | Pyrohydraulic traits: the role of hydraulic segmentation as a hydraulic fuse in resisting fires |
| title_sort | pyrohydraulic traits the role of hydraulic segmentation as a hydraulic fuse in resisting fires |
| topic | Biological Sciences |
| url | http://hdl.handle.net/11427/35640 |
| work_keys_str_mv | AT bloyshonesethora pyrohydraulictraitstheroleofhydraulicsegmentationasahydraulicfuseinresistingfires |