Effects of heat on dehiscence and germination in Eucalyptus globulus Labill.
Joaquim S. Silva A B D , Patrícia dos Santos A C , André Sério B and Filomena Gomes B
+ Author Affiliations
- Author Affiliations
A University of Lisbon, Institute of Agronomy, Centre for Applied Ecology ‘Prof. Baeta Neves’, InBIO, 1349-017 Lisbon, Portugal.
B Polytechnic Institute of Coimbra, School of Agriculture, 3045-601 Coimbra, Portugal.
C University of Lisbon, Faculty of Science, Centre for Ecology, Evolution and Environmental Changes, Campo Grande, 1749-016 Lisbon, Portugal.
D Corresponding author. Email: jss@esac.pt
International Journal of Wildland Fire 25(4) 478-483 https://doi.org/10.1071/WF15078
Submitted: 1 January 2015 Accepted: 17 December 2015 Published: 10 March 2016
Abstract
Fire is a facilitating factor in the naturalisation of Eucalyptus globulus in countries where it has been introduced. In this study, we investigate the effect of heat on dehiscence and germination of free and encapsulated seeds. Twelve combinations of temperature (80, 150, 200°C) and heating exposure time (30, 60, 120, 300 s) were used and a corresponding heat index (H) was computed. Dehiscence was registered on a daily basis and germinability of encapsulated and free seeds was verified through germination tests. Results indicate that dehiscence was strongly dependent on individual trees, but no significant differences were found between the treatments applied, suggesting a direct effect of capsule desiccation rather than heat on seed shed. The percentage of germinated seeds was negatively influenced by the highest temperature and exposure times. The effect of capsule protection on seed germination was positive for 200°C at 60 and 150 s (H = 139 and 220 respectively), but negative at 150°C for 300 s (H = 269). No seeds germinated after treatment at 200°C for 300 s (H = 358). Given the estimated range of temperatures and residence times during wildfires in eucalypt plantations, our results help to explain the high levels of seedling recruitment observed in burned stands.
Additional keywords: capsules, eucalypts, seed shed, seed survival, wildfire.
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