Some like it hot: Seed thermal threshold variation in obligate seeding Acacia pulchella along a climate gradient.

Autor: Overton J; Centre for Ecosystem Science, School of Biological Earth and Environmental Sciences, University of New South Wales, Kensington, NSW, Australia; Kings Park Science, Biodiversity and Conservation Science, Department of Biodiversity, Conservation, and Attractions, Kings Park, WA, Australia. Electronic address: jess.overton@dbca.wa.gov.au., Ooi MKJ; Centre for Ecosystem Science, School of Biological Earth and Environmental Sciences, University of New South Wales, Kensington, NSW, Australia., Tangney R; Centre for Ecosystem Science, School of Biological Earth and Environmental Sciences, University of New South Wales, Kensington, NSW, Australia; Kings Park Science, Biodiversity and Conservation Science, Department of Biodiversity, Conservation, and Attractions, Kings Park, WA, Australia.
Jazyk: angličtina
Zdroj: The Science of the total environment [Sci Total Environ] 2024 Oct 20; Vol. 948, pp. 174929. Date of Electronic Publication: 2024 Jul 20.
DOI: 10.1016/j.scitotenv.2024.174929
Abstrakt: Dormancy in seeds is a key persistence mechanism for many flowering plants. Physically dormant (PY) seeds have water impermeable seed coats, and in fire-prone systems a common mechanism for dormancy release is fire-induced soil heating. However, the thermal thresholds innate to seeds with PY may be influenced by vegetation, climate, and fire regimes, varying substantially between populations of the same species. To investigate intraspecific variation of thermal thresholds in PY seeds, we sampled obligate seeding Acacia pulchella (Fabaceae) which produces PY seeds. Sampling was undertaken from 13 populations across a climate gradient of rainfall and temperature, and between two vegetation communities in fire-prone Mediterranean-type ecosystems of south-west Western Australia. To test a range of weather and fire-induced soil heating dormancy-break scenarios, we conducted dry heat shock experiments between 40 and 140 °C for 10 min and scored germination for 16 weeks. We created population-specific thermal performance curves and extracted the dormancy release temperature at which 50 % of the seeds had germinated (DRT 50 ), the optimum dormancy-breaking temperature to stimulate maximum germination (T 0 ), and the lethal temperature at which 50 % of the seeds were killed (LT 50 ). Generalised linear models were used to examine relationships between thermal thresholds and possible vegetation, climate, and fire regime drivers of intraspecific variation in seed traits. We found that thermal thresholds differed between vegetation communities, with thresholds consistently higher in forest-type ecosystems compared to open woodland, and the influence of climate varied significantly between the two communities. Seeds from Jarrah Forest populations had a DRT 50 16.0 °C higher, a T 0 9.7 °C higher, and LT 50 7.8 °C higher than seeds from Banksia woodlands. A high rate of non-dormancy was identified in one population that had lost fire in its system and displayed significant germination after both summer and fire-related temperatures. The PY thermal thresholds modelled here provide insight into the strong influence of variable soil heating as a function of vegetation and fuel dynamics in fire-prone environments. Our findings highlight the significant intraspecific variation for this species and suggest that fire-induced soil heating generated by vegetation characteristics may be an overlooked element of fire regimes shaping seed traits.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2024 Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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