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Experimental climate warming enforces seed dormancy in South African Proteaceae but seedling drought resilience exceeds summer drought periods

  • Physiological ecology - Original research
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Abstract

Two hypotheses—that elevated night-time temperatures due to climate warming would enforce post-fire dormancy of Proteaceae seed due to low moisture, and that periods without rain during summer would exceed desiccation periods tolerated by Proteaceae seedlings—were tested empirically. Enforced dormancy, i.e., the inability to germinate due to an environmental restraint, was tested by measuring seed germination in 11 Proteaceae species in experimental mesocosms whose soils were artificially elevated by 1.4 and 3.5 °C above ambient by far-red wavelength filtered infrared lamps. Diminished totality of germination and velocities were observed in 91 and 64 %, respectively, of the Proteaceae species tested. Drought resilience was tested in one-year-old seedlings of 16 Proteaceae species by withholding water from potted plants during summer in a greenhouse. The most drought-resilient Proteaceae species displayed the lowest initial transpiration rates at field capacity, the smallest declines in transpiration rate with decreasing soil water content, and the lowest water losses by transpiration. Projected drought periods leading to the complete cessation of transpiration in all Proteaceae species greatly exceeded the number of days without rain per month during summer in the current distribution ranges of those species. It was therefore concluded that enforced seed dormancy induced by elevated night-time temperatures is the post-fire recruitment stage of Proteaceae that is most sensitive to climate warming.

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Acknowledgments

We wish to sincerely thank Mr. L. Powrie for extracting Proteaceae species distributions and environmental records from various databases, and Mr. S. Snyders for assisting with the construction of experimental warming mesocosms and technical support.

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Authors and Affiliations

  1. Climate Change and Bio-Adaptation Division, South African National Biodiversity Institute, Private Bag X7, Claremont, Cape Town, 7735, South Africa

    Judith L. Arnolds & Charles F. Musil

  2. Applied Biodiversity Research Division, South African National Biodiversity Institute, Private Bag X7, Claremont, Cape Town, 7735, South Africa

    Anthony G. Rebelo

  3. Section Botany, School of Environmental Sciences and Development, North-West University, Potchefstroom, 2520, South Africa

    Gert H. J. Krüger

Authors
  1. Judith L. Arnolds
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  2. Charles F. Musil
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  3. Anthony G. Rebelo
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  4. Gert H. J. Krüger
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Correspondence to Judith L. Arnolds.

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Communicated by Allan T. G. Green.

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Arnolds, J.L., Musil, C.F., Rebelo, A.G. et al. Experimental climate warming enforces seed dormancy in South African Proteaceae but seedling drought resilience exceeds summer drought periods. Oecologia 177, 1103–1116 (2015). https://doi.org/10.1007/s00442-014-3173-6

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