Post-fire clumping of seedlings of Cape Proteaceae species: ecological, evolutionary and conservation implications

J. J. Midgley; M. D. Cramer; A. L. Schutte-Vlok; A. Veldtman

doi:10.1071/WF24074

RESEARCH ARTICLE (Open Access)

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Post-fire clumping of seedlings of Cape Proteaceae species: ecological, evolutionary and conservation implications

J. J. Midgley ^A ^* , M. D. Cramer ^A , A. L. Schutte-Vlok ^B ^D and A. Veldtman ^C

+ Author Affiliations

- Author Affiliations

^A Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch, 7701, South Africa.

^B Department of Botany and Plant Biotechnology, University of Johannesburg, PO Box 524, Auckland Park, Johannesburg, 2006, South Africa.

^C Cape Nature, Private Bag x5014, Stellenbosch, 7599, South Africa.

^D Present address: Cape Nature, Private Bag X658, Oudtshoorn, 6620, South Africa.

^* Correspondence to: Jeremy.Midgley@uct.ac.za

International Journal of Wildland Fire 33, WF24074 https://doi.org/10.1071/WF24074

Submitted: 28 April 2024 Accepted: 25 September 2024 Published: 17 October 2024

© 2024 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of IAWF. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

Background

Spatial clumping of plants results in intense competition.

Aims

We analysed the extent of clumping of Proteaceae seedlings across the Cape Floristic Region after fire.

Methods

To demonstrate the extent of clumping in 23 species, we analysed the seedling and adult densities in 290 post-fire surveys each of 100 × 1 m² plots using standard indices of clumping.

Key results

We detected clumping of Cape Proteaceae seedlings, whereas parent plants were less clumped. The clumping is not due to limited safe sites for seedlings because the number of plots at a site with at least one seedling was positively related to the number of seedlings at the site. Sites with seedlings were enriched in nutrients relative to those without.

Conclusions

The possible benefits of clumping are saturation of granivores and co-location of buried seeds with nutrient-rich patches of fire-derived ash and debris. A cause of clumping is seeds sticking together. Clumping, which is strongly intraspecific, has implications for trait evolution and the dominance of reseeders over resprouters. Strong clumping reduces the usefulness of the widely used seedling:parent index to determine whether fires were favourable or not.

Implications

Clumping has implications for understanding seed dispersal distances, seedling versus adult traits, fire responses and demography.

Keywords: Leucadendron, Protea, seedling clumping, seed dispersal, seedlings, self-thinning, serotiny, South Africa.

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