Giant stem rosettes have strong facilitation effects on alpine plant communities in the tropical Andes

ABSTRACT

Background: Giant rosettes constitute one of the most distinctive growth-forms in tropical alpine ecosystems. However, their interactions with other plant species remain unexplored in high Andean páramos.

Aims: Quantify the effect of a dominant rosette (Coespeletia timotensis) on soil and microclimatic conditions and relate the impacts to plant community structure.

Methods: We analysed topsoil temperatures, soil organic matter (SOM) and plant species cover in areas adjacent to C. timotensis and paired areas outside, at three sites (4250–4360 m a.s.l.) in La Culata National Park, Venezuela. Species richness, total vegetation cover and percent cover of each species near and away from the rosettes were compared.

Results: Topsoil temperature amplitudes were lower and SOM greater near C. timotensis stems, compared to areas away from them. C. timotensis had a consistent positive effect on species richness, vegetation cover and the cover of many abundant species (including cushions and herbs).

Conclusions: The facilitation effects of C. timotensis on abiotic conditions and community structure indicate they play a key role as nurse plants, pointing to giant rosettes as foundation species for the maintenance of plant diversity in the alpine tropics.

KEYWORDS:

• Diversity
• ecosystem engineers
• keystone species
• nurse-plants
• plant–plant interactions
• relative interaction index
• soil organic matter
• temperature

Acknowledgements

We thank Fermín Rada, Francisco Pérez, Lynn M. Resler, Laszlo Nagy and two anonymous referees for their excellent comments and suggestions, which greatly improved the manuscript. We also thank Nelson J. Márquez and Luis E. Gámez for their assistance during fieldwork and with the identification of the plant material and J.K. Contreras for the illustration of the sampling design presented in Figure 2.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplementary material for this article can be accessed here.

Additional information

Notes on contributors

María A. Mora

María A. Mora is a M.Sc. student in the Postgrad in Tropical Ecology.

Luis D. Llambí

Luis D. Llambí is an associate professor; he specialises in plant community dynamics and plant–plant interactions in tropical mountain ecosystems.

Lirey Ramírez

Lirey Ramírez is an assistant professor; she specialises in plant community ecology and ecophysiology in tropical mountain ecosystems.