Testing the importance of a common ectomycorrhizal network for dipterocarp seedling growth and survival in tropical forests of Borneo

Abstract

Background: Connections between mature trees and seedlings via ectomycorrhizal (EcM) hyphal networks existing in dipterocarp-dominated tropical rain forests of South-east Asia could have strong implications for seedling growth and survival and the maintenance of high diversity in such forests.

Aim: To test whether EcM hyphal network connections are important for the growth and survival of dipterocarp seedlings.

Methods: We conducted four independent experiments that prevented contact of experimental seedlings with an EcM network by using a series of fine meshes and/or plastic barriers. We measured the growth and survival (and foliar δ¹³C in one experiment) of seedlings of six dipterocarp species over intervals ranging from 11 to 29 months.

Results: Seedling growth (diameter, height or leaf number) was unaffected by exclusion from the EcM network in three experiments and there were no differences in foliar δ¹³C values in the fourth. Seedling survival was reduced following exclusion from the EcM network in one experiment. Our results give little support to the hypothesis that dipterocarp seedlings growing in the shaded forest understorey benefit from being connected, through a common EcM network, to surrounding trees.

Conclusions: We suggest that our negative results, in contrast to studies conducted in low diversity boreo-temperate or tropical forests, are due to these high diversity forests lacking host species-specific EcM fungi and therefore providing little opportunity for adaptive support of seedlings via hyphal networks.

Keywords:

• Borneo
• dipterocarps
• ectomycorrhizas
• mycorrhizal networks
• source-sink relationships

Acknowledgements

For assistance with experimental design, fieldwork and comments on earlier versions of the manuscript, we thank Udin bin Ladin and the Malua field station team, Adzimi Madran, Adzley Madran, Justin Tabai, Dainold Yudat, Daulin Yudat, Rineson Yudat, Karin Saner, Ian Alexander, Yann Hautier, Jan Jansa, Lee Su See, Robert Ong, Malcolm Press and Glen Reynolds. This research is manuscript no. 15 of the Sabah Biodiversity Experiment and part of the Royal Society South-East Asia Rainforest Research Programme (Project No. RS243). All experiments complied with the laws of the country they were conducted in (Malaysia) at the time of the studies.

This project was financially supported through the British Ecological Society, the Ishizaka Foundation, the Darwin Initiative (United Kingdom Department for Environment, Food and Rural Affairs) and the University of Zürich.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental data

Supplemental data for this article can be accessed here.

Additional information

Funding

This project was financially supported through the British Ecological Society, the Ishizaka Foundation, the Darwin Initiative (United Kingdom Department for Environment, Food and Rural Affairs) and the University of Zürich.

Notes on contributors

Francis Q. Brearley

Francis Q. Brearley is an ecologist interested in the functional importance of plant–soil interactions for ecological processes in tropical forests.

Philippe Saner

Philippe Saner is an environmental scientist with a main interest in tropical plant community ecology and the restoration of tropical forests.

Ayuho Uchida

Ayuho Uchida was a Ph.D. student examining the importance of root competition and ectomycorrhizal fungi for dipterocarp seedling growth.

David F. R. P. Burslem

David F.R.P. Burslem is interested in the community and ecosystem ecology of tropical forests with a particular focus on the maintenance of species diversity and the conservation of tropical forests.

Andy Hector

Andy Hector is a community ecologist interested in biodiversity loss and its consequences for the stability and functioning of ecosystems and the provision of ecological services.

Reuben Nilus

Reuben Nilus is an ecologist working on the diversity, distribution and conservation of the forests of Sabah.

Julie D. Scholes

Julie D. Scholes is a physiologist/molecular biologist interested in the role of pathogens and mycorrhizas in the maintenance of dipterocarp diversity in tropical forests.

Simon Egli

Simon Egli has a main interest in mycorrhizal fungi and how they support the resistance and resilience of forest ecosystems in a changing environment.