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Oecologia

, Volume 148, Issue 4, pp 555–563 | Cite as

Competition for pulsed resources: an experimental study of establishment and coexistence for an arid-land grass

  • Mohammad Jankju-BorzelabadEmail author
  • Howard Griffiths
Ecophysiology

Abstract

In arid environments, episodically-pulsed resources are important components of annual water and nutrient supply for plants. This study set out to test whether seedlings have an increased capacity for using pulsed resources, which might then improve establishment when in competition with older individuals. A second aim was to determine whether there is a trade-off in competitive strategies when resources are supplied continuously at low concentrations, or as pulses with pronounced inter-pulse periods. A glasshouse experiment used a target-neighbour design of size-asymmetric competition, with juveniles of Panicum antidotale (blue panicgrass) introduced into contrasting densities of adult plants. Stable isotopes of nitrogen were used for measuring plant resource uptake from pulses, and tolerance to inter-pulse conditions was assessed as the mean residence time (MRT) of nitrogen. A higher root/shoot ratio and finer root system enhanced the capacity of juveniles to use resources when pulsed, rather than when continuously supplied. Higher resource uptake during pulses improved the establishment of juvenile Panicum in mixed cultures with older individuals. However, a trade-off was observed in plant strategies, with juveniles showing a lower MRT for nitrogen, which suggested reduced tolerance to resource deficit during inter-pulse periods. Under field conditions, higher utilization of pulsed resources would lead to the improved seedling establishment of Panicum adjacent to “nurse” plants, whereas mature plants with well-developed roots, exploiting a greater soil volume, maintain more constant resource uptake and retention during inter-pulse periods.

Keywords

Facilitation Nitrogen Panicum antidotale Size-asymmetry Stable isotopes 

Notes

Acknowledgements

We wish to thank all colleagues in Physiological Ecology Laboratory, Cambridge University, and Department of Range and Watershed Management, Yazd University, as well as reviewers, for their supportive views. Dr Charlie Scrimgeour, SCRI Dundee, undertook the stable isotope analyses. The research was supported by a grant awarded by Yazd University Iran, and the ORSAS, UK to M. Jankju-Borzelabad.

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Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  1. 1.Faculty of Natural ResourcesYazd UniversityYazdIran
  2. 2.Department of Plant SciencesUniversity of CambridgeCambridgeUK

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