, Volume 172, Issue 4, pp 937–947 | Cite as

It is risky out there: the costs of emergence and the benefits of prolonged dormancy

  • Jennifer R. Gremer
  • Anna Sala
Physiological ecology - Original research


Prolonged dormancy is a stage in herbaceous perennial plants in which some individuals remain alive below ground for one or more growing seasons instead of emerging. Prolonged dormancy is puzzling, because foregoing opportunities for growth and reproduction seems costly. However, studies have shown that it buffers plants from the negative consequences associated with environmental stochasticity, suggesting that dormancy is a beneficial strategy to avoid the risks of stress above ground. If so, emergence during unfavorable conditions should have significant costs. Here, we test the hypothesis that emergence during times of stress has negative demographic consequences in a native perennial forb, Astragalus scaphoides, and investigate the potential underlying physiological mechanisms. We measured plant responses to a severe seasonal drought and an experimental defoliation to ask: (1) How do emergent plants respond to above-ground stress? (2) Do these responses have negative demographic consequences? and (3) Based on these responses, does stress increase the risk of emergence? Plants showed remarkable physiological tolerance to stress in the short term: high temperatures and low moisture did not have a strong effect on photosynthesis rates, and neither drought nor defoliation significantly impacted stored resources. However, stress did result in demographic costs for emergent plants relative to plants experiencing more favorable conditions. Drought resulted in decreased flowering probabilities relative to the long-term average and defoliation significantly increased mortality rates. These results demonstrate that the risk of emerging and experiencing stress entails considerable costs, supporting the hypothesis that prolonged dormancy is a beneficial strategy to avoid such risk.


Prolonged dormancy Astragalus scaphoides Defoliation Drought Resource allocation 



The authors would like to thank E. E. Crone for valuable discussion and advice on this project. L. Fishman, T. DeLuca, R. Callaway, Rob Salguero-Gómez, and an anonymous reviewer provided valuable comments. We would also like to thank all of those that participated in data collection for the long term monitoring of A. scaphoides, particularly P. Lesica, as well as N. Deyo and J. L. Williams for field assistance. Funding was provided by a National Science Foundation grant to E. E. Crone and A. Sala (NSF DEB 05-15756) and the University of Montana (J. Schmautz scholarship to J. Gremer).

Supplementary material

442_2012_2557_MOESM1_ESM.pdf (168 kb)
Supplementary material 1 (PDF 168 kb)


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Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  1. 1.Division of Biological SciencesUniversity of MontanaMissoulaUSA
  2. 2.Department of Ecology and Evolutionary BiologyUniversity of ArizonaTucsonUSA

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