, Volume 172, Issue 3, pp 751–766 | Cite as

Thresholds in plant–herbivore interactions: predicting plant mortality due to herbivore browse damage

  • E. Penelope HollandEmail author
  • Roger P. Pech
  • Wendy A. Ruscoe
  • John P. Parkes
  • Graham Nugent
  • Richard P. Duncan
Plant-animal interactions - Original research


Patterns of herbivore browse at small scales, such as the rate of leaf consumption or plant preferences, drive the impact of herbivores on whole-plant processes, such as growth or survival, and subsequent changes in plant population structure. However, herbivore impacts are often non-linear, highly variable and context-dependent. Understanding the effect of herbivores on plant populations therefore requires a detailed understanding of the relationships that drive small-scale processes, and how these interact to generate dynamics at larger scales. We derive a mathematical model to predict annual rates of browse-induced tree mortality. We model individual plant mortality as a result of rates of foliage production, turnover and herbivore intake, and extend the model to the population scale by allowing for between-tree variation in levels of herbivore browse. The model is configurable for any broadleaved tree species subject to vertebrate or invertebrate browse, and is designed to be parameterized from field data typically collected as part of browse damage assessments. We parameterized and tested the model using data on foliage cover and browse damage recorded on kamahi trees (Weinmannia racemosa) browsed by possums (Trichosurus vulpecula) in New Zealand forests. The model replicated observed patterns of tree mortality at 12 independent validation sites with a wide range of herbivore densities and browse damage. The model reveals two key thresholds; in plant foliar cover, indicating when individual trees may be at high risk from browse-induced mortality, and in herbivore intake, leading to high rates of mortality across the whole population.


Herbivore impacts Plant–animal interactions Generic model Mechanistic model 



The authors would like to thank Mandy Barron, Duane Peltzer, Alex Dumbrell, Alex James, Sarah Richardson, Dan Tompkins, Christine Bezar, Andrea Byrom and two anonymous referees for constructive comments and helpful discussions. This work was funded by the Landcare Research Capability Fund and the Ministry of Science and Innovation Programme C09X0909. The studies in which the parameterization and validation data were collected were undertaken by Landcare Research, funded by and with the collaboration of staff from the New Zealand Department of Conservation (Projects 2398 and 2083).

Supplementary material

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Supplementary material 1 (PDF 95 kb)
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Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  • E. Penelope Holland
    • 1
    Email author
  • Roger P. Pech
    • 1
    • 3
  • Wendy A. Ruscoe
    • 1
  • John P. Parkes
    • 1
  • Graham Nugent
    • 1
  • Richard P. Duncan
    • 2
  1. 1.Landcare ResearchLincolnNew Zealand
  2. 2.Bio-Protection Research CentreLincoln UniversityLincolnNew Zealand
  3. 3.Joint Graduate School in Biodiversity and Biosecurity, School of Biological SciencesUniversity of AucklandAucklandNew Zealand

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