Plant Ecology

, Volume 214, Issue 2, pp 267–277 | Cite as

Patch identity and the spatial heterogeneity of woody encroachment in exotic-dominated old-field grasslands

  • Noemi MaziaEmail author
  • Pedro M. Tognetti
  • Ezequiel D. Cirino


Most grassland communities in agricultural landscapes comprise a mix of exotic and native plants, where grasses and forbs are disposed in low diversity patches conforming a heterogeneous matrix of vegetation. Within these “novel” ecosystems, woody encroachment is one of the principal causes of ecosystem degradation. Here, we examined the resistance to exotic woody establishment (Gleditsia triacanthos) into four different monospecific patches characteristics of old-field grasslands in Inland Pampa: an annual forb (Conium maculatum), an annual grass (Lolium multiflorum), and two perennial grasses (Cynodon dactylon and Festuca arundinacea). We evaluated the filter to tree recruitment by rodent seed removal and survival and growth of Gleditsia seedlings transplanted into undisturbed and disturbed microsites, within each patch. Beneath intact vegetation seed removal was an important biotic filter to woody establishment whereas disturbances facilitated seed survival in patches of perennial grasses. Patch identity affected tree growth, and Cynodon reduced the final biomass compared to forbs. Disturbance enhanced tree performance independently of patch type. After 2 years, tree survival was independent of disturbance and patch identity. As patch identity may regulate granivory and growth of tree saplings, community susceptibility or resistance to woody invasion rather than representing a static community attribute could vary according to the dynamic changes in the proportion of susceptible-resistant patches. Broadly, our work reinforces the concept that mechanisms regulating vegetation heterogeneity add a component of stochasticity to biotic resistance to community plant invasion.


Pampean grasslands Woody invasion Seed predation Seedling establishment Competition Novel ecosystems 



We thank the staff at Estancia San Claudio for logistic assistance throughout this project. We also acknowledge Gonzalo Ibañez and Luciano Fabi for field assistance. Comments from Enrique Chaneton and Fernando Biganzoli were positive. Two anonymous reviewers provided helpful comments to improve the manuscript. The study was funded by the University of Buenos Aires (Grant G046). EDC was supported by an undergraduate fellowship from Administración de Campos UBA.


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Copyright information

© Springer Science+Business Media Dordrecht 2013

Authors and Affiliations

  • Noemi Mazia
    • 1
    Email author
  • Pedro M. Tognetti
    • 2
  • Ezequiel D. Cirino
    • 1
  1. 1.Departamento de Producción VegetalFacultad de Agronomía, Universidad de Buenos AiresBuenos AiresArgentina
  2. 2.Departamento de Métodos Cuantitativos y Sistemas de InformaciónFacultad de Agronomía, Universidad de Buenos AiresBuenos AiresArgentina

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