Safe sites for tree regeneration in wooded pastures: A case of associational resistance?

Authors

  • Christian Smit,

    Corresponding author
    1. Department of Biology, Unit of Ecology & Evolution, University of Fribourg, Chemin du Musée 10, CH-1700 Fribourg, Switzerland
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  • Daniel Béguin,

    1. Swiss Federal Research Institute WSL-Antenne romande, CP 96, CH-1015 Lausanne, Switzerland
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  • Alexandre Buttler,

    1. Swiss Federal Research Institute WSL-Antenne romande, CP 96, CH-1015 Lausanne, Switzerland
    2. Laboratory of Ecological Systems — ECOS, Swiss Federal Institute of Technology, EPFL, Ecublens, CH-1015 Lausanne, Switzerland
    3. Laboratoire de Chrono-écologie, UMR 6565 CNRS, UFR des Sciences et Techniques, Université de Franche-Comté, F-25030 Besançon, France
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  • Heinz Müller-Schärer

    1. Department of Biology, Unit of Ecology & Evolution, University of Fribourg, Chemin du Musée 10, CH-1700 Fribourg, Switzerland
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  • Nomenclature: Tutin et al. (1964–1980).

* Corresponding author; Fax +41 263009740; E-mail christian.smit@unifr.ch

Abstract

Abstract. Question: Are tree saplings in wooded pastures spatially associated with specific nurse structures or plants that facilitate tree sapling survival?

Location: Wooded pastures in the Jura Mountains, Switzerland.

Methods: In two sites, 73 km apart, we sampled 294 plots of 4 m2, systematically distributed on 1 ha. We recorded number and height of all established Picea abies saplings (> 1 a of age and up to 40 cm in height), and visually estimated cover of rocks, shrubs, tree stumps, overhanging tree branches and unpalatable plant species.

Results: Despite differences in site characteristics, we found overall positive effects of cover of unpalatable plants, rocky outcrops and tree stumps on the density of Picea saplings. Plots with tree stumps and higher cover of rocky outcrops and unpalatable plants were more likely to contain Picea saplings.

Conclusions: Unpalatable plants, rocky outcrops and tree stumps seem to form safe sites for Picea saplings in this grazed system, improving their establishment and survival. Our findings support the idea that associational resistance drives the dynamics of wooded pastures, but experimental evidence for this hypothesis is still required.

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