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Annals of Forest Science

, Volume 66, Issue 5, pp 511–511 | Cite as

Establishment limitation of holm oak (Quercus ilex subsp. ballota (Desf.) Samp.) in a Mediterranean savanna — forest ecosystem

  • Christian Smit
  • Mario Díaz
  • Patrick Jansen
Original Article

Abstract

  • • Tree recruitment in Mediterranean savannas is generally hampered, in contrast with the original oak forests where these savannas are derived from. We asked whether this difference in recruitment success can be explained by differential post-dispersal survival. For one year we monitored experimentally cached holm oak acorns in a savanna — forest ecosystem in Central Spain, and recorded cache pilferage, type of pilferer, boar rooting, seedling emergence, seedling survival and the cause of mortality.

  • • Cache pilferage was significantly lower in savanna (8%) than in forest (21%). However, the higher cache survival was more than offset by lower seedling emergence and, particularly, by nine times higher seedling mortality in savanna, mainly due to desiccation. Wild boar rooting did not differ between experimental caches and controls without acorns, indicating that individual cached acorns do not trigger rooting activity.

  • • Our results indicate that the difference in post-dispersal survival between savanna and forest is due to lower emergence and, primarily, higher seedling mortality in savanna, not to higher cache pilferage. Absence of safe sites such as shrubs, abundantly present in the forest, may well explain the lack of recruitment in the savanna. Management measures appear necessary for long-term persistence of Mediterranean savannas in general.

Keywords

tree recruitment seedling establishment dehesa seed predation 

Limitation de l’installation du chêne vert (Quercus ilex subsp. ballota (Desf.) Samp.) dans un écosystème de savane forestière méditerranéenne

Résumé

  • • Le recrutement des arbres dans les savanes méditerranéennes est généralement entravé, ce qui contraste avec les forêts de chênes originelles dont ces savanes sont issues. Nous nous sommes demandé si cette différence dans le succès du recrutement pouvait être expliqué par une différence de survie post-dissémination. Pendant une année, nous avons suivi expérimentalement des glands de chêne vert cachés dans un écosystème de savane forestière en Espagne centrale, et nous avons enregistré les chapardages des caches, les types de chapardage, la fouille des sangliers, l’émergence des semis, la survie des semis et les causes de la mortalité

  • • Le chapardage dans les caches a été significativement plus faible dans la savane (8 %) que dans la forêt (21 %). Toutefois, la survie plus élevée dans les caches été plus que compensée par une baisse de l’émergence des semis et, en particulier, par une mortalité des semis neuf fois plus élevée dans la savane, principalement due à la dessiccation. La fouille des racines par les sangliers n’est pas différente entre les caches expérimentales et les témoins sans glands, indiquant que les mises en cache des glands ne déclenchent pas activité de fouille des racines.

  • • Nos résultats indiquent que la différence de survie post-dissémination entre la savane et la forêt est due à la baisse d’émergence et en premier lieu, à une mortalité plus élevée des semis dans la savane, et non pas à des chapardages des caches plus élevés. L’absence de sites abris tels que les arbustes, très présents dans la forêt, peut expliquer l’absence de recrutement dans la savane. Des mesures de gestion apparaissent nécessaires pour une persistance à long terme des savanes méditerranéennes.

Mots-clés

installation des semis prédation des graines recrutement des arbres dehesa 

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Copyright information

© Springer S+B Media B.V. 2009

Authors and Affiliations

  1. 1.Departamento de Ciencias Ambientales, Facultad de Ciencias del Medio AmbienteUniversidad de Castilla-La ManchaToledoSpain
  2. 2.Community Ecology and Conservation Ecology group, Centre for Ecological and Evolutionary StudiesUniversity of GroningenAA, HarenThe Netherlands
  3. 3.Instituto de Recursos NaturalesIRN-CCMA-CSICMadridSpain

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