Effect of artificial shelters of dead branches on

Authors: María José Leiva María Vera

Publish Date: 2015/05/24

Volume: 46, Issue: 5-6, Pages: 965-978

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Abstract

Acorn predation is a major bottleneck for oak selfregeneration in grazed Mediterranean oak savannahs dehesas which lack of shrub cover Establishing artificial shelters of dead branches SODBs could decrease acorn predation by protecting the seeds against domestic ungulates However rodents are also common in dehesas and their dual role as acorn predators and dispersers could be affected by the SODBs Two experiments were conducted to assess this role of the SODBs on acorn survival and dispersal They were carried out in six dehesa stands with different levels of rodent activity ie high and low The results revealed a positive effect of the SODBs on the acorns safety in those stands with low level of rodent activity Here the SODBs acted as effective physical barriers against livestock and the acorn survival was significantly higher 3 to 7fold beneath the SODBs than in the Open treatment Conversely in those stands with high level of rodent activity the SODBs significantly increased acorn predation by rodents acorn survival was 16 to 9fold lower beneath the SODBs than in the Open treatment In addition the SODBs acted as preferred sink for dispersed acorns but these acorns were completely predated by mice These results suggest that establishing SODBs could be a suitable and inexpensive method to improve oak regeneration in dehesas and in other disturbed ecosystems especially whether this method is combined with other simple techniques to protect acorns against predation by rodentsOur special thanks go to the management of the Doñana and Sierra Norte de Sevilla Natural Parks Dehesa de Gatos S L and Navalagrulla state for their valuable help support and facilities We also thank to José María Fedriani for useful advices on rodent activity assessment and to Fernando Pulido for advices on acorns tagging Frank Balao helped us with statistical analysis Benjamín Ojeda provided very valuable collaboration in different stages of the experiments development Frank BlancoVelazquez and JC MuñozReinoso helped us with camera traps installation and pictures monitoring Juan Manuel MancillaLeyton and Angel MartínVicente provided useful support in the field and laboratory Two anonymous reviewers helped improve the quality of preliminary version of the manuscript Rachel Baron revised the English version of the manuscript

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