Uncoupling the effects of seed predation and seed dispersal by granivorous ants on plant population dynamics

Arnan X., Molowny-Horas R., Rodrigo A., Retana J. (2012) Uncoupling the effects of seed predation and seed dispersal by granivorous ants on plant population dynamics. PLoS ONE. 7: 0-0.
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Doi: 10.1371/journal.pone.0042869

Resum:

Secondary seed dispersal is an important plant-animal interaction, which is central to understanding plant population and community dynamics. Very little information is still available on the effects of dispersal on plant demography and, particularly, for ant-seed dispersal interactions. As many other interactions, seed dispersal by animals involves costs (seed predation) and benefits (seed dispersal), the balance of which determines the outcome of the interaction. Separate quantification of each of them is essential in order to understand the effects of this interaction. To address this issue, we have successfully separated and analyzed the costs and benefits of seed dispersal by seed-harvesting ants on the plant population dynamics of three shrub species with different traits. To that aim a stochastic, spatially-explicit individually-based simulation model has been implemented based on actual data sets. The results from our simulation model agree with theoretical models of plant response dependent on seed dispersal, for one plant species, and ant-mediated seed predation, for another one. In these cases, model predictions were close to the observed values at field. Nonetheless, these ecological processes did not affect in anyway a third species, for which the model predictions were far from the observed values. This indicates that the balance between costs and benefits associated to secondary seed dispersal is clearly related to specific traits. This study is one of the first works that analyze tradeoffs of secondary seed dispersal on plant population dynamics, by disentangling the effects of related costs and benefits. We suggest analyzing the effects of interactions on population dynamics as opposed to merely analyzing the partners and their interaction strength. © 2012 Arnan et al.

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Post-fire Management of non-serotinous pine forests.

Retana J, Arnan X, Arianoutsou M, Barbati A, Kazanis D, Rodrigo A (2012) Post-fire Management of non-serotinous pine forests. In: (Moreira F, Arianoutsou M, Corona P & De las Heras J Eds) Post-fire management and restoration of southern European forests. Managing Forest Ecosystems Series, Vol. 24. Springer. ISBN 978-94-007-2207-1. pp. 151-170.

Relevance of soil seed bank and seed rain to immediate seed supply after a large wildfire

Rodrigo A., Arnan X., Retana J. (2012) Relevance of soil seed bank and seed rain to immediate seed supply after a large wildfire. International Journal of Wildland Fire. 21: 449-458.
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Doi: 10.1071/WF11058

Resum:

We examined the density and composition of the immediate seed supply (i.e. instant potential post-fire germination from soil seed bank and off-site seed rain) after a large wildfire in a sub-Mediterranean pine forest. We also tested the effects of fire severity and distance from unburned edges on the density and composition of the seed bank and the immediate off-site seed rain. Our results showed that although seed density did not differ between them, their composition was markedly different. The soil seed bank was dominated by species from the Fabaceae family with limited dispersal mechanisms such as autochory and barochory, whereas the seed rain was mainly composed of species from the Asteraceae family with wind-dispersed seeds. These patterns were not affected either by fire severity or distance from the fire edge. The main conclusion of the study is that both the soil seed bank and the seed rain play an important role in providing seeds for immediate regeneration after a large wildfire throughout the burned area. We suggest that the role of seed rain on immediate post-fire recovery of Mediterranean plant communities might be more important than has previously been thought. However, the effective role of this group of species on the longer term should be evaluated. © IAWF 2012.

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