In the last decades, an increasing number of forest decline events and widespread tree mortality have been reported worldwide as a consequence of different global change drivers. Such a general decrease in tree health and cover has a large potential to impact mycorrhizal communities, but this issue remains largely unexplored.We used a Bayesian framework to analyze the impact of Quercus suber decline on spatial patterns of seedling-mycorrhiza interactions in mixed Mediterranean forests in Southern Spain, and evaluate the relative importance of this symbiosis as a driver of oak seedling establishment.Our models showed that the spatial variability found in the patterns of oak seedling colonization by both arbuscular mycorrhizas and ectomycorrhizas was partially linked to the process of Q. suber decline. Moreover, seedling survival and growth was influenced by the intensity of mycorrhizal colonization, but in quite unexpected ways. Arbuscular mycorrhizas had a larger effect on seedling performance than ectomycorrhizas, and the effects of both groups were negative or neutral but never positive.We conclude that because the spatial distribution of the seedling-mycorrhiza association responded to the identity and health status of individual trees, and mycorrhizal infection did in turn affect seedling performance, tree decline might affect forest dynamics through changes in plant-soil biota feedbacks.

We thank the director and technical staff of Los Alcornocales Natural Park for facilities and support to carry out the field work. We are also indebted to Eduardo Gutiérrez, Ana Pozuelos, Maite Domínguez-Núñez, Adela Moreno and several students for invaluable laboratory and field assistance, and to I. Ibáñez for data analysis assistance. This research was supported by the Ministerio de Ciencia e Innovación (MICIIN) projects INTERBOS (CGL2008-04503-C03-03), DIVERBOS (CGL2011-30285-C02-01) and RETROBOS (CGL2011-26877), and the Junta de Andalucía project ANASINQUE (PGC2010-RNM-5782). BI was supported by a Formación de Personal Investigador (FPI)-MICINN grant, J.M.A. by a Formación de Personal Universitario (FPU)-MEC grant and I.M.P.R. by a JAEdoc-Consejo Superior de Investigaciones Científicas (CSIC) contract.

9 páginas.-- 3 figuras.-- 80referencias.-- Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.foreco.2015.05. 014.

Peer reviewed