Juvenile–adult tree associations in a continental Mediterranean ecosystem: no evidence for sustained and general facilitation at increased aridity
Article first published online: 9 SEP 2011
© 2011 International Association for Vegetation Science
Journal of Vegetation Science
Volume 23, Issue 1, pages 164–175, February 2012
How to Cite
Granda, E., Escudero, A., de la Cruz, M., Valladares, F. (2012), Juvenile–adult tree associations in a continental Mediterranean ecosystem: no evidence for sustained and general facilitation at increased aridity. Journal of Vegetation Science, 23: 164–175. doi: 10.1111/j.1654-1103.2011.01343.x
- Issue published online: 9 JAN 2012
- Article first published online: 9 SEP 2011
- Manuscript Accepted: 9 AUG 2011
- Manuscript Received: 3 NOV 2010
- Spanish Ministry for Innovation and Science. Grant Numbers: CSD2008_00040, CGL2010-22180-C03-03
- Juniperus thurifera;
- Pinus nigra;
- Quercus faginea;
- Quercus ilex;
- Spatial patterns;
- Stress-gradient hypothesis;
- Water availability
How do tree species identity, microhabitat and water availability affect inter- and intra-specific interactions between juvenile and adult woody plants?
Continental Mediterranean forests in Alto Tajo Natural Park, Guadalajara, Spain.
A total of 2066 juveniles and adults of four co-occurring tree species were mapped in 17 plots. The frequency of juveniles at different microhabitats and water availability levels was analysed using log-linear models. We used nearest-neighbour contingency table analysis of spatial segregation and J-functions to describe the spatial patterns.
We found a complex spatial pattern that varied according to species identity and microhabitat. Recruitment was more frequent in gaps for Quercus ilex, while the other three species recruited preferentially under shrubs or trees depending on the water availability level. Juveniles were not spatially associated to conspecific adults, experiencing segregation from them in many cases. Spatial associations, both positive and negative, were more common at higher water availability levels.
Our results do not agree with expectations from the stress-gradient hypothesis, suggesting that positive interactions do not increase in importance with increasing aridity in the study ecosystem. Regeneration patterns are species-specific and depend on microhabitat characteristics and dispersal strategies. In general, juveniles do not look for conspecific adult protection. This work contributes to the understanding of species co-existence, proving the importance of considering a multispecies approach at several plots to overcome limitations of simple pair-wise comparisons in a limited number of sites.