Coexistence in Mediterranean oaks

Ignacio Pérez-Ramos et al. have a paper in volume 100, issue 2 titled “Ontogenetic conflicts and rank reversals in two Mediterranean oak species: implications for coexistence“.  Read it here.

The authors have provided some beautiful pictures of their study area and a description of their research and where it was done.

Study area: ´Los Alcornocales` Natural Park (southern Spain).

Vegetation of these forests is dominated by evergreen cork oak (Quercus suber) forests, mixed with winter-deciduous oaks (Q. canariensis), which are more abundant near streams. In heterogeneous environments, such as these Mediterranean-type forests, species segregate spatially in response to selective abiotic and biotic filters occurring throughout plant ontogeny. In the study area, adults of both oak species segregate along environmental gradients of topography and soil moisture, forming forests with distinct canopy cover.  Q. suber tends to dominate in habitats with a lower availability of soil water and nutrients where the overstorey canopy is relatively sparse, whereas Q. canariensis is more abundant in moister habitats with denser canopies.

Mediterranean mixed-oak forests dominated by Quercus canariensis and Q. suber (´Los Alcornocales` Natural Park, southern Spain).

In this study, we used a multi-stage demographic approach aimed at characterizing the main stage-specific probabilities of recruitment (seed survival, seed germination, seedling emergence and survival) in the two coexisting oak species along a wide and continuous gradient of plant cover (used here as a surrogate of microhabitat conditions). In addition, we investigated the implications of seed size variation, using a broad range of seed mass for the two studied oak species. We found some evidence of regeneration niche partitioning in the two coexisting oak species, supporting their current distribution patterns as saplings and adults at the study area. We conclude that within- and among-species differences through plant ontogeny, arising from species differential response to microhabitat heterogeneity and seed size variation, could be of great importance for oak species niche segregation, driving stand dynamics and spatial pattern distribution along the landscape. The information provided by this study could be also applied to optimize management and restoration programmes since it has enabled us to identify the most favourable conditions and traits for recruitment in oak species that exhibit serious constraints for natural regeneration.

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