Authors:F. Sabatini, B. Jiménez-Alfaro, S. Burrascano and C. Blasi
The identification of the drivers of diversity in understorey plant assemblages is a major challenge in forest ecology. However, it is not yet fully understood whether the same factors consistently affect different facets of species organization, such as species richness, composition and turnover. Here, we compare the influence of fine-scale environmental variables and spatial organization on the herb-layer flora of two unmanaged and ecologically different forest stands in the Muniellos Biosphere Reserve, Northern Spain. The aims of our study are to identify the most important factors influencing different facets of herb-layer plant organization, and to test whether the effect of such drivers is consistent across facets and forest types. We used Generalized Linear Models, Redundancy Analysis and Multiple Regression on Distance Matrices to model, respectively, the response of species richness, species composition and species turnover to spatial distances as well as to several environmental factors, including forest structure, light conditions, soil and topographical features. We observed a substantial consistency among variables affecting the different facets of ground-layer species organization within stands, with a subset of topographical variables with a transversal effect across facets. Although potential solar radiation was the main variable influencing species richness in the two stands, the factors shaping species composition and turnover varied across forest types: in the beech stand, slope and canopy openness were the main determinants of herb-layer species diversity and turnover; in the oak stand, the main drivers of species composition were related to topography and spatial structure, while spatial distance was the main driver of species turnover. Our study shows that the ecological processes driving fine-scale variation of ground-layer plant richness and composition are similar to those driving species turnover. Although the ecological factors shaping different facets may be the same, we highlight that, at least in temperate forests, these factors are system-specific and vary according to forest types.
Authors:C. Ricotta, M. Marignani, F. Campaiola, G.C. Avena and C. Blasi
We propose a simple mathematical framework to define consistently the environmental quality of a given landscape based on the relative abundances of the constituting land cover classes. Unlike traditional diversity measures, the new method does not evaluate the simple dispersion of the relative abundances of land cover classes, but assigns a weight to each land cover class according to the rank along a gradient of environmental quality. To clarify the ideas discussed, the method is illustrated with data from a pilot study to assess landscape changes in an Italian periurban area over the last 50 years.
Authors:S. Burrascano, R. Copiz, E. Del Vico, S. Fagiani, E. Giarrizzo, M. Mei, A. Mortelliti, F. M. Sabatini and C. Blasi
In recent decades, the European populations of wild boar have grown substantially, as has the impact of this species, owing above all to its rooting activity. Our aim was to investigate the relationships between vascular plant understorey and wild boar rooting intensity. The questions we addressed are: does rooting intensity influence understorey species composition and diversity? Which functional traits are associated with different levels of rooting? We performed a comparative analysis of plant communities in areas with contrasting levels of rooting intensity within a Mediterranean deciduous lowland forest in central Italy. Besides comparing species composition and diversity, we tested the association between species traits and rooting levels through fourth-corner analysis. We found that contrasting levels of rooting were associated to different understorey species composition and evenness, while we observed no significant difference in species richness. In contrast with our expectations, sites with lower rooting returned i) lower evenness values and ii) a higher proportion of species characterized by traits related to resistance or response to herbivory, i.e., spinescence, clonality, endozoochory, underground storage organs, and low height values. Our findings suggest that current vegetation patterns partly depend on the legacy effect of past rooting disturbance, since the areas currently subjected to low rooting intensity were likely to be intensely rooted in the past. These areas may have developed a marked dominance of clonal thorny species that, in turn, inhibited further feeding activities by wild boar.