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Abstract Shrub encroachment influences several ecosystem services in drylands worldwide. Yet, commonly used strategies to reduce encroachment show a low medium-term success, calling for a better understanding of its causes. Previous works identified multiple drivers responsible for this phenomenon, including anthropogenic and environmental causes. However, the relative effect of climate, topography and edaphic factors on shrub encroachment is not fully understood nor has been properly quantified in Mediterranean Basin drylands. Also, understanding how these drivers lead to changes in plant communities' functional traits associated to shrub encroachment is crucial, considering traits influence ecosystem processes and associated ecosystem services. Here, we studied the understory of a Mediterranean dryland ecosystem composed of savanna-like Holm-oak woodlands, along a regional climatic gradient. We specifically assessed (i) how climatic, topographic and edaphic factors influence understory relative shrub cover (RSC) and (ii) their direct and indirect effects (via RSC) on plant functional traits. We studied the mean and diversity of 12 functional traits related to plant regeneration, establishment, and dispersal, at the community-level. We found that, under similar low-intensity land use, topographic and edaphic factors, namely slope variations and soil C:N ratio, were the most important predictors of shrub encroachment, determining communities' functional characteristics. Climate, namely summer precipitation, had a much lesser influence. Our model explained 52% of the variation in relative shrub cover. Climate had a stronger effect on a set of functional traits weakly involved in shrub encroachment, related to flowering and dispersal strategies. We show that shrub encroachment is largely predicted by topo-edaphic factors in Mediterranean drylands subject to conventional low-intensity land use. Hence, management strategies to reduce encroachment need to take these drivers into account for efficient forecasting and higher cost-effectiveness. Our results suggest that climate change might not greatly impact shrub encroachment in the Mediterranean Basin, but may affect functional structure and reduce functional diversity of plant communities, thus affecting ecosystem functioning. Graphical abstract Unlabelled Image Highlights • Shrub encroachment is a worldwide phenomenon that affects many ecosystem services. • Its causes need to be better understood and quantified in the Mediterranean Basin. • We studied its drivers, and impact on plant functional traits in Holm-oak woodlands. • We found that topo-edaphic factors, not climate, largely predict shrub encroachment. • We help to predict encroachment under climate change and to improve management actions. [ABSTRACT FROM AUTHOR]

Climate change and increasing socio-economic pressure is placing many ecosystems of high ecological and economic value at risk. This is particularly urgent in dryland ecosystems, such as the montado , a multifunctional savannah-like system heavily modeled by grazing. There is still an ongoing debate about the trade-offs between livestock grazing and the potential for ecosystem regeneration. While it is consensual that overgrazing hinders the development of the shrubs and trees in this system, the effects of undergrazing or grazing exclusion are unclear. This study provides the unique opportunity to study the impact of grazing on compositional and structural biodiversity by examining the ecological chronosequence in a long-term ecological research site, located in Portugal, where grazing exclusion was controlled for over 15 years. As the threat of intensification persists, even in areas where climate shifts are evident, there is a critical need to understand if and how the montado might recover by removing grazing pressure. We evaluate succession on structural and compositional diversity after grazing pressure is removed from the landscape at 5, 10, and 15 years post-cattle exclusion and contrast it with currently grazed plots. A LiDAR-derived structural diversity index (LHDI), a surrogate of ecosystem structure and function first developed for the pine-grassland woodland systems, is used to quantify the impact of grazing exclusion on structure and natural regeneration. The distribution of the vegetation, particularly those of the herbaceous and shrub strata (> 10 ≤ 150 cm), presents statistically significant changes. The LHDI closely mimics the compositional biodiversity of the shrubs, with an increase in diversity with increased years without grazing. Under present climate conditions, both shrub regeneration and the establishment of tree saplings were strongly promoted by grazing exclusion, which has important management implications for the long-term sustainability of montado systems. [ABSTRACT FROM AUTHOR]

Forestry plantations, and particularly those of exotic Eucalyptus , are important man-made systems in Europe, and especially in Portugal, where these represent now the largest fraction of forested areas. Eucalyptus plantations may have impacts on vertebrate communities in Europe; however, these have been seldom assessed. Although it is commonly understood that such impacts are contingent on type, shape size and spatial arrangement of landscape elements. Thus, in this study we tested the effects of Eucalyptus plantations and the surrounding native semi-natural ecosystems on small mammal density in Central Portugal. We used a Spatially Explicit Capture-Recapture (SECR) model to estimate density, and Generalized Linear (Mixed) Models (GLM/GLMM) to test the effects of habitat type and understory composition and structure on mammal density. Our results showed no significant effect of Eucalyptus plantations on density of small mammals, but the presence of a developed understory was positively related to density, likely because it provides food and refuge resources. At the species level, we only found a negative effect of Eucalyptus plantations on wood mouse ( Apodemus sylvaticus ) density, most likely because these forests do not provide its preferred food resources (e.g. acorns); this hypothesis was further supported by the positive effect of proximity to ecotone habitat that likely resulted in increased food provisioning. These results highlight that the impact of Eucalyptus plantations on small mammals is mostly species-dependent and determined by management and the location of native habitat patches. [ABSTRACT FROM AUTHOR]

Aridity is a critical driver of the diversity and composition of plant communities. However, how aridity influences the phylogenetic structure of functional groups (i.e. annual and perennial species) is far less understood than its effects on species richness. As perennials have to endure stressful conditions during the summer drought, as opposed to annuals that avoid it, they may be subjected to stronger environmental filtering. In contrast, annuals may be more susceptible to interannual climatic variability. Here we studied the phylogenetic structure of the annual and perennial components of understorey plant communities, along a regional aridity gradient in Mediterranean drylands. Specifically, we asked: (1) How do species richness (S) and phylogenetic structure (PS) of annuals and perennials in plant communities respond to aridity? (2) What is the contribution of other climatic and topo-edaphic variables in predicting S and PS for both components? (3) How does the taxonomic and phylogenetic turnover of annuals and perennials vary with spatial and environmental distances? We assessed annuals' and perennials' species richness, the phylogenetic structure at deep and shallow phylogenetic levels, and taxonomic and phylogenetic turnover along spatial and environmental distances. We found no relationship between annuals' richness and aridity, whereas perennials' richness showed a unimodal pattern. The phylogenetic structure of annuals and perennials showed contrasting responses to aridity and negatively correlated with topo-edaphic variables. We found phylogenetic clustering at intermediate-to-higher aridity levels for annuals, and at lower aridity levels for perennials. Both taxonomic and phylogenetic turnover in annuals and perennials correlated with the environmental distance rather than with spatial distance between communities, suggesting adaptation to local factors. Overall, our results show a decoupling in the response of the phylogenetic structure of annual and perennial components of plant communities to aridity in Mediterranean drylands. Our findings have significant implications for land management strategies under climate change. Unlabelled Image • Aridity is a critical driver of changes in ecological communities. • We studied its effects on the richness and phylogenetic structure of annual and perennial species. • Annual richness was not related to aridity, whereas perennial's showed a unimodal pattern. • Annuals showed phylogenetic clustering at medium-to-higher aridity; perennials at lower. • Our results suggest a decoupling of annuals and perennials and have significant implications for restoration strategies. [ABSTRACT FROM AUTHOR]