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The proliferation of disturbance-adapted species in human-modified landscapes may change the structure of plant communities, but the response of biodiversity to human disturbances remains poorly understood. We examine the proliferation of the palm, Syagrus coronata, in disturbed forest stands and its impacts on the structure of vascular epiphyte assemblages in a human-modified landscape of Brazilian Caatinga dry forest. First, we compared S. coronata density between old-growth and regenerating forest stands. We then surveyed vascular epiphytes on 680 phorophytes (S. coronata and non-palm/control species) across five habitat types with different disturbance levels. There was an eight-fold increase in S. coronata density in regenerating areas compared with in old-growth forest. Syagrus coronota supported richer epiphyte assemblages at local (i.e. per palm) and landscape (i.e. pooling all palms) scale than control phorophytes, supporting more than 11 times the number of species of control phorophytes at both scales. Epiphyte assemblages were more abundant, species-rich and dominated by abiotically dispersed species in forest sites with intermediate disturbance levels (regenerating forest stands). More than simply operating as an exclusive phorophyte for more than 90% of the epiphyte species we recorded here, S. coronata favours epiphyte persistence and structures their assemblages across human-modified landscapes of the Caatinga forest. [ABSTRACT FROM AUTHOR]

• Plant species responsible for forest regeneration in the context of slash-and-burn agriculture are exploited for multiple uses. • Medicinal is the main type of uses of plants occurring in regenerating and old-growth forest stands. • A substantial portion of the flora of regenerating and old-growth forest stands together can be considered vulnerable to human-disturbances. • Tropical regenerating dry forests are considered important sources of useful plants for human populations. • The loss of vulnerable plants will impact the ecosystem functioning, service provision and rural communities. Tropical forests play an important role in maintaining, replenishing and conserving a large portion of the planet's biodiversity. However, these forests have been converted into anthropic landscapes, threatening the persistence of wildlife. The exploitation of forest products can result in different ecological impacts at different levels of biological organization. In this study, we propose a vulnerability index to examine the susceptibility of woody plants used by locals in a human-modified landscape of the Caatinga dry forest (i.e., the Catimbau National Park). We contrasted patterns of (1) plant use by local people (risk of use, collection risk, local importance, and diversity of use), (2) plant reproductive strategies (pollination, sexual and reproductive systems, dispersal mode, flowering and fruiting phenology), and (3) the conservation status of the plant species. We combined this information to propose a vulnerability index expressing species sensitivity to human disturbances in 14 regenerating and 14 old-growth forest stands. We tested the hypothesis that regenerating forest stands will harbor more vulnerable plant species compared to old-growth forest stands. Among the 119 plant species registered in regenerating and old-growth forest stands, 80 species (67.2 %) were recorded as useful for local people in Caatinga. Specifically, about 71.8 % and 70.5 % are exploited by the rural population for some type of use in regenerating and old-growth forest stands, respectively. The most frequent type of use was medicinal, followed by construction and fuel in both regenerating and old-growth forest stands. Regarding the potentially collected plant parts, the total removal of the individual and collection of leaves exhibited similar and higher relevance in regenerating, while leaves were the most collected part in old-growth forest stands. Of the 80 plant species analyzed, 62 % and 58.5 %, respectively, were classified as exhibiting moderate and high vulnerability to extirpation in regenerating and old-growth forest stands; thus not supporting our hypothesis. Our results suggest that in the Caatinga dry forest, (1) woody plant species responsible for forest regeneration in the context of slash-and-burn agriculture are exploited for multiple uses, (2) medicinal use is the main type of use of woody plants occurring in regenerating and old-growth forest stands, (3) total removal of the individual and collection of leaves were the most collected plant parts, and (4) both regenerating and old-growth forest stands showed a high vulnerability to human disturbances in the study area. In the long term, the exploitation of vulnerable plant species may negatively affect the composition and structure of the community and, consequently, the rate and trajectory of succession. It can be expected that as populations of vulnerable plant species are reduced or extirpated from the community, ecological interactions such as pollination and dispersal, which are key to ecosystem maintenance, will change along with the services provided. [Display omitted] [ABSTRACT FROM AUTHOR]