Woody encroachment threatens several ecosystems around the world. In general, management of grasslands includes regulation of fire and grazing regimes. Changes in these two types of disturbances are potential drivers of woody encroachment. Here we assessed how the traditional management carried out by local landholders affects a highland grassland ecosystem in southern Brazil. We hypothesized that grasslands converted to protected areas undergo fast woody encroachment. To reconstruct changes in vegetation, we interviewed former and current landholders and coupled their knowledge with an analysis of aerial and satellite images. During the first 11 years without fire and cattle, woody encroachment in grasslands increased exponentially. Woody encroachment occurred mostly by the replacement of grasslands by shrublands. Meanwhile, grasslands under traditional management remained almost unchanged for the last 40 years. The management of fire by local landholders has been part of their traditional practices for decades. Such management prevents largescale wildfires and maintains natural highland grasslands. The quick pace of shrub encroachment in such grasslands threatens its exclusive diversity, human well-being and regional cultural heritage. Thus, conservation policies are needed to regulate and instruct about the use of fire as a management tool in highland grasslands of southern Brazil. Extensive vegetation change can have important consequences in ecosystem functioning and economy 1. For instance, woody encroachment (or woody plant encroachment), which is the increase in density, cover and biomass of shrubs or woody vegetation in grasslands 2 , has been reported around the world 3. Woody encroachment is caused by several factors such as shifts in climate and biogeochemical cycles, changes in disturbance regimes (e.g. fire and grazing), or modification in ecological succession by introduction of non-native species or predator removal 2-5. Woody encroachment alters fundamental ecological processes of ecosystems, including global carbon balances, reduction of water flow or groundwater recharge and the loss of biodiversity 4,6,7. Because woody encroachment tends to negatively affect herbaceous vegetation, it constitutes a major threat to savanna and grassland ecosystems. Control of woody encroachment is a key concern in rangelands. Woody encroachment reduces forage production, creates habitat for ectoparasites, and hampers animal handling 4. Woody encroachment concerns land managers and methods for control and eradication include either fire, cutting trees, grazing, or a combination of these three methods 8,9. Woody encroachment has been reported all over the world, e.g., southern Ethiopian savanna 8 , North American savanna, shrub-steppe and grasslands ecosystems 10 , southeastern South American savanna 11 ('Campos' 6), and Brazilian savanna ('Cerrado' 12). In highland grasslands of southern Brazil, extensive cattle grazing is part of the traditional management employed for centuries 13. In addition, local ranchers c...

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ResumoO presente estudo verificou a influência dos contingentes florísticos sobre a composição e estrutura de uma sinúsia florestal na região central do Rio Grande do Sul, Brasil. O estudo foi realizado no município de Sinimbu, em uma floresta decidual, onde foram demarcadas 100 unidades amostrais contíguas, totalizando 1 ha. Todos os indivíduos com diâmetro à altura do peito ≥ 4,8 cm foram amostrados e identificados. As famílias com maior riqueza específica foram Myrtaceae (18), Fabaceae (16) e Euphorbiaceae (10). A maior parte das espécies e dos indivíduos amostrados é de ampla distribuição geográfica. Uma elevada proporção das espécies pertenceu ao contingente das florestas estacionais, entretanto, este apresentou baixo número de indivíduos. O contingente Atlântico apresentou, além de um baixo número de indivíduos, também baixa riqueza. A comunidade apresentou três estratos de altura, todos com predominância de plantas de ampla distribuição geográfica. Palavras-chave: Fitogeografia; flora; unidade de conservação; vale do Rio Pardo. Abstract Floristic-geographic relationships in a forest structure at the central region of the State of Rio Grande doSul, Brazil. This work studied the influence of floristic contingents on the composition and structure of a forest in the central region of the State of Rio Grande do Sul, Brazil. The study was carried out in the County of Sinimbu, in a deciduous forest, where 100 contiguous sampling units that totaled 1 ha were established. All individuals with DBH ≥ 4,8 cm were identified and measured. The richest families were Myrtaceae (18), Fabaceae (16) and Euphorbiaceae with 10 species. Most of the species surveyed are widely distributed across southern Brazilian vegetation formations. A large proportion of species belonged to the western seasonal contingent, although it has had contributed with few individuals. The eastern wet contingent presented both, low percentage of species and individuals. The community showed three height layers, all of them showing dominance of wide geographical distribution species.

Spatial distribution, association patterns and richness of tree species in a seasonal forest from the Serra Geral formation, southern Brazil RESUMO (Distribuição, associação espacial e riqueza de espécies arbóreas em uma fl oresta decídua da formação Serra Geral, sul do Brasil). Este estudo objetivou determinar a distribuição espacial das espécies arbóreas mais abundantes num remanescente fl orestal e avaliar relações que possam ser responsáveis por estas distribuições, bem como comparar a riqueza específi ca esperada ao longo da formação Serra Geral no estado do Rio Grande do Sul, Brasil. Uma parcela de 1 hectare, subdividida em 100 unidades amostrais contíguas foi instalada e todos os indivíduos com pelo menos 4,8 cm de diâmetro à altura do peito foram medidos e identifi cados. Cada unidade amostral recebeu uma descrição de sua posição espacial por meio de coordenadas (x,y) para quantifi car o padrão espacial e posteriormente aplicar um índice de associação para as espécies amostradas. A riqueza específi ca foi comparada a outros levantamentos realizados na região da encosta da Serra Geral do estado do Rio Grande do Sul por meio de rarefação. ABSTRACT(Spatial distribution and association patterns of tree species in a seasonal forest from the Serra Geral formation, southern Brazil). Th is study aimed to determine the spatial distribution of the most abundant tree species, to look for relationships that may be responsible for their distribution and to compare the expected richness along the Serra Geral formation in the state of Rio Grande do Sul , Brazil. An one-hectare plot was divided in 100 contiguous 10 x 10 m sampling units and all individuals with at least 4.8 cm diameter at breast high were measured and identifi ed. Each sampling unit received a description of the spatial position through metric coordinates (x,y) in order to quantify the spatial pattern. Later, an association index among species was applied. Th e observed richness was rarefi ed and compared to other surveys located on the slopes of Serra Geral in Rio Grande do Sul. We surveyed 1,063 individuals belonging to 69 species and 33 families, and the Shannon's diversity index showed a diversity of 3.35 nats (Pielou's species evenness -J' = 0.79). Most species showed an aggregated distribution. Both association and dissociation patterns occurred among species leading to distinct forest patches. Th e rarefaction results showed a decrease of Atlantic species, which were replaced by typical seasonal forest species, when analyzing fl oristic contingents towards the west.

We assessed whether Guapira opposita, a common shrub in coastal sand dunes in southern Brazil, was involved in ecological succession and which factors influenced its positive effects (facilitation) on other plant species. Woody plants and bromeliad abundance and richness were higher under the canopy of G. opposita than in open areas. Facilitation was mainly determined by the height of G. opposita individuals, and was not influenced by shrub area, distance to freshwater bodies, to the sea or to forest patches. Our data evidence that facilitator species play a key role in restinga regeneration and their presence is critical to maintain ecosystem diversity.