ABSTRACT Climate change represents one of the greatest threats to global biodiversity. We investigate how climate change will affect the future potential distribution of tree species in subtropical high montane habitats in the Atlantic Forest and identify potential climate refuges for these species. The most frequent and exclusive species in this ecosystem were selected and geographic coordinates were compiled. The maximum entropy algorithm was used for climatic niche modeling. Two scenarios for 2061-2080 were considered for future predictions, one low impact (RCP 4.5) and one high impact (RCP 8.5). Isothermality, mean temperature in the driest quarter, mean temperature in the hottest quarter, rainfall in the driest month, and rainfall in the hottest quarter were the variables that best explained the climatic niche of the majority of species. The areas of potential species occurrence were reduced by 48.37 % (± 13.63 %) (RCP 4.5) and 62.49 % (± 21.87 %) (RCP 8.5) on average. The potential area of Crinodendron brasilense Reitz & L.B.Sm. decreased the most, by 82.11 % (RCP 4.5) and 90.06 % (RCP 8.5), respectively. High elevation areas in the south of Brazil were identified as priorities for conservation to ensure that climate refuges for high montane forest species are maintained in the future. Climate change events may significantly affect the species evaluated in this study.

Resumo O objetivo do presente estudo foi investigar a dinâmica da comunidade arbórea adulta e regenerante em um fragmento de Floresta Nebular em Urubici, Santa Catarina, sujeito ao impacto de gado. Os inventários dos indivíduos arbóreos adultos (diâmetro na altura do peito - DAP ≥ 5 cm) foram realizados em 2011, 2015 e 2019, e dos regenerantes arbóreos (DAP < 5 cm), em 2013, 2015, 2017 e 2019. Para o componente adulto, a amostragem foi realizada em 25 parcelas de 20 × 20 m alocadas de forma sistemática no fragmento. Em cada uma dessas parcelas também foram coletadas variáveis edáficas e topográficas. O componente regenerativo arbóreo foi avaliado em subparcelas conforme classe de tamanho das plantas (classe 1: plantas com altura de 0,15 cm até 1 m, em 5 m2; classe 2: plantas com altura acima de 1 m e até 3 m, em 10 m2, e classe 3: plantas com altura maior que 3 m e DAP < 5 cm, em 20 m2). Foram calculadas as taxas demográficas para a comunidade e as populações de indivíduos adultos e regenerantes. Utilizaram-se Árvores de Regressão (AR), para testar a influência das variáveis ambientais sobre as taxas de dinâmica dos regenerantes, e Análises dos Componentes Principais (PCA), para sintetizar os gradientes representados pelas taxas de dinâmica entre populações. No último período, 2015-2019, a floresta apresentou perda em indivíduos e em área basal, o que sugere um processo de desestruturação. Para os indivíduos regenerantes, as variáveis mais influentes na dinâmica estiveram relacionadas com a fertilidade do solo, os teores de H+Al, a cota altitudinal e a compactação dos solos. Para a conservação da área, medidas, como o cercamento contra entrada de gado, são essenciais para a manutenção da floresta ao longo do tempo.

Abstract The objective of this research was to investigate the dynamics of the adult and regenerating tree community in a Cloud Forest fragment in Urubici, Santa Catarina, subject to livestock impact. Inventories of adult tree individuals were carried out in 2011, 2015, and 2019, and of regenerative trees, in 2013, 2015, 2017, and 2019. For the adult component, sampling was performed within 25 20 x 20 m systematically allocated plots. Within each plot, soil and topographic variables were also collected. The regenerative component was evaluated in subplots according to plant size classes (class 1: plants with a height from 0.15 cm to 1 m in 5 m2; class 2: plants with height above 1 m and up to 3 m in 10 m2; and class 3: plants with height above 3 m and DAP < 5 cm in 20 m2). The demographic rates for the community of adult and regenerating individuals were determined. Regression Trees (RT) were used to test the influence of environmental variables on the dynamics rates of the regenerative component, and Principal Component Analysis (PCA) was performed to synthesize the population dynamics rates. In the last period, 2015-2019, the forest showed a loss of individuals and basal area, which suggests a de-structuring process. For regenerating individuals, the most influential variables in the dynamics were soil fertility, H+Al levels, altitudinal quota, and soil compaction. For the conservation of the area, measures such as fencing to prevent cattle from entering are essential for the maintenance of the forest over time.

RESUMO As florestas nebulares estão ameaçadas devido ao processo de mudanças climáticas. Investigações que buscam prever como estas mudanças afetarão as espécies são de grande importância, pois são fundamentais para gerar estratégias de conservação. Assim, objetivamos detectar como as mudanças climáticas afetarão a distribuição geográfica potencial de Drimys angustifolia Miers, uma espécie arbórea indicadora da floresta nebular na Mata Atlântica subtropical brasileira. As áreas de ocorrência de D. angustifolia foram obtidas a partir de coordenadas geográficas disponíveis em publicações científicas e no banco de dados Global Biodiversity Information. Para a modelagem de nicho climático, usamos o Algoritmo de Máxima Entropia, com 19 variáveis climáticas. Dois cenários de mudanças climáticas foram considerados para o período 2061-2080: um de baixo e outro de alto impacto. D. angustifolia ocorre, predominantemente, nas florestas alto-montanas e está ausente em locais quentes e secos. As variáveis que melhor explicaram o nicho climático de D. angustifolia foram temperatura média no trimestre mais quente, precipitação no mês mais seco e precipitação no trimestre mais quente. Ambos os cenários indicaram mudanças em direção a um clima futuro regional mais tropical. No cenário de baixo impacto de mudanças climáticas, a cobertura de D. angustifolia reduziu 68,24% (±7,32%) em sua área de ocorrência potencial; e diminuiu 79,15% (±9,65%) no cenário de alto impacto. Os resultados nos permitem concluir que D. angustifolia e seu ecossistema associado estão ameaçados pelos possíveis impactos das futuras mudanças climáticas. Assim, destacamos áreas climáticas estáveis para a ocorrência de D. angustifolia, como as localizadas nas partes mais altas das cadeias montanhosas das regiões Sul e Sudeste do Brasil, que devem ser consideradas áreas prioritárias para proteção e conservação.

ABSTRACT The cloud forests are threatened due to the climate change process. Investigations seeking to predict how future climate change will affect species are of great importance as they are fundamental to generating conservation strategies. We aimed to detect how climate change affects the potential geographical distribution of Drimys angustifolia Miers, a tree species that is an indicator of the upper-montane cloud forest in the Brazilian subtropical Atlantic Forest. The areas where D. angustifolia occurs were obtained from geographic coordinates available in scientific publications and the Global Biodiversity Information database. For climate niche modeling, we used the maximum entropy algorithm with 19 climate variables. Two climate change scenarios were considered for 2061-2080: one of low and one of high impact. D. angustifolia predominantly occurs in the upper-montane forests and is absent from dry and warm sites. The variables that best explained the D. angustifolia climatic niche were mean temperature of the warmest quarter, precipitation of driest month, and precipitation of the warmest quarter. Both scenarios indicated changes towards a more tropical regional future climate. Under the low impact climate change scenario, D. angustifolia coverage declined by 68.24% (± 7.32%) across its area of potential occurrence; it declined by 79.15% (± 9.65%) under the high impact scenario. In conclusion, the results of the present study showed that D. angustifolia and its associated ecosystem are threatened by the potential impacts of future climate change. Consequently, we highlight climatically stable areas for the occurrence of D. angustifolia, such as those located in the highest parts of the mountain ranges of the southern and southeastern regions of Brazil, which should be considered as priority areas for protection and conservation.

ABSTRACT: The natural regeneration process is essential for forest maintenance since it is critical for establishing new tree individuals. This study aimed to improve the understanding of the regenerative component dynamics of Araucaria Forests in Southern Brazil. We investigated the effects of climate, light, tree component structure and anthropogenic disturbance on tree species regeneration. Regenerating communities from six different fragments in forest remnants of the “Planalto Sul Catarinense” region was evaluated in permanent plots two years after the first inventory. The following demographic rates were determined: recruitment, mortality, net change in the number of individuals and the changes to both upper and lower height classes. The following variables were measured in each fragment: altitude, climatic variables, light environment, tree component density and cattle presence. Association between dynamics rates, regenerating species abundance and explanatory variables was verified by the fourth-corner and RLQ methods. A total of 4,379 and 5,268 individuals were sampled for the first and second inventories, respectively, with recruitment rate (21 % yr−1) higher than mortality rate (13 % yr−1). The dynamics pattern of the fragment with greater presence of cattle stood out for the intense height increase of regenerating species caused by the presence of fast growth and light-demanding species. Natural regeneration of forest remnants under study is facing a structuring process. The main conclusions of this study were: i) climate and altitude play a relevant role in defining floristic identity and ii) chronic disturbances may influence the definition of ecological strategies.

RESUMO O presente estudo teve como objetivo caracterizar a composição florística do componente regenerante e relacioná-la ao componente arbóreo adulto de um fragmento de Floresta Ombrófila Mista no Sul do Brasil, com o propósito de inferir sobre os processos de construção da comunidade de espécies arbóreas na área. Para isto, foram utilizadas cinco transecções de 100 x 20 m, alocadas em um fragmento florestal localizado no município de Lages-SC. Cada transecção foi formada por cinco parcelas, distantes 20 m entre si, subdividas em tamanhos distintos de acordo com a classe de tamanho da planta avaliada. Os componentes regenerante e adulto foram comparados quanto à organização florístico-estrutural (Análise de Variância Multivariada Permutacional e Análise de Espécies Indicadoras), riqueza (rarefação), distribuição espacial dos indivíduos das populações (Índice de Morisita Padronizado) e padrões de coexistência e segregação das espécies nas parcelas (Índice de C-score). Os resultados demonstraram diferenças significativas entre adultos e regenerantes em relação à similaridade florístico-estrutural e riqueza. O componente adulto apresentou maior proporção de populações com distribuição espacial aleatória e menor coexistência de espécies nas parcelas, em relação ao componente regenerante. Infere-se que a construção da comunidade está sujeita a processos ecológicos distintos, cujas intensidades de atuação dependem do estágio ontogenético considerado.

ABSTRACT This study aimed to describe the floristic composition of the regenerative component and to relate it with the adult component of an Araucaria Forest fragment, in South Brazil, in order to infer about the process of tree species community assemblage. To do so, five 10 x 20 m transection were allocated, in a forest fragment located at municipality of Lages, SC state. Each transect was made up by five plots, 20 m from each other, subdivided in different sizes, according to the sampled size class. The adult and regenerative components were compared each other for floristic-structural organization (Permutational Multivariate Analysis of Variance and Indicator Species Analysis), richness (rarefaction), population, individual spatial distribution (Standardized Morisita Index), and pattern of species coexistence or segregation in the studied plots (C-score Index). The results demonstrated significant differences between adults and regenerating components in relation to floristic-structural similarity and to richness. The adult component presented a greater proportion of populations with a random spatial distribution; and a smaller coexistence of species in plots than the regenerative component. We infer that the tree community assemblage is under influence of different ecological process, which intensity is ontogenetic dependent.