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Cyclones are an increasing disturbance in the subtropical region of South America, but their impacts over the forests are still poorly documented. Here, we evaluate the effects of an extratropical cyclone over tree mortality in Araucaria Forest remnants in southern Brazil. We surveyed 116 sites (10 × 20 m each) and collected data on all tree individuals presenting DBH ≥ 4.8 cm before (2009) and after (2014) the occurrence of an extratropical cyclone. Using GLM models, we checked how the cyclone occurrence, different plant traits (DBH, trunk branching, wood density, successional group and evolutionary distinctiveness) and site characteristics (basal area, exposure, landscape protection, nearest border distance, cyclone border distance and the presence of native bamboo species) could impact tree mortality. The GLM model selection shows that the lowest AIC model considers all predictors separately and their interaction with the cyclone. The results showed that the cyclone occurrence and some site characteristics (bamboo presence, site exposure, landscape protection, nearest border distance and cyclone border distance) and plant traits (successional group and evolutionary distinctiveness) are related to tree mortality. The intense deforestation and fragmentation of the Araucaria Forest coupled with the increase in cyclone frequency expected for the region due to climate change may increase mortality rates of these forests, affecting their resilience and phylogenetic structure. Further biodiversity conservation efforts in the Araucaria Forest need to consider the characteristics of sites for enabling the protection of forest remnants in areas under different exposures to cyclone impacts. [ABSTRACT FROM AUTHOR]

Anuran amphibians are extremely sensitive to changes in the environment and are severely threatened with extinction by human activities. The conversion of natural habitats to tree plantations is expanding in southern Brazil, emphasising the need for both scientists and society to understand the potential effects of this practice on animal communities. Here, we evaluated whether the richness, composition and abundance of leaf‐litter frogs change among natural forests, plantations of the native Araucaria angustifolia and plantations of an introduced pine Pinus spp. We obtained data on the composition of the leaf‐litter frog assemblages by sampling natural forest and tree plantations in the Passo Fundo National Forest, southern Brazil. We sampled leaf‐litter frogs using pitfall trap arrays from March 2017 to February 2018. We used generalised linear mixed models to estimate the effect of habitat type on leaf‐litter frogs while considering variation induced by season effect and spatial autocorrelation. We recorded 311 individual leaf‐litter frogs belonging to nine species and five families. We did not find differences in species richness and composition, total abundance and abundance of the most frequent species Physalaemus cuvieri, P. carrizorum and Rhinella icterica among Pinus plantations, Araucaria angustifolia plantations and natural forests. These results indicate that tree plantations and natural forests can be equally suitable to leaf‐litter frogs. Such suitability is promoted by the light levels of management exerted on these plantations, the old age of the plantations and the heterogeneous mosaic of habitat types maintained within this National Forest. Our study shows that some management decisions can preserve habitat quality to wildlife in modified landscapes. [ABSTRACT FROM AUTHOR]

With the intensification of global warming, the occurrence of large‐scale natural events is becoming even more common in tropical regions, which can impact the structure of plant communities. In this study, we evaluated the isolated and combined effects of an extratropical cyclone and the dominance of a native bamboo species (Merostachys skvortzovii) on floristic composition, diversity, demographic rates and the increment of trees in Atlantic Forest fragments in Southern Brazil. In 2014 (T1) and 2016 (T2), we sampled 56 plots of 200 m² for the effects of an extratropical cyclone in 2009 (T0). We also evaluated another 60 plots of the same size not in the direct path of this cyclone. Half of the plots in each group were covered by dense groupings of bamboos, as a result of past human activities, which could potentially limit natural regeneration. We observed an increase in richness and diversity indices (H′ and 1/D) from the first (T0) to the following assessments (T1 an T2) on the sites affected by the cyclone, when compared to non‐affected sites. After the cyclone, both density and basal area they decreased, but there was an increase in recruitment, mortality, turnover rates and basal area, as well as basal increment. The diameter increment on surviving individuals was higher in cyclone‐affected sites than in non‐affected sites. Bamboo cover did not affect richness or demographic rates (except mortality between T0 and T1). Natural impacts of this nature can lead to significant alterations of demographic rates, allowing the input of new species and influencing the pace of demographic processes. [ABSTRACT FROM AUTHOR]

The theory of complex networks has been recently used to explain ecological associations between nurses and seedlings in plant facilitation systems. The structure of these networks is potentially affected by morphological, ecological and evolutionary factors that can determine the facilitative interactions. In the present study, we evaluate the role of the projected crown area of the nurse plant, the dispersal syndrome, the abundance and the phylogeny relationships with seedlings as drivers of network structure in facilitation networks. To test these parameters, we used an ecotonal forest-grassland system in southern Brazil that experienced historical forest expansion over the grassland in the last few centuries. In two State Parks, Guartelá ( GUA) and Vila Velha ( VVL), we sampled tree species (nurses and seedlings) along four transects parallel to the forest edge, with five sampling stations along each transect. Tree seedlings (height >0.3 m) were sampled below the nurse's crown (i.e. isolated woody plants, height >1.5 m) and over the grassland area. A total of 160 nurses and 358 seedlings were sampled. Seedling abundance and richness were greater below a nurse's crown than on open grassland. Nurse abundance was the best predictor of the observed interaction matrix. Probabilistic matrices based on abundance, abundance and phylogeny, and dominance were able to predict the observed nestedness values, and they were also closest to the observed connectance, although all of the probabilistic matrices have underestimated this property. Specialization was predicted by abundance and phylogeny, abundance and projected crown area drivers for VVL, and the abundance based models were closest to the predicted specialization for GUA. The result of a similar pattern in predictability between sites indicates that the influences of morphology and evolutionary and ecological processes over the facilitation interactions are equivalent on a regional scale. Woody plant abundance was a key factor for the facilitation networks, driving forest expansion along the subtropical forest-grassland ecotone. [ABSTRACT FROM AUTHOR]

In forest-grassland mosaics, patches can result from two processes: forest expansion over grassy ecosystems and forest fragmentation. We tested the hypothesis that patches produced by these processes differed in structure and spatial context in a forest-grassland mosaic in the southern Brazilian highlands. We compared a present-day land cover map with a past vegetation map to identify natural forest patches and forest fragments. Patches were described according to structure (size, core area and shape metrics) and spatial context (distance from roads and urban areas, edge contrast). Principal component analyses were used to examine gradients of patch types, and differences were tested by analysis of variance with randomization test. We found 878 natural patches and 214 fragments. Natural forest patches, riparian forest patches and forest fragments differed in structure and spatial context. In comparison to natural forest patches, fragments tend to be larger, with larger core areas, and more irregular and complex in shape. Fragments are situated in a different spatial context, tending to be closer to roads and urban areas and to present higher edge contrast. Riparian natural forest patches are similar to natural forest patches, except for shape. The smaller area and regular shape of natural patches probably result from the mechanisms involved in nucleus formation in the grassland matrix and from current grassland management. Natural patches are less exposed to some anthropogenic stresses, since most of them remain in a native grassland matrix context. Our results show that inferring process from pattern is not trivial, because different processes - forest expansion and forest fragmentation - may lead to either distinct or similar patterns of patch shape and spatial context. Studying patch structure and spatial context may then provide further insight into understanding changes in vegetation pattern at landscape scale, and in disentangling the effects of concurrent processes. [ABSTRACT FROM AUTHOR]

We studied the seed predation and scatter-hoarding behaviour of Azara's agoutis Dasyprocta azarae ( Rodentia: Dasyproctidae) in relation to the seeds of the Brazilian 'pine', Araucaria angustifolia ( Araucariaceae), the rodent's main winter food source. We compared seed-removal rates, seed-caching rates, cache distances and recovery rates between a summer period of food abundance (with a low demand for A. angustifolia seeds and no such seeds naturally available) and a winter period of food scarcity (with a high demand for A. angustifolia seeds). We investigated whether the relative seed value affected the rodent's seed-handling behaviour. We predicted that during the high seed-demand period (winter): (1) cache distances would be greater; (2) fewer seeds would be stored; (3) more seeds would be recovered and the seed-recovery time would be lower. In support of our first two predictions, the caching distances were greater in winter (mean ± SE = 15.67 ± 5.11 m) than in summer (9.40 ± 1.59 m), and agoutis hoarded >9 times more seeds in summer (55) than in winter (6). Our third prediction was not supported, and the proportion of unrecovered caches and buried seed recovery times did not differ between winter (mean ± SE = 3.00 ± 0.00 days, n = 5 seeds) and summer (11.05 ± 3.68 days, n = 20 seeds). The high resource density (during summer) rather than the density of A. angustifolia seeds likely influenced seed fate. Agoutis acted mainly as predators, leaving few intact seeds, caching a low proportion of handled seeds (≅ 8%) and rapidly consuming the caches. Agoutis may cache seeds to keep them safe from competitors on a short-term basis rather than maintaining medium- or long-term reserves for use during food-scarcity periods. [ABSTRACT FROM AUTHOR]

Araucaria angustifolia (Bertol.) O. Kuntze (Araucariaceae) is a Neotropical tree, widely distributed in subtropical mountain rain forests and nearby natural grasslands of Southern Brazil. This species produces annual growth rings, but its dendroclimatic potential is barely known. In the present paper, the long-term growth patterns of A. angustifolia were investigated using annual growth ring time series and association to climate over the last century. Wood cores of A. angustifolia trees growing in forest and grassland habitats were obtained with an increment borer. The cores were surfaced, measured and cross-dated. The dated ring-width time series were standardized and submitted to correlation and principal component analysis to verify growth trends among sites and trees. Growth-climate relationships were investigated using correlation and regression analyses, comparing the ordination axes scores to regional time series of precipitation and temperature. Due to anatomical irregularities, mainly partial rings, only 35 out of 60 trees were cross-dated. The correlation and ordination analyses showed common tree-growth trends within and between sites, indicative of a regional environmental force determining inter-annual cambial activity variation. Despite growing in distinct habitats and disturbance regimes, A. angustifolia trees share a common long-term growth pattern, which is significantly related to thermal conditions during the current and previous growing seasons. Moreover, site-specific characteristics may have influenced opposite growth responses and association to climate conditions between forest and grassland trees. [ABSTRACT FROM AUTHOR]

Araucaria Forest expansion over grassland takes place under wet climate conditions and low disturbance and it is hypothesized that isolated trees established on grassland facilitate the establishment of forest woody species beneath their canopies. Forest with Araucaria angustifolia is a particular type of Brazilian Atlantic Forest and the main forest type on the highland plateau in south Brazil, often forming mosaics with natural Campos grassland. The objectives of this paper were to evaluate the role of isolated shrubs and trees as colonization sites for seedlings of Araucaria Forest woody species on grassland, to determine which species function as preferential nurse plants in the process and the importance of vertebrate diaspore dispersal on the structure of seedling communities beneath nurse plants. The study was conducted in São Francisco de Paula, Rio Grande do Sul State, where we sampled isolated shrubs and trees in natural grassland near Araucaria Forest edges. Seedlings were counted and identified, and seedling diaspore dispersal syndromes, size and colour were registered. We detected 11 woody species with a potential role in nucleating grassland colonization by forest species. Beneath the canopies of nurse plants more forest species seedlings were found compared with open field grassland and the seedlings had diaspores mostly dispersed by vertebrates. Also, more seedlings were found under the canopy of A. angustifolia than beneath other nurse plant species. We conclude that A. angustifolia trees established on grassland act as nurse plants, by attracting disperser birds that promote colonization of the site by other forest species seedlings, and that under low level of grassland disturbance, conservation of frugivorous vertebrate assemblages may increase forest expansion over natural grassland and also facilitate the regeneration of degraded forest areas. [ABSTRACT FROM AUTHOR]

We investigated patterns of spatial distribution and microhabitat selection of rodents in a patch (26 ha) of mixed ombrophilous forest (or Araucaria forest), dominated by the Araucaria‘pine’ Araucaria angustifolia, in the National Park of Aparados da Serra, RS, in southern Brazil. We conducted monthly trapping sessions lasting 6 days (from June 2000 to June 2001) using a square grid of 121 trap stations, separated by 15 m (2.25 ha). We measured 10 microhabitat variables that could influence species distribution. These variables were related to the occurrence of mammals by using canonical correspondence analysis (CCA) and stepwise multiple regression. The distribution patterns of the three most common rodents differed significantly (χ2 = 38.6; P < 0.002), with Delomys dorsalis being more clumped than the other two species. Both CCA and multiple regression analysis showed a significant effect of microhabitat variables on species occurrence. The multiple regression parameters for Oligoryzomys nigripes were R2 = 0.142, P < 0.05, for Akodon montensis were R2 = 0.222, P < 0.01, and for D. dorsalis R2 = 0.323, P < 0.001. Variables that significantly influenced species distribution were vegetation density at 1 m height and length of fallen logs for O. nigripes, canopy cover for A. montensis, and vegetation density at 2 m height, quantity of leaves of Araucaria trees (negative relationship), tree density (except Araucaria trees), and number of potential shelters, for D. dorsalis. The results indicated that D. dorsalis is the most habitat specialist among the rodent species and that there are no apparent competitive interactions. [ABSTRACT FROM AUTHOR]