Ary Teixeira de Oliveira-Filho

Neotropical Seasonally Dry Forests: Diversity, Endemism, and Biogeography of Woody Plants

Neotropical seasonally dry forests are found from northwestern Mexico to northern Argentina and southwestern Brazil in separate areas of varying size (fig.1-1). Their different variants have not always been considered the same vegetation type (e.g., Hueck 1978) or biogeographic unit (e.g., Cabrera and Willink 1980), but recent work has helped to define the extent, distribution, and phytogeography of seasonally dry tropical forest (SDTF) as a coherent biome with a wide Neotropical distribution (Prado and Gibbs 1993; Pennington et al. 2000; Pennington, Lewis et al. 2006). This unified interpretation is important both for biogeographic inference and for setting conservation priorities in Neotropical SDTF, which is the most threatened tropical forest type in the world (Miles et al. 2006).

Identity and relationships of the Arboreal Caatinga among other floristic units of seasonally dry tropical forests (SDTFs) of north-eastern and Central Brazil

The tree species composition of seasonally dry tropical forests (SDTF) in north-eastern and central Brazil is analyzed to address the following hypotheses: (1) variations in species composition are related to both environment (climate and substrate) and spatial proximity; (2) SDTF floristic units may be recognized based on peculiar composition and environment; and (3) the Arboreal Caatinga, a deciduous forest occurring along the hinterland borders of the Caatinga Domain, is one of these units and its flora is more strongly related to the caatinga vegetation than to outlying forests. The study region is framed by the Brazilian coastline, 50th meridian west and 21st parallel south, including the Caatinga Domain and extensions into the Atlantic Forest and Cerrado Domains. Multivariate and geostatistic analyses were performed on a database containing 16,226 occurrence records of 1332 tree species in 187 georeferenced SDTF areas and respective environmental variables. Tree species composition varied significantly with both environmental variables and spatial proximity. Eight SDTF floristic units were recognized in the region, including the Arboreal Caatinga. In terms of species composition, its tree flora showed a stronger link with that of the Cerrado Dry Forest Enclaves. On the other hand, in terms of species frequency across sample areas, the links were stronger with two other units: Rock Outcrops Caatinga and Agreste and Brejo Dry Forests. There is a role for niche-based control of tree species composition across the SDTFs of the region determined primarily by the availability of ground water across time and secondarily by the amount of soil mineral nutrients. Spatial proximity also contributes significantly to the floristic cohesion of SDTF units suggesting a highly dispersal-limited tree flora. These units should be given the status of eco-regions to help driving the conservation policy regarding the protection of their biodiversity.

Alienígenas na sala: o que fazer com espécies exóticas em trabalhos de taxonomia, florística e fitossociologia?

(Aliens in the room: what to do with exotic species in taxonomic, floristic and phytosociological studies?): The ever-growing presence of exotic organisms (many of which become invasive) throughout the planet has led to the emergence of biological invasions as a field of study within ecology. To enable communication between scientists in this field, a terminology has developed. However, this terminology has been ignored by many botanists in Brazil where there is confusion regarding definition of exotic, naturalized, invasive, weed and ruderal species, leading to inconsistent use of the concepts. Moreover, different authors have adopted antagonistic positions when dealing with exotic species existing in their study areas, either in the preparation of taxonomic treatments or in floristic and phytosociological surveys. While some authors include in floras cultivated, non reproducing species, others exclude even widespread and common invasives. We present here, in Portuguese, the main concepts related to the theme of bioinvasion and draw the attention of Brazilian authors to the necessity for consistent use of the terminological framework available for biological invasions. We also propose that authors should clearly label exotic plants reported in their work, differentiating exotics from native species. Finally, we suggest criteria to help botanists decide when exotic plants should or should not be included in taxonomic treatments or in floristic surveys.

Composição, estrutura e similaridade florística da Floresta Atlântica, na Serra Negra, Rio Preto – MG

Serra Negra is a region surrounded by some stretches of mountain, covered by Atlantic Forests and cloud scrubs, located in the southern part of Zona da Mata of Minas Gerais, in Serra da Mantiqueira, between the rises of the massif of Itatiaia (RJ, SP e MG) and the Serra do Ibitipoca (MG). The aim of this study was to determine the composition, structure and floristic similarity of arboreal flora among three forest types of Atlantic Forest (Alluvial, Montane and Cloud Forest) and also the similarity with other studies. A total of 2,572 individuals was sampled, from 194 species, 59 families and 118 genera. The highest number of species was recorded in the families Myrtaceae (30 morphospecies), Lauraceae (20), Melastomataceae (17) and Fabaceae (13). The three vegetation types associated with different environmental conditions differ in their composition and structure. The alluvial proved with low diversity and stature and high ecological dominance. The cloud forest stood out for its typical elements of altitude over other common species in the area below the range, where diversity was higher. The tree flora of Sierra Negra presents various indicator species to characteristic distribution of highlands of southeastern Brazil.

Effects of Quaternary Climatic Fluctuations on the Distribution of Neotropical Savanna Tree Species

&NA; In order to develop niche models for tree species characteristic of the cerrado vegetation (woody savannas) of central South America, and to hindcast their distributions during the Last Glacial Maximum and Last Inter‐Glacial, we compiled a dataset of tree species checklists for typical cerrado vegetation (n = 282) and other geographically co‐occurring vegetation types, e.g. seasonally dry tropical forest (n = 355). We then performed an indicator species analysis to select ten species that best characterize typical cerrado vegetation and developed niche models for them using the Maxent algorithm. We used these models to assess the probability of occurrence of each species across South America at the following time slices: Current (0 ka pre‐industrial), Holocene (6 ka BP), Last Glacial Maximum (LGM – 21 ka BP), and Last Interglacial (LIG – 130 ka BP). The niche models were robust for all species and showed the highest probability of occurrence in the core area of the Cerrado Domain. The palaeomodels suggested changes in the distributions of cerrado tree species throughout the Quaternary, with expansion during the LIG into the adjacent Amazonian and Atlantic moist forests, as well as connections with other South American savannas. The LGM models suggested a retraction of cerrado vegetation to inter‐tableland depressions and slopes of the Central Brazilian Highlands. Contrary to previous hypotheses, such as the Pleistocene refuge theory, we found that the widest expansion of cerrado tree species seems to have occurred during the LIG, most probably due to its warmer climate. On the other hand, the postulated retractions during the LGM were likely related to both decreased precipitation and temperature. These results are congruent with palynological and phylogeographic studies in the Cerrado Domain.

Humidity, low temperature extremes, and space influence floristic variation across an insightful gradient in the Subtropical Atlantic Forest

The use of well-sampled regions and insightful environmental gradients can provide important theoretical knowledge for understanding the drivers of tropical forest patterns and processes, which are necessary for biological conservation. We investigated the variation in tree species composition across a vegetation gradient in the Subtropical Atlantic Forest, as well as various predictors that could impact such patterns. The exploratory and confirmatory analyses included 178 sampling units distributed among 13 different forest types containing binary occurrence records for 935 species from 25,546 trees. Confirmatory analyses were conducted considering spatial autocorrelation, a well-known factor responsible for type I error inflations. The floristic heterogeneity of the study area was revealed by clear patterns of floristic differentiation between vegetation types, as well as by the significant improvements in local models (GWR—geographically weighted regressions) over global models (OLS—ordinary least squares). We found that the observed floristic variation has most likely been driven by humidity from the Atlantic Ocean, low temperature extremes and geographic distance. The latter was revealed by the high contribution of spatial components to the partial models. These results from a shrinking biological hotspot, particularly those concerning the importance of temperature extremes, represent crucial data for identifying conservation priorities, especially considering the seriousness of the temperature shifts predicted by global climate change scenarios.

The Brazilian Atlantic Forest: new findings, challenges and prospects in a shrinking hotspot

The Brazilian Atlantic Forest has been explored and degraded for more than 500 years (Morellato and Haddad 2000; Ribeiro et al. 2011). The forest fragments that still exist, except in protected areas such as National Reserves and Biological Reserves, are concentrated on the tops of mountains and/or steeper slopes, where agricultural activity is difficult or unfeasible, either for access or due to the generally low soil fertility (Moreno et al. 2003). This biome is, however, recognized as one of the 35 world hotspots for conservation priorities (Myers et al. 2000; Zachos and Habel 2011), and has even been referred as a ‘‘hottest hotspot’’ (Laurance 2009), ‘‘shrinking hotspot’’ (Ribeiro et al. 2011), or ‘‘top hotspot’’ (Eisenlohr et al. 2013). It is for this reason that a special issue is devoted to these forests here. Researchers have responded to this scenario, addressing important floristic and phytogeographic features of the Atlantic Forest vegetation, and producing works revealing major implications for biodiversity conservation (e.g. Oliveira-Filho and Fontes 2000; Marques et al. 2011; Werneck et al. 2011). These studies focused on tree species, the component on which there is far more available data than on most other plant types. However, in recent years, the number of surveys dealing with other growth forms has increased, along with the inclusion of life-forms other than trees in sampling protocols and floristic surveys. Including non-tree life-forms in investigations contributes to our knowledge of the geographic limits and the historical processes acting in the Atlantic Forest, in addition to providing a sounder basis for the development and technical planning of conservation policies.

Tree species composition and richness along altitudinal gradients as a tool for conservation decisions: the case of Atlantic semideciduous forest

Altitude is one of the major environmental variables influencing the distribution of tree taxa around the world, and can be a useful parameter for the development of conservation strategies. Our objectives were to obtain an overview of the conservation status of taxa from the Atlantic semideciduous seasonal forests of southeastern Brazil and check, among the floristically consistent altitudinal zones, which had the largest number of endemic, threatened and indicator species. To accomplish this, we used species occurrence and geo-climatic data from the ‘NeoTropTree’ database. First, we checked which zones were floristically consistent using an ordination method (non-metric multidimensional scaling, NMS) followed by an analysis of variance. Then, we conducted an indicator species analysis, estimated species richness, calculated the taxonomic distinctness index for all zones and evaluated important aspects for conservation, such as endemism and threat of extinction. Taxa richness, and number of endemic and threatened species decreased with increasing altitude, while the amount of indicator species for each zone increased with altitudinal elevation. These variations related to the altitudinal gradient should be considered when developing conservation strategies. We also should prioritise the conservation of the entire gradient and, whenever possible, include endemic and endangered species in forest recovery programs.

Landforms and soil attributes determine the vegetation structure in the Brazilian semiarid

The semiarid region of Brazil consists of a great variety of landscapes, soils and vegetation forms, with complex interrelations. In order to better understand this interplay, we posed two questions: Are there greater pedological similarities among the different landforms of the same catena or among the same landforms from different catenas? Which soil attributes could be the most important to segregate communities of plants? We sampled soils and vegetation on different landforms in four different catenas and performed NMS (non-metric multidimensional scaling) and ANOVA (analysis of variance) to address the first question; also, we carried another NMS following GLM (general linear model regression) to answer the second question. The first NMS indicated the existence of a fertility gradient, grouping communities in relation to similar landforms, confirmed by ANOVA. The second NMS indicated the same gradient whereas the GLM showed that is controlled by aluminum saturation, sodium saturation, phosphorous and sand content. One extreme of the gradient has uplands associated with cerrado vegetation forms whereas the other extreme slopes were associated with dry forests. The lowlands associated with dry forest represent the central position of the fertility gradient. In general, soils at similar landforms showed greater pedological similarity, and their physico-chemical attributes determined the formation and structure of vegetation. This similarity across the same landform refers to the comparable soil formation at each landform and soil age at landscape scale. The characteristics of the vegetation and soils in the Brazilian southern semiarid region indicated a previously wetter climate, during which deep weathered latosols (oxisols) were formed and remain as relics in the present semiarid.

Human Impacts Affect Tree Community Features of 20 Forest Fragments of a Vanishing Neotropical Hotspot

The loss in forest area due to human occupancy is not the only threat to the remaining biodiversity: forest fragments are susceptible to additional human impact. Our aim was to investigate the effect of human impact on tree community features (species composition and abundance, and structural descriptors) and check if there was a decrease in the number of slender trees, an increase in the amount of large trees, and also a reduction in the number of tree species that occur in 20 fragments of Atlantic montane semideciduous forest in southeastern Brazil. We produced digital maps of each forest fragment using Landsat 7 satellite images and processed the maps to obtain morphometric variables. We used investigative questionnaires and field observations to survey the history of human impact. We then converted the information into scores given to the extent, severity, and duration of each impact, including proportional border area, fire, trails, coppicing, logging, and cattle, and converted these scores into categorical levels. We used linear models to assess the effect of impacts on tree species abundance distribution and stand structural descriptors. Part of the variation in floristic patterns was significantly correlated to the impacts of fire, logging, and proportional border area. Structural descriptors were influenced by cattle and outer roads. Our results provided, for the first time, strong evidence that tree species occurrence and abundance, and forest structure of Atlantic seasonal forest fragments respond differently to various modes of disturbance by humans.