Francisca Soares de Araújo

Flora e aspectos auto-ecológicos de um encrave de cerrado na chapada do Araripe, Nordeste do Brasil

This study subject to investigate the floristic composition and richness, the reproductive phenological patterns, the dispersal syndromes and life forms of species of a disjunt cerrado in semiarid climate at Araripe plateau during a one year period. We found 107 species and 41 families. Fabaceae, Myrtaceae, Poaceae, Apocynaceae, Euphorbiaceae and Malpighiaceae showed the largest number of species. For 47 of the woody species found, we studied the geographical distribution based on 27 papers of the Brazilian cerrados. Twelve species are of widespread occurence in the cerrado, and 13 are restricted to the Araripe plateau. Zoocory, autocory, and anemocory are the predominant syndromes of dispersal. The predominant life forms were phanerophytes (50.7%), hemicriptophytes (14.9%) and camephytes (13.1%). The cerrado of Araripe have lower species richness than continous cerrados, but a similar pattern of reproductive phenology, dispersal syndromes and life forms in more humid zones.

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.

Florística e formas de vida ao longo de um gradiente topográfico no centro-oeste do estado do Ceará, Brasil

To test whether the flora is organized in discrete or continuous units along a topographic gradient, three physiognomies were assessed on different soil classes in a semi-arid region of northeastern Brazil: caatinga (xeric shrubland) at altitudes from 300 to 500 m, deciduous forest at altitudes from 500 to 700 m and carrasco (deciduous shrubland) at 700 m. In each physiognomy a species inventory was carried out, and plants were classified according to life- and growth-forms. Species richness was higher in the deciduous forest (250) than in the carrasco (136) and caatinga (137). The caatinga shared only a few species with the carrasco (6 species) and the deciduous forest (18 species). The highest species overlap was between the deciduous forest and the carrasco (62 species). One hundred and four species occurred only in the caatinga, 161 only in the deciduous forest and 59 only in the carrasco. Woody species predominated in physiognomies on sedimentary soils with latosol and arenosol: 124 species occurred in the deciduous forest and 68 in the carrasco. In the caatinga on crystalline basement relief with predominance of planosol, herbs showed the highest species richness (69). Comparing the biological spectrum of Brazilian plant life-forms, the caatinga stood out with higher proportion of therophytes and chamaephytes. Considering the flora of the three phytophysiognomies studied here, we can affirm that the caatinga is a discrete floristic unit.

Densidade, germinação e flora do banco de sementes no solo, no final da estação seca, em uma área de caatinga, Quixadá, CE

This study investigated density, germinability and floristic composition of the soil seed bank in an area of caatinga (thorny deciduous woodland). Random soil samples were collected in a single sampling at Fazenda Nao Me Deixes, Quixada, CE, from litter (n=100), 0-5cm depth layer (n=100) and 510cm layer (n=80). The seedling emergence method was used to determine density and germination curve. The floristic composition was determined using seedling morphology. The total density of the bank was 807 seeds.m2 and specific densities were 352 seeds.m-2 (litter), 304 seeds.m-2 (0-5cm) and 108 seeds.m-2 (5-10cm). Most of the seeds germinated between the first and fourth weeks: 91% (n=1278 ; litter), 88% (n=1061 ; 0-5cm depth) and 89% (n=307; 5-10 depth), but some seeds germinated for up to 14th week. We determined 40 different morphospecies. The germination of about 88% of the seeds between the first and fourth week suggests that most caatinga seeds germinate at the onset of the favorable season, probably losing dormancy, if it exits, during the dry season.

The Role of Edaphic Environment and Climate in Structuring Phylogenetic Pattern in Seasonally Dry Tropical Plant Communities

Seasonally dry tropical plant formations (SDTF) are likely to exhibit phylogenetic clustering owing to niche conservatism driven by a strong environmental filter (water stress), but heterogeneous edaphic environments and life histories may result in heterogeneity in degree of phylogenetic clustering. We investigated phylogenetic patterns across ecological gradients related to water availability (edaphic environment and climate) in the Caatinga, a SDTF in Brazil. Caatinga is characterized by semiarid climate and three distinct edaphic environments – sedimentary, crystalline, and inselberg –representing a decreasing gradient in soil water availability. We used two measures of phylogenetic diversity: Net Relatedness Index based on the entire phylogeny among species present in a site, reflecting long-term diversification; and Nearest Taxon Index based on the tips of the phylogeny, reflecting more recent diversification. We also evaluated woody species in contrast to herbaceous species. The main climatic variable influencing phylogenetic pattern was precipitation in the driest quarter, particularly for herbaceous species, suggesting that environmental filtering related to minimal periods of precipitation is an important driver of Caatinga biodiversity, as one might expect for a SDTF. Woody species tended to show phylogenetic clustering whereas herbaceous species tended towards phylogenetic overdispersion. We also found phylogenetic clustering in two edaphic environments (sedimentary and crystalline) in contrast to phylogenetic overdispersion in the third (inselberg). We conclude that while niche conservatism is evident in phylogenetic clustering in the Caatinga, this is not a universal pattern likely due to heterogeneity in the degree of realized environmental filtering across edaphic environments. Thus, SDTF, in spite of a strong shared environmental filter, are potentially heterogeneous in phylogenetic structuring. Our results support the need for scientifically informed conservation strategies in the Caatinga and other SDTF regions that have not previously been prioritized for conservation in order to take into account this heterogeneity.

Composição florística e estrutura de um fragmento de vegetação savânica sobre os tabuleiros pré-litorâneos na zona urbana de Fortaleza, Ceará

Urban growth promotes reduction in the vegetation cover, introduction of exotic species and has serious implications for biological conservation. In the urban area of Fortaleza, Ceara state, a vegetation fragment with savannic physiognomy (24 ha – 3o47’55”S and 38o29’10”W) was sampled for a floristic survey and had 1 ha subjected to a phytosociological inventory. The floristic list of the fragment, considered a priority area for municipal conservation, is showed here. Phytosociological data have also been sampled, providing more information about the savannas from the Brazilian’s Northeast coast. For the floristic list, species from all growth forms present in the fragment were collected. For the description of the structure of the vegetation, we assigned randomly eight transects with 5 × 250 m (1ha in total) in which the perimeters at ground level (PNS) and the total height of individual plants were measured for all woody plants with PNS greater than or equal to 9 cm. In the floristic survey we collected 151 species (138 indigenous and 13 exotic) and in the phytosociological study, 37 species (35 native). The density and basal coverage of the community were 1218 ind/ha and 7.34 m2/ha, respectively. The average height and average diameter were respectively 2.53 ± 1.29 m and 6.68 ± 5.67 cm. Although our study site is geographically out of the Cerrado domain, it has structural variables compatible with the ones observed within the range of variations found in other Cerrado areas.

Composição florística da floresta estacional decídua montana de Serra das Almas, CE, Brasil

In the Brazilian semi-arid region, the flora in the sedimentary basins has been poorly studied, but the few surveys already done indicate great floristic and physiognomic heterogeneity. Even neighboring sites may be floristically different. To test this hypothesis, the floristic composition and the biological spectrum of the seasonal deciduous forest at Serra das Almas, Ceara, was analyzed and compared to those of 14 other northeastern Brazil sedimentary areas. A total of 104 species belonging to 40 families were found at the 1 ha site. Fabaceae, Euphorbiaceae, Erythroxylaceae and Myrtaceae were the families with the most species and phanerophytes the main life form, comprising 87% of the species. About 72% of the species were trees and shrubs, 15% were lianas, 6% understory shrubs and 7% herbs. A cluster analysis of the woody flora of the 14 areas, using the Jaccard index and a posteriori group averages, indicated the formation of groups as a function of geographical proximity of the areas. However, this effect was not significant, according to the Mantel test, demonstrating floristic heterogeneity even in neighboring areas. The flora of the forest at Serra das Almas was most similar to that of the vegetation found atop the Ibiapaba plateau.

Physiognomy and structure of a caatinga with Cordia oncocalyx (Boraginaceae), a new type of community in Andrade-Lima's classification of caatingas

Recentemente foi proposta a inclusao de fisionomias com Cordia oncocalyx Allemao (Boraginaceae) como um novo tipo/unidade a classificacao de caatingas de Andrade-Lima (CFFAL). Porem, nenhum estudo avaliou quantitativamente essa proposta. Este estudo visou descrever a fisionomia e estrutura de uma caatinga com C. oncocalyx comparando-a a outros estudos para verificar diferencas estruturais e fisionomicas. Amostrou-se 1795 individuos de 25 especies, somando uma area basal de 35,26 m2. C. oncocalyx e Mimosa caesalpiniifolia Benth. (Fabaceae) representaram 48% do VI total. A fisionomia foi caracterizada pelo predominio de individuos de altura intermediaria (3‒4 m) e concentracao de area basal nos individuos altos (> 8 m). Dentre as cinco especies com maior valor de importância (VI), apenas uma teve frequencia alta dentre as cinco especies de maior VI de levantamentos compilados (16/35). Desses levantamentos, apenas dois eram comparaveis a este estudo e so um pode ser classificado conforme a CFFAL, inserindo-se dentre caatingas arboreas abertas. Nesse caso, a comunidade era densa e dominada por individuos finos e baixos, em contraste a caatinga aqui estudada. Os resultados indicam a adequacao da inclusao das caatingas com C. oncocalyx dentre caatingas florestais medias e baixas da CFFAL. Porem, o baixo numero de estudos comparaveis limita o alcance de generalizacoes.

Septoglomus fuscum and S. furcatum, two new species of arbuscular mycorrhizal fungi (Glomeromycota)

Two new arbuscular mycorrhizal fungal species, (Glomeromycota) Septoglomus fuscum and S. furcatum, are described and illustrated. Spores of S. fuscum usually occur in loose hypogeous clusters, rarely singly in soil or inside roots, and S. furcatum forms only single spores in soil. Spores of S. fuscum are brownish orange to dark brown, globose to subglobose, (20–)47(–90) μm diam, rarely ovoid, 21–50 × 23–60 μm. Their spore wall consists of a semi-persistent, semi-flexible, orange white to golden yellow, rarely hyaline, outer layer, easily separating from a laminate, smooth, brownish orange to dark brown inner layer. Spores of S. furcatum are reddish brown to dark brown, globose to subglobose, (106–) 138(–167) μm diam, rarely ovoid, 108–127 × 135–160 μm, usually with one subtending hypha that is frequently branched below the spore base, or occasionally with two subtending hyphae located close together. Spore walls consists of a semipermanent, hyaline to light orange outermost layer, a semipermanent, hyaline to golden yellow middle layer, and a laminate, smooth, reddish brown to dark brown innermost layer. None of the spore-wall layers of S. fuscum and S. furcatum stain in Melzer’s reagent. In the field, S. fuscum was associated with roots of Arctotheca populifolia colonizing maritime dunes located near Strand in South Africa and S. furcatum was associated with Cordia oncocalyx growing in a dry forest in the Ceará State, Brazil. In single-species cultures with Plantago lanceolata as host plant, S. fuscum and S. furcatum formed arbuscular mycorrhizae. Phylogenetic analyses of the SSU, ITS and LSU nrDNA sequences placed the two new species in genus Septoglomus and both new taxa were separated from described Septoglomus species.

Do vegetative and reproductive phenophases of deciduous tropical species respond similarly to rainfall pulses

Deciduous trees with high-density wood that occur in dry seasonal tropical regions respond to rainfall seasonality with synchrony in phenophases. However, they may exhibit interannual differences in synchrony and intensity of phenophases, as strategy for large variations in duration and intensity of rainfall pulses. Nevertheless, it remains unknown how phenophases of deciduous trees of the Brazilian semi-arid region respond to rainfall variations. The phenology of Cordia oncocalyx was monitored in deciduous thorny woodland (Caatinga), from April 2009 to March 2011, and was correlated with rainfall, soil humidity, temperature, and photoperiod. The rainy years 2009 and 2011 exhibited higher duration of rainfall pulses and lower frequency of interpulses, but in 2010 pulse duration and total rainfall were lower. Circular statistics showed leaf flush followed by flowering and fruiting in the rainy season, and leaf fall and seed dispersal in the dry season. Both the vegetative and reproductive phenophases respond similarly to variations in rain pulses, with adjustments in time, duration, and intensity, which were correlated with variations in rainfall and soil humidity, excluding photoperiod as a trigger. Total defoliation occurred in the driest months of each year, November to December 2009 and August to October 2010. A sporadic leaf flush in November 2010 was triggered by occasional rains. Vegetative and reproductive synchronies were high in rainy years, but in 2010 synchrony was low, flowering was delayed and reduced, and, despite the low fruiting, we recorded high density in the seed bank. Lower synchrony, temporal separation of phenophases, and storage of fruits on the ground were risk-spreading strategies used by the population in the dry year, which suggest intrapopulation variability in responses to hydric stress. We believe that this plasticity contributes to high species density in the Caatinga.