Rafael Carvalho da Costa

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.

Vegetação, unidades fitoecológicas e diversidade paisagística do estado do Ceará

article presents a review of the vegetation types occurring in Ceara state, Northeastern Brazil. We explain how climate and geomorphology have produced the different landscapes in Ceara and aim to characterize the main features, distribution and anthropogenic threats for each vegetation type. To achieve this we performed fieldwork and evaluated available maps and the literature in order to summarize the main attributes of each vegetation type. We also compiled floristic surveys for Ceara state and used multivariate analysis to compare the similarity of species composition among the different phytoecological units and to interpret the biogeographical patters observed.