Floristic List from a Caatinga Remnant in Poço Verde , Sergipe , Brazil

A study of the vegetation in a 71,42 ha fragment of Caatinga in Poco Verde, state of Sergipe, was carried out, and the occurrence of 170 species, 129 genera and 46 botanical families was recorded. Fabaceae (25 spp.); Euphorbiaceae (16 spp.); Solanaceae (nine spp.); Poaceae (eight spp.); Malvaceae (seven spp.); and Apocynaceae, Asteraceae, Convolvulaceae, Lamiaceae and Verbenaceae (six spp.) were the most represented families, corresponding to 55.8% of the sampled flora. The genera which represented greater floristic richness were: Croton (eight spp.), Solanum (six spp.), Senna and Mimosa (four spp.). We found 39 species of trees, 47 of shrubs, 15 of lianas and 69 of herbs. Among the species found in the studied area, 10.2% are considered endemic to the Caatinga. Compared to other areas of Caatinga, the studied area is characterized by a dry and dense forest which has suffered a medium impact due to plant extraction, being found today in a natural state of regeneration.


Introduction
The Caatinga is the type of vegetation found in the semi-arid part of northeastern Brazil, occupying an area of approximately 734.478 Km2 (UFPE 2002), which corresponds to 10% of the Brazilian territory (Ab'Saber 2003;Fernandes 2003).It covers parts of the states of Piauí, Ceará, Rio Grande do Norte, Paraíba, Pernambuco, Alagoas, Sergipe, Bahia and the northern part of Minas Gerais; it is considered the main terrestrial ecosystem in the northeastern region of Brazil.
The Caatinga began to be more studied only in the last decade.Previously, it was seen as a poor ecosystem regarding its biodiversity.Until today, less is known about its biodiversity when compared to other Brazilian biomes (Santos et al. 2011) and although taxonomically many species have been described, little is known about their physiological aspects (Leal et al. 2003).
The floristic study of a forest represents the initial step towards acquiring knowledge because, associated to information about its structure and dynamics, it provides a base that subsidizes a better biogeographical understanding, the conservation of genetic resources, the conservation of similar areas, and the restoration of degraded forest fragments, contributing substantially towards their management or towards the conservation of the fragments (Arruda and Daniel 2005;Moro and Martins 2011).
This study aimed to describe the floristic composition of a Caatinga fragment, located at "Santa Maria da Lage" settlement, in Poço Verde municipality, state of Sergipe, northeastern Brazil, with the objective of recording the floristic composition of the species in the studied area, especially based on data from taxonomic studies.The results of this work will expand the knowledge about the Abstract: A study of the vegetation in a 71,42 ha fragment of Caatinga in Poço Verde, state of Sergipe, was carried out, and the occurrence of 170 species, 129 genera and 46 botanical families was recorded.Fabaceae (25 spp.);Euphorbiaceae (16 spp.);Solanaceae (nine spp.);Poaceae (eight spp.);Malvaceae (seven spp.); and Apocynaceae, Asteraceae, Convolvulaceae, Lamiaceae and Verbenaceae (six spp.) were the most represented families, corresponding to 55.8% of the sampled flora.The genera which represented greater floristic richness were: Croton (eight spp.), Solanum (six spp.), Senna and Mimosa (four spp.).We found 39 species of trees, 47 of shrubs, 15 of lianas and 69 of herbs.Among the species found in the studied area, 10.2% are considered endemic to the Caatinga.Compared to other areas of Caatinga, the studied area is characterized by a dry and dense forest which has suffered a medium impact due to plant extraction, being found today in a natural state of regeneration.
In the settlement there is an area of about 71.42 ha (called "Reserva Legal") which is destined to protect the vegetation.This area was already explored, being characterized by a dry and dense forest, which has suffered medium intensity impacts, such as selective logging, but is now in a natural stage of regeneration.

Collection of data
The collection of the botanical material was carried out between the months of October 2009 and November 2010, registering plants with herbaceous, shrubby and arboreal habits.Reproductive samples of all species were collected, following the usual procedures suggested by Mori et al. (1989), with an effort to include the largest number of species representing plants of all habits.The collected botanical materials are deposited in the Herbarium of the Federal University of Sergipe (ASE).
The identifications were made through comparisons with existing exsiccates in the Herbarium ASE and consultations of the literature and specialists.The classification of the species into families followed the system of the Angiosperm Phylogeny Group III (APG III 2009).

Results and Discussion
A total of 243 plants, belonging to 170 species, distributed into 129 genera and 46 botanical families (Table 1) were collected, of which 153 taxa were identified to the species level.
The families Fabaceae and Euphorbiaceae are often found in studies carried out in other areas of Caatinga (Araújo et al. 1995;Alcoforado-Filho et al. 2003).These results confirm the observations by Rodal et al. (1992) who indicated these as the main families for the Caatinga, in number of genera, species and abundance of plants.Pereira et al. (2001) highlighted that the occurrence of the Rubiaceae family was also recorded in the woody component of other areas of Caatinga, but only in areas of higher humidity.
According to Andrade et al. (2005), Myracrodruon urundeuva Allemão, Commiphora leptophloeos (Mart.)J.B. Gillett and Capparis flexuosa L. are more commonly found in protected areas or in well conserved forests and are rarely found in strongly disturbed sites.These species were found in the present study, which may indicate that the area is under recovery.
The families with the highest number of genera were Fabaceae (18), Euphorbiaceae and Malvaceae (seven each), Poaceae and Asteraceae (six each), Apocynaceae, Orchidaceae and Rubiaceae (five each), and Anacardiaceae, Araceae, Cactaceae and Verbenaceae (four each).Twenty three families (50%) had only one genus.The richest genera were: Croton, with eight species; Solanum, with six; Senna and Mimosa, with four; and Ruellia, Hyptis, Jatropha, Cnidoscolus, Capparis, Mimosa and Lantana, with three species each.The other genera (108) were represented by one or two species.The high frequency of representatives of the genus Croton, especially in the understory, confirms the importance of the Euphorbiaceae family in the Caatinga.
The habits found were trees, shrubs, lianas, and herbs, with the herbaceous component representing the largest number of species (69 species or 40% of the total flora) distributed into 28 families.The richest families in the non-woody component were Poaceae, with seven species, and Asteraceae, Lamiaceae and Verbenaceae, with six species each (Table 1).The high percentage of herbaceous habits found in the area demonstrates the importance of this component in the protection of the soil and in the availability of resources for the local fauna.
The arboreal and shrubby components were represented by 39 and 47 species, respectively.For the arboreal component, the most representative families were Fabaceae, with seven species, and Anacardiaceae, with five species.The most notable arboreal elements were Aspidosperma pyrifolium (Apocynaceae), Poincianella pyramidalis (Fabaceae) and Capparis jacobinae (Capparaceae), cited in most of the surveys carried out in the Caatinga vegetation from northeastern Brazil (Araújo et al. 1995;Ferraz et al. 1998).Besides these species, the presence of Psidium schenckianum (Myrtaceae) was recorded, even though it is more common in wet mountain forests ("brejos de altitude").This probably occurred as a result of the higher local humidity.The occurrence of this species was also observed by Alcoforado-Filho et al. (2003) in a Caatinga site in the state of Pernambuco.
Regarding the shrubby extract, the more relevant families were: Euphorbiaceae and Fabaceae, with 14 and 11 species, respectively, representing species common to other areas of the Caatinga.Giulietti et al. (2002) observed that Euphorbiaceae presented the highest number of species among shrubs (Kent and Coker 1992) in less dry areas of thorny deciduous vegetation, being substituted by cacti in drier areas.Regarding the 15 species of climbers (8.8% of the total recorded species), these were distributed among eight families, of which Fabaceae was the richest, represented by three species.Thus, contrary to what has been suggested in the literature (Rizzini 1979), the semiarid vegetation presents a considerable number of species in this component.The studied Caatinga fragment presents a high diversity of species.Besides the typical species of the Caatinga vegetation, species that are generally found in wetter areas contributed towards a richer flora than most of the studied areas of Caatinga in the state of Sergipe.

Table 1 .
Species list with popular name, habits and voucher numbers in the ASE herbarium, recorded in the Caatinga forest fragment from Santa Maria da Lage settlement, Poço Verde municipality, state of Sergipe, Brazil.