Acta Botanica Brasilica 27(3): 613-623. 2013. Do edaphic aspects alter vegetation structures in the Brazilian restinga? Francisco Soares Santos-Filho1,4, Eduardo Bezerra Almeida Jr2 and Carmen Sílvia Zickel3 Received: 23 May, 2011. Accepted: 24 July, 2013 ABSTRACT The vegetation of the Brazilian restinga (coastal woodland) presents a variety of species and different characteristics, encompassing fields, fruit groves and forests on quartzarenic neosols. We hypothesised that the structure of the restinga landscape along the coast of the state of Piauí is influenced by edaphic factors and presents a pattern similar to that of other northeastern restingas. We evaluated three restingas in Piauí, using the quarter method to determine their structure. Composite soil samples were collected to determine their chemical and physical properties. Edaphic variables were correlated with plant species by canonical correspondence analysis (CCA). Phytosociological data for all three areas indicated regenerating vegetation comprising several small individuals, 82.5% of which showed a diameter at ground level ≤ 13 cm. We also observed considerable tillering. In two of the areas, there was a predominance of Fabaceae species, such as Caesalpinia pyramidalis and Copaifera martii. Although the structural characteristics of the restingas studied were similar to those of other northeastern restingas, the former showed lower Shannon diversity indices (2.18-2.44). The CCA indicated that species distribution was influenced by edaphic factors such as pH, alu- minium content and amount of organic matter. The restingas studied were similar to others along the Brazilian coast. Key words: canonical correspondence analysis, coastal vegetation, edaphic interactions Introduction processes, regeneration and occupation of areas, are still incipient for this region (Zickel et al. 2004). The Brazilian restinga (coastal woodland) occupies In the northeastern Brazilian state of Piauí, the coastline, areas along the coastline, with a variety of characteristics which forms the northern border of the state, is relatively that vary depending on edaphic factors, especially those short (66 km) and lies completely within the Parnaíba Delta related to water and nutrient availability due to the influence Protected Area. The state is considered an ecotonal zone of the sea (Scarano 2000), as well as on topographical and because of the influences it receives from central Brazil, sub- climatic factors. Although the restingas present an wide -humid areas of the Amazon and semi-arid areas of other variety of species, many originated in the Atlantic Forest. northeastern states (Farias & Castro 2004). This unique Those species could have adapted in order to colonise the situation, along with the position of the restingas, which geologically young plains (Matallana et. al. 2005). According are located near the equator, can have a strong influence to Scarano (2002), the restinga does not present endemism, on the distribution of species in the region (Gentry 1988). because of its relatively recent establishment. We hypothesised that the structure of the restinga lan- Although the coast of Brazil, with all its recesses, is dscape along the coast of the state of Piauí is influenced by more than 9000 km in length, there have been few studies edaphic factors and presents a pattern similar to that of other of its vegetation, especially in the northeast, which has a northeastern restingas. We opted to study the coast of Piauí longer coastline than does any other region of the country because it is part of a natural, protected area and because of (Araújo 1984; 2000). Most studies of the vegetation of the the lack of studies of the vegetation along the northern coast northeastern coast have focused on the state of Pernambuco of Brazil. We aimed to test the influence of edaphic factors (Zickel et al. 2007; Sacramento et al. 2007; Silva et al. 2008; related to the structure of the woody vegetation. We attemp- Almeida et al. 2009). Despite such studies, little is known ted to answer the following questions regarding the restingas about the environment, relationships within plant com- of Piauí: “Is the occurrence of woody plant species related to munities, and ecological processes along the northeastern the chemical and physical conditions of the soil?”; “Is there coast. Phytosociological studies, which are fundamental to similarity among areas in terms of the vegetation structure?”; understanding the landscape and structural organisation and “Do the structural patterns follow those reported for of plant assemblies, as well as to elucidating recruitment other restingas along the northeastern coast of Brazil?” 1 Universidade Estadual do Piauí, Centro de Ciências da Natureza, Teresina, PI, Brazil 2 Universidade Federal do Maranhão, Centro de Ciências Biológicas e da Saúde, Departamento de Biologia, São Luís, MA, Brazil 3 Universidade Federal Rural de Pernambuco, Recife, PE, Brazil 4 Author for correspondence: [email protected] Francisco Soares Santos-Filho, Eduardo Bezerra Almeida Jr and Carmen Sílvia Zickel Material and methods According to the Köppen climate classification system, the climate of the region is type Aw, which is defined as Characterisation of the study sites mega-thermal, with a rainy summer and a dry winter (Peel et al. 2007). The average annual temperature of 27.5°C, and The Piauí coast is composed of small coves and has four the average annual precipitation is 1223 mm, April being estuarine zones, created by the Parnaíba, Portinho, Camu- the rainiest month (average precipitation, 297.3 mm) and rupim and Ubatuba/Timonha Rivers (Baptista 1981). The September being the driest (average precipitation, 2.8 mm). coastal zone is located on two geologic formations: deposits of quartzose sand from the Quaternary, which are situated west and extend to the border of the state of Maranhão; and Vegetation sampling barriers from the Tertiary, which are located to the east, up In all three sampling areas, we used the point-centred to the border with the state of Ceará (Sousa & Rodrigues- quarter method to collect phytosociological data (Cottam -Neta 1996). Along the Piauí coast, mangroves are present in & Curtis 1956). In each area, five parallel transects were the estuaries and there are tabuleiro forests (coastal lowland established, 10 m apart. On each transect, 10 points were forests on Tertiary deposits) further inland, in addition to marked, also 10 m apart, for a total of 50 points. Only plants the restingas occupying the backshore region on quartzare- with a diameter at ground level (DGL) ≥ 3 cm were included nic neosols (Fernandes et al. 1996). In the region with the in the analysis. most restinga formations, some characteristic differences can be observed. Extensive areas are occupied by fields or Collection and identification of the botanical material bush formations (fruit groves), and forest formations occur in other areas. The data collection and identification of the botanical We selected three restinga landscapes in which there had material occurred between October 2006 and March 2008. been little disturbance related to human activity (Fig. 1), The botanical material was collected from the studied located in the following municipalities within Piauí: Ilha areas and identified according to standard methodology Grande (02°50’84”S; 41°47’39”W, 6.7 km inland); Parnaíba in vegetal taxonomy by using bibliographical resources (02°55’48”S; 41°40’67”W, 5.9 km inland) and Luiz Correia (identification keys, original descriptions and a specialised (02°55’89”S; 41°30’49”W, 2.3 km inland). These areas are bibliography). In cases of uncertainty, samples were sent for situated over recent geologic compartments (quartzose analysis by specialists. The specimens were added to the sand deposits - BRAZIL 2006) and represent all of the plant collection of the Dárdano de Andrade Lima Herbarium of formations located on deposits from the Quaternary. the Pernambuco State Institute of Agronomy (code, IPA). Figure 1. Map of the three sampled areas in the phytosociological studies of the restinga vegetation in the Parnaíba Delta Protected Area, state of Piauí, Brazil. 614 Acta bot. bras. 27(3): 613-623. 2013. Do edaphic aspects alter vegetation structures in the Brazilian restinga? The floristic list was organized according to the classification areas were tested with the Hutcheson t-test (Hutcheson, system established in the Angiosperm Phylogeny Group II 1970). Using the software PC-ORD for Windows, Version guidelines (APG II 2003). 4.14 (McCune & Mefford 1999), we performed a canonical correspondence analysis (CCA) to test the correlations be- Collection and analysis of soil samples tween species and edaphic factors. Among other functions, the CCA allows direct gradient order analysis, in order A total of 25 soil samples were collected from each area, to describe the arrangement of species in relation to the at depths of 0-20 cm. In each transect, five samples were edaphic variables. Two matrices were built for the CCA collected at the beginning of the crosspiece, as defined by analyses. In the first matrix, data related to the absolute a sketch, according to the phytosociological method. The frequency of species represented by two or more indivi- samples were homogenised based on the recommendations duals were included; rare species (represented by a single of Rocha et al. (2004). Each transect was represented by a individual) were excluded (Martins 1989). The second composite sample, with a total