Hoehnea 45(1): 149-158, 1 tab., 5 fi g., 2018 http://dx.doi.org/10.1590/2236-8906-79/2017 Phytosociological study of a riverine forest remnant from Taquari river, State of Rio Grande do Sul, Brazil Fabiane Lucheta 1,5, Gabriel Nicolini2, Gerson Luiz Ely Junior2, Marilaine Tremarin2, Marelise Teixeira2, Úrsula Arend3, Natália Mossmann Koch4 and Elisete Maria de Freitas2 Received: 19.10.2017; accepted: 1.02.2018 ABSTRACT - (Phytosociological study of a riverine forest remnant from Taquari river, State of Rio Grande do Sul, Brazil). Aiming to characterize the structure of the arboreal community in a riverine forest remnant of the Taquari river, State of Rio Grande do Sul, 42 sampling units of 100 m2 (10 × 10 m) were located. Phytosociological parameters were also assessed and the indexes of Shannon diversity (H’) and Pielou evenness (J) were evaluated. A total of 39 species, 21 families, 2.83 nats ind-1 for H’ and 0.77 for J were recorded. Among the species found, the endemic Callisthene inundata O.L. Bueno, A.D. Nilson & R.G. Magalh. and Picrasma crenata (Vell.) Engl. are included in the list of endangered species. The density found was of 1,557.14 ind ha-1. Luehea divaricata Mart. and Lonchocarpus nitidus Benth. showed the highest indexes of importance values. Besides contributing to the knowledge of species distribution and community structure, this study points out the need for conservation of existing native forest remnants. Keywords: alien species, arboreal community, endemic species, riparian vegetation, Taquari-Antas river basin RESUMO - (Estudo fi tossociológico de um remanescente da fl oresta ribeirinha do rio Taquari, Estado do Rio Grande do Sul, Brasil). Com o objetivo de caracterizar a estrutura da comunidade arbórea de um remanescente de fl oresta ribeirinha do rio Taquari, foram estabelecidas 42 unidades amostrais de 100 m2 (10 × 10 m) e calculados os parâmetros fi tossocioló- gicos e índices de diversidade de Shannon (H’) e Equabilidade de Pielou (J). Foram amostradas 39 espécies, 21 famílias, 2,83 para H’ e 0,77 para J. Dentre as espécies Callisthene inundata O.L. Bueno, A.D. Nilson & R.G. Magalh. é endêmica, estando, junto com Picrasma crenata (Vell.) Engl., na lista das espécies ameaçadas de extinção. A densidade encontrada foi de 1.557,14 ind. ha-1. Luehea divaricata Mart. e Lonchocarpus nitidus Benth. apresentaram os maiores índices de valores de importância. Além de contribuir para o conhecimento da distribuição das espécies e estrutura da comunidade, este estudo alerta para a necessidade de conservação dos remanescentes fl orestais nativos existentes. Palavras-chave: bacia hidrográfi ca do rio Taquari-Antas, comunidade arbórea, espécies endêmicas, espécies exóticas invasoras, vegetação ripária Introduction terrestrial and aquatic (Lima & Zachia 2001), it is essential to understand the variation of this vegetation Vegetation along watercourses and around type in a large number of riverine areas and its role in springs, known as riverine forest, is characterized by maintaining fl oral biodiversity. the combination of local climate, hydrology, geology Due to these environmental characteristics, in and geomorphology factors, as they defi ne landscape Brazil, riparian formations are considered Permanent and ecological conditions (Rodrigues & Leitão-Filho Preservation Areas (PPA) protected by the Forest Code 2001). These factors, combined with sedimentation, (Law No. 4.771/65) since September 1965 (Brasil erosion and flooding, promote floristic diversity 1965). In 2012, the approval of the new Brazilian and heterogeneity in these formations (AB’Saber Forest Code (Law 12.651) repealed the Law 4.771/65, 2001, Lima & Zakia 2001). Due to the importance continuing riverine forest protection (Brasil 2012). they represent for the maintenance and development Even so, riverine formations are extremely fragmented of fundamental environmental processes for the as a result of human interference, which is responsible, conservation of animal and plant diversity, both in large part, by species abundance and composition 1. Universidade FEEVALE, Campus II, Rodovia 239, 2755. Novo Hamburgo, 93525-075 RS, Brasil 2. Universidade do Vale do Taquari - Univates, Av. Avelino Tallini, 171, 95900-000 Lajeado, RS, Brasil 3. Universidade do Vale do Taquari - Univates, Museu de Ciências Naturais, Av. Avelino Tallini, 171, 95900-000 Lajeado, RS, Brasil 4. Universidade Federal de Mato Grosso do Sul, Av. Costa e Silva, s/n, 79070-900 Campo Grande, MS, Brasil 5. Corresponding author: [email protected] 150 Hoehnea 45(1): 149-158, 2018 pattern changes, ecological processes alteration According to the Brazilian Institute of Geography (Rambaldi & Oliveira 2005) and performance losses and Statistics (IBGE 2012), the local formation belongs in their environmental functions. to the Atlantic Forest and is inserted in the Seasonal Degradation of river and stream banks from Deciduous Forest phytoecological formation. The soil Taquari-Antas river Basin (BHRTA), State of Rio is characterized by presenting a complex association Grande do Sul (RS), Brazil, took place as in all other of Eutrophic Litholic Soils (IBGE 2017). According Brazilian river basins, where few fragments remain to Köppen classification, regional climate is humid preserved (Lima et al. 2007, Rempel et al. 2007) - subtropical (Cfa) (Peel et al. 2007). today it represents around 26% of the basin area. Data Collection - In order to evaluate the arboreal These fragments need to be studied in order to know component, a fixed area method was used by their floristic and community structural diversity to systematic distribution of 42 sample units (SU’s) of create a baseline for the elaboration and implantation 100 m² (10 × 10 m) distributed at every 20 meters of projects aiming to recover the degraded portions in transects that were parallel to the riverbed and 10 of the riverbanks, favoring remnant fragments meters away from each other. The first transect was connection (Santos 2007). The floristic and structural arranged as close as possible to the river bank. In each heterogeneity of these formations, even when they of the SU’s, height was obtained by visual estimation. are close to other remnants, have to be considered Then, circumference at breast height (CBH) of all when elaborating recovering projects, and studies to trees with equal or higher than 20 cm was measured. assess this structure are crucial. Besides, native plant When specimens had two or more stems, measurement formations are being intensively threatened due to of all stems was conducted if at least one stem had the presence of invasive alien species, probably as a consequence of the fast dispersion of their seeds by CBH ≥ 20 cm, then the basal area of each stem was flood (Ede & Hunt 2008), among others. Invasive alien defined and the sum of stems was made. species usually grow rapidly, affecting native species During sampling, fertile and infertile botanical negatively and resulting in habitat alterations and material was collected for further identification loss of floristic diversity (Lealet al. 2008). Knowing using specific dichotomous keys (Sobral et al. 2013) the phytosiocologial parameters of alien species in and consulting experts. If fertile, the material was relation to native species can alert to the need of herborized and incorporated into the HVAT Herbarium measures to control such invasions. of the Universidade do Vale do Taquari - Univates Therefore, in order to contribute to information University Center Natural Sciences Museum. Native on riverine forests from RS, the objective of this study species nomenclature followed the International Plant was to characterize the tree community structure of a Names Index (http://www.ipni.org), while Tropicos riverine forest remnant from Taquari river belonging to from Missouri Botanical Garden (http://www. BHRTA in the municipality of Muçum, RS, assessing tropicos.org/) was used for alien species. Families floristic diversity, forest structure and the presence were classified according to the code for Angiosperm of alien species, besides endangered and endemic Phylogeny Group (APG IV 2016). species. Material and methods Study Area - The present study was conducted in a riverine forest remnant located on the right bank of Taquari river, Taquari-Antas river Basin, municipality of Muçum, Rio Grande do Sul (figure 1). The fragment, with 3.4 hectares, is located on a river curve where the stream floods the forest during heavy rain periods. The forest remnant appears to be well preserved, making limit with an area of cattle grazing on its upper portion, and an area of agriculture farming and forest vegetation with high incidence of alien Figure 1. Location of the study area in the municipality of Muçum, species on the sides. State of Rio Grande do Sul, Brazil. Lucheta et al.: Phytosociological study of a riverine forest 151 Data Analysis - For each sampled species, basal the distance matrix of the original data (Legendre & area (BA), density (D) absolute (A) and relative (R), Legendre 1998). frequency (F) A and R, dominance (Do) A and R and importance value index (IVI) were calculated (Muller- Results Dombois & Ellemberg 1974). Arboreal component A total of 654 living arboreal individuals diversity was estimated by the Shannon Diversity belonging to 39 species, 36 genera and 21 botanical Index (H’), and evenness was evaluated by Pielou’s families were sampled. Sampling proved to be enough Index (J) using the Past program, 3.0 version (Hammer to represent the community, as the 39 species found et al. 2001). In order to estimate expected species in this study accounted for 93% of the total estimated richness, “Bootstrap” estimator was used through by “Bootstrap” richness estimator (figure 2). a presence and absence matrix in the “EstimateS” Families with the highest species richness were software (Colwell 2006). Myrtaceae, with eight species (23.08%), Fabaceae, Based on height estimation, individuals were with seven species (17.95%) and Euphorbiaceae, with grouped into six height classes (with one meter four species (10.26%), followed by Moraceae and increment), adapted from Budke et al.