ABSTRACT This study aims at identifying the formation of clusters and to evaluate the influence of chemical attributes in the soil on the groups and species in a riparian forest fragment in Campos de Cima da Serra, Rio Grande do Sul (RS). Thirteen plots (10 × 20 m) were demarcated to carry out the study. Forest inventory data were employed in a multivariate analysis using the Twinspan method and the correlation between vegetation data and chemical characterization of the soil was carried out by Canonical Correspondence Analysis (CCA). Thirty-one species were sampled (DBH ≥ 30 cm) and two floristic groups were identified. The results indicated a structural difference between the two environments, likely due to the steeper slope and less influence of groundwater. Variables such as sulfur, calcium and organic matter were explanatory of the vegetation grouping known as riparian forest of hillside and aluminum, aluminum saturation and copper of riparian forest with flat topography.

The objective of this research was to define which irrigation regime, whether or not combined with water retaining polymer doses added to the substrate, is recommended in the production of Cordia trichotoma seedlings. The substrate was used with different dosages of water retaining polymers (0, 1.5, 3.0 and 4.5 g L-1). After emergence the seedlings were subjected to different irrigation regimes (4-4-4, 4-8-8, 4-8-12, 8-8-8, 8-12-12 and 12-12-12 mm day-1, alternating them every 60 days). The experiment was conducted in a completely randomized design in a split plot scheme, where the main plot was formed by the different irrigation regimes and subplots by doses of a hidroretentor polymer. After 180 days of applying the irrigation blades, the following morphological and physiological variables were obtained. Seedlings are intolerant to water stress after 180 days under blade 4 or 12 mm constant irrigation. The permanent use of the 4 mm day-1 blade is possible, since associated with an addition of approximately 2.4 g L-1 dose of a water retaining polymer to the substrate. A suitable growth of seedlings was obtained with blades of 4-8-8 mm day-1, alternating every 60 days with the possibility of using a smaller blade at the start of growth, thereby reducing water consumption.

El objetivo de este trabajo fue definir el régimen de riego que combinado, o no, con dosis de polímero hidroretenedor en el sustrato, es indicado para la producción de plantas de Cordia trichotoma. En el sustrato fueron agregados diferentes dosis de polímero hidroretenedor (0, 1,5, 3,0 y 4,5 g L-1). Luego de la emergencia, las plantas fueron sometidas a diferentes regímenes de riego (4-4-4, 4-8-8, 4-8-12, 8-8-8, 8-12-12 y 12-12-12 mm dia-1, alternados cada 60 días). El experimento fue conducido en un diseño completamente aleatorio, en esquema de parcelas subdivididas, en que la parcela principal estuvo compuesta por diferentes regímenes de riego y la subparcela por las dosis del polímero hidroretenedor. Después de 180 días de la aplicación de las láminas de riego fueron obtenidas las variables morfológicas y fisiológicas. Las plantas presentaron estrés hídrico a los 180 días bajo la lámina de 4 o 12 mm constantes de irrigación. La utilización constante de láminas de 4 mm dia-1 es posible desde que sea asociada a la adición de, aproximadamente, 2,4 g L-1 de polímero hidroretenedor al sustrato. Se obtuvo crecimiento adecuado de las mudas con láminas de 4-8-8 mm dia-1, alternados cada 60 días, siendo posible la utilización de una menor lámina en el inicio del crecimiento, reduciendo de esta manera el consumo de agua.

RESUMO Foi realizado estudo da vegetação em fragmento de floresta estacional decidual em processo de sucessão, em área da Associação Tabor (29o43’S; 53o47’W), no município de Santa Maria (RS), Brasil. Utilizaram-se dezesseis unidades amostrais de 10 x 20 m distribuídas de forma sistemática para avaliação (medição e identificação) dos indivíduos com Circunferência à Altura do Peito (CAP) igual ou maior de 30 cm e subunidades circulares com raios de 1,78 m para identificação e contagem da regeneração (indivíduos menores de 30 cm). Observou-se a ocorrência de 64 espécies arbóreas e arbustivas de 54 gêneros e 31 famílias. As espécies com maior valor de importância foram Myrocarpus frondosus, Cupania vernalis, Ocotea puberula, Patagonula americana, Casearia sylvestris, Luehea divaricata, Enterolobium contortisiliquum e Helietta apiculata. Na regeneração, as espécies com maior densidade de indivíduos foram Trichilia elegans, Nectandra megapotamica, Actinostemon concolor, Piper gaudichaudianum, Cupania vernalis, Hybanthus bigibbosus, Aiouea saligna e Parapiptadenia rigida. Constatou-se o contínuo processo de sucessão por meio da substituição de espécies nos estratos da floresta e algumas bem-representadas desde a regeneração até o estrato superior.

ABSTRACT This work aimed at studying the vegetation in a fragment of Deciduous Seasonal Forest under successional process, in an area of the Tabor Association (29043’ S; 53047’ W), municipal district of Santa Maria, RS, Brazil. Sixteen sample units (10x20m) were systematically located in the area to allow the recording (measurement and indentification) of individual plants with a Circumference at Breast Height equal to or larger than 30cm. Sampling was also carried out in circular units with radii of 1,78m to count up and identify the regeneration (individual with CBH smaller than 30 cm). The occurrence of 64 species of trees and shrubs comprising 54 genera and 31 botanical families was observed. The most important species were Myrocarpus frondosus, Cupania vernalis, Ocotea puberula, Patagonula americana, Casearia sylvestris, Luehea divaricata, Enterolobium contortisiliquum and Helietta apiculata. In the regeneration the species with higher density of individuals were Trichilia elegans, Nectandra megapotamica, Actinostemon concolor, Piper gaudichaudianum, Cupania vernalis, Hybanthus bigibbosus, Aiouea saligna and Parapiptadenia rigida. It was demonstrated the evidence of a continuous successional process, through the replacement of species in the several strata of the forest, with some well represented from the regeneration up to the higher forest stratum.