The objective of this study was to determine the species richness and abundance of the seed bank and the influence of soil attributes along an elevation gradient (800–1400 m a.s.l.). We examined the floristic similarity among areas and determined the regional diversity along this gradient in Serra do Cipó (Minas Gerais, Brazil). A total of 1975 individuals from 149 species were germinated. Richness and abundance were not linearly related to elevation, and exhibited a threshold at 1200 m. The low degree of similarity among the areas reflects environmental heterogeneity, resulting from a rich mosaic of habitats, distinguished by the substrate configuration, continuity of vegetation, floristic composition, and proportion of exposed rock. The diversity between plots of different areas (β2) contributed to regional diversity, and species turnover was the most important factor. The physical variables and base saturation, which had high spatial heterogeneity, may be the most important factors with which to determine species turnover and β diversity. The studied seed bank is strongly influenced by edaphic variables, with a gradient of increasing acidity and proportion of fine sand, and decreasing proportion of clay and organic matter, with elevation. In addition, species richness was influenced by cation exchange capacity, organic matter, and clay; and abundance was influenced by cation exchange capacity, H + Al, organic matter, and base saturation.

RESUMOEste trabalho apresenta a estrutura de trechos de Floresta Estacional Sempre-Verde do Rio das Pacas e avalia a similaridade florística de dez áreas localizadas nas Bacias Hidrográficas Pacuneiro e Pacas, Mato Grosso. Foram alocadas 14 parcelas (25 × 10 m) em cada trecho (nascente, meio e foz), sendo amostrados todos os indivíduos com Circunferência à Altura do Peito ≥ 15 cm e realizada a análise dos parâmetros fitossociológicos, além da similaridade florística pelo Índice de Jaccard. A densidade total foi de 1.606 ind./ha. As famílias com maior riqueza foram Anonnaceae (9 espécies); Fabaceae (9); Melastomataceae (6) e Burseraceae (5). ABSTRACTThis study presents the structure of forest stands of an Evergreen Seasonal Forest along the Pacas River and evaluates the floristic similarity of ten areas located in the Pacuneiro and Pacas river basins in Mato Grosso state, Brazil. Each section (source, middle, and mouth) was divided into 14 plots (25x10 m). All individuals with diameter at breast height (DBH) ≥ 15 cm were sampled. Phytosociological parameters and floristic similarity (by Jaccard index) were analyzed. Total density was 1,606 ind./ha. The most commonly found families in number of species were Anonnaceae (9), Fabaceae (9), Melastomataceae (6), and Burseraceae (5). The species Jacaranda copaia (Aubl.) D. Don, Ocotea caudata (Nees) Mez, Ocotea guianensis Aubl., and Zigia cataractae (Kunth) L. Rico presented the highest importance values. The Shannon (3.67) and equability (0.86) indexes found were similar to those of other riparian forests. The areas of the source and middle of the river showed the highest floristic similarity (J = 0.71).

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RESUMOObjetivou-se, com este trabalho, caracterizar a embebição e avaliar a qualidade fisiológica de sementes de Apuleia leiocarpa após o osmocondicionamento. O estudo da embebição foi realizado em sementes intactas e escarificadas, em água destilada durante 96 horas. No estudo do osmocondicionamento, as sementes escarificadas foram separadas em três sublotes (L1; L2; L3), o primeiro foi condicionado em água destilada (controle), o segundo e o terceiro foram osmocondicionados em PEG 6000, nos potenciais de -0,4 e -0,8 MPa, respectivamente, por 10 horas. Posteriormente, as sementes foram acondicionadas em sacos plásticos e mantidas sob temperatura controlada de 3 ± 1°C. A semeadura foi realizada após 0, 30, 60, 90 e 120 dias do osmocondicionamento. A qualidade das sementes foi avaliada pelos testes: germinação, índice de velocidade de germinação, frequência relativa de germinação, comprimento da parte aérea e radicular e massa seca das plântulas. A embebição das sementes escarificadas de Apuleia leiocarpa segue o modelo trifásico de absorção de água, com início após três horas e culmina com a protrusão da raiz primária após 72 horas. As sementes osmocondicionadas em -0,8 MPa de PEG mantiveram a qualidade fisiológica, enquanto as sementes osmocondicionadas em água e em -0,4 MPa de PEG reduziram linearmente a porcentagem e a velocidade de germinação, o comprimento e a biomassa seca das plântulas. ABSTRACTThe aim of this work was to characterize the imbibition and to evaluate the physiological quality of Apuleia leiocarpa seeds after priming. It was done the immersion of intact and scarified seeds in distilled water for 96 hours. In the study of priming, the scarified seeds were separate on three lots (L1, L2, L3), the first has been conditioned in distilled water only (control), the second and the third were osmoconditioned in PEG 6000, at potentials of -0.4 and -0.8 MPa, respectively, for 10 hours. Then, the seeds were placed in plastic bags and kept under controlled temperature of 3°C ± 1. Sowing was performed after 0, 30, 60, 90 and 120 days of priming. Seed quality was evaluated by: germination percentage, germination speed index, relative frequency of germination, root length, shoot length, and seedling dry weight. The seed imbibition of Apuleia leiocarpa follows the three-phase model of water absorption, starting after three hours and culminates with the primary root protrusion after 72 hours. The primed seeds in -0.8 MPa of PEG maintained the physiological quality of seeds, while seeds primed in water and -0.4 MPa of PEG linearly

Canopy species can act changing abundance, survival and spatial distribution of other species below. The present study investigated the potential of four native species from the Atlantic Forest (Bixa arborea Huber, Inga laurina (Sw.) Willd., Joannesia princeps Vell. and Senna multijuga var. verrucosa (Vogel) H.S. Irwin & R.C. Barneby) at two spacings (2 9 2 and 3 9 3 m) in facilitating natural regeneration in areas undergoing forest restoration in southeastern Brazil. Circular plots were established under the canopies of each individual of these species and in open areas. All regenerating tree species were counted and identified. Joannesia princeps and S. multijuga var. verrucosa supported a greater richness of species under their canopy compared to the control area, but did not differ from the other species. The richness of regenerating trees under Bixa arborea and Inga laurina canopy did not differ from the control area. A greater abundance of regenerating trees was found below Inga laurina, Joannesia princeps and S. multijuga var. verrucosa. Trees planted at 2 9 2 m spacing sheltered a greater richness of regenerating tree species than at 3 9 3 m spacing. The species Joannesia princeps and S. multijuga var. verrucosa and the use of 2 9 2 m spacing are therefore recommended for accelerating the natural succession of degraded areas. Knowledge of the best combinations of species and spacing schemes to use to restore Atlantic rain forest is valuable because this design can guide the structuring and composition of regenerated forests.