No abstract

No abstract

andRéa lúcia teixeiRa de Souza 5 RESUMO -Neste estudo foi descrito a biometria de frutos e de sementes de uma população de Hymenaea stigonocarpa var. stigonocarpa foi avaliado o efeito da massa de sementes na proporção e no tempo de germinação, sob condições de laboratório (câmara de germinação) e em viveiro, considerando como critérios de germinação a protrusão da raiz primária e a expansão de eófilos. Esta população de jatobá-do-cerrado apresentou uma grande variação no tamanho de frutos e de sementes. A massa das sementes variou entre 0,546 e 7,666 g e estas foram classificadas em pequenas, médias e grandes. Uma proporção maior de sementes classificadas como médias, emitiu a raiz primária em relação às grandes, enquanto as pequenas ocuparam posição intermediária. A massa de sementes não influencia a proporção de sementes que apresenta expansão de eófilos. As sementes grandes emitem a raiz primária mais rapidamente que as pequenas. O tempo médio da expansão de eófilos decresce com a redução da massa de sementes. Apesar das sementes médias e pequenas possuírem maior potencial para expor a raiz primária, estas apresentam maior taxa de mortalidade na transição entre as fases de protrusão da raiz primária e de expansão de eófilos.Termos para indexação: biometria, protrusão da raiz primária, expansão de eófilos. FRUIT AND SEED SIZE AND THEIR INFLUENCE ON THE GERMINATION OF Hymenaea stigonocarpa var. stigonocarpa Mart. ex Hayne (LEGUMINOSAE-CAESALPINOIDEAE)ABSTRACT -This study describes the biometry of the fruits and seeds of a population of Hymenaea stigonocarpa var. stigonocarpa. The effect of seed weight on the proportion and time of germination was evaluated under laboratory (BOD incubator) and nursery conditions, considering as criteria for germination, primary root protusion and eophylum expansion. This population of H. stigonocarpa var. stigonocarpa varied significantly in fruit and seed size with seed weights ranging between 0.546 and 7.666 g and classified as small, medium and large. A higher proportion of medium-sized seeds emitted the primary root compared to large seeds, whereas small seeds showed an intermediate pattern. However, seed weight did not influence the proportion of seeds that expanded the eophylum. The primary root of large seeds emerged faster than those of small

No abstract

The influence of the architecture of vegetative branches on the distribution of plant-dwelling spiders has been intensively studied, and the effects on the aggregation of individuals in several spider species on plants include variation in prey abundance, availability of predator-free refuges and smoother microclimate conditions. The emergence of inflorescences at the reproductive time of the plants changes branch architecture, and could provide higher prey abundance for the spiders. The distribution of spiders between inflorescences and vegetative branches was compared on four widespread plant species in a Brazilian savannah-like system. Inflorescences attracted more spiders than vegetative branches for all plant species sampled. The influence of branch type (inflorescence and vegetative) on spider distribution was also evaluated by monitoring branches of Baccharis dracunculifolia DC. in vegetative and flowering periods for 1 year, and through a field experiment carried out during the same period where artificial inflorescences were available for spider colonization. Artificial inflorescences attached to B. dracunculifolia branches attracted more spiders than non-manipulated vegetative branches for most of the year. However, this pattern differed among spider guilds. Foliage-runners and stalkers occurred preferentially on artificial inflorescences relative to control branches. The frequencies of ambushers and web-builders were not significantly different between treatment and control branches. However, most ambush spiders (65%) occurred only during the flowering period of B . dracunculifolia , suggesting that this guild was influenced only by natural inflorescences. The experimental treatment also influenced the size distribution of spiders: larger spiders were more abundant on artificial inflorescences than on vegetative branches. The hypothesis that habitat architecture can influence the spider assemblage was supported. In addition, our observational and experimental data strongly suggest that inflorescences can be a higher quality microhabitat than non-reproductive branches for most plant-dwelling spiders.

We compared the abundance of foliage‐living spiders among seven widespread plant species comprising a gradient of levels of structural complexity in a tropical savannah‐like region in southeastern Brazil. Spider abundance among plant species was positively related to the foliage density of their branches. A field experiment using artificial branches was carried out to isolate foliage density effects on spider abundance, thus controlling both biomass and texture effects. Artificial branches were attached to branches of three plant species with similar foliage density, Baccharis dracunculifolia, Diplusodon virgatus, and Microlicia fasciculata. Two treatments were set up: artificial branches with higher foliage density attracted more spiders than those with lower foliage density. The guild structure of hunting spiders was compared among vegetative branches of three plant species with different levels of foliage density: B. dracunculifolia, D. virgatus, and Bidens gardneri. Stalker, and ambusher spiders were more abundant on branches of B. dracunculifolia, which had the highest foliage density. Foliage‐runners constituted the dominant guild on D. virgatus and B. gardneri, which have lower foliage density branches. Our results suggest that branch architecture is the most important factor determining the abundance of plant‐dwelling spiders in the study area independently of branch biomass, leaf surface area or texture.

The successful establishment of trees in pastures may he related to species, seed size, and weed control treatments. This study experimentally evaluated the emergence, establishment after 2 years, and growth of individuals of 7 tree species with different seed sizes sowed under three weeding methods (no weeding, grasses clipped, and grasses removed). The experiment was carried out in a tropical abandoned pasture in Midwestern Brazil, dominated by the exotic invasive grass Urochloa brizantha. The effect of seed size on seedling emergence was significant and was more intense in the no weeding and weeding treatment plots than in grasses clipped. Furthermore, an increase in seed size resulted in an increase in the probability of establishment of tree species, although this pattern also differed among weeding treatments. The increase in seed size reflected negatively on tree growth in the absence of grasses, whereas in the presence of grasses there was an inverse relationship. The experimental results suggested that the use of seeds of different sizes for direct seeding in pastures is a possible strategy of Fabaceae tree species reintroduction in pastures within the Cerrado. Fabaceae species with seeds larger than 100 mg can establish in areas with no weeding, whereas species with seeds smaller than 50 mg can establish preferentially in areas with weeding, growing faster than larger ones. Thus, weeding strategies can determine the success of direct seeding of different species in restoration projects of tropical pastures.

RESUMO -(Fitossociologia de um trecho da mata ciliar do rio da Prata, Jardim, MS, Brasil). O presente estudo teve como objetivos descrever a riqueza e a diversidade em espécies e analisar os aspectos fitossociológicos de um trecho da mata ciliar do rio da Prata, localizado na Fazenda Nossa Senhora Aparecida no município de Jardim, MS. Seis transectos de 150 m cada foram distribuídos aleatoriamente perpendiculares à margem do rio e subdivididos em 90 parcelas de 10 m×10 m. Em cada parcela foram amostrados todos os indivíduos com diâmetro à 1,30 m de altura do solo (DAP) ≥ 3,18 cm, totalizando 661 indivíduos pertencentes a 33 famílias, 57 gêneros e 66 espécies. As famílias Meliaceae, Mimosaceae, Sapindaceae, Euphorbiaceae, Fabaceae, Myrtaceae e Rutaceae destacaram-se pelo elevado número de espécies. Myrcianthes pungens (O. Berg) D. Legrand, Adelia membranifolia (Müll. Arg.) Chodat & Hassl., Dalbergia sp., Holocalyx balansae Micheli, Unonopsis lindmanii R.E. Fr., Guarea kunthiana A. Juss., Trichilia claussenii C. DC., Guarea guidonea (L.) Sleumer, Averrhoidium paraguaiense Radlk.e Astronium graveolens Jacq. foram as espécies de maior valor de importância. O índice de diversidade de Shannon (H') obtido foi 3,413 nats/indivíduo e a eqüabilidade (J') foi 0,815. A densidade e a área basal estimada foi 734,44 indivíduos/ha e 21,32 m²/ha respectivamente. Os resultados obtidos neste trabalho reforçam a necessidade de preservação da mata ciliar do rio da Prata e são de extrema importância para subsidiar projetos de manejo e recomposição nestas formações. Palavras-chave: mata ciliar, comunidade arbóreo-arbustivo, fitossociologia, Serra da BodoquenaABSTRACT -(Phythossociologic along a riparian forest at rio da Prata, Jardim, Mato Grosso do Sul State, Brazil). The present study describes species richness and diversity, and analyses phythossociologic aspects of a riparian forest at Rio da Prata, Jardim district, Mato Grosso do Sul State, Brazil. The phytosociological study was carried out on six 150 m transects perpendicular to the river subdivided in 90 quadrats (10 m×10 m). All trees and shrubs with a minimum of 3,18 cm diameter at breast height were recorded, totalizing 661 individuals of 33 families, 57 genera and 66 species. The families with high number of species are Meliaceae, Mimosaceae, Sapindaceae, Euphorbiaceae, Fabaceae, Myrtaceae and Rutaceae. The species with the highest importance values are Myrcianthes pungens (O. Berg) D. Legrand, Adelia membranifolia (Müll. Arg.) Chodat & Hassl., Dalbergia sp., Holocalyx balansae Micheli, Unonopsis lindmanii R.E. Fr., Guarea kunthiana A. Juss., Trichilia claussenii C. DC., Guarea guidonea (L.) Sleumer, Averrhoidium paraguaiense Radlk. and Astronium graveolens Jacq. The Shannon diversity index is H'=3,413 nats/individual and eqüability is J=0,815. The density and basal area are respectively 734,44 ind./ha and 21,32 m²/ha. The results obtained in this study reinforce the protection of belt of riparian vegetation in the Rio da Prata, and will support management and restoration ...