Fenologia e chuva de sementes em Floresta Estacional Semidecidual no município de Viçosa, Minas Gerais, Brasil. / Phenology and seed rain in Semidecidual Seasonal Forest in Viçosa, Minas Gerais, Brazil

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The present study was divided in two chapters. On the first it was aimed to study the phenology of 20 arboreal species and to answer the following questions: (1) Which is the seasonality degree in the production of flowers, fruits, falling and leaf shooting? (2) Are there any flowering and fructification synchrony intra and interespecific? (3) What is the influence of weather conditions on the phenological cycles? (4) The production of diaspores, zoocorics and anemorics would be related to climatic seasonality? (5) The phenological behavior of the studied species would be favoring their abundance in the area of study? The studies were carried out for 2 consecutive years, from December 2004 to November 2006 and the selected species represented the local arboreal community, because they totalized 81.25% of the relative density and 75.65% of the significance value to the interval of the studied fraction, a Semidecidual Seasonal Forest in Viçosa (2045S and 4255W), Minas Gerais, located in the campus at the Universidade Federal de Viçosa and it has been regenerated for 81 years. The phenological observations were done monthly and 10 adult individuals were followed for each species, totalling 200 individuals. Piptadenia gonoacantha and Chrysophyllum gonocarpum neither flowered nor showed defined falling and leaf shooting. The flowering of the other species, as a whole, was continuous. The flowering of most species was annual: Protium warmingianum, Siparuna guianensis, Plinia glomerata and Dalberia nigra flowered in the dry season and the others in the rainy season. Four out of the 18 species that flowered, werent fruitful: Casearia decandra, C. ulmifolia, Anadenanthera peregrina and Myrciaria axilaris. There was a predominance of the species with zoocorics diaspores (65%) and zoochory was noted in species with varied deciduality degree, while anemochory prevailed in decidual and semidecidual species. The vegetative phenology showed a marked seasonality; all the species that showed decidual or semidecidual behavior, the leaf falling was concentrated in the dry season. Significant correlations among the phenophases and the climatic variables were recorded. Within the two years of study, it was recorded the stability on the phenologic behavior of Rollinia sylvatica, Trichilia pallida, Siparuna guianensis, Brosimum glaziovii, Sorocea bonplandi, Plinia glomerata, Coutarea hexandra, Allophylus edulis and Luehea grandiflora, showing that they are adapted to the conditions in which they are submitted and that they showed higher probabilities to remain in the local of the study. On the other hand, species in early succession phase such as Piptadenia gonoacantha and Anadenanthera peregrina seemed to show reproductive restraints and likely to leave the system. In the second chapter it was aimed to evaluate, by analyzing the seed rain, the floristic composition and density and frequency of seeds, in 25 traps along one hectare in the same fraction in the Semidecidual Seasonal Forest of the previous chapter. Besides that, to classify the identified taxons regarding to life form, syndromes of dispersion, and on the arboreal regarding to the phase of succession and to verify floristic similarities among the species identified in the seed rain and the arboreal seeds located in the same plots. The work was carried out in the same year, that is, from December 2004 to November 2006. Monthly, all the material placed in the traps, was harvested for identification and separation of the diaspores and counting of the seeds. Forty three taxons were recognized at the specific level, 5 at the generic level, 3 at the family level and 5 were unsettled. Seventeen families were identified, Leguminosae was represented by 11 species. The dominant life form was arboreal (63.1%) in which 70.8% were classified as early secondaries; 20.8% as late secondaries and 84% as pioneers. Lianas were represented by 28.9% of the sampled species, herbaceous by 5.3% and shrubs by 2.6%. In the two years of study 16,986 seeds were counted, 712 in the first year and 16,274 in the second. The seed mean density in the first year was 113.92 seeds / m2 and 2.603,84 seeds / m2 in the second year. Those differences showed spatial and seasonal heterogeneity of a seed rain. The floristic similarity was found by Sorensen index among the species in the seed rain and the arboreal species from the studied interval was 32%, a value considered to be low (a 50%). This result showed that the adjacent arboreal vegetation composition had a low influence on the seed rain.

ASSUNTO(S)

seed rain floresta estacional semidecidual botanica aplicada fenologia phenology chuva de sementes semidecidual seasonal forest

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