Universidade Federal de Viçosa

About: Universidade Federal de Viçosa is a education organization based out in Viçosa, Brazil. It is known for research contribution in the topics: Population & Dry matter. The organization has 16012 authors who have published 26711 publications receiving 353416 citations.

Sucessão ecológica da vegetação arbórea em uma Floresta Estacional Semidecidual, Viçosa, MG, Brasil

Abstract: O trabalho foi realizado no municipio de Vicosa (20 o45'S e 42 o07'W), no sudeste do Estado de Minas Gerais. O objetivo foi analisar as alteracoes ocorridas no estande entre os levantamentos realizados em 1984 e 1998. Para tanto, as especies foram classificadas em tres grupos ecologicos: pioneiras, secundarias iniciais e secundarias tardias. Tambem comparou-se a variacao ocorrida na distribuicao diametrica e na densidade absoluta. As comparacoes foram analisadas estatisticamente, sendo utilizado o teste "t" de Student, o teste de qui-quadrado (chi2). O estande estava composto por nove pioneiras, 56 secundarias iniciais e 29 secundarias tardias. Analisando as diferencas das medias dos numeros de individuos das secundarias iniciais, exceto Plinia glomerata (Berg.) Amshoff e Sorocea bonplandii (Daill.) Burger. Lanjow & Boer, nao foi observado estatisticamente acrescimo na densidade absoluta. A mesma situacao pode ser observada para as especies pioneiras, nao havendo excecoes. Essas constatacoes revelam tendencia de reducao da importância desses grupos, ao passo que a unica secundaria tardia (Protium warmingianum March.) que pode ser analisada, obteve estatisticamente aumento de sua densidade absoluta. Esses fatos demonstram melhoria nas condicoes de suporte da area para os grupos ecologicos mais avancados na escala sucessional.

Characterization and genetic diversity analysis of cotton cultivars using microsatellites

Abstract: Genetic diversity and the relationship between varieties are of great importance for cotton breeding. Our work was designed to estimate the informativeness of the cotton (Gossypium hirsutum L.) simple sequence repeat (SSR) microsatellite locus and to estimate the genetic distance between 53 cotton cultivars as well as to select a set of SSR primers able to differentiate between the 53 cotton cultivars studied. After extracting DNA from the 53 cultivars and characterized it using 31 pairs of SSR primers we obtained a total of 66 alleles with an average of 2.13 alleles per SSR locus and values of polymorphism information content (PIC) varying from 0.18 to 0.62, the dissimilarity coefficient varying from zero to 0.41. Statistical analysis using the unweighted pair-group method using arithmetic average (UPGMA) revealed seven subgroups which were consistent with the genealogical information available for some of the cultivars. The SSR genetic profile obtained for each of the cultivars made it possible to discriminate 52 of the 53 cultivars. This study of the genetic diversity of cotton cultivars with SSR markers support the need to introduce new alleles into the gene pool of the breeding cultivars.

Inserting Tropical Dry Forests Into the Discussion on Biome Transitions in the Tropics

Abstract: Tropical moist forests and savannas are iconic biomes. There is, however, a third principal biome in the lowland tropics that is less well known: tropical dry forest. Discussions on responses of vegetation in the tropics to climate and land-use change often focus on shifts between forests and savannas, but ignore dry forests. Tropical dry forests are distinct from moist forests in their seasonal drought stress and consequent deciduousness and differ from savannas in rarely experiencing fire. These factors lead tropical dry forests to have unique ecosystem function. Here, we discuss the underlying environmental drivers of transitions among tropical dry forests, moist forests and savannas, and demonstrate how incorporating tropical dry forests into our understanding of tropical biome transitions is critical to understanding the future of tropical vegetation under global environmental change.