José Carlos Silva

Banco de sementes em cerrado sensu stricto sob queimada e sistemas de cultivo

The objective of this work was to evaluate the burning and cultivation effects on soil seedbanks originally under cerrado vegetation. Two areas under cerrado sensu stricto were sampled, one burned and the other one not burned, as well as areas under tilled crop and pasture. There was no reduction on seedbank, although lower number of species and families and diversity index (Shannon and Simpson) with burning were observed. There was also greater importance value index (IVI) and number of native species, in the non burned area, and of weeds in the burned one. It was observed that the crop area had higher seed density than the pasture and cerrado areas. The species with the highest IVI in the areas were those considered as weeds and forages. The crop area presented lower IVI of native species than the pasture and cerrado areas; besides, it presented diversity indexes (Shannon and Simpson) and native species percentage lower than pasture and cerrado. The cultivation with crop cause higher disturbance in the areas than burning.

Características físicas de um latossolo vermelho-escuro no Cerrado de Planaltina, DF, submetido à ação do fogo

Os principais efeitos do fogo como manejo de solo estao relacionados a alteracoes biologicas e quimicas do solo. A queima pode ainda alterar a umidade do solo em razao de mudancas na taxa de infiltracao, na taxa de transpiracao, na porosidade e na repelencia do solo a agua. O objetivo deste trabalho foi avaliar as caracteristicas fisicas de um Latossolo Vermelho-Escuro muito argiloso, plano, fase campo cerrado, submetido a acao do fogo, apos ser utilizado durante 20 anos em pastagem nativa sem queima. Uma area de 1,25 ha foi submetida a acao bienal do fogo, e uma area adjacente, do mesmo tamanho, foi mantida protegida da acao do fogo. Apos seis anos, nao houve variacoes marcantes nas caracteristicas fisicas do solo induzidas pelo fogo, exceto no aumento da umidade do solo nas parcelas nao queimadas. Nas parcelas onde se aplicou o fogo, observou-se tendencia para o aumento da microporosidade, que pode ser atribuida a compactacao promovida pelo impacto das gotas de chuva no solo desnudado pelo fogo. Conclui-se, entretanto, que a queima bienal nao foi suficiente para provocar degradacao no periodo estudado.

CARACTERÍSTICAS MORFOLÓGICAS E VARIABILIDADE GENÉTICA DE ARATICUM UTILIZANDO MARCADORES RAPD E MICROSSATÉLITES

ABSTRACTThis study aimed to evaluate the genetic variability of the araticum collections from Embrapa Cerrados and others regions near to the Federal District, using RAPD and microsatellites markers as well as morphological analysis. Young leaves of 18 araticum accessions were collected and used for genomic DNA extraction. Genomic DNA samples from each accession were amplified for obtaining RAPD and microsatellites markers. Morphological analysis were performed using 23 characteristics of each araticum accession. Genetic dissimilarities among the 18 araticum accessions showed high genetic variability among them and cluster analysis led to the formation of three similarity groups. It was observed low genetic dissimilarities among accessions from Embrapa Cerrados and high genetic dissimilarities among accessions from others regions. These accessions are important as genetic variability sources to enlarge the current Embrapa Cerrados collection and for future studies of morphological and agronomic germplasm characterization.