Eficiência do uso de nutrientes ao longo de uma transição de mata de galeria e cerrado no Distrito Federal

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

In the cerrado landscape, gallery forests occur along the streams and are surrounded by open forms of cerrado vegetation, accompanied by edaphic gradients. Transitions between forest physiognomies and adjacent open cerrado forms involve not only changes in the structure, dynamics, floristic composition of vegetation and species distribution, but also variations in nutrient availability in soil, nutrient use efficiency and productivity of these ecosystems. Thus, the objective of the present study was to evaluate the differences in the production of litter, its nutrient concentrations and nutrient use efficiency along a transition between a gallery forest and a cerrado at the Ecological Reserve of IBGE in the Federal District of Brazil. The hypotheses tested were that the nutrient soil availability in the soil, litter production and nutrient concentrations in litter decrease along the gradient from the gallery forest to the cerrado, and that the nutrient use efficiency tends to increase from the gallery forest to the cerrado. Four parallel transects 40 m apart, and extending 30 m into each physiognomy, were established perpendicular to the gallery forest-cerrado boundary. Leaf area index (LAI) of woody species showed sharp changes in the vegetation gradient defining well the interruption of forest canopy. Tree species typical from gallery forests were encountered in the cerrado, but cerrado species were rarely observed in the gallery forest. Soil samples up to 30 cm depth were collected at 5m intervals along each transects to determine nutrient availability. Litter traps of 0,25 m were used to collect litter every two weeks for a period of one year beginning October 2007. Branches greater than 1 cm id diameter were discarded and pooled samples (for each month or trimester) of each fraction (leaves and miscellaneous) were analyzed separately for nutrient concentrations. The annual litter production was greater during the dry period and was significantly higher in the forest (6,3 t ha-1) than in the cerrado (3,5 t ha-1). Significant reduction in the availability of Ca and Mg and total N and organic carbon concentration in the soil was observed along the gradient from the forest to the cerrado. The concentration of K, Ca and Mg in the leaf litter and the concentration of N, Ca and Mg in the miscellaneous fraction decreased from the forest to the cerrado. Nutrient efficiencies for these nutrients and P (leaves) increased along the transition from the forest to the cerrado.

ASSUNTO(S)

serapilheira engenharias cerrado mata de galeria nutrientes

ACESSO AO ARTIGO

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