scholarly journals Macroinvertebrates under stochastic hydrological disturbance in Cerrado streams of Central Brazil

2012 ◽  
Vol 102 (4) ◽  
pp. 448-452 ◽  
Author(s):  
Victor S. Saito ◽  
Gustavo R. Mazão
Keyword(s):  
Analysis Of Variance ◽  
Correspondence Analysis ◽  
High Density Polyethylene ◽  
Detrended Correspondence Analysis ◽  
Dry Season ◽  
High Density ◽  
Faunal Composition ◽  
First Order ◽  
Cerrado Vegetation ◽  
Central Brazil

In the Cerrado vegetation, where the seasonal is well defined, rainfall has an important role in controlling the flow of streams and consequently on the structure of macroinvertebrates community. Despite the effects of rainfall associated with seasonality are well studied, little is known about the effects of stochastic rains on the community. In the present study we evaluated the structure and faunal composition of four first-order streams in Central Brazil during the dry season in two years, with and without stochastic rains. Community sampling was done by colonization of boards of high density polyethylene (HDPE), removed after one month submerged in streams. Analysis of Variance (ANOVA) performed indicated no difference in rarefied richness between the two periods, different from numeric density of organisms that was higher in the period without disturbance; moreover, the Detrended Correspondence Analysis (DCA) revealed differences in faunal composition between the two periods. Our results indicate that stochastic rainfall is an important factor in structuring the macroinvertebrates community in studied region.

scholarly journals The length of the dry season may be associated with leaf scleromorphism in cerrado plants

2015 ◽  
Vol 87 (3) ◽  
pp. 1691-1699 ◽  
Author(s):  
MARCELO C. SOUZA ◽  
AUGUSTO C. FRANCO ◽  
MUNDAYATAN HARIDASAN ◽  
DAVI R. ROSSATTO ◽  
JANAÍNA F. DE ARAÚJO ◽  
...  
Keyword(s):  
Soil Fertility ◽  
Specific Leaf Area ◽  
Woody Species ◽  
Dry Season ◽  
Core Region ◽  
The Other ◽  
Low Fertility ◽  
Fertility Rates ◽  
Cerrado Vegetation ◽  
Central Brazil

Despite limitations of low fertility and high acidity of the soils, the cerrado flora is the richest amongst savannas. Many cerrado woody species show sclerophyllous leaves, which might be related to the availability of water and nutrients in the soil. To better understand the function and structure of cerrado vegetation within its own variations, we compared two cerrado communities: one in its core region in central Brazil (Brasília, DF) and the other on its southern periphery (Itirapina, SP). We contrasted the length of the dry season, soil fertility rates, leaf concentrations of N, P, K, Ca and Mg and the specific leaf area (SLA) between these communities. The dry season was shorter on the periphery, where the soil was more fertile although more acidic. Plants from the periphery showed higher SLA and higher leaf concentrations of N, P, Ca and Mg. We propose that the higher SLA of plants from the periphery is related to the shorter dry season, which allows better conditions for nutrient uptake.

STRUCTURE AND FLORISTICS OF THE ARBOREAL COMPONENT OF A DYSTROPHIC CERRADÃO AND COMPARISON WITH OTHER CERRADÕES IN CENTRAL BRAZIL

2011 ◽  
Vol 68 (3) ◽  
pp. 401-418 ◽  
Author(s):  
G. M. Araújo ◽  
A. R. T. Nascimento ◽  
S. F. Lopes ◽  
R. F. Rodrigues ◽  
J. A. Ratter
Keyword(s):  
Plant Community ◽  
Correspondence Analysis ◽  
Nutrient Availability ◽  
Detrended Correspondence Analysis ◽  
Soil Samples ◽  
Central Portion ◽  
Cosmopolitan Species ◽  
Diameter At Breast Height ◽  
Central Brazil ◽  
Breast Height

This study describes the structure of the arboreal plant community in a cerradão fragment located at the Serra de Caldas Novas State Park, Goiás, central Brazil. It also compares the collected data with information from 10 other cerradão sites on dystrophic and mesotrophic soils. All trees of 4.77 cm or more diameter at breast height, in twenty-five 20 m × 20 m plots, were surveyed. Soil samples were analysed to determine the availability of nutrients. The vegetation had a discontinuous canopy, with a high density of small and medium-sized trees, and the soil was classified as dystrophic according to nutrient availability. Under ordination using Detrended Correspondence Analysis, species characteristic of the study site, such asSclerolobium paniculatumandEmmotum nitens, were positioned in the central portion, while cosmopolitan species formed distinct groups, separated along the two axes. The community showed a low level of similarity in comparison to cerradões reported in the literature in other parts of Brazil, having more than 50% similarity only with three geographically close sites.

Composition and Surface Topography Effects on Apatite-Forming Ability of Ceramic-Polymer Composites

2003 ◽  
Vol 774 ◽  
Author(s):  
Susan M. Rea ◽  
Serena M. Best ◽  
William Bonfield
Keyword(s):  
Surface Topography ◽  
High Density Polyethylene ◽  
High Density ◽  
Apatite Layer ◽  
Biologically Active ◽  
Human Blood Plasma ◽  
Apatite Formation ◽  
Polyethylene Matrix ◽  
Composite Surface ◽  
X Ray

AbstractHAPEXTM (40 vol% hydroxyapatite in a high-density polyethylene matrix) and AWPEX (40 vol% apatite-wollastonite glass ceramic in a high density polyethylene matrix) are composites designed to provide bioactivity and to match the mechanical properties of human cortical bone. HAPEXTM has had clinical success in middle ear and orbital implants, and there is great potential for further orthopaedic applications of these materials. However, more detailed in vitro investigations must be performed to better understand the biological interactions of the composites and so the bioactivity of each material was assessed in this study. Specifically, the effects of controlled surface topography and ceramic filler composition on apatite layer formation in acellular simulated body fluid (SBF) with ion concentration similar to those of human blood plasma were examined. Samples were prepared as 1 cm × 1 cm × 1 mm tiles with polished, roughened, or parallel-grooved surface finishes, and were incubated in 20 ml of SBF at 36.5 °C for 1, 3, 7, or 14 days. The formation of a biologically active apatite layer on the composite surface after immersion was demonstrated by thin-film x-ray diffraction (TF-XRD), environmental scanning electron microscopy (ESEM) imaging and energy dispersive x-ray (EDX) analysis. Variations in sample weight and solution pH over the period of incubation were also recorded. Significant differences were found between the two materials tested, with greater bioactivity in AWPEX than HAPEXTM overall. Results also indicate that within each material the surface topography is highly important, with rougher samples correlated to earlier apatite formation.

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