99 research outputs found
Diversidade de aranhas de solo (Arachnida: araneae) em sistema alternativo de cultivo de dendê Elaeis guineensis no Pará, Brasil.
Obznane
Kroatologija
God. 2, br. 1, Zagreb 2011. – str. VIII + 255
Daniel Chandler
Semiotics: The Basics
Routledge, London/New York 2007. – str. XVIII + 307
Nina Janich
Werbesprache
Narr Francke Attempto Verlag, Tübingen 2010. – str. 32
A model for net-baryon rapidity distribution
In nuclear collisions, a sizable fraction of the available energy is carried
away by baryons. As the baryon number is conserved, the net-baryon
retains information on the energy-momentum carried by the incoming nuclei. A
simple and consistent model for net-baryon production in high energy
proton-proton and nucleus-nucleus collisions is presented. The basic
ingredients of the model are valence string formation based on standard PDFs
with QCD evolution and string fragmentation via the Schwinger mechanism. The
results of the model are presented and compared with data at different
centre-of-mass energies and centralities, as well as with existing models.
These results show that a good description of the main features of net-baryon
data is possible in the framework of a simplistic model, with the advantage of
making the fundamental production mechanisms manifest.Comment: 9 pages, 12 figures; in fig. 11 a) the vertical scale was correcte
Plant communities as a tool in temporary ponds conservation in SW Portugal
Pond conservationTemporary ponds are seasonal wetlands
annually subjected to extreme and unstable ecological
conditions, neither truly aquatic nor truly terrestrial.
This habitat and its flora have been poorly
studied and documented because of the ephemeral
character of the flora, the changeable annual weather
that has a great effect on the small, herbaceous taxa
and the declining abundance of temporary ponds. The
objectives of this study are: (a) to define plant
community diversity in terms of floristic composition of ephemeral wetlands in SW Portugal, (b) to identify
temporary pond types according to their vegetation
composition and (c) to identify those ponds that
configure the European community priority habitat
(3170* – Mediterranean temporary ponds).
Vegetation sampling was conducted in 29 ponds,
identifying 168 species grouped among 15 plant
communities. Soil texture, pH, organic C and N
content were measured, but only N and percent of
clay appear to be related with the distribution of each
community type. The results showed that ephemeral
wetlands could be classified into four type: vernal
pools, marshlands, deep ponds and disturbed wetlands.
Vernal pools correspond to the Mediterranean
temporary ponds (3170*), protected as priority habitat
under the EU Habitats Directive. Submersed
Isoetes species (Isoetes setaceum and Isoetes velatum)
represents, together with Eryngium corniculatum,
the indicator species for vernal pools. We
identify also indicator plant communities of this
priority habitat, namely I. setaceum and E. corniculatum–
Baldellia ranunculoides plant communities. In
this region, the conservation of temporary ponds has
so far been compatible with traditional agricultural
activities, but today these ponds are endangered by
the intensification of agriculture and the loss of
traditional land use practices and by the development
of touris
The spectrum of natural forest disturbances and the Amazon forest carbon balance.
Estimates of the atmospheric accumulation of anthropogenic CO2 emissions indicate a large terrestrial carbon sink in recent decades. Intact tropical forests may contribute a substantial fraction of this. While current estimates are based on data from forest inventory plots, these plot studies have been criticized for failure to represent landscape scale processes especially the frequency of severe natural disturbances. Here we characterize the frequency distribution of disturbance events in natural forests from 0.01 ha to 2,651 ha size throughout Amazonia using a novel combination of forest inventory, airborne lidar and satellite remote sensing data. We find that small-scale mortality events are responsible for aboveground biomass losses of about 88.3% over the entire Amazon region. We also find that intermediate-scale disturbances account for losses around 12.7%, and that the largest-scale disturbances as a result of blow-downs only accounts for losses of around 0.02%. Stochastic simulation of growth and mortality based on data from the forest plot census network and the region-wide disturbance spectrum together indicate that rare large disturbances are outweighed by the net biomass gains measured, supporting the inference of a substantial carbon sink in old-growth Amazon forests
Spatial and temporal dimensions of landscape fragmentation across the Brazilian Amazon
The Brazilian Amazon in the past decades has been suffering severe landscape alteration, mainly due to anthropogenic activities, such as road building and land clearing for agriculture. Using a high-resolution time series of land cover maps (classified as mature forest, non-forest, secondary forest) spanning from 1984 through 2011, and four uncorrelated fragmentation metrics (edge density, clumpiness index, area-weighted mean patch size and shape index), we examined the temporal and spatial dynamics of forest fragmentation in three study areas across the Brazilian Amazon (Manaus, Santarém and Machadinho d’Oeste), inside and outside conservation units. Moreover, we compared the impacts on the landscape of: (1) different land uses (e.g. cattle ranching, crop production), (2) occupation processes (spontaneous vs. planned settlements) and (3) implementation of conservation units. By 2010/2011, municipalities located along the Arc of Deforestation had more than 55% of the remaining mature forest strictly confined to conservation units. Further, the planned settlement showed a higher rate of forest loss, a more persistent increase in deforested areas and a higher relative incidence of deforestation inside conservation units. Distinct agricultural activities did not lead to significantly different landscape structures; the accessibility of the municipality showed greater influence in the degree of degradation of the landscapes. Even with a high proportion of the landscapes covered by conservation units, which showed a strong inhibitory effect on forest fragmentation, we show that dynamic agriculturally driven economic activities, in municipalities with extensive road development, led to more regularly shaped, heavily fragmented landscapes, with higher densities of forest edge
Relação da vegetação de caatinga com a condição geomorfométrica local
Objetivou-se, com o presente trabalho, avaliar o potencial das variáveis geomorfométricas extraídas de dados SRTM (Shuttle Radar Topographic Mission) para identificação de tipos vegetacionais da Reserva Particular do Patrimônio Natural de Serra das Almas, CE. Em estudo conduzido na escala de 1:100.000, as variáveis geomorfométricas (elevação, declividade, orientação de vertente, curvatura vertical e curvatura horizontal) foram confrontadas com o mapa de vegetação referência, através de análises de histogramas e análises discriminantes. As variáveis mais importantes na distinção entre os tipos vegetacionais, foram a elevação, a declividade e a curvatura vertical, embora se pudesse observar preferências de tipos mapeados em relação às demais variáveis. Apesar dos dados geomorfométricos mostrarem potencial indicativo das classes de vegetação pela interpretação dos padrões, as análises sob abordagem numérica resultaram em discriminação em um nível aquém do detalhamento temático do mapa referência. Concluiu-se que os dados geomorfométricos representaram significativos insumos para o mapeamento fitogeográfico, devendo ser explorados de forma integrada, em complementaridade às demais variáveis já utilizadas.The objective of this work was to assess the potential of geomorphometric variables, derived from SRTM (Shuttle Radar Topographic Mission) data, to help in identifying vegetation types in the Serra das Almas National Park (CE). A 1:100.000 survey vegetation map was used as reference and the geomorphometric variables (elevation, slope, aspect and profile and plan curvatures) were compared to the mapped units. The variables elevation, slope and profile curvature were shown as the most important for their high discrimination power of the vegetation types. Although geomorphometric data had strong potential for characterizing vegetation through map comparisons, the achieved thematic detail levels were under those of the reference map when data was analyzed under a numerical approach. It was concluded that geomorphometric data were important input for vegetation mapping, and should be employed together with currently used data
Fish bycatch of the laulao catfish Brachyplatystoma vaillantii (Valenciennes, 1840) trawl fishery in the Amazon Estuary
Temporal patterns in the occurrence of selected tropical fishes in mangrove creeks: implications for the fisheries management in north Brazil
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