272 research outputs found
Coleopteran diversity and abundance in different habitats near Kihansi waterfall, in the Udzungwa Mountains, Tanzania
Coleoptera diversity at the family level was investigated along the Kihansi gorge near a 700 m
high waterfall system which will be taken to hydropower use, and the current river flow will be diverted
due to dam construction. The coleopteran communities of three micro-habitats: spray zone, forest site and
riverine site were compared by sweepnetting and pitfall trap methods. The highest Coleopteran family
level diversity was found in the spray zone where the Shannon–Weaver index of diversity was 0.71 (forest
site 0.31; riverine site 0.50). Coleopterans were most abundant in the forest site where 44% of all sampled
individuals were found (spray zone 31%; riverine site 23%). Most of less frequently recorded families
were found in the spray zone. Coleoptera families were found to be unequally partitioned in all three
micro-habitats. The highest percentage similarity index (85%) was found between forest and riverine sites
(spray/forest 76%; spray/riverine 79%). Distributions of abundances of coleopteran families were significantly
different between all studied habitats. The study revealed that the spray generated by the waterfall
provide a special micro-habitat for Coleoptera. It is suggested that conservation efforts and monitoring in
the study area using selected taxonomic indicator Coleopteran groups should be carried out in order to help
to adjust mitigation measures
Spatial variation of arthropod communities in virgin and managed sites in the Kibale Forest, western Uganda.
http://www.elsevier.com/locate/issn/03781127The structure of arthropod communities in the forest floor vegetation in four differently managed forest sites (virgin forest,
lightly selectively logged, heavily selectively logged, and exotic Pinus caribaea plantation) in Kibale Forest National Park,
western Uganda, was studied by sweep net between March and May 1985 and July 1995. For the analysis three (or four) 800
sweeps samples were collected from each habitat. In the samples eight arthropod groups (Araneae, Hymenoptera, Heteroptera,
Homoptera, Coleoptera, Orthoptera, Lepidoptera, caterpillars (Lepidoptera larvae)) formed over 95% of all the individuals of
the arthropod caught in all habitats. The variation within one habitat was smaller than variation between habitats in samples of
the same year. Thus, the arthropod communities in differently managed forests differ from each other after over 20 years of
management practices (selective logging and clear-cut plus pine plantation) as well as from adjacent virgin forest, and the
differences seem to become greater during the succession in managed sites. Samples taken in the same habitat type, 10 years
apart, differed greatly from each other. This is the result of both long-term succession and seasonal variation
The largest oxigen bearing organic molecule repository
We present the first detection of complex aldehydes and isomers in three
typical molecular clouds located within 200pc of the center of our Galaxy.
We find very large abundances of these complex organic molecules (COMs) in
the central molecular zone (CMZ), which we attribute to the ejection of COMs
from grain mantles by shocks. The relative abundances of the different COMs
with respect to that of CH3OH are strikingly similar for the three sources,
located in very different environments in the CMZ. The similar relative
abundances point toward a unique grain mantle composition in the CMZ. Studying
the Galactic center clouds and objects in the Galactic disk having large
abundances of COMs, we find that more saturated molecules are more abundant
than the non-saturated ones. We also find differences between the relative
abundance between COMs in the CMZ and the Galactic disk, suggesting different
chemical histories of the grain mantles between the two regions in the Galaxy
for the complex aldehydes. Different possibilities for the grain chemistry on
the icy mantles in the GC clouds are briefly discussed. Cosmic rays can play an
important role in the grain chemistry. With these new detections, the molecular
clouds in the Galactic center appear to be one of the best laboratories for
studying the formation of COMs in the Galaxy.Comment: 20 pages, 4 figures, accepted in Ap
Water Striders (Heteroptera Gerridae) as bioindicators of heavy metal pollution
Heavy metal contents of water striders collected near a steel factory and from control sites were analyzed by AAS. The average concentrations µg/g of dry weight found near the factory vs. the control areas were: Al 76, 65; Fe 840, 330; Mn 49, 37; Zn 310, 280; Cu 44, 42; Cd 1.6, 6.5, respectively. In most cases Ni and Pb concentrations were below the determination limit in both sites. There were significant differences between sites in the concentrations of iron and cadmium. Fifth instar larvae had higher iron content than adults, but sexes did not differ in heavy metal content. There were also significant differences between different water strider species as accumulators of zinc, aluminium and cadmium. It is concluded that water striders seem suitable as bioindicators of heavy metals
Revealing the environs of the remarkable southern hot core G327.3-0.6
We present a submm study of the massive hot core G327.3-0.6 that constrains
its physical parameters and environment. The APEX telescope was used to image
CO and N2H+ emission, to observe lines from other molecules toward a hot and a
cold molecular core, and to measure the continuum flux density of the hot core.
In the C18O J=3-2 line, two clumps were found, one associated with the HII
region G327.3-0.5 and the other associated with the hot core. An additional
cold clump is found 30 arcsec (0.4 pc) northeast of the hot core in bright N2H+
emission. From the the continuum data, we calculate a mass of 420 Msol and a
size of 0.1 pc for the hot core. A new, more accurate position of the hot core
is reported, which allows the association of the core with a bright
mid-infrared source. The luminosity of the hot core is estimated to be between
5 and 15 10^4 Lsol. This study revealed several different evolutionary stages
of massive star formation in the G327.3-0.6 region.Comment: APEX A&A special issue, accepte
Effects of a hydropower plant on Coleopteran diversity and abundance in the Udzungwa Mountains, Tanzania
The effects of river flow diversion on biodiversity were assessed using Coleoptera as an
indicator group in three habitats of the Kihansi Gorge (Udzungwa Mountains, Tanzania), before and after
commissioning of a hydropower plant. Data collected using sweep netting and pitfall traps showed that
the effect of diversion of the river flow was site-specific, affecting particularly the spray habitat.
Rarefaction analysis of both sweep netting and pitfall samples indicated that the expected richness of
Coleoptera declined significantly in all habitats after commissioning of the power plant. Sweep netting
and pitfall samples showed that the highest Shannon-Wiener diversity index value before the diversion
of the river flow was in the spray zone, but the index value decreased after diversion. Changes in the
other two habitats were less prominent. Analysis of variance using diversity index values from five pitfall
samples in each habitat type before and after commissioning indicated that there were no statistically
significant differences in the diversity index between the two sampling periods or among the three habitat
types. Renkonen's similarity index between habitats showed that pitfall samples had higher similarity
(87%) than did samples from sweep netting (69%). It is suggested that for mitigation purposes,
artificial spray systems, which have been installed in other wetlands of the Kihansi Gorge, also be
installed to cover the whole Lower Wetland in which this study was undertaken. In order to maintain
overall biodiversity in the Kihansi Gorge, it is suggested that the ecosystem conservation approach be
prioritised
Comparative study of complex N- and O-bearing molecules in hot molecular cores
We have observed several emission lines of two Nitrogen-bearing (C2H5CN and
C2H3CN) and two Oxygen-bearing (CH3OCH3 and HCOOCH3) molecules towards a sample
of well-known hot molecular cores (HMCs) in order to check whether the chemical
differentiation seen in the Orion-HMC and W3(H_2O) between O- and N-bearing
molecules is a general property of HMCs. With the IRAM-30m telescope we have
observed 12 HMCs in 21 bands, centered at frequencies from 86250 to 258280 MHz.
The rotational temperatures obtained range from ~100 to ~150 K in these HMCs.
Single Gaussian fits performed to unblended lines show a marginal difference in
the line peak velocities of the C2H5CN and CH3OCH3 lines, indicating a possible
spatial separation between the region traced by the two molecules. On the other
hand, neither the linewidths nor the rotational temperatures and column
densities confirm such a result. By comparing the abundance ratio of the pair
C2H5CN/C2H3CN with the predictions of theoretical models, we derive that the
age of our cores ranges between 3.7 and 5.9x10^{4} yrs. The abundances of
C2H5CN and C2H3CN are strongly correlated, as expected from theory which
predicts that C2H3CN is formed through gas phase reactions involving C2H5CN. A
correlation is also found between the abundances of C2H3CN and CH3OCH3, and
C2H5CN and CH3OCH3. In all tracers the fractional abundances increase with the
H_2 column density while they are not correlated with the gas temperature.Comment: Accepted for publication in A&A, 56 page
Submillimeter spectroscopy of southern hot cores: NGC6334(I) and G327.3-0.6
High-mass star-forming regions are known to have a rich molecular spectrum
from many species. Some of the very highly excited lines are emitted from very
hot and dense gas close to the central object(s). The physics and chemistry of
the inner cores of two high mass star forming regions, NGC6334(I) and
G327.3-0.6, shall be characterized. Submillimeter line surveys with the APEX
telescope provide spectra which sample many molecular lines at high excitation
stages. Partial spectral surveys were obtained, the lines were identified,
physical parameters were determined through fitting of the spectra. Both
sources show similar spectra that are comparable to that of the only other high
mass star forming region ever surveyed in this frequency range}, Orion-KL, but
with an even higher line density. Evidence for very compact, very hot sources
is found.Comment: APEX A&A special issue, accepte
Infrared spectroscopy of solid CO-CO2 mixtures and layers
The spectra of pure, mixed and layered CO and CO2 ices have been studied
systematically under laboratory conditions using infrared spectroscopy. This
work provides improved resolution spectra (0.5 cm-1) of the CO2 bending and
asymmetric stretching mode, as well as the CO stretching mode, extending the
existing Leiden database of laboratory spectra to match the spectral resolution
reached by modern telescopes and to support the interpretation of the most
recent data from Spitzer. It is shown that mixed and layered CO and CO2 ices
exhibit very different spectral characteristics, which depend critically on
thermal annealing and can be used to distinguish between mixed, layered and
thermally annealed CO-CO2 ices. CO only affects the CO2 bending mode spectra in
mixed ices below 50K under the current experimental conditions, where it
exhibits a single asymmetric band profile in intimate mixtures. In all other
ice morphologies the CO2 bending mode shows a double peaked profile, similar to
that observed for pure solid CO2. Conversely, CO2 induces a blue-shift in the
peak-position of the CO stretching vibration, to a maximum of 2142 cm-1 in
mixed ices, and 2140-2146 cm-1 in layered ices. As such, the CO2 bending mode
puts clear constraints on the ice morphology below 50K, whereas beyond this
temperature the CO2 stretching vibration can distinguish between initially
mixed and layered ices. This is illustrated for the low-mass YSO HH46, where
the laboratory spectra are used to analyse the observed CO and CO2 band
profiles and try to constrain the formation scenarios of CO2.Comment: Accepted in A&
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