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Two, 1400-ha blocks of rangeland in western South Dakota were treated aerially with malathion liquid spray or carbaryl – bran bait in early July 1986 to determine the immediate and 2nd-year impact of treatments on grasshopper populations. Total grasshopper populations were reduced by 92 and 47% in the malathion and carbaryl – bran bait treatment plots, respectively, within 48 h after treatment and remained at a low level throughout the summer. Populations did not change in the control plots. Populations of the two most abundant species, Ageneotettix deorum (Scudder) and Melanoplus sanguinipes (F.), declined by 65 and 87%, respectively, in the carbaryl – bran bait plots but populations of bran "rejectors" (predominantly Trachyrhachys kiowa [Thomas]) did not change.
Densities of the bran "acceptors" (Melanoplus spp., Phoetaliotes nebrascensis [Thomas], and A. deorum), as a group, did not change significantly in the control plots between the pre-treatment and July 1987 sampling dates. Densities within both sets of treatment plots were significantly lower in the 2nd year of the study than on the pre-treatment sampling date. Although 2nd-year populations of bran acceptors, as a group, did not increase to pre-treatment levels in the treated plots, populations of M. sanguinipes did increase to pre-treatment levels in both sets of treatment plots. Populations of bran rejectors generally remained low in treatment and control plots.
Analysis of covariance of the densities of 2nd-year populations of total grasshoppers and bran rejectors indicated that treatment had no significant effect on populations of these grasshoppers, but the covariable, pre-treatment density, was significantly correlated with 2nd-year densities. Densities of 2nd-year populations of bran acceptors were also significantly correlated with pre-treatment densities.
It was concluded that both the insecticidal spray and bait were effective in controlling most economically important species of rangeland grasshoppers. Although both treatments may have suppressed populations of bran acceptors, as a group, in the 2nd year of the study, neither suppressed populations of M. sanguinipes which increased to pre-treatment levels regardless of treatment. The effect of treatments on 2nd-year populations of bran rejectors could not be determined because populations of this group also declined in control plots.
A study was conducted in Butte County of western South Dakota to determine the relationships between habitat characteristics and spatial and temporal changes in community structure of grasshoppers on mixed-grass rangeland. Detrended correspondence analysis (DCA) of 29 undisturbed grasshopper communities and correlation analysis of DCA axis values and habitat variables denned specific spatial gradients underlying the community structure of grasshoppers. Results indicated that grasshopper communities changed along a primary gradient of percentage of coverage of grasses, particularly Buchloe dactyloides (Nutt.) Engelm., and a secondary gradient of percentage composition of clay and sand in the soil.
DCA of 24 grasshopper communities sampled in 1986 and 1987, multiple regression analysis, and factor analysis were used to determine the relationships between specific habitat characteristics and changes in communities of grasshoppers treated with either a nonselective insecticidal spray (malathion) or a selective insecticidal bait (bran bait with carbaryl). Results indicated that between-year change in community composition, or the difference between post-treatment communities in 1986 and 1987, was positively correlated with percentage of coverage of total grasses and forbs. Community malleability, defined as the tendency of a community to return to its predisturbed state, was greater in habitats with high coverages of Agropyron smithii Rydb. and Carex spp., low coverage of Bouteloua gracilis (H.B.K.) Lag. ex Steud., and low species richness of grasses. Our results emphasize the importance of habitat characteristics in structuring undisturbed grasshopper communities and in community change after perturbation with insecticides.
The science of extra-solar planets is one of the most rapidly changing areas of astrophysics and since 1995 the number of planets known has increased by almost two orders of magnitude. A combination of ground-based surveys and dedicated space missions has resulted in 560-plus planets being detected, and over 1200 that await confirmation. NASA's Kepler mission has opened up the possibility of discovering Earth-like planets in the habitable zone around some of the 100,000 stars it is surveying during its 3 to 4-year lifetime. The new ESA's Gaia mission is expected to discover thousands of new planets around stars within 200 parsecs of the Sun. The key challenge now is moving on from discovery, important though that remains, to characterisation: what are these planets actually like, and why are they as they are?
In the past ten years, we have learned how to obtain the first spectra of exoplanets using transit transmission and emission spectroscopy. With the high stability of Spitzer, Hubble, and large ground-based telescopes the spectra of bright close-in massive planets can be obtained and species like water vapour, methane, carbon monoxide and dioxide have been detected. With transit science came the first tangible remote sensing of these planetary bodies and so one can start to extrapolate from what has been learnt from Solar System probes to what one might plan to learn about their faraway siblings. As we learn more about the atmospheres, surfaces and near-surfaces of these remote bodies, we will begin to build up a clearer picture of their construction, history and suitability for life.
The Exoplanet Characterisation Observatory, EChO, will be the first dedicated mission to investigate the physics and chemistry of Exoplanetary Atmospheres. By characterising spectroscopically more bodies in different environments we will take detailed planetology out of the Solar System and into the Galaxy as a whole.
EChO has now been selected by the European Space Agency to be assessed as one of four M3 mission candidates.
Spectral features corresponding to methane and water opacity were reported based on transmission spectroscopy of HD 189733b with Hubble/NICMOS. Recently, these data, and a similar data set for XO-1b, have been reexamined in Gibson et al. (2010), who claim they cannot reliably reproduce prior results. We examine the methods used by the Gibson team and identify two specific issues that could act to increase the formal uncertainties and to create instability in the minimization process. This would also be consistent with the GPA10 finding that they could not identify a way to select among the several instrument models they constructed. In the case of XO-1b, the Gibson team significantly changed the way in which the instrument model is defined (both with respect to the three approaches they used for HD 189733b, and the approach used by previous authors); this change, which omits the effect of the spectrum position on the detector, makes direct intercomparison of results difficult. In the experience of our group, the position of the spectrum on the detector is an important element of the instrument model because of the significant residual structure in the NICMOS spectral flat field. The approach of changing instrument models significantly complicates understanding the data reduction process and interpreting the results. Our team favors establishing a consistent method of handling NICMOS instrument systematic errors and applying it uniformly to data sets.
The ALADDIN concept is an integrated Antarctic-based L-band experiment whose purpose is to demonstrate nulling interferometry and to prepare the DARWIN mission. Because of their privileged location, the relatively modest collectors (1 m) and baseline (up to 40 m) are sufficient to achieve a sensitivity (in terms of detectable zodi levels) which is about twice better than that of a nulling instrument on a large interferometer (such as GENIE at the VLTI), and to reach the 20-zodi threshold value identified to carry out the DARWIN precursor science. These numbers are based on a preliminary design study by Alcatel Alenia Space and were obtained using the same simulation software as the one employed for GENIE. The integrated design enables top-level optimization and full access to the light collectors for the duration of the experiment, while reducing the complexity of the nulling breadboard.
The Antarctic Planet Interferometer (API) is a concept for an infrared interferometer located at the best accessible site on Earth. Infrared interferometry is strongly effected by both the strength and vertical distribution of thermal and water vapor turbulence. The combination of low temperature, low wind speed, low elevation turbulence, and low precipitable water vapor make the Concordia base at Antarctic Dome C the best accessible site on Earth for infrared interferometry. The improvements in interferometer sensitivity with respect to other terrestrial sites are dramatic; an interferometer with two meter class telescopes could make unique infrared measurements of extra solar planets that might otherwise only be possible with a space-based interferometer.
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