Climate variability, vegetation productivity and people at risk

Human domination of ecosystems has been pervasive over the last century, with nearly half of Earth's surface transformed by human actions. It is widely accepted that humans appropriate up to 50% of global net primary production (NPP), the energy base of all the trophic levels on the land surface. Yet, despite the important role of vegetation productivity for defining Earth habitability, the covariation of NPP and human population distribution has not been analyzed in depth. We used recently available satellite-based NPP estimates, along with gridded population at 0.5° resolution, first, to identify the global distribution of human population with reference to average NPP and to the various climatic constraints (temperature, water and cloud cover) that limit NPP, second, to analyze recent trends in global NPP in relation to population trends, and third, to identify populations that are vulnerable to changes in NPP due to interannual variability in climate. Our results indicate that over half of the global human population is presently living in areas with above the average NPP of 490 g C m⁻² year⁻¹. By 1998, nearly 56% of global population lived in regions where water availability strongly influences NPP. Per capita NPP declined over much of Africa between 1982 and 1998, in spite of the estimated increases in NPP over the same period. On average, NPP over 40% of the total vegetated land surface has shown significant correlations with ENSO-induced climate variability affecting over 2.8 billion people.     

Crustal growth of the central-eastern Paleoproterozoic domain,SW Amazonian craton: Juvenile accretion vs. reworking

The Trans-Amazonian cycle was an important rock-forming event in South America, generating voluminous juvenile and reworked fractions of continental crust. The Bacajá domain, in the southern sector of the Maroni-Itacaiúnas Province in the Amazonian craton, is an example of the Trans-Amazonian terranes adjacent to the Archean Carajás block. Zircon Pb-evaporation and whole-rock Sm–Nd analyses were carried out on representative samples of six lithological units, and allowed the proposal of a comprehensive tectonic-magmatic evolutionary sequence for the central and eastern parts of this domain, from the Neoarchean to the Rhyacian. Gneisses with ages of ca. 2.67 and 2.44 Ga are the oldest rocks recorded in the region, and probably represent remnants of island and continental arcs. The Três Palmeiras succession, emplaced between 2.36 and 2.34 Ga, hosts gold deposits and represents the first record of Siderian supracrustal rocks in the Amazonian craton. It was probably part of an island arc/ocean floor accreted to a craton margin. Rhyacian granitogenesis lasted for ca. 140 My (2.22–2.08 Ga), marking different stages of the Trans-Amazonian cycle. The first stage is represented by continental arc granitoids formed by melting of Archean crust at 2.22–2.18 Ga. The second is characterized by the production of juvenile material between 2.16 and 2.13 Ga. The third and final stage at ca. 2.08 Ga is represented by a large volume of granitoids originated from either juvenile material or reworked crust during compressive stresses. Nd isotopes reveal that juvenile rocks dominated in the northern part of the domain, whereas those formed from reworked crust predominate in the south. The present-day configuration of the Bacajá domain results from collision against the Archean Carajás block at the end of the Trans-Amazonian cycle.     

Observations of X/M asteroids across multiple wavelengths

We have conducted a radar-driven observational campaign of main-belt asteroids (MBAs) focused on X/M class asteroids using the Arecibo radar and NASA Infrared Telescope Facilities (IRTF). M-type asteroids have been identified as metallic, enstatite chondrites and/or heavily altered carbonaceous chondrites [Bell, J.F., Davis, D., Hartmann, W.K., Gaffey, M.J., 1989. In: Binzel, R.P., Gehrels, T., Matthews, M.S. (Eds.), Asteroids II. Univ. of Arizona Press, Tucson, pp. 921-948; Gaffey, M.J., McCord, T.B., 1979. In: Gehrels, T., Matthews, M.S. (Eds.), Asteroids. Univ. of Arizona Press, Tucson, pp. 688-723; Vilas, F., 1994. Icarus 111, 456-467]. Radar wavelength observations can determine whether an asteroid is metallic and provide information about the porosity and regolith depth. Near-infrared observations can help determine the grain size, porosity and composition of an object. Concurrent observations with these tools can give us a wealth of information about an object. Our objectives for this observation program were to (a) determine if there are any consistent relationships between spectra in the near-infrared wavelengths and radar signatures and (b) look for rotationally resolved relationships between asteroid radar properties and near-infrared spectral properties. This paper describes preliminary results of an ongoing survey of near-infrared observations of M-type asteroids and is a companion paper to radar observations reported by Shepard [Shepard, M.K., and 19 colleagues, 2008a. Icarus 195, 184-205]. In the analysis of 16 asteroid near-infrared spectra and nine radar measurements, we find a trend indicating a correlation between continuum slope from 1.7 to 2.45 μm and radar albedo—an asteroid with a steep continuum slope also has a bright radar albedo, which suggests a significant metal content. This may provide a means to use near-IR observations to predict the most likely metallic candidates for radar studies.     

Ecological assessment of highly heterogeneous systems: The importance of taxonomic sufficiency

We assess the effects of taxonomic resolution (genus-family levels) on the ecological assessment of 39 highly heterogeneous ponds located in north-western Spain.Non-metric multidimensional scaling (MDS) and one-way analysis of similarities (ANOSIM) were used to investigate the effects of taxonomic resolution on the macroinvertebrate assemblage structure. The Mann Whitney U-test and discrimination efficiency were used to assess the ability of nine diversity measures (total richness, rarefied richness samples of 25, 50 and 100 individuals, Margalef's index, Pielou's evenness, Shannon-Weaver's index, Simpson's index and percent dominant taxon) to discriminate between acceptable (best available and good conditions) and unacceptable (moderate, poor and very poor) conditions using three levels of taxonomic resolution: (i) family, (ii) family plus subfamilies of benthic non-biting midges and (iii) genus level.Based on non-metric MDS, the macroinvertebrate assemblages of ponds of acceptable (A) and unacceptable (N) conditions were statistically undistinguishable, both at genus and family levels. On the other hand, based on several community metrics (total richness, Margalef index, etc.) the two sets of samples were statistically different, although only when the genus or the subfamily level was used and after Bonferroni correction. These results suggest that the structure of macroinvertebrate assemblages by itself is more sensitive than the specific composition in distinguishing the fauna living in acceptable and unacceptable conditions. Moreover, dealing with families including many taxa generally showing different tolerance to disturbance may lead to misclassification of ponds. We agree, however, that the two approaches, i.e. assemblage composition and diversity measures, are conceptually different and hence they should be used in combination for a better understanding of the response of single metrics.     

A two-color CCD survey of the North Celestial Cap: I. The method

We describe technical aspects of an astrometric and photometric survey of the North Celestial Cap (NCC), from the Pole (δ=90°) to δ=80°, in support of the TAUVEX mission. This region, at galactic latitudes from ∼17° to ∼37°, has poor coverage in modern CCD-based surveys. The observations are performed with the Wise Observatory one-meter reflector and with a new mosaic CCD camera (LAIWO) that images in the Johnson–Cousins R and I bands a one-square-degree field with sub-arcsec pixels. The images are treated using IRAF and SExtractor to produce a final catalogue of sources. The astrometry, based on the USNO-A2.0 catalogue, is good to ∼1 arcsec and the photometry is good to ∼0.1 mag for point sources brighter than R=20.0 or I=19.1 mag. The limiting magnitudes of the survey, defined at photometric errors smaller than 0.15 mag, are 20.6 mag (R) and 19.6 (I). We separate stars from non-stellar objects based on the object shapes in the R and I bands, attempting to reproduce the SDSS star/galaxy dichotomy. The completeness test indicates that the catalogue is complete to the limiting magnitudes.     

The Ricker Hills Tillite provides evidence of Oligocene warm-based glaciation in Victoria Land, Antarctica

The relationship between the Ricker Hills Tillite (RHT), which represents the northernmost outcrop of lithified continental glacial deposits in Victoria Land, is discussed with respect to the glacial landscape assemblage of the Ricker Hills, a nunatak at the internal border of the Transantarctic Mountains. A warm-based ice sheet deposited the tillite and induced syn- to post-depositional glacial deformation under wet conditions both of the tillite and of the bedrock. The thickness of the ice sheet on the nunatak is estimated to have been 600 m, at most. The area had been deeply eroded before deposition of the RHT as documented by the low elevation of tillite outcrops located in overdeepened depressions of the nunatak. Micropaleontological analysis evidences only the presence of Permian to Jurassic palynomorphs. X-ray diffraction and SEM–EDS analyses of clay minerals in the RHT indicate continental chemical weathering under wet conditions after the RHT deposition. As documented by clay mineral assemblage variation in CRP drillholes, the progressive cooling of the Antarctic continent allowed chemical weathering in “warm” conditions until the Late Oligocene period in southern Victoria Land, leading to a chronological constrain for RHT deposition. Conservatively estimating the sea level to have been between the tillite outcrops and the erosional trimline limiting horns in the Ricker Hills, at the time of RHT deposition, we suggest that the maximum uplift of the area would not have exceeded 900–1500 m since at least Late Oligocene.     

The composition and conservation of Romania's plant cover

Romania is characterised by great floristic diversity and there are many distinctive aspects to the distribution of vegetation units. However, even the sparsely-populated mountainous country has been affected by anthropic activity, increasing in intensity through the expansion of agriculture during the nineteenth century and the recent emphasis on industrial development. It is therefore essential that the diverse plant cover should be given the protection of national park or nature reserve status. The present designations are substantial, though not yet adequate, and careful monitoring is needed to establish the extent or further provision.