Paleoenvironmental dynamics in central-eastern Brazil during the last 23 000 years: tropical peatland record in the Cerrado biome

The Cerrado biome is the second largest in Brazil, but the evolution of the Cerrado during the late Quaternary is not yet fully known. This study identifies paleoenvironmental changes during the last 23 000 years, based on a tropical mountain peatland record, in the Serra do Espinhaço Meridional in central-eastern Brazil. A multi-proxy approach was used that involved palynological analysis, stable isotopes (δ¹³C, δ¹⁵N), geochemistry, radiocarbon dating and multivariate statistics derived from a peatland core from Rio Preto (Minas Gerais state). The study reveals a very humid and cold climate during the late Pleistocene, with an increase in temperature and decrease in humidity at the Pleistocene–Holocene transition. During this period there was strong instability in the landscape (episodes of erosion). At the beginning of the Holocene there was a reduction in humidity with greater landscape stability. The current sub-humid climatic conditions seem to have been established in the mid-/late Holocene, with periods of landscape instability. Our findings agree with other Cerrado records that contradict previously established hypotheses, such as the Amazonian Refuge and the Pleistocene Arc.     

Tomographic inversion using ℓ1-norm regularization of wavelet coefficients

We propose the use of ℓ₁ regularization in a wavelet basis for the solution of linearized seismic tomography problems   A m = d   , allowing for the possibility of sharp discontinuities superimposed on a smoothly varying background. An iterative method is used to find a sparse solution m that contains no more fine-scale structure than is necessary to fit the data d to within its assigned errors.     

Temporal dynamics and persistence of sponge assemblages in a Central Pacific atoll lagoon

Sponges are important components of coral reef fauna, although little is known of their temporal dynamics. Sponges dominate the lagoon system at Palmyra Atoll in the Central Pacific, which may not be its natural state. Here we examined the temporal variability and recruitment rates of these sponge assemblages to determine if they are stable and examined the evidence that a recent transition has occurred from a coral‐ to sponge‐dominated system. We found 24 sponge species in permanent quadrats in the lagoon between 2009 and 2011, and 11 species on our recruitment panels. The sponge assemblage composition and abundance did not vary significantly between years and appear stable. Many sponge recruits were found in both years that the panels were examined although higher rates were recorded in the second year of the study. While it seems very possible that a change to a sponge‐dominated lagoon is associated with declining environmental quality at Palmyra as a result of modifications over 70 years ago, without pre‐modification data on reef assemblage composition this remains speculative. Our observations of short‐term temporal stability in the sponge assemblages at Palmyra highlight the potential for sponge‐dominated reef states to be maintained in degraded reef environments that are seemingly unsuitable for coral survival.     

Dust in the solar system and in extra-solar planetary systems

Among the observed circumstellar dust envelopes a certain population, planetary debris disks, is ascribed to systems with optically thin dust disks and low gas content. These systems contain planetesimals and possibly planets and are believed to be systems that are most similar to our solar system in an early evolutionary stage. Planetary debris disks have been identified in large numbers by a brightness excess in the near-infrared, mid-infrared and/or submillimetre range of their stellar spectral energy distributions. In some cases, spatially resolved observations are possible and reveal complex spatial structures. Acting forces and physical processes are similar to those in the solar system dust cloud, but the observational approach is obviously quite different: overall spatial distributions for systems of different ages for the planetary debris disks, as opposed to detailed local information in the case of the solar system. Comparison with the processes of dust formation and evolution observed in the solar system therefore helps understand the planetary debris disks. In this paper, we review our present knowledge of observations, acting forces, and major physical interactions of the dust in the solar system and in similar extra-solar planetary systems.     

The effects of controlled drainage on subsurface outflow from level agricultural fields

Daily outflow frequencies and recession curves were used to identify differences in storage–outflow relationships between two different drainage systems, conventional and controlled drainage. A three‐year (1996–1999) field drainage experiment was carried out on a loamy sand soil in southern Sweden. Plots with an area of 0·2 hectares were drained by conventional subsurface drainage (CD) or by controlled drainage (CWT1 and CWT2). The controlled drainage system allowed the groundwater level in the soil to be varied during the year. It was kept at least 70 cm below the soil surface during the growing season but allowed to rise to a maximum of 20 cm below the soil surface during the rest of the year. Measurements were performed to record precipitation, drain outflow and groundwater levels. Daily values of outflow were divided into 10 categories, based on the size of outflow. Recession curves of hourly measurement of outflow were selected. They behaved like single reservoirs and a linear storage–outflow model was applied. Least squares estimates of the parameters initial outflow, initial storage volume and retention constant were calculated. Controlled drainage had a significant effect on total drain outflow and outflow pattern during the three years of measurement. The total drain outflow was 70% to 90% smaller in CWT than in CD. The analysis revealed that the initial outflows were higher, the retention constant and the temporary storage lower in CWT. The hydrological impacts of the reduction in temporary storage were higher peak flow, shorter lag time and shorter recession time and these effects increased with an increased groundwater level. Copyright © 2003 John Wiley & Sons, Ltd.     

Melanistic southern right‐whale dolphins (Lissodelphis peronii) off Kaikoura,New Zealand,with records of other anomalously all‐black cetaceans

Reports of anomalously pigmented cetaceans, including melanistic (all‐black) individuals are infrequent. We observed four melanistic southern right‐whale dolphins (Lissodelphis peronii) including a calf, off Kaikoura (42°34'S, 173°50'E), New Zealand. We also compiled records of melanistic individuals from five other species of cetaceans. The ecological context of melanistic pigmentation of cetaceans is not well understood; however, it may increase heat absorption, affect ability to capture prey, impair visual/social communication, and/or increase conspicuousness to predators.     

Causal thinking and support for climate change policies: International survey findings

Few comparative international studies describe the climate change policies people are willing to support and the reasons for their support of different policies. Using survey data from 664 economics and business undergraduates in Austria, Bangladesh, Finland, Germany, Norway, and the United States, we explore how perceived risk characteristics and mental models of climate change influence support for policy alternatives. General green policies such as funding research on renewable technologies and planting trees were the overwhelmingly most popular policy alternatives. Around half the students support carbon reduction policies such as requiring higher car fuel efficiency and increasing taxes on fossil fuels. Least popular were engineering alternatives such as fertilizing the oceans and replacing fossil fuels with nuclear power. Variations among nations are generally small. Support for different policy alternatives corresponds with different causal thinking. Those who hold a pollution model of the causes of climate change, tend to blame environmental harms (e.g., air pollution from toxic chemicals), see general green policy alternatives as effective, and support general green policies. Support of carbon reduction strategies is associated with seeing carbon emissions as the cause and reducing carbon emissions as effective solutions. Support of engineering solutions increases with identifying volcanoes among causes and regarding engineering solutions as effective. Although these international students agree that climate change is a threatening problem, their causal thinking correlates with support for different mitigative policy actions, with the most popular ones not necessarily the most effective.     

Oxygen, hydrogen, and helium isotopes for investigating groundwater systems of the Cape Verde Islands, West Africa

Stable isotopes (δ¹⁸O, δ²H), tritium (³H), and helium isotopes (³He, ⁴He) were used for evaluating groundwater recharge sources, flow paths, and residence times of three watersheds in the Cape Verde Islands (West Africa). Stable isotopes indicate the predominance of high-elevation precipitation that undergoes little evaporation prior to groundwater recharge. In contrast to other active oceanic hotspots, environmental tracers show that deep geothermal circulation does not strongly affect groundwater. Low tritium concentrations at seven groundwater sites indicate groundwater residence times of more than 50 years. Higher tritium values at other sites suggest some recent recharge. High ⁴He and ³He/⁴He ratios precluded ³H/³He dating at six sites. These high ³He/⁴He ratios (R/R_a values of up to 8.3) are consistent with reported mantle derived helium of oceanic island basalts in Cape Verde and provided end-member constraints for improved dating at seven other locations. Tritium and ³H/³He dating shows that São Nicolau Island’s Ribeira Fajã Basin has groundwater residence times of more than 50 years, whereas Fogo Island’s Mosteiros Basin and Santo Antão Island’s Ribeira Paul Basin contain a mixture of young and old groundwater. Young ages at selected sites within these two basins indicate local recharge and potential groundwater susceptibility to surface contamination and/or salt-water intrusion.     

Climate change and the effect of temperature backlashes causing frost damage in Picea abies

In boreal and nemoboreal forests, tree frost hardiness is modified in reaction to cues from day length and temperature. The dehardening processes in Norway spruce, Picea abies, could be estimated to start when the daily mean temperature is above 5 °C for 5 days. Bud burst will occur approximately after 120–170 degree-days above 5 °C, dependent on genetic differences among provenances. A reduced cold hardiness level during autumn and spring and an advanced onset of bud burst are expected impacts of projected future global warming. The aim of this study was to test if this will increase the risk for frost damage caused by temperature backlashes. This was tested for Sweden by comparing output from the Hadley Centre regional climate model, HadRM3H, for the period 1961–1990 with future IPCC scenario SRES A2 and B2 for 2070–2099. Different indices for calculating the susceptibility to frost damage were used to assess changes in frost damage risk. The indices were based on: (1) the start of dehardening; (2) the severity of the temperature backlash; (3) the timing of bud burst; and (4) the cold hardiness level. The start of dehardening and bud burst were calculated to occur earlier all over the country, which is in line with the overall warming in both climate change scenarios. The frequency of temperature backlashes that may cause frost damage was calculated to increase in the southern part, an effect that became gradually less pronounced towards the north. The different timing of the onset of dehardening mainly caused this systematic latitudinal pattern. In the south, it occurs early in the year when the seasonal temperature progression is slow and large temperature variations occur. In the north, dehardening will occur closer to the spring equinox when the temperature progression is faster.