Pedogeomorphology, geochronology and paleobotany of soil profiles obtained in the Nagqu area, central Tibet

Vast areas on the Tibetan Plateau are covered by alpine sedge mats consisting of different species of the genus Kobresia. These mats have topsoil horizons rich in rhizogenic organic matter which creates turfs. As the turfs have recently been affected by a complex destruction process, knowledge concerning their soil properties, age and pedogenesis are needed. In the core area of Kobresia pygmaea mats around Nagqu (central Tibetan Plateau, ca. 4500 m a.s.l.), four profiles were subjected to pedological, paleobotanical and geochronological analyses concentrating on soil properties, phytogenic composition and dating of the turf. The turf of both dry K. pygmaea sites and wet Kobresia schoenoides sites is characterised by an enrichment of living (dominant portion) and dead root biomass. In terms of humus forms, K. pygmaea turfs can be classified as Rhizomulls mainly developed from Cambisols. Wet-site K. schoenoides turfs, however, can be classified as Rhizo-Hydromors developed from Histic Gleysols. At the dry sites studied, the turnover of soil organic matter is controlled by a non-permafrost cold thermal regime. Below-ground remains from sedges are the most frequent macroremains in the turf. Only a few pollen types of vascular plants occur, predominantly originating from sedges and grasses. Large amounts of microscopic charcoal (indeterminate) are present. Macroremains and pollen extracted from the turfs predominantly have negative AMS 14C ages, giving evidence of a modern turf genesis. Bulk-soil datings from the lowermost part of the turfs have a Late Holocene age comprising the last ca. 2000 years. The development of K. pygmaea turfs was most probably caused by an anthropo(zoo)-genetically initiated growth of sedge mats replacing former grass-dominated vegetation ('steppe'). Thus the turfs result from the transformation of pre-existing topsoils comprising a secondary penetration and accumulation of roots. K. schoenoides turfs, however, are characterised by a combined process of peat formation and penetration/accumulation of roots probably representing a (quasi) natural wetland vegetation.

Oligocene plaktonic foraminifera of the Indian Ocean ODP Leg 115 sites

We drilled 13 holes on Ocean Drilling Program Leg 115 in the Indian Ocean and recovered Paleogene sediments that consisted primarily of pelagic components. Planktonic foraminifer assemblages displayed high diversity throughout the Paleogene from the late Paleocene to the Oligocene/Miocene boundary and consist of predominantly warm-water species. Faunas of middle Eocene age are remarkably well represented. Biostratigraphic assignment was, however, very difficult because of the turbiditic character of most of the Paleogene sediments. Reworking is a constant feature of the middle Eocene through early Oligocene planktonic faunas, with reworked faunas frequently overwhelming the younger ones. Preservation within turbidites ranges from excellent to very poor to total destruction of planktonic foraminifers. A major dissolution episode is recorded in the interval that spans most of the late Eocene through the early Oligocene, especially at the deeper sites where the source area was probably well below the lysocline. Redeposition decreases markedly by the mid-Oligocene, but it is only by late Oligocene Zone P22 that normal sedimentation resumes and/or redeposition decreases even at the most affected sites (such as Hole 709C). Comparison with other sites drilled previously in the Indian Ocean reveals that mixed assemblages were already known for sediments from the Mascarene Plateau-Seychelles Bank and surrounding basins during that time span. Because of the disturbances that characterize Paleogene deposits, hiatuses are difficult to detect; nevertheless, a hiatus of less local importance, spanning Subzone P21b, was detected in three holes at different water depths.

(Table A1) Species list of the high Antarctic Weddell Sea food web

Human-induced habitat destruction, overexploitation, introduction of alien species and climate change are causing species to go extinct at unprecedented rates, from local to global scales. There are growing concerns that these kinds of disturbances alter important functions of ecosystems. Our current understanding is that key parameters of a community (e.g. its functional diversity, species composition, and presence/absence of vulnerable species) reflect an ecological network's ability to resist or rebound from change in response to pressures and disturbances, such as species loss. If the food web structure is relatively simple, we can analyse the roles of different species interactions in determining how environmental impacts translate into species loss. However, when ecosystems harbour species-rich communities, as is the case in most natural systems, then the complex network of ecological interactions makes it a far more challenging task to perceive how species' functional roles influence the consequences of species loss. One approach to deal with such complexity is to focus on the functional traits of species in order to identify their respective roles: for instance, large species seem to be more susceptible to extinction than smaller species. Here, we introduce and analyse the marine food web from the high Antarctic Weddell Sea Shelf to illustrate the role of species traits in relation to network robustness of this complex food web. Our approach was threefold: firstly, we applied a new classification system to all species, grouping them by traits other than body size; secondly, we tested the relationship between body size and food web parameters within and across these groups and finally, we calculated food web robustness. We addressed questions regarding (i) patterns of species functional/trophic roles, (ii) relationships between species functional roles and body size and (iii) the role of species body size in terms of network robustness. Our results show that when analyzing relationships between trophic structure, body size and network structure, the diversity of predatory species types needs to be considered in future studies.

(Table 4) Concentrations of radionuclides in waters of the Barents and Kara Seas in August 2003

A methodology of experimental simulation of state of spent nuclear fuel that occurs on the sea floor due to some catastrophes or dumping is developed. Data on long-term (more than 2000 days) experiments on estimation of 85Kr and 137Cs release rate from spent nuclear fuel (fragments of irradiated UO2 pellets) were firstly obtained; these estimates prove correctness of a hypothesis offered by us in early 1990s concerning to earlier 85Kr release (by one order of magnitude higher than that of 137Cs) as compared to other fission fragments in case of loss of integrity of fuel containment as a result of corrosion on the sea floor. A method and technique of onboard 85Kr and 137Cs sampling and extraction (as well as sampling of tritium, product of triple 235U fission) and their radiometric analysis at coastal laboratories are developed. Priority data on 85Kr background in bottom layers of the Barents and Kara Seas and 137Cs and 3H in these seas (state of 2003) are presented. Models necessary for estimation of dilution of fission products of spent nuclear fuel and their transport on the floor in accident and dumping regions are developed. An experimental method for examination of state of spent nuclear fuel on the sea floor (one expedition each 2-3 years) by 85Kr release into environment (a leak tracer) is proposed; this release is an indicator of destruction of fuel containment and release of products of spent nuclear fuel in case of 235UO2 corrosion in sea water.

Benthic foraminifera and stable isotope composition in Paleocene-Eocene sediments

In the late Paleocene to early Eocene, deep sea benthic foraminifera suffered their only global extinction of the last 75 million years and diversity decreased worldwide by 30-50% in a few thousand years. At Maud Rise (Weddell Sea, Antarctica; Sites 689 and 690, palaeodepths 1100 m and 1900 m) and Walvis Ridge (Southeastern Atlantic, Sites 525 and 527, palaeodepths 1600 m and 3400 m) post-extinction faunas were low-diversity and high-dominance, but the dominant species differed by geographical location. At Maud Rise, post-extinction faunas were dominated by small, biserial and triserial species, while the large, thick-walled, long-lived deep sea species Nuttallides truempyi was absent. At Walvis Ridge, by contrast, they were dominated by long-lived species such as N. truempyi, with common to abundant small abyssaminid species. The faunal dominance patterns at the two locations thus suggest different post-extinction seafloor environments: increased flux of organic matter and possibly decreased oxygen levels at Maud Rise, decreased flux at Walvis Ridge. The species-richness remained very low for about 50 000 years, then gradually increased. The extinction was synchronous with a large, negative, short-term excursion of carbon and oxygen isotopes in planktonic and benthic foraminifera and bulk carbonate. The isotope excursions reached peak negative values in a few thousand years and values returned to pre-excursion levels in about 50 000 years. The carbon isotope excursion was about -2 per mil for benthic foraminifera at Walvis Ridge and Maud Rise, and about -4 per mil for planktonic foraminifera at Maud Rise. At the latter sites vertical gradients thus decreased, possibly at least partially as a result of upwelling. The oxygen isotope excursion was about -1.5 per mil for benthic foraminifera at Walvis Ridge and Maud Rise, -1 per mil for planktonic foraminifera at Maud Rise. The rapid oxygen isotope excursion at a time when polar ice-sheets were absent or insignificant can be explained by an increase in temperature by 4-6°C of high latitude surface waters and deep waters world wide. The deep ocean temperature increase could have been caused by warming of surface waters at high latitudes and continued formation of the deep waters at these locations, or by a switch from dominant formation of deep waters at high latitudes to formation at lower latitudes. Benthic foraminiferal post-extinction biogeographical patterns favour the latter explanation. The short-term carbon isotope excursion occurred in deep and surface waters, and in soil concretions and mammal teeth in the continental record. It is associated with increased CaC03-dissolution over a wide depth range in the oceans, suggesting that a rapid transfer of isotopically light carbon from lithosphere or biosphere into the ocean-atmosphere system may have been involved. The rapidity of the initiation of the excursion (a few thousand years) and its short duration (50 000 years) suggest that such a transfer was probably not caused by changes in the ratio of organic carbon to carbonate deposition or erosion. Transfer of carbon from the terrestrial biosphere was probably not the cause, because it would require a much larger biosphere destruction than at the end of the Cretaceous, in conflict with the fossil record. It is difficult to explain the large shift by rapid emission into the atmosphere of volcanogenic CO2, although huge subaerial plateau basalt eruptions occurred at the time in the northern Atlantic. Probably a complex combination of processes and feedback was involved, including volcanogenic emission of CO2, changing circulation patterns, changing productivity in the oceans and possibly on land, and changes in the relative size of the oceanic and atmospheric carbon reservoirs.

Chemical and isotopic compositions of authigenic carbonates from bottom sediments of Northwest Pacific marginal seas

The paper presents data on authigenic carbonate distribution in Holocene - Upper Pleistocene deposits of the Okhotsk, Japan, East China, Philippine and South China Seas. Description of carbonate samples, their chemical and isotope compositions are given. Chemical analysis of the samples indicates that almost all authigenic carbonates are composed of calcite or magnesian calcite; and only in one case, of siderite. Oxygen isotopic composition (d18O) ranges from +37.7 to +26.1 per mil (SMOW); it is, probably, connected with different temperatures of carbonate formation. A distinct geographic regularity is traced. Decrease in d18O values is observed from the cold Okhotsk Sea to the warm South China Sea. A very wide range of carbon isotopic composition (d13C from -42 to +3.8 per mil) indicates different sources of carbonic acid required for formation of these carbonates. As a basis for carbon isotopic composition we can distinguish three sources of carbonic acid in the studied sediments: microbiological methane oxidation, organic matter destruction during sediment diagenesis, and dissolved organogenic limestone. Thus, formation of authigenic carbonates in sediments from the marginal seas of the Northwest Pacific results from: 1) sediment diagenesis, 2) methane oxidation in zones of gas anomalies, 3) their precipitation from the supersaturated by carbonates sea shoal waters of tropical sea lagoons.

Soil chemistry and particle size distribution of mountainous tundra soils in the Rai-Iz Massif

Gravelly clay loamy and clayey soils developed from the derivatives of ultramafic rocks of the dunite-harzburgite complex of the Rai-Iz massif in the Polar Urals have been studied. They are represented by raw-humus pelozems (weakly developed clayey soils) under conditions of perfect drainage on steep slopes and by the gleyzems (Gleysols) with vivid gley color patterns in the eluvial positions on leveled elements of the relief. The magnesium released from the silicates with the high content of this element (mainly from olivine) specifies the neutral-alkaline reaction in these soils. Cryoturbation, the accumulation of raw humus, the impregnation of the soil mass with humic substances, gleyzation, and the ferrugination of the gleyed horizons are also clearly pronounced in the studied soils. Despite the high pH values, the destruction of supergene smectites in the upper horizons and ferrugination (the accumulation of iron hydroxides) in the microfissures dissecting the grains of olivine, pyroxene, and serpentine, and in decomposing plant tissues take place. The development of these processes may be related to the local acidification (neutralization) of the soil medium under the impact of biota and carbonic acids. The specificity of gleyzation in the soils developing from ultra-mafic rocks is shown in the absence of iron depletion from the fine earth material against the background of the greenish blue gley color pattern.