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The climatic changes on earth may have serious implications for the carbon (C) cycle in the terrestrial Arctic throughout the 21st century. Arctic vegetation takes up carbon dioxide (CO2) from the atmosphere producing biomass. In a cold and often moist soil environment, dead organic matter is preferentially preserved as soil organic matter (SOM) due to the inhibition of decomposition processes. However, viable soil microbes exhale huge amounts of CO2 and methane (CH4) annually. Hence, Arctic ecosystems exhibit annual fluxes of both carbon-based (CO2 and CH4) greenhouse gases (GHGs) that are in an order of magnitude of millions of tons. Rising Arctic temperatures lead to the degradation of much of today's permafrost in the long run. As a result, large quantities of frozen SOM may become available for decomposers, and GHGs that are entrapped in permafrost may be released. At the same time, warming tends to stimulate the growth, development, and reproduction of many Arctic plants, at least transiently. The present northward migration of boreal shrubs and trees into southern tundra areas may be amplified by that, increasing the ecosystems' gross primary production and, thus, their C sequestration. On the other hand, rising temperatures boost SOM decomposition and microbial respiration rates. In general, soil temperature and soil moisture are key environmental variables to control the, intensity of aerobic and anaerobic respiration by microbes, and autotrophic respiration by plants. On the basis of published data on Arctic CO2 and CH4 fluxes, the calculations on the terrestrial C-based Arctic GHG balance made in this review reveal a current annual GHG exchange that ranges between a weak storage of <= 225 Tg CO2 equivalent (eq.) y(-1) and a huge release of 1990 Tg CO2 eq. y(-1). Hence, the Arctic GHG balance does apparently already contribute positively to the climatic changes at present. Regarding the future, the relative development of the uptake and release of CO2 and

Floodplain soils at the Elbe river are frequently polluted with metals and arsenic. High contents of these pollutants were detected down to subsoil layers. NH4NO3-extractable (phytoavailable) Cd, Ni, and Zn were elevated in horizons with high acidity. Among five common floodplain plant species, Artemisia vulgaris showed highest concentrations of Cd, Cu, and Hg, Alopecurus pratensis of As and Phalaris arundinacea of Ni, Pb, and Zn. Relationships were weak between metal concentrations in plants and phytoavailable stocks in soil. As and Hg uptake seems to be enhanced on long submerged soils. Enrichments of Cd and Hg are linked to a special plant community composition. Grassland herbage sampled in July/August revealed higher concentrations of As (+122%), Hg (+124%), and Pb (+3723%) than in May. To limit harmful transfers into the food chain, low-lying terraces and flood channels revealing highest contaminations or phytoavailabilities should be excluded from mowing and grazing. Soils in the Elbe river floodplains are highly polluted with metals and arsenic and a critical enrichment in the grassland herbage seems to be most likely in flood channels or within special plant species.

The characterization of topsoils has recently received enhanced attention, particularly for environmental monitoring. Traditional national and international soil taxonomies hardly consider the topsoil in spite of its importance for soil quality. Consequently, the FAO "Topsoil Characterization for Sustainable Land Management" was developed to be used additionally for describing topsoils and to combine it with the World Reference Base for Soil Resources (WRB). In this paper, recommendations for a first step of a revision and expansion of the FAO "Topsoil Characterization" are made. On the one hand, common rules for soil description as used in the FAO "Guidelines for Profile Description" were incorporated in the FAO "Topsoil Characterization". On the other hand, new characteristics for the description of the organic matter and of biological features of the topsoils were introduced. At first, the proposed German systematics of humus forms is presented and correlated with different national systematics, for validation in the international context. Secondly, a correlation of the new German systematics of humus forms with the FAO "Topsoil Characterization for Sustainable Land Management" and other topsoil systematics is made. Thirdly, additional qualifiers are described focussing on the organic layers and the biological features. A coincidence between the characterization of humus forms and topsoils was found which appears to be an appropriate basis for the incorporation of humus forms in the FAO "Topsoil Characterization". Investigations have shown that the topsoils in forests can be described comprehensively by additional qualifiers for the organic layers. Grassland or arable land which usually lack organic layers can be characterized in detail by qualifiers concerning soil biological activity in the A horizon. The methodology was already applied successfully in temperate regions. But there is still a need for further discussion of the revision and for tests in tropical