Aim Savannas and seasonally-dry ecosystems cover a significant part of the world's land surface. If undisturbed, these ecosystems might be expected to show a net uptake of methane (CH 4 ) and a limited emission of nitrous oxide (N 2 O). Land management has the potential to change dramatically the characteristics and gas exchange of ecosystems. The present work investigates the contribution of warm climate seasonally-dry ecosystems to the atmospheric concentration of nitrous oxide and methane, and analyses the impact of land-use change on N 2 O and CH 4 fluxes from the ecosystems in question.Location Flux data reviewed here were collected from the literature; they come from savannas and seasonally-dry ecosystems in warm climatic regions, including South America, India, Australasia and Mediterranean areas.Methods Data on gas fluxes were collected from the literature. Two factors were considered as determinants of the variation in gas fluxes: land management and season. Land management was grouped into: (1) control, (2) 'burned only' and (3) managed ecosystems. The season was categorized as dry or wet. In order to avoid the possibility that the influence of soil properties on gas fluxes might confound any differences caused by land management, sites were grouped in homogeneous clusters on the basis of soil properties, using multivariate analyses. Inter-and intra-cluster analysis of gas fluxes were performed, taking into account the effects of season, land management and main vegetation types.Results Soils were often acid and nutrient-poor, with low water retention. N 2 O emissions were generally very low (median flux 0.32 mg N 2 O m )2 day )1 ), and no significant differences were observed between woodland savannas and managed savannas. The highest fluxes (up to 12.9 mg N 2 O m )2 day )1 ) were those on relatively fertile soils with high air-filled porosity and water retention. The effect of season on N 2 O production was evident only when sites were separated in homogeneous groups on the basis of soil properties. CH 4 fluxes varied over a wide range ()22.9 to 3.15 mg CH 4 m )2 day )1 , where the negative sign denotes removal of gas from the atmosphere), with an annual average daily flux of )0.48 ± 0.96 (SD) mg CH 4 m )2 day )1 in undisturbed (control) sites. Land-use change dramatically reduced this CH 4 sink. Managed sites were weak sinks of CH 4 in the dry season and became sources of CH 4 in the wet season. This was particularly evident for pastures. Burning alone did not reduce soil net CH 4 oxidation, but decreased N 2 O production.Main conclusions Despite the low potential for N 2 O production, both in natural and managed conditions, tropical seasonally-dry ecosystems represent a significant source of N 2 O (4.4 Tg N 2 O year )1 ) on a global scale, as a consequence of the large area they occupy. The same environments represent a potential CH 4 sink of 5.17 Tg CH 4 year )1 . However, assuming that c. 30% of the tropical land is

The study of soils formed by human activities is one of the concerns of modern pedology. In Italy, data on highly human‐disturbed soils are not available. We investigated the soils from a recently dismantled iron and steel production plant, and compared them with natural soils in undisturbed adjacent areas. The industrial activity in question started 80 yr ago. The dominant morphology of the disturbed soils results from the stratification of materials used in and derived from the industrial process, which were variously mixed with earthy materials. Layers with variable thickness occur up to the 2‐m depth. The spoil layer sequence is rarely interrupted by an applied natural soil, or in situ formed horizons, indicating the continuity of material deposition. Natural subsurface primary horizons are either obliterated or highly disturbed. We also recognized highly disturbed soils without significant spoil materials. All soils show high variability in their characteristics. They also have morphological and chemical features, such as horizonation, pH, organic C and total N content, distinctly different from those of natural soils. Problems emerged in classifying the investigated soils consistently with the current requirements of the U.S. soil taxonomy. To overcome such difficulty, we propose the adoption of the foundric subgroup of the Xerorthents. Such soils may be of interest in the discussion of the International Committee on Anthropogenic Soils (ICOMANTH), which is charged with studying and defining criteria for an appropriate taxonomic classification of highly human‐influenced soils.

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Reclamation activities in alluvial depressions in Volturno River Plain resulted in the occurrence of soils with vertic characteristics and properties. We studied the genesis and properties of soils in alluvial areas known to be reclaimed by the alluvion system about 100 yr ago, and compared these soils with natural, adjacent alluvial soils. Soils in the reclaimed areas were characterized by cracks, slickensides, and high clay contents. Soils were satisfactorily classified within the existing Vertisol order of U. S. soil taxonomy. Soils with similar vertic morphology and properties also occurred in nonreclaimed adjacent alluvial areas, where they were associated with coarser textured Entisols. Since no important morphological evidence for the reclamation activity was identified in the soils in the reclaimed areas, the anthropogenic origin of such soils only emerged from historical records. The introduction of relational properties such as historical records is currently suggested to interpret and classify soils of various proposed taxonomic classes at different categorical levels. Therefore we discuss some critical aspects of the use of the historical records for classifying the soils in the reclaimed areas into genetic and technical soil categories that are currently being defined by the International Committee on Anthropogenic Soils (ICOMANTH).