RESUMO
Melting glaciers release new ground surfaces, which may be either a source of greenhouse gas emissions or a sink for carbon dioxide. Studies carried out in subpolar and alpine ecosystems confirm the relatively rapid soil development and increase of carbon and nitrogen pools. However, observations from high-mountain glacier forelands in cold and dry climate are very scarce. This study analyses the impact of major environmental factors related to climate, topography, and vegetation, over a time-scale, on soil development and spatial soil differentiation in the foreland of Uisu Glacier, East Pamir Mountains. Moreover, the usefulness of the World Reference Base (WRB) and Soil Taxonomy in the classification of poorly developed soils in the ultracontinental climate was assessed. Geomorphological, pedological, and botanical surveys covered a sequence of terraces, alluvial fans, and end-moraines. Typical characteristics of the soils in the glacier foreland were: very high stoniness, coarse texture, high content of calcium carbonate, alkaline reaction, and low salinity. Soil development has extremely low intensity and was manifested in (a) soil organic carbon pools being among the lowest reported in the world (up to 1.4 kg m-2 in the layer 0-50 cm), and (b) the presence of cambic/calcic horizons only on landforms older than of Mid-Holocene age (estimated). It was concluded that both the extremely cold and extremely dry climate conditions in the Uisu Glacier foreland limit the water flux and availability, suppress vegetation density and variability, and slow down the rate of soil development. Both WRB and Soil Taxonomy were able to reflect the advances in soil development and spatial soil differentiation (Calcaric Hyperskeletic Leptosols - Calcaric Cambisols - Cambic Calcisols, and Gelifluvents - Haplocambids - Haplocalcids, respectively); however, highlighting different features developed under an extremely cold and dry climate conditions of the East Pamir Mountains.
RESUMO
The eastern part of the Pamir Mountains, located in Central Asia, is characterized by great climatic continentality and aridity. Wetlands developed in this hostile region are restricted to spring areas, terraces of shallow lakes or floodplains along rivers, and provide diversified ecosystem services e.g. as water reservoirs, refugia for rare species and pastures for domestic cattle. These ecosystems are particularly susceptible to climate changes, that in the Pamir Mountains result in increased temperatures, intense permafrost/glacial melt and alterations of precipitation patterns. Climatic changes affect pasture management in the mountains, causing overutilization of sites located at lower elevations. Thus, both climate and man-induced disturbances may violate the existing ecological equilibrium in high-mountain wetlands of the Eastern Pamir, posing a serious risk to their biodiversity and to food security of the local population. In this context, we sought to assess how environmental drivers (with special focus on soil features and potential water sources) shape the distribution and diversity of halophytic plant communities developed in valleys in the Eastern Pamir. This task was completed by means of a vegetation survey and comprehensive analyses of habitat conditions. The lake terraces and floodplains studied were covered by a repetitive mosaic of plant communities determined by differences in soil moisture and salinity. On lower, wetter sites, this patchwork was formed by Blysmus rufus dominated salt marshes, saline small sedge meadows and saline meadows with Kobresia royleana and Primula pamirica; and on drier, elevated sites, by endemic grasslands with Hordeum brevisubulatum and Puccinellia species and patches of xerohalophytic vegetation. Continuous instability of water sources and summer droughts occurring in the Pamir Mountains may lead to significant structural and functional transformations of described wetland ecosystems. Species more tolerant to decreased soil moisture and/or increased soil salinity will expand, leading to alterations of ecosystem services provided by the Pamirs' wetlands. The described research will help to assess the current state of the wetlands and to predict directions of their future changes.
