Plant and Soil, Feb, 2012, Vol.351(1-2), p.293(15)
Byline: Roger Funk (1), Yong Li (2), Carsten Hoffmann (1), Matthias Reiche (1), Zhuodong Zhang (1,2), Junjie Li (2), Michael Sommer (1,3) Keywords: [.sup.137]Cs; Grassland; Wind erosion; Dust deposition; Reference site Abstract: Aims The aims of this study were to identify areas of wind erosion and dust deposition and to quantify the effects of different grazing intensities on soil redistribution rates in grasslands based on the 137.sup.Cs technique. Because the method uses a reference inventory as threshold for erosion or deposition, the classification of any other site as source or sink for dust depends on the accurate selection of this reference site. Methods Measurements of 137.sup.Cs inventories and depth distributions were carried out at pasture sites with predominant species of Stipa grandis and Leymus chinensis which are grazed with different intensities. Additional measurements were made at arable land, plant-covered sand dunes and alluvial plains. Wind-induced soil erosion and dust deposition rates were calculated from 137.sup.Cs inventories by means of the "Profile-Distribution" and the "Mass Balance II" models. Results The selection of the reference site was based on fluid dynamical and process-determining parameters. The chosen site should meet the following four conditions: (i) located at a summit position with obviously low deposition rates, (ii) sufficient vegetation cover to prevent wind erosion, (iii) plane to exclude water erosion and (iv) in the wind/dust shadow of a higher elevation. The measured reference inventory of 137.sup.Cs was 1967(+-102) Bqm.sup.-2 located at a summit position of moderately grazed Leymus chinensis steppe. The 137.sup.Cs inventories at other sites ranged from 1330 Bqm.sup.-2 at heavily grazed sites to 5119 Bqm.sup.-2 at river deposits, representing annual average soil losses of up to 130 tkm.sup.-2 and deposits of up to 540 tkm.sup.-2, respectively. The calculated annual averages of dust depositions at ungrazed Leymus chinensis sites were related to the dust storm frequencies of the last 50 years resulting in a description of the temporal variability of annual dust depositions from about 154 tkm.sup.-2 in the 1960s to 26 tkm.sup.-2 at recent times. Based on this quantification already 80% of the total dust depositions can be related to the 20 years between the 1960s and the end of the 1970s and only 20% to the time between 1980 and 2001. Conclusions [.sup.137]Cs technique is a promising method to assess the effect of grazing intensity and land use types on the spatial variability of wind-induced soil and dust redistribution processes in semi-arid grasslands. However, considerable efforts are needed to identify a reliable reference site, because erosion and deposition induced by wind may occur at the same places. The combination of the dust deposition rates derived from 137.sup.Cs profile data with the dust storm frequencies is helpful for a better reconstruction of the temporal variability of dust deposition and wind erosion in this region. The calculated recent deposition rates of about 20 tkm.sup.-2 are in good agreement with data of other authors. Author Affiliation: (1) Leibniz-Centre for Agricultural Landscape Research, Institute of Soil Landscape Research, Eberswalder Str. 84, 15374, Muncheberg, Germany (2) Chinese Academy of Agricultural Sciences, Institute of Environment and Sustainable Development in Agriculture, Zhongguancun South Str. 12, 100081, Beijing, People's Republic of China (3) Institute of Earth and Environmental Science, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476, Potsdam, Germany Article History: Registration Date: 15/08/2011 Received Date: 18/02/2011 Accepted Date: 14/08/2011 Online Date: 10/09/2011 Article note: Responsible Editor: Hans Lambers.
Soil Erosion -- Analysis ; Steppes -- Analysis ; Dunes -- Analysis ; Sandstorms -- Analysis ; Sustainable Development -- Analysis ; Dust Storms -- Analysis
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