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Under frozen conditions, the differences between simulated and measured water contents could be also related to soil structural changes. Further work should establish a relation between the impedance factor and soil hydraulic properties that can be measured in the field. It is possible that measurements of soil moisture characteristic curves under both frozen and unfrozen conditions are helpful to provide a basis for this aspect. A detailed knowledge of the soil-atmosphere interface is needed to improve the surface runoff algorithm in the “freezing module”. Our contributions to MAGIM project 146 We mostly explored the spatial distribution of various regionalized variables, which not only helped to quantify the environmental changes due to the grazing effects at various scales, but also provided a basis for the regionalization, interpolation, transferability and model upscaling from local scale to a large area where the MAGIM project took place. Especially, we deliver a better process understanding for grazing-induced changes in physical and hydraulic soil properties and their effects on local and regional water and heat fluxes in semi-arid regions. This should improve the assessment and prediction of ecosystem changes caused by grazing management. For further studies and possibly future prediction, the hydrological model HYDRUS including freezing and thawing processes was parameterized and validated. This is an important part for the integrated model network of MAGIM. The calibrated hydraulic and thermal parameters is useful to other models, e.g. SWAT model that will be used to calculate C, N and water fluxes in the Xilin River catchment. The modeling products are also essential for inter-verification between the related models. In addition, the modeling products are essential as the additional information, which provide some data for the time and place which sampling is not available. Certainly, the model will definitely serve to characterize the present conditions, and further to predict the future conditions.
References Chapter 7 General discussion and conclusions Bremer, D.J., L.M. Auen, J.M. Ham, and C.E. Owensby. 2001. Evapotranspiration in a prairie ecosystem: Effects of grazing by cattle. Agono. J. 93(2):338–348. Casa, R., and A. Castrignanò. 2007. Analysis of spatial relationships between soil and crop variables in a durum wheat field using a multivariate geostatistical approach. Eur. J. Agron. doi:10.1016/j.eja.2007.10.001. Christensen, L., M.B. Coughenour, J.E. Ellis, and Z.Z. Chen. 2004. Vulnerability of the Asian typical steppe to grazing and climate change. Climatic Change 63:351–368. Drewry, J.J., 2006. Natural recovery of soil physical properties from treading damage of pastoral soils in New Zealand and Australia: a review. Agr. Ecosyst. Environ. 114:159–169. Flerchinger, G.N., and K.E. Saxton. 1989. Simultaneous heat and water model of a freezing snow-residue-soil system I. Theory and development. Trans. ASAE 32:565–571. Gifford, G.F., and R.H. Hawkins. 1978. Hydrologic impact of grazing on infiltration: a critical review. Water Resour. Res. 14:305–313. Gómez-Plaza, A., J. Alvarez-Rogel, J. Albaladejo, and V.M. Castillo. 2000. Spatial patterns and temporal stability of soil moisture across a range of scales in a semi-arid environment. Hydrol. Proc. 14:1261-1277. Greenwood, K.L., and B.M. McKenzie. 2001. Grazing effects on soil physical properties and the consequences for pastures: a review. Austr. J. Exp. Agr. 41:1231–1250. Hansson, K., J., Šimůnek, M. Mizoguchi, L.-C., Lundin, and M.T., van Genuchten. 2004. Water flow and heat transport in frozen soil: numerical solution and freeze-thaw applications. Vadose Zone J. 3:693–704. Krümmelbein, J., Z. Wang, Y. Zhao, S. Peth, and R. Horn. 2006. Influence of various grazing intensities on soil stability, soil structure and water balance of grassland soils in Inner Mongolia, P. R. China. In: R. Horn, H. Fleige, S. Peth, and X. Peng (Eds.). Advances in Geoecology, Vol. 38, pp. 93–101. 147
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SCHRIFTENREIHE Institut für Pflanz
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Aus dem Institut für Pflanzenernä
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I Table of contents I Table of cont
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controlling soil moisture are of pa
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Zusammenfassung Überweidung wird a
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Die Beweidung beieinflusst besonder
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II List of figures Fig. 2.1. Locati
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measured soil moisture in time stab
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III List of tables Table 2.1. Descr
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1.1 Background Chapter 1 Introducti
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Chapter 1 Introduction water in spr
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Chapter 1 Introduction requires the
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Chapter 1 Introduction Krümmelbein
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Y orientation Chapter 4 Temporal st
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MRD(%) MRD(%) 100 80 60 40 20 0 -20
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Soil water content (%) 40 30 20 10
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Chapter 5 Modeling Grazing Effects
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