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84 Mines, Golden. Starr, G.C. 2005. Assessing temporal stability and spatial variability of soil water patterns with implications for precision water management, Agr. Water Manage. 72:223–243. Thomasson, M.J., P.J. Wierenga, T.P.A. Ferre. 2006 A Field Application of the Scaled-Predictive Method for Unsaturated Soil. Vadose Zone J. 5:1093–1109. Vachaud,G., A. Passerat de Silans, P. Balabanis, and M. Vauclin. 1985. Temporal stability of spatially measured soil water probability density function. Soil Sci. Soc. Am. J. 49:822–828. Zhang, R. 1997. Determination of soil sorptivity and hydraulic conductivity from the disk infiltrometer. Soil Sci. Soc. Am. J. 61:1024–1030. Zhao, Y., Peth, S., Horn, R., Wang, X.Y., Giese, M., Steffens, M., Hoffmann, C., Gao. Y.Z. 2008a. Spatio-temporal variability of soil moisture in grazed steppe areas by multivariate geostatistics. (Revision for Journal of Hydrology) Zhao, Y., S. Peth, J. Krümmelbein, B. Ketzer, Y.Z. Gao, X.H. Peng, C. Bernhofer, and R. Horn. 2008b. Modeling grazing effects on coupled water and heat fluxes in Inner Mongolia grassland. (Submitted to Vadose Zone Journal)
Chapter 5 Modeling Grazing Effects on Coupled Water and Heat Fluxes in Inner Mongolia Grassland 5. Modeling Grazing Effects on Coupled Water and Heat Fluxes in Inner Mongolia Grassland Ying Zhao, Stephan Peth, Julia Krümmelbein, Bettina Ketzer, Yingzhi Gao, Xinhua Peng, Rainer Horn, and Christian Bernhofer Submitted to: Vadose Zone Journal. ABSTRACT Over-grazing is regarded as a main cause for grassland degradation in semi-arid regions. To evaluate how soil water and heat fluxes respond to grazing, investigations on soil, plant and meteorological parameters were conducted at four sites with different grazing intensities (i.e., ungrazed since 1979, ungrazed since 1999, winter grazed, and heavily grazed), through three growing periods (2004-2006) in a steppe ecosystem of Inner Mongolia. Our results showed that heavy grazing resulted in an increased meso-pore volume and a decreased total- and macro-pore volume, accompanied by a reduction of saturated hydraulic conductivity. These soil structural changes were parameterized by Laboratory-derived hydraulic parameters (LDP model) based on HYDRUS-1D. In addition, to account for effects of the site-specific plant on the bo<strong>und</strong>ary condition, we used the model SHAW to estimate interception and partitioned evapotranspiration via a weighing lysimeter. On the basis of former calibration, HYDRUS-1D was verified with a good agreement between modeled and measured soil moisture and temperature. The modeled results indicated that soil heat fluxes increased with increasing grazing intensity. In comparison with the two ungrazed sites, winter grazing did not show clear effects on the water household components, while heavy grazing remarkably decreased interception by 50-55% and transpiration by 20-30%, and increased evaporation by 25-40%. We conclude that intensive grazing deteriorated soil functions and reduced plant available water, consequently reduced grassland productivity and enhanced the soil risks for wind and water erosion. 85
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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 is also unce
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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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Chapter 2 Spatial variability of so
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Chapter 6 Modeling of Coupled Water
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Chapter 6 Modeling of Coupled Water
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Chapter 7 General discussion and co
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References Chapter 7 General discus
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8. ACKNOWLEDGMENTS Firstly I would
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Curriculum Vitae M.Sc. Ying Zhao Of
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Schriftenreihe des Instituts Neuere
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