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from the view of model. The purposes of this study are: i) to investigate the temporal stability of soil moisture <strong>und</strong>er different water conditions, ii) to explore the grazing impact on temporal stability of soil moisture, and iii) to infer whether time stability concept can be availably applied for the hydraulic model to make reliable estimations. 2. Material and Methods Research area and field measurements 68 The study was carried out in a semi-arid steppe ecosystem of Inner Mongolia (North China). The region is marked by a continental climate with cold winter and warm summer (Chen and Wang, 2000). Mean annual precipitation is about 350 mm, 85% of which is happened during the growing period (May to September). The soils are sandy loamy Calcic Chemozems according to IUSS Working Group (2006). Field measurements were carried out on experimental areas of the Inner Mongolia Grassland Ecosystem Research Station (IMGERS, 43 o 37′50′′N, 116 o 42′18′′E), where four plots characterized by different grazing intensities were investigated. Two plots were protected from grazing since 1979 (denoted as UG 79, 24 ha) and 1999 (UG 99, 35 ha). The other two plots were grazed: one was grazed only during winter time with 0.5 sheep units (ewe and lamb) ha -1 yr -1 (WG, 40 ha) and the other was heavily grazed with 2 sheep units ha -1 yr -1 (HG, 100 ha) during the whole year. Before fencing, all plots were moderately grazed. On the geostatistical area consisted of 80 points on a regular 15 m x 15 m grid and additional 20 points nested into the grid at 5 m distance, topsoil moisture content (0-6 cm) was measured at each of the four plots (Fig. 1). Soil moisture was measured with the Theta-probe (Type ML2x, Delta-T Devices, Cambridge, UK) at regular time intervals (biweekly) during the growing period of 2004-2006. Additionally, we conducted in situ measurements for hydraulic conductivity (Mini-disk Infiltrometer, Decagon devices, USA), bulk density, and soil texture at each grid point. Time stability of soil moisture was analysed for 12 sampling dates in 2004, for 8 sampling dates in 2005, and for 10 sampling dates in 2006.
Y orientation Chapter 4 Temporal stability of soil moisture and its application in model result validation 4822400 4822380 4822360 4822340 4822320 4822300 4822280 4822260 4822240 4822220 4822200 473580 1 2 71 61 51 93 72 41 94 62 31 21 42 52 73 11 63 32 53 22 74 43 12 64 33 54 75 23 13 88 44 65 87 55 3 34 76 14 24 45 66 35 56 4 25 77 46 67 15 36 57 5 26 78 47 81 16 68 37 82 58 27 79 6 83 48 17 69 38 7 59 28 89 97 90 80 49 18 98 8 60 70 29 39 50 19 40 9 30 20 10 84 85 86 96 95 92 91 99 100 473600 473620 473640 473660 473680 X orientation 473700 473720 473740 N 473760 Fig. 4.1. Demonstration of sample grids in the experimental site (example for UG 79). Each site has an area of 105 m×135 m. Sampling points are spaced every 15 m with a subgrid spacing of 5 m (Hollow circles donate the field long-term monitoring positions). Time stability 1985): δ δ i j i j = , , The mean relative difference (MRD) is expressed as follows (Vachaud et al., S − S 1 S m i = ∑ m j= 1 j δ j i, j where S i, j is soil moisture at location i (1-100) and time j, and S j is spatially mean soil moisture at the same time, and δ i, j is the relative difference of the spatially mean soil moisture,. Subsequently, the MRD δ i are calculated by averaged δ i, j over the m sampling dates during the considered period for each location. Following Grayson and Western (1998), sampling locations are considered to be time stable when δ i is close to zero and the standard deviation (1) (2) 69
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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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Page 59 and 60: Chapter 3 Spatio-temporal variabili
Page 73 and 74: Chapter 3 Factors controlling spati
Page 85 and 86: Chapter 4 Temporal stability of soi
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Page 93 and 94: MRD(%) MRD(%) 100 80 60 40 20 0 -20
Page 101 and 102: Soil water content (%) 40 30 20 10
Page 105 and 106: Chapter 5 Modeling Grazing Effects
Page 135 and 136: 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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