SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...

Recommendations

Info

(ewe and lamb) ha -1 yr -1 (WG, 40 ha), one continuously grazed site with 1.2 sheep units ha -1 yr -1 (CG, 250 ha) and one heavily grazed site with 2.0 sheep units ha -1 yr -1 (HG, 100 ha). In each plot, a regular sampling grid (Fig. 1), positioned by differential GPS with UTM system, has been set up for the geostatistical analysis. The individual grids covered an area of 105 m×135 m with a sampling spacing of 15 m and subgrid spacing of 5 m. 100 points in each plot were used for geostatistical analysis. In addition, two larger geostatistical grids in WG and CG covering an area of 300 m×550 m with a sampling spacing of 50 m and subgrid spacing of 10 m had been installed to further explore possible scale effects (data not shown). 2.2. Measurement of soil properties 16 On the grid sites, soil moisture was measured at the surface soil layer (0-6 cm) by a HH2 Moisture Meter (Theta-probe Type ML2x, Delta-T devices Ltd, England) after soil specific calibration. Water repellency was quantified using the water drop penetration time test by recording the elapsed time of a distilled water droplet (0.5 mm 3 , using a standard glass pipette) infiltrating completely into a smooth soil surface. According to De Bano (1981), the water repellency was classified as wettable (600 s). Shear strength was measured by a Hand-held vane tester (Geonor H-60, Norway). Hydraulic conductivity was measured by a Mini-disk Infiltrometer (Decagon devices, USA) at a suction of 2 hPa. The soil surface was cleaned from litter prior to the measurement to ensure a good contact between the soil and the infiltrometer. Infiltration time was recorded at regular volume intervals from which the hydraulic conductivity has been calculated according to Zhang (1997). The calibrated van Genuchten parameters were obtained from RETC software based on laboratory analysis of the water retention curve. In addition, <strong>und</strong>isturbed samples were taken in triplicate at each grid point using a stainless steel cylinder (100 cm 3 ) for lab analysis. Bulk density of the soil was calculated with the mass of the oven-dry soil (105° C) divided by the core volume. Total C concentration was determined in duplicate by dry combustion on a Vario Max CNS elemental analyzer (Elementar Analysensysteme GmbH, Hanau). All
Chapter 2 Spatial variability of soil properties affected by grazing intensity in Inner Mongolia grassland samples were free of carbonate so that the total C concentration equals the organic carbon concentration. Soil particle size distribution was measured with the pipette method. 2.3. Statistical analysis Measured variables in the data set were firstly analyzed using descriptive statistical methods. The Shapiro-Wilk test revealed that all measured variables were approximately normally distributed, only K and WDPT showed a negative skewness. Natural logarithmic transformation Y*=Ln(y+1) (where y is the recorded value) for WDPT and Y*=Ln(y) for K were performed to obtain a nearly normal distribution before proceeding with the geostatistical analysis (Jongman et al., 1987). Data were not transformed back in order to simplify multiple linear regression analysis. Correlations among different analyzed parameters were tested using Pearson’s correlation coefficient. Semivariograms was used to determine the degree of spatial variability. Appropriate model functions were fitted to the semivariogram obtained by the maximum likelihood cross-validation method (Samper and Carrera, 1990). Before applying the geostatistical tests, each variable was also checked for drift, trend and anisotropy (Iqbal et al., 2005). The semivariogram (γh) was calculated as follows: N ( h) ⎧ ⎫ 1 2 γ ( h) = 2N ( h) ⎨∑ [ Z( xi + h) − Z( xi )] ⎬ (1) ⎩ i= 1 ⎭ where γ(h) is the semivariance for interval class h, N(h) is the number of pairs separated by the lag distance h, Z(xi) and Z(xi+h) are values of the measured variable at spatial locations i and i+h, respectively. A semivariogram model consists of three basic parameters which describe the spatial structure: γ(h)=Co+Cs. Co represents the nugget effect; Cs is the structural component; Co+Cs is the sill; and the distance at which the sill is reached is the range. Value of the proportion of spatial structure Cs/(C0+Cs) is a measure of the proportion of sample variance (C0+Cs) that is explained by spatially structured variance (Cs). Following Cambardella et al. (1994), The classes of spatial dependence were distinguished: strongly spatial dependence (Cs/(C0+Cs) >75%), moderately spatial dependence (Cs/(C0+Cs) >25% and
Page 1 and 2: SCHRIFTENREIHE Institut für Pflanz
Page 3 and 4: Aus dem Institut für Pflanzenernä
Page 5: I Table of contents I Table of cont
Page 8 and 9: controlling soil moisture are of pa
Page 11 and 12: Zusammenfassung Überweidung wird a
Page 13 and 14: Die Beweidung beieinflusst besonder
Page 15 and 16: II List of figures Fig. 2.1. Locati
Page 17 and 18: measured soil moisture in time stab
Page 19 and 20: III List of tables Table 2.1. Descr
Page 21 and 22: 1.1 Background Chapter 1 Introducti
Page 23 and 24: Chapter 1 Introduction is also unce
Page 25 and 26: Chapter 1 Introduction water in spr
Page 27 and 28: Chapter 1 Introduction requires the
Page 29 and 30: Chapter 1 Introduction Krümmelbein
Page 31 and 32: Chapter 2 Spatial variability of so
Page 35: Chapter 2 Spatial variability of so
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
Page 87 and 88:
Chapter 4 Temporal stability of soi
Page 89 and 90:
Y orientation Chapter 4 Temporal st
Page 91 and 92:
Page 93 and 94:
MRD(%) MRD(%) 100 80 60 40 20 0 -20
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Soil water content (%) 40 30 20 10
Page 103 and 104:
Page 105 and 106:
Chapter 5 Modeling Grazing Effects
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Chapter 6 Modeling of Coupled Water
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Chapter 7 General discussion and co
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
References Chapter 7 General discus
Page 169 and 170:
Page 171 and 172:
8. ACKNOWLEDGMENTS Firstly I would
Page 173 and 174:
Curriculum Vitae M.Sc. Ying Zhao Of
Page 175:
Schriftenreihe des Instituts Neuere
show all

SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?