Field determination of unsaturated hydraulic conductivity of forest soils
This study introduces a field method to determine unsaturated hydraulic conductivity which is applicable to sloping terrain with a limited water supply. A single steel ring infiltrometer and an artificial rainfall simulator are used in this method to reduce the amount of water required to attain a steady-state flux condition. Six tensiometers and a time domain reflectometry (TDR) are employed as the soil capillary pressure head and the volumetric soil water content measurement devices, respectively. Water contents measured by the TDR are corrected using a simple calibration method suggested by Hook and Livingston (1996). Unsaturated hydraulic conductivities are computed based on the instantaneous profile method using capillary pressure head and water content changes measured during a drainage process. The proposed method was applied to a forest soil profile in Rokko Mountain range. Results showed that the relationships between the unsaturated hydraulic conductivity and capillary pressure head developed by the proposed method coincide well with those measured by the conventional steady-state laboratory experiment. The proposedin-situ method is the effective simple means to determine unsaturated hydraulic conductivities of forest soils, since this method is enough accurate and consuming less amount of water and time.
Errors in Converting Time Domain Reflectometry Measurements of Propagation Velocity to Estimates of Soil Water Content
The determination of soil water content by time domain reflectometry (TDR) involves the measurement of the propagation velocity of a radio frequency (RF) pulse in soil and the conversion of this measurement to an estimate of soil water content. The objective of this study was to quantify errors in this conversion. A comprehensive error analysis can only be carried out if a well-defined measurement procedure is followed. We define and recommend such a procedure and identify the physical origin and the magnitude of each of the error sources in the procedure. Total measurement errors are calculated as the root mean square sum of each of the individual errors. We express propagation velocity measurements in terms of time intervals, that is, the travel time of an RF pulse in soil (T) relative to that in air (T air ). Our measurement and error calculation procedure is based on an analysis of our own and published data for nonclay soils, which reveals that in all cases, there is a linear relation between T/T air and volumetric water content (θ v ) with a mutually independent slope and intercept. A theoretical explanation for this observation is presented. We show that the dominant measurement error source is the transition time of the TDR reflection, which in turn is a function of θ v . Absolute measurement errors range from 0.015 to 0.028 m 3 m -3 if the T/T air vs. θ v intercept is known and increase to 0.023 to 0.034 m 3 m -3 if a nominal value (1.55) is used. We recommend that a T/T air vs. θ v slope value of 0.1193 (5% less than theory) be used for measurements in nonclay agricultural soils. This leads to little loss in accuracy. Measurement resolution is primarily a function of the time base error of the TDR instrument and can be as good as 0.0018 m 3 m -3 .
The Invention of the Jewish People
'All modern nation states have a story of their origins, passed down through both official and popular culture, and yet few of these accounts have proved as divisive and influential as the Israeli national myth. The well-known tale of Jewish exile at the hands of the Romans during the first century AD, and the assertion of both cultural and racial continuity through to the Jewish people of the present day, resonates far beyond Israel's borders. Despite its use as a justification for Jewish settlement in Palestine and the project of a Greater Israel, there have been few scholarly investigations into the historical accuracy of the story as a whole. In this bold and ambitious new book, Shlomo Sand shows that the Israeli national myth has its origins in the nineteenth century, rather than in biblical times - when Jewish historians, like scholars in many other cultures, reconstituted an imagined people in order to model a future nation. Sand forensically dissects the official story - and demonstrates the construction of a nationalist myth and the collective mystification that this requires. A bestseller in Israel and France, Shlomo Sand's book has sparked a widespread and lively debate. Should the Jewish people regard themselves as genetically distinct and identifiable across the millennia - or should that doctrine now be left behind and if the myth of the Jewish state is dismantled, could this open a path toward a more inclusive Israeli state, content within its borders?'