We discuss a simplifed, conceptual model for the dynamics of the soil-vegetation system in drylands. The model considers the different dynamical processes taking place in vegetated and non-vegetated soil and it distinguishes between the upper soil layer, where rapid evaporation dominates, and the deeper root layer where only plant transpiration takes place. We explore the role of rainfall inter...

A novel experimental approach to determine soil hydraulic material properties for the dry and very dry range is presented. Evaporation from the surface of a soil column is controlled by a constant flux of preconditioned air and the resulting vapour flux is measured by infrared absorption spectroscopy. The data are inverted under the assumptions that (i) the simultaneous movement of water in the...

[ 1 ] We examine the effects of two different parameterizations of potential evaporation on long-term trends in soil moisture, evaporative flux and runoff simulated by the water balance model underlying the Palmer Drought Severity Index. The first, traditional parameterization is based on air temperature alone. The second parameterization is derived from observations of evaporation from class-A...

Remote sensing data in the thermal infra red (TIR) part of the spectrum provides indirect estimates of water stress – defined as a function of the ratio between actual and potential evaporation rates – at the earth surface. During the first stage of evaporation (‘‘energy limited’’ evaporation), this ratio is close to one. During the second stage of evaporation (‘‘soil controlled’’ evaporation) ...

Each fortified and control sample, moistened to 40~ saturation, was inoculated and kept in an enameled tray loosely covered with a glass plate to retard water evaporation, substrate volatilization, and photodecomposition. Thus, the substrates would be subject to possible microbial degradation, chemical degradation, and adsorption to soil colloids, but not losses due to leaching or soil transpor...

A recursive claim that there is a ’scarcity of global data on evaporative partitioning’ is used to justify the development of the STEAM model (see e.g. pg. 206, L23). However, over the last decade, there have been numerous efforts to derive the separate components of the terrestrial evaporative flux at the global scale, not just from land surface models and climate reanalyses, but also by combi...

In the Soil Moisture Simulation Workshop, a number of numerical experiments was conducted with fourteen representative schemes and the results compared with HAPEX-MOBILHY data. This paper documents the general outcomes of the workshop, and provides the background information for the other papers presented in this special issue, which deal with more specific aspects of soil moisture simulation a...

[1] The goal of this study is to understand the interaction between belowground and aboveground ecohydrologic dynamics as facilitated by hydraulic redistribution. We analyze the partitioning of moisture and energy between tall and understory vegetation, and soil evaporation. Both the competitive and facilitative dependencies are examined using a shared resource model where the soil serves as a ...

Delineating protected areas for sensitive species is a growing challenge as changing climate alters the geographic pattern of habitats as well as human responses to those shifts. When human impacts are expected within projected ranges of threatened species, there is often demand to demarcate the minimum habitat required to ensure the species' persistence. Because diminished or wide-ranging popu...