Simulating plant water availability in dry lands under climate change: A generic model of two soil layers

Abstract

[1] Dry lands are exposed to a highly variable environment and face a high risk of degradation. The effects of climate change are likely to increase this risk; thus a profound knowledge of the system dynamics is crucial for evaluating management options. This applies particularly for the interactions between water and vegetation, which exhibit strong feedbacks. To evaluate these feedbacks and the effects of climate change on soil moisture dynamics, we developed a generic, process-based, spatially explicit soil moisture model of two soil layers, which can be coupled with vegetation models. A time scale relevant for ecological processes can be simulated without difficulty, and the model avoids complex parameterization with data that are unavailable for most regions of the world. We applied the model to four sites in Israel along a precipitation and soil type gradient and assessed the effects of climate change by comparing possible climatic changes with present climate conditions. The results show that in addition to temperature, the total amount of precipitation and its intra-annual variability are an important driver of soil moisture patterns. This indicates that particularly with regard to climate change, the approach of many ecological models that simulate water dynamics on an annual base is far too simple to make reliable predictions. Thus, the introduced model can serve as a valuable tool to improve present ecological models of dry lands because of its focus on the applicability and transferability.

Threshold behaviour in hydrological systems as (human) geo-ecosystems: manifestations, controls, implications

“…Semi-arid savannah ecosystems contain over 50% of the global livestock (Tietjen et al, 2009b). These ecosystems thus provide a service that is most crucial for global food production, especially in developing countries; the provision of ecosystem service depends crucially on the fragile equilibrium between woody and herbaceous vegetation.…”

“…Vegetation, when abundant, is often arranged into patterns that consist of patches with strong plant cover that alternate with low-cover or bare soil patches (Tietjen and Jeltsch, 2007;Tietjen et al, 2009b). Typical patterns are either characterised as spotted or stippled, consisting of dense irregularly shaped vegetation clusters that are surrounded by bare soil .…”

An experiment to gauge an ungauged catchment: rapid data assessment and eco-hydrological modelling in a data-scarce rural catchment

“…Jackson et al (2009) underpin the strong link between hydrology and ecology and point out that in agricultural systems this link is very simplified and degrees of freedom are reduced. In a semi-arid setting, complexity can be even further reduced, as plant growth is mainly driven by water availability (Rodriguez-Iturbe et al 1999, Tietjen et al 2009). …”

“…The functional soil map is the result of a RS classification of the same Landsat 7 data; the five functional soil classes and three sub-classes as in Table 1. (Hundecha and Bárdossy 2004), (b) mechanistic representation of the major functionality in the water cycle (Tietjen et al 2009), (c) data-driven look-up table referencing (Güntner and Bronstert 2004), and (d) optimality-based approaches (Lei et al 2008, Schymanski 2008. Jackson et al (2009) underpin the strong link between hydrology and ecology and point out that in agricultural systems this link is very simplified and degrees of freedom are reduced.…”

Linking Climate Change and Groundwater

“…Tietjen et al (2009) made a case for at least two soil layers in a soil-vegetation model that simulated soil-water dynamics under different climatic conditions. Others have applied relatively complex, spatially distributed subsurface models and coupled surface-groundwater models (Goderniaux et al 2009;Hunt et al 2013;van Roosmalen et al 2007van Roosmalen et al , 2009).…”