The impact of climate change on geomorphology and desertification along a mediterranean-arid transect

7.33 Semiarid Hillslope Processes

“…The high sediment yields observed in the semiarid domain are generally attributed to the presence of bare areas between vegetated areas. Lavee et al (1998) presented a model showing changes in overland-flow processes in relation to climate and vegetation cover based on a transect study in Israel ( Figure 3). The importance of vegetation and how it dynamically interacts with geomorphological and hydrological processes are discussed in more detail below after having discussed the role of soil-surface properties and slope properties.…”

“…Not only the amount of organic matter is important but also its disposition (Tisdall and Oades, 1982;Graham et al, 1995;Six et al, 2004). Soil organic matter levels in the soil are also dependent on annual rainfall, and directly affect soil aggregate stability and, therefore, erodibility of the soil (Lavee et al, 1998;Sarah, 2006). Soils in semiarid environments generally have low organic matter contents (Singer and Le Bissonnais, 1998), which is related to the low biomass production in such ecosystems.…”

“…However, other soil constituents also are important such as clay content, carbonates and other salts, iron and aluminum oxides, as well as soil roots and other biota (Emerson, 1983;Bronick and Lal, 2005). Lavee et al (1998) showed that a clear threshold-like drop exists in organic matter and soil structural stability under semiarid conditions with respect to subhumid Mediterranean and arid desert environments. Soil organic matter levels in the soil are also dependent on annual rainfall, and directly affect soil aggregate stability and, therefore, erodibility of the soil (Lavee et al, 1998;Sarah, 2006).…”

“…Reproduced from Lavee, H.,Imeson, A.C., Sarah, P., 1998. Reproduced from Lavee, H.,Imeson, A.C., Sarah, P., 1998.…”

Water Scarcity, Land Degradation and Desertification in the Mediterranean Region

“…This suggests that a relatively small climatic change would suffice to initiate a spatio-temporal transformation of the Mediterranean semiarid to arid drylands (Lavee et al, 1988). For example, the results of a fieldexperimental study along the aridity gradient within Israel demonstrated that the rate of change along the aridity gradient, from semiarid to arid drylands, of organic matter contents, soil aggregate size and stability, the sodium adsorption ratio and the runoff coefficient change is non-linear.…”