Assessing and monitoring desertification with soil indicators

Do variations on a model of landscape function assist in interpreting the growth response of vegetation to rainfall in arid environments?

“…It has been suggested that landscapes may respond differently to rainfall (Holm, 2000) depending on their resilience to disturbance (Walker et al, 1981;Holling, 1986;Tongway & Hindley, 2000). There is some evidence that fragile or non-resilient landscapes shed more rainfall and have lower rainfall-use efficiency when degraded (Snyman, 1999).…”

“…Similar classifications have been proposed previously, for example, division into 'resilient' and 'non-resilient' types (Holling, 1973;Walker et al, 1981;Holling, 1986;Whitford, 1995), which we treat synonymously with the terms robust and fragile. In non-resilient or fragile landscapes, it is argued that loss of vegetated patches results in increased soil erosion and loss of soil and nutrients from landscapes through increased run-off (Snyman & Fouche, 1993;Tongway & Hindley, 2000). In robust or resilient landscapes, rainfall and mobilized soil and nutrients are retained (Williams et al, 1993;Whisenant & Tongway, 1995) and degradation processes are ameliorated because of factors such as terrain-shape and soils with greater infiltration rates Illius & O'Connor, 1999;Tongway & Hindley, 2000).…”

“…Recently, Tongway & Hindley (2000) proposed variations to this general model of landscape function by further subdivision of landscapes into 'fragile' and 'robust' types. Similar classifications have been proposed previously, for example, division into 'resilient' and 'non-resilient' types (Holling, 1973;Walker et al, 1981;Holling, 1986;Whitford, 1995), which we treat synonymously with the terms robust and fragile.…”

“…In non-resilient or fragile landscapes, it is argued that loss of vegetated patches results in increased soil erosion and loss of soil and nutrients from landscapes through increased run-off (Snyman & Fouche, 1993;Tongway & Hindley, 2000). In robust or resilient landscapes, rainfall and mobilized soil and nutrients are retained (Williams et al, 1993;Whisenant & Tongway, 1995) and degradation processes are ameliorated because of factors such as terrain-shape and soils with greater infiltration rates Illius & O'Connor, 1999;Tongway & Hindley, 2000). Landscapes such as these may be re-colonized by alternative species and even accompanied by a change in patch-scale (for example, grassland to shrubland or woodland; Schlesinger et al, 1990;Archer, 1995) and with no apparent loss in primary productivity (Friedel & Shaw, 1987;Reynolds et al, 1997).…”

Relationships between empirical and nominal indices of landscape function in the arid shrubland of Western Australia

“…It is less successful when vegetated patches occur as linear groves (which was generally not the case in the low-woodland of this study) where the estimated patch area is likely to be influenced by transect orientation. Tongway & Hindley (2000) recommended longer transects orientated along potential flow gradients (i.e. landscape slope or prevailing wind direction).…”