Spatial organisation of landscapes and its function in semi-arid woodlands, Australia

Abstract

The spatial organisation of three major landscape types within the semi-arid woodlands of eastern Australia was studied by a detailed analysis of gradient-oriented transects (gradsects). The aim was to characterise the spatial organisation of each landscape, and to account for that organisation in functional terms related to the differential concentration of scarce resources by identifiable processes. Terrain, vegetation and soils data were collected along each gradsect. Boundary analysis was used to identify the types of landscape units at a range of scales. Soil analyses were used to determine the degree of differential concentration of nutrients within these units, and to infer the role of fluvial and aeolian processes in maintaining them. All three major landscape systems were found to be highly organised systems with distinctive resource-rich units or patches separated by more open, resource-poor zones. At the largest scale, distinct groves of trees were separated by open intergroves. At smaller-scales, individual trees, large shrubs, clumps of shrubs, fallen logs and clumps of grasses constituted discrete patches dispersed across the landscape. Our soil analyses confirmed that these patches act as sinks by filtering and concentrating nutrients lost from source areas (e.g., intergroves). We suggest that fluvial runoff-runon and aeolian saltation-deposition are the physical processes involved in these concentration effects, and in building and maintaining patches; biological activities also maintain patches. This organisation of patches as dispersed resource filters (at different scales) has the overall function of conserving limited resources within semi-arid landscape systems. Understanding the role of landscape patchiness in conserving scarce resources has important implications for managing these landscapes for sustainable land use, and for the rehabilitation of landscapes already degraded.

Scale‐Dependent Feedback and Regular Spatial Patterns in Young Mussel Beds

“…A similar effect of spatial patterning was found in arid ecosystems, in that resilience, growth, and persistence of vegetation at low rainfall levels were strongly improved (Ludwig et al 1999;von Hardenberg et al 2001;Rietkerk et al 2002;van de Koppel and Rietkerk 2004). Spatial redistribution of surface water between patches because of lateral flow improved the efficiency of water harvesting by the vegetation, increasing production and lowering water losses from the system (Ludwig and Tongway 1995;Ludwig et al 1999;. Hence, our study highlights that self-organization may influence the flow of resources through the ecosystem and thereby affects the functioning of ecosystems at larger spatial scales.…”

The fate of seeds in the soil: a review of the influence of overland flow on seed removal and its consequences for the vegetation of arid and semiarid patchy ecosystems

“…These water-limited landscapes frequently show a clear spatial pattern of vegetated patches interspersed within a bare soil matrix (Aguiar and Sala, 1999) which gives rise to a mosaic-like structure of sources and sinks of resources, the bare and vegetated patches, respectively, with very different soil properties and variable interconnection (e.g. Schlesinger et al, 1990;Ludwig and Tongway, 1995;Bochet et al, 1999Bochet et al, , 2000Puigdefábregas, 2005). Vegetated patches have often been com- Temporal evolution of the total number of papers on seed fate and dispersal in drylands published between 1974 and 2013, along with the evolution of the relative number of papers focusing on secondary seed dispersal.…”

Changes in seed dispersal processes and the potential for between‐patch connectivity for an arid land daisy

“…Vegetation traps seeds and litter and reduces the intensity of wind near the ground, and thus potentially has a large influence on seed dispersal. Reduced vegetation cover, along with soil surface compaction, also results in higher water run-off, which impacts resource accumulation and redistribution Tongway 1995) and can affect seed redistribution by water flow. Although introduced herbivores clearly modify ecological processes, their potential impacts on seed transport and deposition have not been adequately assessed (Tremont 1994).…”