ORCID Profile
0000-0003-4854-0607
Current Organisation
University of Goettingen
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Publisher: Wiley
Date: 18-01-2002
DOI: 10.1046/J.1523-1739.2002.99552.X
Abstract: Abstract: Aspects of within‐population spatial structure are often neglected in the modeling of population viability. To analyze the relevance of the spatial structure of single populations to population persistence, we compared the results of three models developed for the territorial, arboreal gecko Oedura reticulata : (1) a spatially structured model in which both low and high densities incur mortality costs due to increased movement, (2) a spatially structured model in which the Allee effect is removed, and (3) a spatially unstructured model in which there are no effects of density on mortality. Compared with nonspatial model populations, spatially structured populations exhibited reduced persistence. The Allee effect contributed only a small amount to the reduction in persistence. Increased mortality at high densities caused by difficulties in finding territories markedly reduced persistence in the spatially structured models compared with the density‐independent nonspatial model. We argue that the inclusion of elements of spatial structure may considerably influence the estimation of extinction risk in population viability analyses.
Publisher: Wiley
Date: 21-09-2021
Publisher: Wiley
Date: 20-04-2012
Publisher: Wiley
Date: 02-2019
DOI: 10.1002/ECS2.2620
Publisher: Springer Science and Business Media LLC
Date: 03-11-2021
DOI: 10.1007/S10980-021-01358-9
Abstract: Vegetation patterns in hummock grasslands of Australia’s arid interior can be very complex. Additionally, the grasslands are interspersed with variable amounts of trees and shrubs. To better understand the spatial arrangement of this vegetation structure, and in particular the unvegetated bare-soil gaps, we analyzed the scale-dependent patterns of gaps, trees, and shrubs. We focused on two size categories of grassland gaps, large gaps ≥ 4 m 2 known as fairy circles (FCs) and small gaps 1 to 4 m 2 , and on trees and shrubs. We mapped four 200 m × 200 m study plots located east of the town of Newman in Western Australia, using drone-based aerial images and LiDAR. The RGB images were converted into binary images and the gaps and woody plants were automatically segmented. The spatial patterns of the four vegetation components were analyzed, as well as the shape properties of the vegetation gaps. The most striking result was that small gaps appeared consistently at about 5 m distance away from the FCs, which are known as the most water-depleted locations in the grassland. The FCs were also rounder than the small gaps and this symmetry underlines their function as an extra source of water for the surrounding matrix vegetation. Trees and shrubs had spatial patterns that were unrelated to FCs, which likely results from their water uptake in deeper sub-soil layers. The consistent distance of small gaps to FCs is further support that the Australian fairy circles are a self-organized vegetation pattern that results from ecohydrological feedbacks.
Publisher: Proceedings of the National Academy of Sciences
Date: 09-2016
Publisher: Springer Science and Business Media LLC
Date: 2004
Publisher: Proceedings of the National Academy of Sciences
Date: 14-03-2016
Abstract: Pattern-formation theory predicts that vegetation gap patterns, such as the fairy circles of Namibia, emerge through the action of pattern-forming biomass–water feedbacks and that such patterns should be found elsewhere in water-limited systems around the world. We report here the exciting discovery of fairy-circle patterns in the remote outback of Australia. Using fieldwork, remote sensing, spatial pattern analysis, mathematical modeling, and pattern-formation theory we show that the Australian gap patterns share with their Namibian counterparts the same characteristics but are driven by a different biomass–water feedback. These observations are in line with a central universality principle of pattern-formation theory and support the applicability of this theory to wider contexts of spatial self-organization in ecology.
No related grants have been discovered for Kerstin Wiegand.