Wiegand, Kerstin

[["dc.bibliographiccitation.firstpage","E5368"],["dc.bibliographiccitation.issue","37"],["dc.bibliographiccitation.journal","Proceedings of the National Academy of Sciences"],["dc.bibliographiccitation.lastpage","E5369"],["dc.bibliographiccitation.volume","113"],["dc.contributor.author","Getzin, Stephan"],["dc.contributor.author","Yizhaq, Hezi"],["dc.contributor.author","Bell, Bronwyn"],["dc.contributor.author","Erickson, Todd E."],["dc.contributor.author","Postle, Anthony C."],["dc.contributor.author","Katra, Itzhak"],["dc.contributor.author","Tzuk, Omer"],["dc.contributor.author","Zelnik, Yuval R."],["dc.contributor.author","Wiegand, Kerstin"],["dc.contributor.author","Wiegand, Thorsten"],["dc.contributor.author","Meron, Ehud"],["dc.date.accessioned","2017-09-07T11:52:22Z"],["dc.date.available","2017-09-07T11:52:22Z"],["dc.date.issued","2016"],["dc.identifier.doi","10.1073/pnas.1611877113"],["dc.identifier.gro","3148899"],["dc.identifier.pmid","27588904"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/5536"],["dc.language.iso","en"],["dc.notes.intern","Wiegand Crossref Import"],["dc.notes.status","public"],["dc.notes.submitter","chake"],["dc.relation.issn","0027-8424"],["dc.relation.orgunit","Abteilung Ökosystemmodellierung"],["dc.title","Reply to Walsh et al.: Hexagonal patterns of Australian fairy circles develop without correlation to termitaria"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","no"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Ecography"],["dc.bibliographiccitation.lastpage","11"],["dc.bibliographiccitation.volume","38"],["dc.contributor.author","Getzin, Stephan"],["dc.contributor.author","Wiegand, Kerstin"],["dc.contributor.author","Wiegand, Thorsten"],["dc.contributor.author","Yizhaq, Hezi"],["dc.contributor.author","von Hardenberg, Jost"],["dc.contributor.author","Meron, Ehud"],["dc.date.accessioned","2017-09-07T11:52:23Z"],["dc.date.available","2017-09-07T11:52:23Z"],["dc.date.issued","2014"],["dc.description.abstract","The mysterious ‘fairy circles' are vegetation-free discs that cover vast areas along the pro-Namib Desert. Despite 30 yr of research their origin remains unknown. Here we adopt a novel approach that focuses on analysis of the spatial patterns of fairy circles obtained from representative 25-ha aerial images of north-west Namibia. We use spatial point pattern analysis to quantify different features of their spatial structures and then critically inspect existing hypotheses with respect to their ability to generate the observed circle patterns. Our working hypothesis is that fairy circles are a self-organized vegetation pattern. Finally, we test if an existing partial-differential-equation model, that was designed to describe vegetation pattern formation, is able to reproduce the characteristic features of the observed fairy circle patterns. The model is based on key-processes in arid areas such as plant competition for water and local resource-biomass feedbacks. The fairy circles showed at all three study areas the same regular spatial distribution patterns, characterized by Voronoi cells with mostly six corners, negative correlations in their size up to a distance of 13 m, and remarkable homogeneity over large spatial scales. These results cast doubts on abiotic gas-leakage along geological lines or social insects as causal agents of their origin. However, our mathematical model was able to generate spatial patterns that agreed quantitatively in all of these features with the observed patterns. This supports the hypothesis that fairy circles are self-organized vegetation patterns that emerge from positive biomass-water feedbacks involving water transport by extended root systems and soil-water diffusion. Future research should search for mechanisms that explain how the different hypotheses can generate the patterns observed here and test the ability of self-organization to match the birth- and death dynamics of fairy circles and their regional patterns in the density and size with respect to environmental gradients."],["dc.identifier.doi","10.1111/ecog.00911"],["dc.identifier.gro","3148905"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/5542"],["dc.language.iso","en"],["dc.notes.intern","Wiegand Crossref Import"],["dc.notes.status","public"],["dc.notes.submitter","chake"],["dc.relation.issn","0906-7590"],["dc.relation.orgunit","Abteilung Ökosystemmodellierung"],["dc.title","Adopting a spatially explicit perspective to study the mysterious fairy circles of Namibia"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","no"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","399"],["dc.bibliographiccitation.journal","Journal of Ecology"],["dc.bibliographiccitation.lastpage","416"],["dc.bibliographiccitation.volume","109"],["dc.contributor.author","Getzin, Stephan"],["dc.contributor.author","Erickson, Todd E."],["dc.contributor.author","Yizhaq, Hezi"],["dc.contributor.author","Muñoz‐Rojas, Miriam"],["dc.contributor.author","Huth, Andreas"],["dc.contributor.author","Wiegand, Kerstin"],["dc.date.accessioned","2020-12-08T08:09:43Z"],["dc.date.available","2020-12-08T08:09:43Z"],["dc.date.issued","2021"],["dc.description.abstract","1. So‐called fairy circles (FCs) comprise a spatially periodic gap pattern in arid grasslands of Namibia and north‐west Western Australia. This pattern has been explained with scale‐dependent ecohydrological feedbacks and the reaction‐diffusion, or Turing mechanism, used in process‐based models that are rooted in physics and pattern‐formation theory. However, a detailed ecological test of the validity of the modelled processes is still lacking. 2. Here, we test in a spinifex‐grassland ecosystem of Western Australia the presence of spatial feedbacks at multiple scales. Drone‐based multispectral analysis and spatially explicit statistics were used to test if grass vitality within five 1‐ha plots depends on the pattern of FCs that are thought to be a critical extra source of water for the surrounding matrix vegetation. We then examined if high‐ and low‐vitality grasses show scale‐dependent feedbacks being indicative of facilitation or competition. Additionally, we assessed facilitation of grass plants for different successional stages after fire at fine scales in 1‐m2 quadrats. Finally, we placed soil moisture sensors under bare soil inside the FC gap and under plants at increasing distances from the FC to test if there is evidence for the ‘infiltration feedback’ as used in theoretical modelling. 3. We found that high‐vitality grasses were systematically more strongly associated with FCs than low‐vitality grasses. High‐vitality grasses also had highly aggregated patterns at short scales being evidence of positive feedbacks while negative feedbacks occurred at larger scales. Within 1‐m2 quadrats, grass cover and mutual facilitation of plants was greater near the FC edge than further away in the matrix. Soil moisture after rainfall was lowest inside the FC with its weathered surface crust but highest under grass at the gap edge, and then declined towards the matrix, which confirms the infiltration feedback. 4. Synthesis. The study shows that FCs are a critical extra source of water for the dryland vegetation, as predicted by theoretical modelling. The grasses act as ‘ecosystem engineers’ that modify their hostile, abiotic environment, leading to vegetation self‐organization. Overall, our ecological findings highlight the validity of the scale‐dependent feedbacks that are central to explain this emergent grassland pattern via the reaction‐diffusion or Turing‐instability mechanism."],["dc.description.sponsorship","German Research Foundation ‐ DFG"],["dc.identifier.doi","10.1111/1365-2745.13493"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/69461"],["dc.language.iso","en"],["dc.notes.intern","DeepGreen Import"],["dc.relation.issn","0022-0477"],["dc.relation.issn","1365-2745"],["dc.relation.orgunit","Abteilung Ökosystemmodellierung"],["dc.rights","CC BY 4.0"],["dc.subject.gro","ecosystem engineer"],["dc.subject.gro","Normalized Difference Vegetation Index"],["dc.subject.gro","reaction-diffusion mechanism"],["dc.subject.gro","scale-dependent feedback"],["dc.subject.gro","spatial periodicity"],["dc.subject.gro","Turing dynamics"],["dc.subject.gro","unmanned aerial vehicle"],["dc.subject.gro","vegetation self-organization"],["dc.title","Bridging ecology and physics: Australian fairy circles regenerate following model assumptions on ecohydrological feedbacks"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","669"],["dc.bibliographiccitation.issue","6"],["dc.bibliographiccitation.journal","Ecological Entomology"],["dc.bibliographiccitation.lastpage","675"],["dc.bibliographiccitation.volume","40"],["dc.contributor.author","Getzin, Stephan"],["dc.contributor.author","Wiegand, Kerstin"],["dc.contributor.author","Wiegand, Thorsten"],["dc.contributor.author","Yizhaq, Hezi"],["dc.contributor.author","von Hardenberg, Jost"],["dc.contributor.author","Meron, Ehud"],["dc.date.accessioned","2017-09-07T11:52:19Z"],["dc.date.available","2017-09-07T11:52:19Z"],["dc.date.issued","2015"],["dc.identifier.doi","10.1111/een.12267"],["dc.identifier.gro","3148898"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/12542"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/5535"],["dc.language.iso","en"],["dc.notes.intern","Wiegand Crossref Import"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","final"],["dc.notes.submitter","chake"],["dc.relation.issn","0307-6946"],["dc.relation.orgunit","Abteilung Ökosystemmodellierung"],["dc.rights","CC BY-NC-ND 4.0"],["dc.rights.uri","https://creativecommons.org/licenses/by-nc-nd/4.0"],["dc.title","Clarifying misunderstandings regarding vegetation self-organisation and spatial patterns of fairy circles in Namibia: a response to recent termite hypotheses"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","no"],["dc.type.subtype","original_ja"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.journal","Landscape Ecology"],["dc.contributor.author","Getzin, Stephan"],["dc.contributor.author","Löns, Christian"],["dc.contributor.author","Yizhaq, Hezi"],["dc.contributor.author","Erickson, Todd E."],["dc.contributor.author","Muñoz-Rojas, Miriam"],["dc.contributor.author","Huth, Andreas"],["dc.contributor.author","Wiegand, Kerstin"],["dc.date.accessioned","2021-12-01T09:22:59Z"],["dc.date.available","2021-12-01T09:22:59Z"],["dc.date.issued","2021"],["dc.description.abstract","Abstract Context 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. Objectives 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. Methods 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. Results 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. Conclusions 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."],["dc.identifier.doi","10.1007/s10980-021-01358-9"],["dc.identifier.pii","1358"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/94533"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-478"],["dc.relation.eissn","1572-9761"],["dc.relation.issn","0921-2973"],["dc.relation.orgunit","Abteilung Ökosystemmodellierung"],["dc.rights","CC BY 4.0"],["dc.title","High-resolution images and drone-based LiDAR reveal striking patterns of vegetation gaps in a wooded spinifex grassland of Western Australia"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.subtype","original_ja"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","125698"],["dc.bibliographiccitation.journal","Perspectives in Plant Ecology, Evolution and Systematics"],["dc.contributor.author","Getzin, Stephan"],["dc.contributor.author","Holch, Sönke"],["dc.contributor.author","Yizhaq, Hezi"],["dc.contributor.author","Wiegand, Kerstin"],["dc.date.accessioned","2022-11-16T12:29:17Z"],["dc.date.available","2022-11-16T12:29:17Z"],["dc.date.issued","2022"],["dc.identifier.doi","10.1016/j.ppees.2022.125698"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/117081"],["dc.relation.issn","1433-8319"],["dc.relation.orgunit","Abteilung Ökosystemmodellierung"],["dc.title","Plant water stress, not termite herbivory, causes Namibia’s fairy circles"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","e02620"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Ecosphere"],["dc.bibliographiccitation.volume","10"],["dc.contributor.author","Getzin, Stephan"],["dc.contributor.author","Yizhaq, Hezi"],["dc.contributor.author","Muñoz-Rojas, Miriam"],["dc.contributor.author","Wiegand, Kerstin"],["dc.contributor.author","Erickson, Todd E."],["dc.date.accessioned","2019-07-09T11:50:12Z"],["dc.date.available","2019-07-09T11:50:12Z"],["dc.date.issued","2019"],["dc.description.abstract","Fairy circles (FCs) are extremely ordered round patches of bare soil within arid grasslands of southwestern Africa and northwestern Australia. Their origin is disputed because biotic factors such as insects or abiotic factors such as edaphic and eco-hydrological feedback mechanisms have been suggested to be causal. In this research, we used a multi-scale approach to shed light on the origin of Australian FCs. At a local scale, we investigated the potential cause of FCs using analyses of soil compaction and texture within FCs, the surrounding matrix vegetation, and in nearby large bare-soil areas. We found that soil hardness and clay content were similarly higher inside the FCs and in the large bare-soil areas. When compared to the matrix soils with protective grass cover, the 2.6–2.8 times higher clay content in FCs and large bare-soil areas is likely sourced via multiple abiotic weathering processes. Intense rainfall events, particle dispersion, surface heat, evaporation, and mechanical crust building inhibit plant growth in both areas. At the landscape scale, a systematic survey of 154 soil excavations within FCs was undertaken to evaluate the presence of pavement termitaria that could inhibit plant growth. We show that in up to 100% and most of the excavations per plot, no hard pavement termitaria were present in the FCs. This fact is substantiated by the observation that small, newly forming FCs are initiated on soft sand without evidence of termite activity. At the regional scale, we investigated the spatial properties of FCs and common termite-created gaps in Western Australia, using spatially explicit statistics. We mapped three 25-ha FC plots with a drone and compared them with three aerial images of typical vegetation gaps created by harvester and spinifex termites. We demonstrate that the small diameters, the lower ordering, and the heterogeneous patterns of these common termite gaps strongly differ from the unique spatial signature of FCs. Our multi-scale approach emphasizes that FCs are not trivial termite gaps and that partial correlation with termites at some sites does not imply causation. Instead, we highlight the need to study the edaphic and ecohydrological drivers of vegetation-pattern formation in water-limited environments."],["dc.identifier.doi","10.1002/ecs2.2620"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/15879"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/59720"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.relation.issn","2150-8925"],["dc.relation.orgunit","Abteilung Ökosystemmodellierung"],["dc.rights","CC BY 3.0"],["dc.rights.uri","https://creativecommons.org/licenses/by/3.0"],["dc.subject.ddc","570"],["dc.subject.gro","clay crust"],["dc.subject.gro","cyclone"],["dc.subject.gro","emergent vegetation patterns"],["dc.subject.gro","heterogeneity"],["dc.subject.gro","hydrology"],["dc.subject.gro","nearest-neighbor distance"],["dc.subject.gro","pair-correlation function"],["dc.subject.gro","spatial periodicity"],["dc.subject.gro","Triodia basedowii"],["dc.subject.gro","vegetation self-organization"],["dc.subject.gro","wavelength"],["dc.subject.gro","weathering"],["dc.title","A multi-scale study of Australian fairy circles using soil excavations and drone-based image analysis"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.subtype","original_ja"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","3551"],["dc.bibliographiccitation.issue","13"],["dc.bibliographiccitation.journal","Proceedings of the National Academy of Sciences"],["dc.bibliographiccitation.lastpage","3556"],["dc.bibliographiccitation.volume","113"],["dc.contributor.author","Getzin, Stephan"],["dc.contributor.author","Yizhaq, Hezi"],["dc.contributor.author","Bell, Bronwyn"],["dc.contributor.author","Erickson, Todd E."],["dc.contributor.author","Postle, Anthony C."],["dc.contributor.author","Katra, Itzhak"],["dc.contributor.author","Tzuk, Omer"],["dc.contributor.author","Zelnik, Yuval R."],["dc.contributor.author","Wiegand, Kerstin"],["dc.contributor.author","Wiegand, Thorsten"],["dc.contributor.author","Meron, Ehud"],["dc.date.accessioned","2017-09-07T11:52:25Z"],["dc.date.available","2017-09-07T11:52:25Z"],["dc.date.issued","2016"],["dc.description.abstract","Vegetation gap patterns in arid grasslands, such as the “fairy circles” of Namibia, are one of nature’s greatest mysteries and subject to a lively debate on their origin. They are characterized by small-scale hexagonal ordering of circular bare-soil gaps that persists uniformly in the landscape scale to form a homogeneous distribution. Pattern-formation theory predicts that such highly ordered gap patterns should be found also in other water-limited systems across the globe, even if the mechanisms of their formation are different. Here we report that so far unknown fairy circles with the same spatial structure exist 10,000 km away from Namibia in the remote outback of Australia. Combining fieldwork, remote sensing, spatial pattern analysis, and process-based mathematical modeling, we demonstrate that these patterns emerge by self-organization, with no correlation with termite activity; the driving mechanism is a positive biomass–water feedback associated with water runoff and biomass-dependent infiltration rates. The remarkable match between the patterns of Australian and Namibian fairy circles and model results indicate that both patterns emerge from a nonuniform stationary instability, supporting a central universality principle of pattern-formation theory. Applied to the context of dryland vegetation, this principle predicts that different systems that go through the same instability type will show similar vegetation patterns even if the feedback mechanisms and resulting soil–water distributions are different, as we indeed found by comparing the Australian and the Namibian fairy-circle ecosystems. These results suggest that biomass–water feedbacks and resultant vegetation gap patterns are likely more common in remote drylands than is currently known."],["dc.identifier.doi","10.1073/pnas.1522130113"],["dc.identifier.gro","3148914"],["dc.identifier.pmid","26976567"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/5552"],["dc.language.iso","en"],["dc.notes.intern","Wiegand Crossref Import"],["dc.notes.status","final"],["dc.notes.submitter","chake"],["dc.relation.issn","0027-8424"],["dc.relation.orgunit","Abteilung Ökosystemmodellierung"],["dc.title","Discovery of fairy circles in Australia supports self-organization theory"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","no"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]