The global biogeography and environmental drivers of fairy circles

Guirado, Emilio; Delgado-Baquerizo, Manuel; Benito, Blas M.; Molina-Pardo, José Luis; Berdugo, Miguel; Martínez-Valderrama, Jaime; Maestre, Fernando T.

doi:10.1073/pnas.2304032120

Cited by 11 publications

(6 citation statements)

References 98 publications

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“…The novelty of this study lies in the integration of machine learning-based modelling of the distribution of a biogeomorphological landform and prediction of its future changes. This methodology also holds the potential to be applied in other geomorphological studies, showcasing its versatility beyond the scope of this research (Deblauwe et al, 2008;Guirado et al, 2023). Last but not least, the findings of this study are of significance for biodiversity and geodiversity conservation in arid regions.…”

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confidence: 84%

Biogeomorphological niche of a landform: Machine learning approaches reveal controls on the geographical distribution of Nitraria tangutorum nebkhas

Zhang,

Li,

Mason

et al. 2024

Earth Surf Processes Landf

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Nebkhas are distinctive biogeomorphological landforms prevalent in global drylands and coastal environments. They play a crucial role in supporting local biodiversity and preventing land desertification and often serve as an indicator of local environmental change. Despite their significance, the environmental factors that affect their geographical distribution and how they respond to climate change have not been fully explored. This study represents a novel application of machine learning models to quantifying the biogeomorphological niche of Nitraria nebkhas in northern China and simulating their geographical distribution under future climate change conditions. Findings underscore that climatic variables influence the growth of formative shrub species on nebkhas, whereas climate, soil and geomorphological conditions, along with their spatial configuration, determine the probability of nebkha occurrence. Predictions under medium and high greenhouse gas emission scenarios indicate a northward shift in the potential distribution of nebkhas in northern China by the end of the century, accompanied by a decrease in the south due to rising temperatures. Given the potential impact of nebkha field degradation on biodiversity and soil hydrological conditions, adaptive land use strategies should be designed to protect nebkhas and mitigate the impact of climate change. Our study not only provides valuable insights for informing policy‐making and conservation initiatives but also serves as an example for quantifying the niche of biogeomorphological landforms and simulating their dynamics by integrating machine learning approaches into empirical geomorphological studies.

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confidence: 84%

Biogeomorphological niche of a landform: Machine learning approaches reveal controls on the geographical distribution of Nitraria tangutorum nebkhas

Zhang,

Li,

Mason

et al. 2024

Earth Surf Processes Landf

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“…100 km inland from the southwestern African coast, spanning the Namib Desert [1], and also in the Pilbara region of Western Australia (Figures 1,2) [2][3][4][5]. A recent work, based on remote sensing analysis [6], claimed that FC-like patterns are globally distributed and discovered 263 new sites of vegetation gaps, but more detailed fi eld work is needed to understand the formative mechanisms (physical and ecological) at these new sites and to distinguish between FC-like patterns to true FCs. While there are multiple hypotheses for their origin, two currently prevail [7].…”

Section: Introductionmentioning

confidence: 99%

Microbial Factors May Contribute to the Persistence of Australian Fairy Circles

Klipcan,

Kamennaya,

Than Aye

et al. 2024

J Biomed Res Environ Sci

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Fairy Circles (FCs) are roughly circular, spatially periodic barren patches occurring both along the southwestern African coast, spanning the Namib Desert (NFCs), and in the Pilbara region of Western Australia (AFCs). The origin of both NFC and AFC patterns is still debatable and a subject of ongoing research. Recently, it was argued that pathogenic soil microbes may contribute to ring formation of the Triodia basedowii grass which is the same grass species that forms the AFCs. We have analyzed, under controlled laboratory conditions, soil samples taken from different parts of AFCs (center, periphery and m3atrix) for microbiological activities by Lettuce germination experiments under different manipulations. In seven different circles, out of an average of 13, root lengths of germinated seeds were strongly inhibited in the samples taken from the center, and to a lesser extent, in the samples taken from the periphery and the matrix. Quantitative analyses of the soil microbial community from the FC center found no support to the hypothesis that phytotoxic effect was caused by soil crust cyanobacteria due their low abundance. However, in soil of the FCs it identified both heterotrophic bacteria and fungi that may contribute to the phytotoxic effect. Although our study was not done with seeds of Triodia basedowii it supports the idea that microbial activities in the soil may contribute to AFC persistence by inhibiting plant germination and development in the bare soil gaps in addition to the physical soil crusts resulting from weathering. This suggests that negative plant-soil feedback can act in concert with the main driver mechanism of the AFCs, the scale-dependent plant-water feedback.

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“…These vegetation patterns can survive drier conditions than the uniform vegetation and they are very important for the ecological system in these harsh environments [4]. A recent work, based on remote sensing analysis [7], claimed that FC-like patterns are globally distributed, and discovered 263 new sites of vegetation gaps, but more detailed field work is needed to understand the formative mechanisms (physical Land 2024, 13,197 2 of 14 and ecological) at these new sites and to distinguish between FC-like patterns (vegetation gaps) to proper FCs [8].…”

Section: Introductionmentioning

confidence: 99%

Aeolian Sand Sorting and Soil Moisture in Arid Namibian Fairy Circles

Yizhaq,

Rein,

Saban

et al. 2024

Land

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We studied fairy circles 20 km west of Sesriem at one of the driest locations of fairy circles in Namibia, at the foot of the popular Sossusvlei dunes. These fairy circles lack the typical hexagonal order of the Namibian fairy circles. After years of drought, their pattern is more similar to that of vegetation rings, due to the sparse vegetation in the area between the circles. Cross-section measurements of the soil water content (SWC) show that the upper layer (12 cm) is very dry (~1%) and much below the wilting point of Stipagrostis ciliata grasses, whereas the deeper soil layer is wetter (4%). The grain size distribution of soil samples taken from inside and outside the fairy circles reveals considerable heterogeneity in the size fractions due to aeolian (wind-driven) sand sorting. The bare soil inside the fairy circles contains coarser grains, and the ground surface is covered by sand megaripples. There is a linear trend between the vertical soil moisture gradient and the median grain diameter. Fine particles trapped on the vegetated edges of the fairy circle result in small nebkhas that increase the soil water retention at the surface. The dry and loose coarser topsoil inside the fairy circles may prevent the recolonization of new seedlings with short root lengths inside the fairy circles. Our results highlight the role of aeolian sand transport and deposition in desert vegetation environments and seem to support the notion that fairy circle formation may be affected by the interplay between sand sorting and soil moisture gradients.

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The global biogeography and environmental drivers of fairy circles

Cited by 11 publications

References 98 publications

Biogeomorphological niche of a landform: Machine learning approaches reveal controls on the geographical distribution of Nitraria tangutorum nebkhas

Biogeomorphological niche of a landform: Machine learning approaches reveal controls on the geographical distribution of Nitraria tangutorum nebkhas

Microbial Factors May Contribute to the Persistence of Australian Fairy Circles

Aeolian Sand Sorting and Soil Moisture in Arid Namibian Fairy Circles

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