Geodiversity, self-organization, and health of three-phase semi-arid rangeland ecosystems, in the Israeli Negev

Stavi, Ilan; Shem-Tov, Rahamim; Chocron, M.; Yizhaq, Hezi

doi:10.1016/j.geomorph.2015.01.004

Cited by 13 publications

(19 citation statements)

References 27 publications

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“…Also, despite not being available for vegetation uptake, since hygroscopic moisture content is positively affected by the physical quality of soil (Stavi et al ., ), its greater mean value in the heterogeneous hillslopes at the end of the growing season (May) of this two‐year study, suggest better soil conditions than those in the homogeneous hillslopes.…”

Section: Discussionmentioning

confidence: 99%

Geodiversity decreases shrub mortality and increases ecosystem tolerance to droughts and climate change

Stavi

Rachmilevitch

Hjazin

et al. 2018

Earth Surf Processes Landf

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Mass mortality of shrubs, especially the Noaea mucronata species, has been observed in the semi‐arid Negev of Israel since the early twenty‐first century. This has followed a long‐term drought episode, and suggests a hysteresis‐like effect. However, recent studies have revealed that the mortality has been varied across the region. Therefore, we assessed the depth and stoniness of the soil profile, in homogeneous and heterogeneous hillslopes. Then, we studied the volumetric moisture content during two consecutive growing seasons, in the topsoil of shrubby patches and of inter‐shrub spaces in these hillslopes. The study shows that geodiversity – characterized by shallow soil, a high content of stones in the soil, and a high cover of rock fragment on the surface – reduced shrub mortality. This was attributed to the soil moisture content, which was considerably greater in the heterogeneous hillslopes, than that in the homogeneous hillslopes. It is proposed that the shallow soil halted the growth of herbaceous vegetation in the inter‐shrub spaces of the heterogeneous hillslopes. Therefore, under rainstorms, this hillslope configuration results in considerable generation of overland water flow in the inter‐shrub spaces. The water accumulates in the shrubby patches, allowing them to thrive, even during long‐term dry episodes. In hillslopes with a deep soil layer, no stoniness in the soil profile, and no cover of rock fragments, the herbaceous vegetation is well developed, covering a considerable share of the inter‐shrub spaces. This negates runoff formation and source–sink relations, limiting water availability for the shrubs, and resulting in their mass mortality. Despite no direct pastoral value for livestock, the shrubs play an important role in overall ecosystem functioning. This is due to their capacity to transect hydraulic connectivity, and negate ecosystem collapse. We propose a conceptual model for demonstrating the role played by geodiversity in alleviating drought stress in drylands. Copyright © 2018 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 99%

Geodiversity decreases shrub mortality and increases ecosystem tolerance to droughts and climate change

Stavi

Rachmilevitch

Hjazin

et al. 2018

Earth Surf Processes Landf

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“…This is due to the highly compacted soil of the routes – which act almost as a net source area of water – that flow downslope and accumulate in the shrubby patches and in the remainder of the interpatch spaces. At the same time, the low incline of routes compared with the general slope, composed of ~ 5° and 15°, respectively, sharpens the step‐like profile of hillslopes (Stavi et al ., ). Therefore, we propose that the livestock trampling routes have a simultaneous impact on surface hydrological connectivity in two spatial scales.…”

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confidence: 97%

“…Particularly, this was revealed by the preliminary study of the effects of trampling routes, by using numerical simulations of a well‐known mathematical model of vegetation patterns in drylands (Kéfi et al ., ). In this model, the pattern‐forming feedback is based on the infiltration contrast between vegetated and bare‐soil domains, which is dictated by the parameter α that stands for maximum soil‐water infiltration (Kéfi et al ., ; Yizhaq et al ., ; Stavi et al ., ). We used the same set of parameters as in Kéfi et al .…”

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confidence: 97%

“…Particularly, this was revealed by the preliminary study of the effects of trampling routes, by using numerical simulations of a wellknown mathematical model of vegetation patterns in drylands . In this model, the pattern-forming feedback is based on the infiltration contrast between vegetated and bare-soil domains, which is dictated by the parameter α that stands for maximum soil-water infiltration Yizhaq et al, 2014;Stavi et al, 2015). We used the same set of parameters as in Kéfi et al (2010), including cumulative annual precipitation rates (although with a lower biomass diffusion coefficient value), in order to illustrate the ecosystem response to prolonged drought and to simulate the vegetation patterns in a specific site.…”

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confidence: 99%

“…Regardless, it is important to stress that once livestock density becomes too high (overstocking), it can result in the complete clearing of vegetation cover (Gamoun et al, 2010), or in the expansion of unpalatable woody vegetation (Schlesinger et al, 1990). One way or another, under each of these scenarios, herbaceous vegetation cover becomes extinct, pastoral productivity gets lost, and the three-phase pattern vanishes (Stavi et al, 2015). Regardless, unlike the widely common perception, this short report shows the overall positive impact of moderate livestock grazing on rangeland functioning and productivity.…”

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confidence: 99%

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Small‐scale Geodiversity Regulates Functioning, Connectivity, and Productivity of Shrubby, Semi‐arid Rangelands

2016

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Geodiversity has recently been attracting increasing attention as a measure of diversity for the physical components of natural environments. It has shown positive relations with biodiversity, as well as with several ecosystem services. Yet, so far, geodiversity studies have focused on relatively large spatial scales, ranging between hillslope, basin, and landform scales. It is proposed that either natural-induced or anthropogenic-induced, small-scale (centimeter-scale to few decimeter-scale) geodiversity has a large impact on the hydrological connectivity and overall functioning of semi-arid rangelands and other shrubby and woody drylands. It is further proposed that greater small-scale geodiversity increases the on-site retention of water and soil resources, decreasing the vulnerability of rangelands to prolonged droughts and climatic changes. Particularly, positive impact of moderate grazing intensity on rangelands functioning is demonstrated by the formation of livestock trampling routes, which transect hillslopes, increase ecosystem geodiversity, and modify the spatial redistribution of scarce water and soil resources at the patch scale. Numerical simulations of a mathematical model for vegetation patterns in water-limited systems show that the trampling routes increase the survivability of vegetation patches under prolonged droughts. In practical terms, the concept of smallscale geodiversity is relevant for the determination, monitoring, and assessment of land degradation, as well as for restoration projects of eroded lands and degraded ecosystems.

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Positive impacts of livestock and wild ungulate routes on functioning of dryland ecosystems

Stavi

Yizhaq

Osem

et al. 2021

Ecology and Evolution

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Geodiversity, self-organization, and health of three-phase semi-arid rangeland ecosystems, in the Israeli Negev

Cited by 13 publications

References 27 publications

Geodiversity decreases shrub mortality and increases ecosystem tolerance to droughts and climate change

Geodiversity decreases shrub mortality and increases ecosystem tolerance to droughts and climate change

Small‐scale Geodiversity Regulates Functioning, Connectivity, and Productivity of Shrubby, Semi‐arid Rangelands

Positive impacts of livestock and wild ungulate routes on functioning of dryland ecosystems

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