What stabilizes biological soil crusts in the Negev Desert?
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Biological soil crusts (biocrusts) are widespread in many drylands, where plant growth is limited due to water scarcity. One of their most important functions is the stabilization of the topsoil, particularly in regions with sandy soils prone to desertification. Since the mechanisms playing a role in soil stabilization are poorly understood, this study aims to shed light on the connection between crust stability and different cementing agents.
We measured the penetration resistance and the concentrations of different cementing agents of biocrusts in the Israeli Negev Desert. Structural equation modelling was performed to examine the direct and indirect effects of the variables analyzed and identify variables that are best able to explain the observed patterns of penetration resistance.
All observed variables showed a high variability within and between sites. Structural equation modelling revealed that the main parameters explaining penetration resistance are the content of fines and the electrical conductivity, while carbonates and organic carbon only have an indirect effect.
Our results suggest that adding silt and clay to (natural or induced) biocrusts is very likely to produce stronger, more stable crusts, which will be more effective in combating desertification and improve their ability to survive trampling by livestock.
KeywordsPenetration resistance Biocrust Surface stability Grazing potential Desertification Structural equation modelling Ecosystem restoration
We thank the German Research Foundation (DFG) for funding this research in the framework of the trilateral project “Biotic and abiotic factor affecting biological soil crust formation and recovery in a semiarid dune ecosystem, Gaza and NW Negev” (Project FE 218/14-2), and the Arid Ecosystems Research Center of the Hebrew University of Jerusalem. Special thanks go to Simon Berkowicz for his support during fieldwork and to Günter Weber for assistance in the lab. We would also like to thank David Eldridge, as well as two anonymous reviewers for their constructive comments, which considerably improved a previous version of this manuscript.
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