Journal of Geographical Sciences ›› 2021, Vol. 31 ›› Issue (8): 1187-1204.doi: 10.1007/s11442-021-1892-2

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Dead shrub patches as ecosystem engineers in degraded drylands

Ilan STAVI1,2(), Eli ZAADY3, Alexander GUSAROV1, Hezi YIZHAQ4   

  1. 1. Dead Sea and Arava Science Center, Yotvata 88820, Israel
    2. Eilat Campus, Ben-Gurion University of the Negev, Eilat 88100, Israel
    3. Department of Natural Resources, Agricultural Research Organization, Gilat Research Center, 85280 Negev, Israel
    4. Department of Solar Energy and Environmental Physics, Blaustein Institutes for Desert Research, Ben- Gurion University of the Negev, Sede Boqer Campus 84990, Israel
  • Received:2020-12-31 Accepted:2021-03-16 Online:2021-08-25 Published:2021-10-25
  • About author:Ilan STAVI, E-mail address: istavi@adssc.org

Abstract:

A long-term drought has led to the mass mortality of shrubs in the semi-arid Israeli Negev. The most impacted shrub species is the Noaea mucronata (Forssk.) Asch. and Schweinf. In a four-year study, we found that herbaceous vegetation growth was greater in the dead shrub patches than in the surrounding inter-patch biocrusted spaces, suggesting that the dead shrub patches encompass improved micro-habitats. However, unexpectedly, the soil moisture in the dead shrub patches was consistently lower than that of the inter-patch biocrusted spaces. At the same time, soil quality in the dead shrub patches was higher than that in the inter-patch spaces. Therefore, it seems that the overall better soil conditions in the dead patches overcome the scarcity of soil-water, supporting increased herbaceous productivity. For explaining the discrepancy between herbaceous vegetation and soil-water, we formulated a conceptual framework, which highlights the key factors that regulate soil-water dynamics in this dryland ecosystem. We demonstrate that herbaceous vegetation is facilitated in the dead shrub patches by a legacy effect that takes place long after the shrubs have died. The dead shrub patches encompass a unique form of ecosystem engineering. The study high- lights the complex and unpredicted impacts of prolonged droughts on dryland ecosystems.

Key words: allogenic ecosystem engineers, climate change, legacy mechanism, patchy vegetation, small-scale geodiversity, vegetation transition