Dead shrub patches as ecosystem engineers in degraded drylands

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 highlights the complex and unpredicted impacts of prolonged droughts on dryland ecosystems.

Automated summary

A long-term drought in the semi-arid Israeli Negev has caused mass mortality of shrubs, impacting the ecosystem in unexpected ways. The study found that dead shrub patches had better soil quality and supported higher herbaceous vegetation growth despite lower soil moisture levels. The research highlights the complex and unpredictable impacts of prolonged droughts on dryland ecosystems.