Live and dead shrubs and grasses have different facilitative and interfering effects on associated plants in arid Arabian deserts

• Live grasses negatively affected the density of associated plants.
• Dead grasses showed facilitative effects on associated plants.
• Dead and live shrubs had positive effects on the density of associated plants.
• Nurse shrubs and grasses improved the physical and chemical properties of soil.
• The facilitative effects of nurse plants extended beyond their life span.

The Arab Gulf desert region is dominated by few shrubs and grasses, although mostly devoid of vegetation. The impact of both live and dead shrubs and grasses on plant diversity and community composition on sand dunes of the United Arab Emirates was assessed. Species richness, diversity indices (Simpson, Shannon–Wiener, and Brillouin), and plant abundance were significantly greater under dead grasses than in the surrounding open areas. However, the opposite was true for live grasses. Dead and live shrubs did not differ significantly in species richness and abundance. The relative interaction index indicated that live nurse grasses inhibited 13 species and facilitated only one species, whereas dead grasses facilitated 13 species and did not inhibit any species. Live shrubs facilitated four species and inhibited two, but dead shrubs facilitated 10 species and inhibited none. Organic matter and most of the assessed soil nutrients were significantly higher under both shrubs and grasses than in the barren spaces in-between. The facilitative effect of dead grasses on soil characteristics was more obvious. The results support the feasibility of growing nurse shrubs and grasses to restore degraded arid desert environment.