Impacts of native and invasive exotic Prosopis congeners on soil properties and associated flora in the arid United Arab Emirates

• Two native and exotic Prosopis trees are growing in the arid deserts of the UAE.
• The allelopathic effect on germination of associated plants was greater for the exotic tree.
• Both species improve soil characters, i.e., facilitate the growth of associated plants.
• The allelopathic effect of invasive might override its facilitative effect.

The native Prosopis cineraria and exotic invasive P. juliflora are present in arid habitats of the United Arab Emirates (UAE). The objective of this study was to assess the impacts of allelopathy and soil properties on plants associated with the two species in arid deserts. Density and other community attributes of the associated species were assessed beneath, at the margin and outside the canopies of 20 Prosopis individuals. Aqueous extracts of fresh and old leaves of both Prosopis species were assessed on germination of five native plants. Soil samples were collected from beneath and next to canopies of the two species and their chemical properties were analyzed. The effect on the associated flora was depressive for P. juliflora, but was positive for P. cineraria canopy. The depressive effect of P. juliflora was more obvious on the annual compared with perennial plants. The negative effect of the aqueous extract of P. juliflora was much greater on germination, especially for annual plants. Canopies of both species improved soil properties that would facilitate the association of other native plants. The allelopathic effect of P. juliflora, however, may override its facilitative effect and consequently resulted in a depressive effect on the associated flora.