Relationships between landforms, soil characteristics and dominant xerophytes in the hyper-arid northern United Arab Emirates

• Multivariate analysis has classified landforms into four groups.
• Each landform has a specific vegetation type.
• Landforms and soil characteristics affect the distribution of dominant plants.
• Soil salinity and texture control the distribution of the dominant plants.
• The long-lived trees enhance the presences of dominant perennials.

Processes limiting the distribution and abundance of plants are directly linked to landform characteristics. The relationships between soil characteristics and dominant xerophytes were assessed in the major landforms in the hyper-arid deserts of the Northern Emirates (NE) of the United Arab Emirates, northeast of the Arabian Peninsula. Dominant and co-dominant perennial plants were recorded in a total of 1058 stands in 13 landforms. Soil texture, electrical conductivity (EC) and pH were assessed in each stand. Two methods of multivariate analysis (TWINSPAN and DCA) classified the landforms into four groups, each with specific indicator(s) species. Canonical Correspondence Analysis ordination showed positive correlations of the halo-xerophytic shrubs along a gradient of EC. Zygophyllum qatarense and Salsola drummondi showed the highest correlation with soil salinity. The psammophytic species Cyperus conglomeratus and the shrubby Calotropis procera and Calligonum comosum are correlated along gradients of high sand content, high pH, and low EC. Acacia tortilis is correlated with increasing silt and clay and it prefers soils with low EC. The grasses Pennisetum divisum and Panicum turgidum are located around the middle of the soil texture, pH and EC gradients. The associations between A. tortilis and other species, e.g. C. comosum, Prosopis cineraria, and S. drummondi, were correlated along gradients of silt and clay. More perennials were associated with both the keystone trees A. tortilis and Prosopis juliflora, but the association was more for the first, compared to the latter species.