Relationships between landforms, soil characteristics and dominant xerophytes in the hyperarid Northern United Arab Emirates.

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.