Two Microenvironments at the Soil Surface of Saline Wetlands in Monegros, Spain

Non‐trodden soils free of human and livestock pedestrian activity occur on the floors of hypersaline playa‐lakes in the Monegros' inland wetlands in Spain. A soil surface vesicular crust (herein designed as A1v horizon) organized in decimetric polygonal plates is the main observable feature of these rare soils inhabited by the perennial halophyte shrub Arthrocnemum macrostachyum(Moric.) Moris (A.m.). The vesicular organization of the A1v, together with its discontinuity with the soil underneath, suggests the existence of two contrasting soil microenvironments. Thirty‐three sites of seven wetlands inhabited by A.m.were sampled: the A horizon from 0 to 15 cm, that is, including A1v; and separately the A1v and the underneath A2 horizon up to 15‐cm depth. Measurements included Munsell color, moisture, and salinity at different soil/water ratios, during both the dry and wet seasons along with determinations of gypsum content, calcium carbonate equivalent, and organic matter. Evidence of the mulching effect of A1v and its contrasting conditions against the underlying A2 is supported by the significant differences in 1:5 soil/water extracts electrical conductivity, with a July mean EC1:5 of 22.3 dS m−1in A1v vs. 14.0 dS m−1in A2, and by similar significant differences in all major ions, except Ca. In July, total dryness (0%) can be achieved by A1v whereas A2 retained some moisture (5% minimum). Significant moisture differences were found for A1v and A2 in December together with a homogenizing effect. These are significant traits to be considered both in halophyte germination and establishment studies, and in ecological and restoration plans.