SOIL MICROSTRUCTURE IN SOILS OF THE COLORADO PLATEAU - THE ROLE OF THE CYANOBACTERIUM MICROCOLEUS-VAGINATUS

The role of the cyanobacterium Microcoleus vaginatus in cold-desert so il crusts is investigated using scanning electron microscopy. Crusts f rom sandstone-, limestone-, and gypsum-derived soils are examined. Whe n dry, polysaccharide sheath material from this cyanobacterium can be seen winding through and across all three types of soil surfaces, atta ching to and binding soil particles together. When wet, sheaths and li ving filaments can be seen absorbing water, swelling and covering soil surfaces even more extensively. Addition of negatively charged materi al, found both as sheath material and attached clay particles, may aff ect cation exchange capacity of these soils as well. As a result of th ese observations, we propose that the presence of this cyanobacterium may significantly enhance soil stability, moisture retention, and fert ility of cold-desert soils.