NITROGEN MINERALIZATION POTENTIALS OF SHRUB-STEPPE SOILS WITH DIFFERENT DISTURBANCE HISTORIES

The soil N-mineralization potential (No) was determined for two arid ecosystems, an undisturbed perennial shrub-steppe and an annual grassland. The No decreased with soil depth until the 10- to 15-cm soil depth, when all soils had the same value. The production of plant-available N will, therefore, be largely limited to the soil surface, and losses from the first 5 cm of soil will be detrimental to both ecosystems. Spatial distribution of plant species in the arid ecosystem result in "islands' where enhanced N mineralization occurs. -from Authors