ABSTRACT
Deserts include arid and semi-arid lands where evaporation plus transpiration exceeds precipitation. The 2005 Millennium Ecosystem Assessment categorized dryland climates as hyper-arid, arid, semi-arid and sub-humid. Particular components of desert ecosystems might be degraded or missing. Only one component might require restoration if the rest of the ecosystem is healthy, or several components could require restoration within a comprehensive ecological framework. Annual plants can be restored through seeding and indirectly through establishing perennial plants or improving site conditions. Perennial plants in natural desert ecosystems typically facilitate recruitment of annual plants, and diversifying the perennial plant community can increase diversity of annual plants. In deserts, annual plants are components of both early colonizing and mature ecosystems, though annuals may only be present in high-rainfall years. Species in some desert shrublands and grasslands re-sprout if their tops are killed. Thus.
