ASSOCIATION OF OVERSTORY PLANT CANOPIES AND NATIVE GRASSES IN SOUTHERN ARIZONA

In arid regions, overstory plants may influence establishment and pers istence of understory species. Identifying relationships between overs tory and understory plants may increase success of revegetation effort s. This research considered whether three desirable grasses native to the Sonoran Desert, Arizona cottontop (Digitaria californica), plains lovegrass (Eragrostis intermedia) and bush muhly (Muhlenbergia portern ), differ in density or cover under overstory species compared to open areas. Selection of sites in southern Arizona (two or three per speci es) was based on abundance of study species and elevation. Density and cover of Arizona cottontop and plains lovegrass was highly variable b etween canopied and open areas among sites. Bush muhly had greater den sity and cover under canopies at all sites. No association was noted b etween precipitation or elevation and density or cover ratios. Identif ying understory species well-adapted to shaded sites may aid in determ ining the best use of existing vegetation for revegetation in this reg ion. (C) 1997 Academic Press Limited.