The influence of biological soil crusts on mineral uptake by associated vascular plants

Soil surfaces dominated by cyanobacteria and cyanolichens (such as Collema sp.) are widespread in deserts of the world. The influence of these biologi cal soil crusts on the uptake of bioessential elements is reported for the first time for six seed plants of the deserts of Utah. This sample almost d oubles the number of species for which the influence of biological soil cru sts on mineral uptake of associated vascular plants is known. These new cas e studies, and others previously published, demonstrate that cyanobacterial or cyanobacteria-Collema crusts significantly alter uptake by plants of ma ny bioessential elements. In studies now available, these crusts always inc rease the N content of associated seed plants. Uptake of Cu, K, Mg, and Zn is usually (>70% of reported cases) increased in the presence of the biolog ical soil crusts. Soil crusts are generally negatively associated with Fe a nd P levels in associated seed plant tissue, while plant tissue levels of C a, Mn, and Na are positively as often as negatively associated with the pre sence of soil crusts. Increases in bioessential elements in vascular plant tissue from biologically-crusted areas are greatest for short-lived herbs t hat are rooted primarily within the surface soil, the horizon most influenc ed by crustal organisms. The mineral content of a deeply rooted shrub (Cole ogyne ramosissima) was less influenced by co-occurrence of biological soil crusts. (C) 2001 Academic Press.