Kt. Killingbeck et Wg. Whitford, HIGH FOLIAR NITROGEN IN DESERT SHRUBS - AN IMPORTANT ECOSYSTEM TRAIT OR DEFECTIVE DESERT DOCTRINE, Ecology, 77(6), 1996, pp. 1728-1737
Nitrogen concentrations in green and senesced leaves of perennial dese
rt shrubs were compiled from a worldwide literature search to test the
validity of the doctrine that desert shrubs produce foliage and leaf
litter much richer in nitrogen than that in the foliage of plants from
more mesic environments. Mean nitrogen concentration in the green lea
ves of 78 species of shrubs growing in 11 deserts on five continents (
2.2%) was not different from that in 67 species of trees and shrubs gr
owing in deciduous, and mixed deciduous forests (2.2%), and only sligh
tly higher than that in overstory (2.0%) and understory (2.1%) plants
growing in tropical wet forest. Mean nitrogen concentration in the gre
en leaves of a ubiquitous shrub that dominates large areas of desert i
n the United States (Larrea tridentata, 2.1%), and in the green-stem t
issues of leafless desert shrubs (2.1%) were also similar to that in p
lants from mesic environments. Mean green-leaf nitrogen was similar in
shrubs growing in different deserts. Mean nitrogen concentration in l
eaf litter was 1.1% for 11 species of desert shrubs, and 1.0% for the
10 species of this group that were not capable of symbiotic nitrogen f
ixation. Both concentrations were lower than those routinely provided
to describe nitrogen in the litter of desert shrubs (1.5-1.7%), and on
ly slightly higher than the mean nitrogen concentration in 77 species
of woody perennials growing in a wide variety of environments worldwid
e (0.9%). Nitrogen in the leaf litter of one desert shrub (0.4%, Brick
ellia laciniata) was nearly as low as the lowest leaf-litter nitrogen
concentration known for any woody species (0.3%). Because nitrogen con
centrations in the foliage of desert shrubs are not higher than those
in plants growing in more mesic environments, the tenet that desert sh
rubs support extraordinarily nitrogen-rich foliage can no longer be su
pported.