My. Cui et Mm. Caldwell, A LARGE EPHEMERAL RELEASE OF NITROGEN UPON WETTING OF DRY SOIL AND CORRESPONDING ROOT RESPONSES IN THE FIELD, Plant and soil, 191(2), 1997, pp. 291-299
To assess changes in soil nutrients, root growth and mycrorrhizal infe
ction in response to rain events, a water pulse was applied to a very
dry soil. Wetting of a dry soil in the Great Basin of the Western Unit
ed States led to a striking pulse of available soil nitrate in a field
plot, but available phosphate was not affected. This is the first fie
ld demonstration of this phenomenon in the Great Basin as far as we ar
e aware. This pulse was only apparent for a few days, probably due to
microbial immobilization of the nitrogen. Root ammonium uptake capacit
y increased within one day of the water pulse, but new root growth was
not apparent until 3 days after the water pulse. Thus, to capture thi
s ephemeral release of nitrogen, enhanced uptake capacity of existing
roots was probably more important than development of new roots. Mycor
rhizal infection was not affected by the water pulse treatments. Howev
er, since the water pulse only affected nitrogen availability and myco
rrhizae are generally most effective in facilitating acquisition of le
ss mobile nutrients such as phosphate, mycorrhizae likely do not play
an important role in taking advantage of this opportunity provided by
the pulse of water.