Ca. Busso et Jh. Richards, DROUGHT AND CLIPPING EFFECTS ON TILLER DEMOGRAPHY AND GROWTH OF 2 TUSSOCK GRASSES IN UTAH, Journal of arid environments, 29(2), 1995, pp. 239-251
Tiller demography and growth were determined for clipped and unclipped
plants of crested wheatgrass (Agropyron desertorum) and bluebunch whe
atgrass Pseudoroegneria spicata under drought, natural or irrigated co
nditions from 1984 until 1986. Mild water stress during the 1984 growi
ng season did not reduce herbage accumulation at the end of that seaso
n on plants of both species. However, green leaf number, rate of leaf
initiation, height and total green leaf area were all reduced on tille
rs of both species when predawn leaf xylem pressure potentials fell be
low - 2.5 MPa during two or more growth periods. In the 3rd year of re
peated treatments, the lowest daughter tiller production and growth we
re observed under the simultaneous influence of drought and clipping.
Repeated late and severe grazing of these species under long-term drou
ghts (2 or more years) could then be expected to rapidly reduce their
persistence in the community.