CHANGES IN PINYON-JUNIPER WOODLANDS IN WESTERN UTAH PINE-VALLEY BETWEEN 1933-1989

Changes in woodland vegetation integrate the consequences of livestock grazing intensity, the alteration of fire regimes, and possible clima te alteration, as well as other factors. Quantitative measurements of these changes, if taken over sufficient intervals, can allow evaluatio n of conservation management strategies. In 1993, vegetation along a 3 7-km transect in southern Pine Valley, Utah was described from circula r 19-m2 plots located every 42 m. The major intermediate management tr eatment has been reduction of grazing pressure by introduced animals, although a fraction of the area was chained and burned in 1977. During a period climatically and phenologically similar to the original stud y, we re-examined representative segments of this transect by a more d etailed updating of the original ''square-foot-density'' method. Signi ficantly greater shrub and perennial grass covers (more than threefold increases) were found in 1989, even where overall dominance is still by pinyon-juniper [Pinus monophylla (Torrey & Fremont) and Juniperus o steosperma (Torrey) Little]. This change is more obvious on steeper sl opes away from roads and water, where both human and livestock disturb ances would be expected to be minimized. Except in the chained portion , the observed shifts in dominance/diversity are contrary to widely ac cepted expectations.