Tp. Yorks et al., CHANGES IN PINYON-JUNIPER WOODLANDS IN WESTERN UTAH PINE-VALLEY BETWEEN 1933-1989, Journal of range management, 47(5), 1994, pp. 359-364
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.