Woody Plants Reestablishment in Modified Pinyon-Juniper Woodlands, New Mexico

Abstract

Pinyon (Pinus edulis Engelm.), one-seed juniper (Juniperus monosperma (Engelm.) Sarg.), and alligator juniper (J. deppeana Steud.) woodlands in southwestern New Mexico were thinned, were pushed with bulldozers leaving slash in place, and were pushed and then slash piled and burned. There were no significant differences (P>0.05) in densities of these trees 13 and 18 years later between untreated (379 trees/ha) and thinned (489 trees/ha) plots or between pushed/left (67 trees/ha) and pushed/piled/burned plots (49 trees/ha). Differences between bulldozed treatments and untreated/thinned treatments were significant (P<0.05). Total shrubs, 75% of which were gray oak (Quercus grisea Liebm.) and hairy mountainmahogany (Cercocarpus breviflorus Gray), were significantly more abundant in untreated areas (672 shrubs/ha), than in any of the treatments. No differences were noted among treatments (493, 393, 329 shrubs/ha for thinned, pushed/left, and pushed/piled/burned, respectively). Rates of pinyon reestablishment increased slowly up to the mid-1960's (from 1.1 to 1.3 trees/ha/year) then accelerated to 10 to 13 trees/ha/year. Pinyon and juniper densities were about 120 trees/ha when reestablishment rates increased.