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Ecology, 80(7), 1999, pp. 23852396 1999 by the Ecological Society of America
 

Summary: 2385
Ecology, 80(7), 1999, pp. 23852396
1999 by the Ecological Society of America
SHRUB INVASION OF GRASSLAND: RECRUITMENT IS CONTINUOUS
AND NOT REGULATED BY HERBACEOUS BIOMASS OR DENSITY
JOEL R. BROWN1
AND STEVE ARCHER
Department of Rangeland Ecology and Management, Texas A&M University,
College Station, Texas 77843-2126 USA
Abstract. Proliferation of woody plants in grasslands and savannas since the 1800s
has been widely documented. In the southwestern United States, increased abundance of
honey mesquite (Prosopis glandulosa var. glandulosa) has been attributed to heavy grazing
by livestock. Here, we test the hypothesis that P. glandulosa invasion of grasslands requires,
first, reductions in herbaceous biomass and density such as those that accompany livestock
grazing and, second, episodes of high soil moisture availability.
No combination of grass density (nonmanipulated or reduced 50%) or defoliation (none,
moderate, heavy) significantly affected P. glandulosa seedling emergence within a watering
regime (natural and supplemented) at our field site in semiarid southern Texas. Seedling
emergence on plots receiving only natural rainfall was high (42%), despite the fact that
precipitation was substantially below normal. Supplemental watering, to generate moisture

  

Source: Archer, Steven R. - Savanna/Woodland Ecology Lab., School of Natural Resources and the Environment, University of Arizona

 

Collections: Environmental Sciences and Ecology