Summary: 907
Ecology, 84(4), 2003, pp. 907­919
2003 by the Ecological Society of America
WOODY PLANT ESTABLISHMENT AND SPATIAL HETEROGENEITY
IN GRASSLANDS
P. N. JURENA1
AND STEVE ARCHER2
Department of Rangeland Ecology and Management, Texas A&M University, College Station, Texas 78243-2126 USA
Abstract. Root exclusion experiments demonstrated the importance of belowground
competition between grasses and Prosopis glandulosa (honey mesquite) during the critical
seeding establishment phase of the woody plant life cycle. Belowground available volume
accounted for 67% and 79% of the variance in first- and second-year Prosopis seedling
growth and survival, respectively. Available volume in the vertical dimension was more
important than that in the horizontal dimension. Trials spanned years with contrasting annual
precipitation, suggesting that root competition occurs in years of near-average as well as
below-average annual rainfall. Spatial heterogeneity in canopy gaps and belowground bio-
mass was also quantified in a Schizachayriuim­Paspalum grassland matrix and evaluated
with respect to Prosopis seedling establishment. Of the 100 grid points encountered in four
grass stands, 62% were unoccupied; and 50% of these exceeded 80 cm2
( 10 cm diameter).

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

Collections: Environmental Sciences and Ecology