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Oak Canopy Effects on the Distribution Patterns of Two Annual Grasses: The Role of Competition and Soil Nutrients
Kevin J. Rice and Eric S. Nagy
American Journal of Botany
Vol. 87, No. 11 (Nov., 2000), pp. 1699-1706
Published by: Botanical Society of America, Inc.
Stable URL: http://www.jstor.org/stable/2656747
Page Count: 8
You can always find the topics here!Topics: Grasses, Habitats, Grassland soils, Species, Forest canopy, Understory, Population growth, Soil nutrients, Import competition, Plants
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Within the oak woodlands of California there is often a distinct shift in the botanical composition between the open grassland and the herbaceous understory beneath oak canopy. Botanical sampling at two woodland sites indicated that the annual grass Bromus diandrus was dominant under deciduous blue oak canopy, while a congener, Bromus hordeaceus, was dominant in open grassland. We examined the relative importance of congeneric competition and edaphic factors in creating these differences in species distribution in two separate field experiments that manipulated both congeneric and intraspecific competition, as well as soil type. We used the demographic measure of relative reproductive rate as an index of population growth. In general, demographic performance correctly predicted the distribution of the two annual grasses in the field. Our results indicate that reduced abundance of B. hordeaceus under canopy reflects the negative effects of competition with B. diandrus. In contrast, B. diandrus is little affected by competition from B. hordeaceus. The reduced abundance of B. diandrus in open grassland may result, in part, from its inability to adapt as well as B. hordeaceus to lower nutrient availability in soils of the open grassland.
American Journal of Botany © 2000 Botanical Society of America, Inc.