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The effect of <i>Juniperus virginiana</i> on plant species composition in an Oklahoma grassland

Linneman, J. S., Palmer, M. W.
Community ecology 2006 v.7 no.2 pp. 235-244
Juniperus virginiana, forbs, graminoids, grasses, grasslands, shade tolerance, species diversity, trees, woody plants, Oklahoma
We established transects under twenty <i>Juniperus virginiana</i> trees that invaded an unburned central Oklahoma grassland within the last 20 years to determine their effects on plant species composition. Species richness and stem density increased as distance from the trunk increased. Stem density was also higher towards the south side of trees. Graminoid, forb and total cover were related to distance from the trunk and transect direction. Ordination revealed weak compositional gradients related to “openness” and compass direction. Woody species tended to be most abundant underneath <i>J. virginiana</i> canopies whereas grass and forb species were most abundant in the prairie. Woody and shade-tolerant species preferentially occurred in north transects and quadrats underneath the tree. Conversely, forbs had highest abundance on edge quadrats whereas graminoids dominated south transects and prairie quadrats. Thus, invasion of grasslands by <i>J. virginiana</i> influences species composition in a spatially complex manner.