We established transects under twenty Juniperus virginiana 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 J. virginiana canopies whereas grass and forb species were most abundant in the prairie. Woody and shadetolerant 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 J. virginiana influences species composition in a spatially complex manner.

We studied species composition after Juniperus virginiana tree and litter removal in a central Oklahoma grassland. Tree removal had the most significant effect on stems per quadrat and vegetation cover. Litter removal effects were not as strong. However, stems per quadrat and vegetation cover in litter removal treatments were higher than in litter intact treatments. Species richness increased for all treatments in the first year post-treatment, after which species richness declined at every sampling period and in every treatment for the duration of the study. Absolute cover of typical prairie species increased in the cut with no litter treatment whereas cover of woody forest species increased in the no cut with no litter treatment. We suggest that even without prescribed fire, redcedar tree removal may result in a return of prairie vegetation. However, additional efforts besides tree removal may be required to restore some invaded grasslands.