The effect ofJuniperus virginianaon plant species composition in an Oklahoma grassland

Abstract

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.

Vegetation composition, structure and soil properties across coastal forest–barren ecotones

“…The presence of forest patches on the barrens landscape thus adds to overall species diversity at the landscape level, as it does in other systems (Manning et al 2006). Other work on these coastal barrens, however, shows that rare species are consistently associated with the low shrub communities (Oberndorfer and Lundholm 2009) that are replaced as forest vegetation spreads out from treed patches, as in other grassland or heathland systems (Andrés and Ojeda 2002;Rhoades et al 2005;Linneman and Palmer 2006;Price and Morgan 2008). Therefore further tree expansion may pose a threat to these rare species.…”

Long-term streamflow relations with riparian gallery forest expansion into tallgrass prairie in the Southern Great Plains, USA

“…For instance, at Konza Prairie (3487 ha) in the Flint Hills of Kansas, GIS analysis of historical aerial photographs uncovered an increase in riparian gallery forest from 157 ha in 1939 to 241 ha in 1985 (Knight et al, 1994). Eastern redcedar (Juniperus virginiana) encroachment into Great Plains rangelands (Linneman and Palmer, 2006;Coppedge et al, 2007;Crawford and Hoagland, 2009;Van Els et al, 2010;Wine et al, 2011) has been more widely documented than riparian gallery expansion. Similar to riparian gallery expansion, eastern redcedar encroachment is attributed to reduced fire frequency (Arend, 1950).…”

Changes in forest understory associated with Juniperus encroachment in Oklahoma, USA

“…By drastically altering the open character of the forest, J virginiana encroachment affects understory environmental conditions and may have important implications for plant diversity and productivity. In prairies, J. virginiana encroachment has the potential to increase litter depth (Norris et al 2001), raise soil pH through litter deposition (McBain 1983), alter soil carbon and nitrogen (Norris et al 2001; McKinley & Blair 2008) and decrease light availability for herbaceous plants (Linneman & Palmer 2006). These changes cause a trend towards a community dominated by woody and shade‐tolerant herbaceous species (Linneman & Palmer 2006).…”

“…In prairies, J. virginiana encroachment has the potential to increase litter depth (Norris et al 2001), raise soil pH through litter deposition (McBain 1983), alter soil carbon and nitrogen (Norris et al 2001; McKinley & Blair 2008) and decrease light availability for herbaceous plants (Linneman & Palmer 2006). These changes cause a trend towards a community dominated by woody and shade‐tolerant herbaceous species (Linneman & Palmer 2006). These changes also reduce cover of most species (Smith & Stubbendieck 1990; Gehring & Bragg 1992; Linneman & Palmer 2006) and decrease species richness (Linneman & Palmer 2006).…”

“…These changes cause a trend towards a community dominated by woody and shade‐tolerant herbaceous species (Linneman & Palmer 2006). These changes also reduce cover of most species (Smith & Stubbendieck 1990; Gehring & Bragg 1992; Linneman & Palmer 2006) and decrease species richness (Linneman & Palmer 2006).…”