51
variable compared to former grasslands (Schlessinger et al. 1990 ; Jurena and Van
Auken 1998 ; Schlesinger et al. 1999 ; Throop and Archer 2008 ). Nutrient and
organic concentrations are higher below the woody plant or shrub canopy rather
than the interspaces. Soil nitrogen levels are higher below the canopy of encroaching woody legumes such as Prosopis, Senegalia, and Vachellia (Bush 2008 ; Jurena
and Van Auken 1998 ).
With true invasive species, pools of biogeochemicals and material fl uxes have
changed, but there is considerable variability (Ehrenfeld 2010 ) and considerable
effort to prevent the establishment of the invaders. Where various other woody species are encroaching or have encroached into grasslands, changes in soil resources
are just being revealed. In xeric sites, encroachment caused a decrease in aboveground net primary production, but in more mesic sites, there was an increase in
production because of high woody plant leaf area (Knapp et al. 2008b ) which is
woody plant production. In central North American Juniperus woodlands, carbon
and nitrogen increased in woody plant biomass, but there was little change in soil
availability of nitrogen (McKinley and Blair 2008 ). There were small changes in
nitrogen cycle processes in these same woodlands that were recently converted
from grasslands (McKinley et al. 2008a ).
Demonstrated biggest changes in the location of the biomass from belowground
in the grassland to aboveground in the woodland and the form of the biomass from
herbaceous to woody are very important to most of the herbivorous animals.
Herbaceous biomass supports the grazers, while the woody biomass supports some
browsers. Because of the shift in plant biomass, these former grassland communities
Fig. 8.2 Photograph demonstrates the management potential of using fi re in grassland ecosystems
to control or reduce the encroachment and establishment of woody plants. Picture was taken in the
direction of a fi rebreak along an access road which is near the center of the photograph. To the left
of the fi rebreak, the prairie was burned infrequently (once every 10 years). The encroachment of a
variety of woody plants is easily seen. To the right of the fi rebreak, the prairie was burned frequently (once every 2 years). The lack of woody plants is obvious (this fi gure is modifi ed from Van
Auken ( 2009 ) and was taken by McKinley DC)
8 Management and Community Restoration
variable compared to former grasslands (Schlessinger et al. 1990 ; Jurena and Van
Auken 1998 ; Schlesinger et al. 1999 ; Throop and Archer 2008 ). Nutrient and
organic concentrations are higher below the woody plant or shrub canopy rather
than the interspaces. Soil nitrogen levels are higher below the canopy of encroaching woody legumes such as Prosopis, Senegalia, and Vachellia (Bush 2008 ; Jurena
and Van Auken 1998 ).
With true invasive species, pools of biogeochemicals and material fl uxes have
changed, but there is considerable variability (Ehrenfeld 2010 ) and considerable
effort to prevent the establishment of the invaders. Where various other woody species are encroaching or have encroached into grasslands, changes in soil resources
are just being revealed. In xeric sites, encroachment caused a decrease in aboveground net primary production, but in more mesic sites, there was an increase in
production because of high woody plant leaf area (Knapp et al. 2008b ) which is
woody plant production. In central North American Juniperus woodlands, carbon
and nitrogen increased in woody plant biomass, but there was little change in soil
availability of nitrogen (McKinley and Blair 2008 ). There were small changes in
nitrogen cycle processes in these same woodlands that were recently converted
from grasslands (McKinley et al. 2008a ).
Demonstrated biggest changes in the location of the biomass from belowground
in the grassland to aboveground in the woodland and the form of the biomass from
herbaceous to woody are very important to most of the herbivorous animals.
Herbaceous biomass supports the grazers, while the woody biomass supports some
browsers. Because of the shift in plant biomass, these former grassland communities
Fig. 8.2 Photograph demonstrates the management potential of using fi re in grassland ecosystems
to control or reduce the encroachment and establishment of woody plants. Picture was taken in the
direction of a fi rebreak along an access road which is near the center of the photograph. To the left
of the fi rebreak, the prairie was burned infrequently (once every 10 years). The encroachment of a
variety of woody plants is easily seen. To the right of the fi rebreak, the prairie was burned frequently (once every 2 years). The lack of woody plants is obvious (this fi gure is modifi ed from Van
Auken ( 2009 ) and was taken by McKinley DC)
8 Management and Community Restoration