54
Reversing the encroachment or succession process or going from a woodland or
shrubland to grassland is complex and diffi cult (Ansley and Wiedemann 2008 ).
Potential biotic controls are usually more sophisticated, may be combined with fi re
or mechanical treatment, and may include genetic manipulation of some of the
browsing species (Taylor 2008 ; Taylor et al. 2012 ).
If intermittent or periodic fi res are not allowed or do not occur in these grasslands
communities, they will be converted to savannas, shrublands, or woodlands
(Fig. 8.5 ). The frequency of fi re in native grasslands in the past was and still is quite
variable, but there seems to be general agreement that recurring fi res are required to
control or reduce the encroachment, establishment, density, and growth of woody
plants in most if not all grasslands (Collins and Wallace 1990 ; Scholes and Walker
1993 ; Simmons et al. 2007 ). The use of various types of models have produced similar fi ndings, heavy grazing or low fi re frequency results in encroachment of woody
plants which is followed by increased woody plant density (Fuhlendorf et al. 2008 ).
Fire results are not simple, and there are a number of potential environmental and
ecological interactions that could occur between fi res and topography, soil type,
temperature, rainfall, number and kind of herbivores, and amount of light, fl uffy
fuel. These factors will determine the nature, density, and location of woody plants
in a given landscape (Humphrey 1958 ; Collins and Wallace 1990 ; McPherson 1995 ).
Fig. 8.5 Three examples of unburned grassland recently encroached by Juniperus ( top left ),
Opuntia ( top right ), and Prosopis and a different species of Opuntia ( bottom ). Photographs were
taken by the senior author
8 Management and Community Restoration
Reversing the encroachment or succession process or going from a woodland or
shrubland to grassland is complex and diffi cult (Ansley and Wiedemann 2008 ).
Potential biotic controls are usually more sophisticated, may be combined with fi re
or mechanical treatment, and may include genetic manipulation of some of the
browsing species (Taylor 2008 ; Taylor et al. 2012 ).
If intermittent or periodic fi res are not allowed or do not occur in these grasslands
communities, they will be converted to savannas, shrublands, or woodlands
(Fig. 8.5 ). The frequency of fi re in native grasslands in the past was and still is quite
variable, but there seems to be general agreement that recurring fi res are required to
control or reduce the encroachment, establishment, density, and growth of woody
plants in most if not all grasslands (Collins and Wallace 1990 ; Scholes and Walker
1993 ; Simmons et al. 2007 ). The use of various types of models have produced similar fi ndings, heavy grazing or low fi re frequency results in encroachment of woody
plants which is followed by increased woody plant density (Fuhlendorf et al. 2008 ).
Fire results are not simple, and there are a number of potential environmental and
ecological interactions that could occur between fi res and topography, soil type,
temperature, rainfall, number and kind of herbivores, and amount of light, fl uffy
fuel. These factors will determine the nature, density, and location of woody plants
in a given landscape (Humphrey 1958 ; Collins and Wallace 1990 ; McPherson 1995 ).
Fig. 8.5 Three examples of unburned grassland recently encroached by Juniperus ( top left ),
Opuntia ( top right ), and Prosopis and a different species of Opuntia ( bottom ). Photographs were
taken by the senior author
8 Management and Community Restoration