56
and the intervals would probably depend on the rainfall. With a reasonable schedule
of burning and reduced levels of herbivory, grasslands could remain as grasslands
and animal productivity could be sustained. The level of herbivory would certainly
have to be adjusted to area conditions especially rainfall.
Can woody legume and other woody plant savannas or woodlands be maintained
or restored to grasslands? This is a diffi cult question without easy answers. Yes it
can probably be done, but not cheaply. Two hundred to 300 or more years of excessive grazing and harvest cannot be overcome with one fi re followed by a return to a
previous ineffective management system. Recovery or return of a savanna or woodland to a grassland state will not be easy. The “spray and pray” philosophy of the
past did not and will not work.
The future of these woody legume communities or former grasslands is diffi cult
to predict, especially in our changing world. Secondary succession is occurring
or has occurred, and the communities will be different in the world of the future.
These communities are very dynamic and they are also economically, biologically,
and ecologically necessary and needed. Knowledge gained from observations and
experiments reported here and other places are critical in defi ning observations
and experiments needed in the future. The track through the future is not clear, but
each new discovery helps light the way.
References
Ansley RJ, Wiedemann HT (2008) Reversing the woodland steady state: vegetation responses during restoration of Juniperus -dominated grasslands with chaining and fi re. In: Van Auken OW
(ed) Western North American Juniperus communities: a dynamic vegetation type, vol 196.
Springer, New York, pp 272–290
Archer S (1994) Woody plant encroachment into southwestern grasslands and savannas: rates,
patterns and proximate causes. In: Vavra M, Laycock WA, Pieper RD (eds) Ecological implications of livestock herbivory in the west. Society for Range Management, Denver, pp 13–69
Archer SR, Schimel DS, Holland EH (1995) Mechanisms of shrubland expansion: land use, climate or CO 2 . Climate Change 29:91–99
Bahre CJ (1991) A legacy of change: historic human impact on vegetation on the Arizona borderlands. University of Arizona Press, Tucson
Bahre CJ (1995) Human impacts on the grasslands of southeastern Arizona. In: McClaran MP, Van
Devender TR (eds) The desert grassland. The University of Arizona Press, Tucson, pp
230–264
Bahre CJ, Shelton ML (1993) Historic vegetation change, mesquite increases, and climate in
southeastern Arizona. J Biogeogr 20:489–504
Browning DM, Archer SR, Asner GP, McClaran MP, Wessman CA (2008) Woody plants in grasslands: post-encroachment stand dynamics. Ecol Appl 18:828–944
Bush JK (2008) Soil nitrogen and carbon after twenty years of riparian forest development. Soil
Sci Soc Am J 72:815–822
Bush JK, Van Auken OW (1995) Woody plant-growth related to planting time and clipping of a
C-4 grass. Ecology 76:1603–1609
Campbell BD, Stafford-Smith DM, McKeon GM (1997) Elevated CO 2 and water supply interactions in grasslands: a pastures and rangelands management perspective. Global Change Biol
3:177–187
8 Management and Community Restoration
and the intervals would probably depend on the rainfall. With a reasonable schedule
of burning and reduced levels of herbivory, grasslands could remain as grasslands
and animal productivity could be sustained. The level of herbivory would certainly
have to be adjusted to area conditions especially rainfall.
Can woody legume and other woody plant savannas or woodlands be maintained
or restored to grasslands? This is a diffi cult question without easy answers. Yes it
can probably be done, but not cheaply. Two hundred to 300 or more years of excessive grazing and harvest cannot be overcome with one fi re followed by a return to a
previous ineffective management system. Recovery or return of a savanna or woodland to a grassland state will not be easy. The “spray and pray” philosophy of the
past did not and will not work.
The future of these woody legume communities or former grasslands is diffi cult
to predict, especially in our changing world. Secondary succession is occurring
or has occurred, and the communities will be different in the world of the future.
These communities are very dynamic and they are also economically, biologically,
and ecologically necessary and needed. Knowledge gained from observations and
experiments reported here and other places are critical in defi ning observations
and experiments needed in the future. The track through the future is not clear, but
each new discovery helps light the way.
References
Ansley RJ, Wiedemann HT (2008) Reversing the woodland steady state: vegetation responses during restoration of Juniperus -dominated grasslands with chaining and fi re. In: Van Auken OW
(ed) Western North American Juniperus communities: a dynamic vegetation type, vol 196.
Springer, New York, pp 272–290
Archer S (1994) Woody plant encroachment into southwestern grasslands and savannas: rates,
patterns and proximate causes. In: Vavra M, Laycock WA, Pieper RD (eds) Ecological implications of livestock herbivory in the west. Society for Range Management, Denver, pp 13–69
Archer SR, Schimel DS, Holland EH (1995) Mechanisms of shrubland expansion: land use, climate or CO 2 . Climate Change 29:91–99
Bahre CJ (1991) A legacy of change: historic human impact on vegetation on the Arizona borderlands. University of Arizona Press, Tucson
Bahre CJ (1995) Human impacts on the grasslands of southeastern Arizona. In: McClaran MP, Van
Devender TR (eds) The desert grassland. The University of Arizona Press, Tucson, pp
230–264
Bahre CJ, Shelton ML (1993) Historic vegetation change, mesquite increases, and climate in
southeastern Arizona. J Biogeogr 20:489–504
Browning DM, Archer SR, Asner GP, McClaran MP, Wessman CA (2008) Woody plants in grasslands: post-encroachment stand dynamics. Ecol Appl 18:828–944
Bush JK (2008) Soil nitrogen and carbon after twenty years of riparian forest development. Soil
Sci Soc Am J 72:815–822
Bush JK, Van Auken OW (1995) Woody plant-growth related to planting time and clipping of a
C-4 grass. Ecology 76:1603–1609
Campbell BD, Stafford-Smith DM, McKeon GM (1997) Elevated CO 2 and water supply interactions in grasslands: a pastures and rangelands management perspective. Global Change Biol
3:177–187
8 Management and Community Restoration