41
logarithmic relationship was found ( y = −0.27ln( x ) + 0.612, R
2 = 0.75, P = 0.0039).
As B. curtipendula belowground or root dry mass increased, total P. glandulosa dry
mass decreased until it reached approximately zero at a B. curtipendula belowground or root dry mass of approximately 36 g/100 cm
2 .
There are additional fi eld and greenhouse experiments that should be completed
to further our understanding of the interactions of both C 3 and C 4 grasses and the
woody legumes and other woody plants that are and have been encroaching into arid
and semiarid tropical and subtropical grasslands around the world. Is competition
important in the encroachment or invasion of these grasslands? Yes, it is important,
but it is not the only factor that should be considered. The grasses suppress or reduce
the growth of the woody legumes and other encroaching species. We have seen this
in all the experiments that we have completed. However, there were no woody
legume mortalities. Another factor is important in preventing encroachment of
woody plants, including the woody legumes into the arid and semiarid grasslands.
That factor seems to be fi re, both intensity and frequency.
References
Begon M, Townsend CR, Harper JL (2006) Ecology: from individuals to ecosystems, 4th edn.
Blackwell, Malden, MA
Bush JK, Van Auken OW (1989) Soil resource levels and competition between a woody and herbaceous species. Bull Torrey Bot Club 116:22–30
Bush JK, Van Auken OW (1991) Importance of time of germination and soil depth on growth of
Prosopis-glandulosa (leguminosae) seedlings in the presence of a C-4 grass. Am J Bot
78:1732–1739
Bush JK, Van Auken OW (1995) Woody plant-growth related to planting time and clipping of a
C-4 grass. Ecology 76:1603–1609
Cohn EJ, Van Auken OW, Bush JK (1989) Competitive interactions between Cynodon-dactylon
and Acacia-smallii seedlings at different nutrient levels. Am Midl Nat 121:265–272
Correll DS, Johnston MC (1979) Manual of the vascular plants of Texas. The University of Texas
at Dallas, Richardson, TX
Gould FW (1969) Texas plants: a checklist and ecological summary. Texas Agricultural Experiment
Station Bull, College Station, TX
Grace JB (1995) On the measurement of plant competition intensity. Ecology 76:305–308
Grace JB, Tilman D (1990) Perspectives on plant competition. Academic, New York
Grime JP (1979) Plant strategies and vegetation processes. Wiley, New York
Harper JL (1977) Population biology of plants. Academic, New York
Taylor FB, Hailey RB, Richmond DL (1966) Soil survey of Bexar County, Texas. USDA, Soil
Conservation Service, Washington
Twolan-Strutt L, Keddy PA (1996) Above- and belowground competitive intensity in two contrasting wetland plant communities. Ecology 77:256–270
Van Auken OW (1994) Changes in competition between a C 4 grass and a woody legume with differential herbivory. Southwestern Nat 39:114–121
Van Auken OW (2000) Shrub invasions of North American semiarid grasslands. Annu Rev Ecol
Syst 31:197–215
Van Auken OW (2009) Causes and consequences of woody plant encroachment into western North
American Grasslands. J Environ Manage 90:2931–2942
References
logarithmic relationship was found ( y = −0.27ln( x ) + 0.612, R
2 = 0.75, P = 0.0039).
As B. curtipendula belowground or root dry mass increased, total P. glandulosa dry
mass decreased until it reached approximately zero at a B. curtipendula belowground or root dry mass of approximately 36 g/100 cm
2 .
There are additional fi eld and greenhouse experiments that should be completed
to further our understanding of the interactions of both C 3 and C 4 grasses and the
woody legumes and other woody plants that are and have been encroaching into arid
and semiarid tropical and subtropical grasslands around the world. Is competition
important in the encroachment or invasion of these grasslands? Yes, it is important,
but it is not the only factor that should be considered. The grasses suppress or reduce
the growth of the woody legumes and other encroaching species. We have seen this
in all the experiments that we have completed. However, there were no woody
legume mortalities. Another factor is important in preventing encroachment of
woody plants, including the woody legumes into the arid and semiarid grasslands.
That factor seems to be fi re, both intensity and frequency.
References
Begon M, Townsend CR, Harper JL (2006) Ecology: from individuals to ecosystems, 4th edn.
Blackwell, Malden, MA
Bush JK, Van Auken OW (1989) Soil resource levels and competition between a woody and herbaceous species. Bull Torrey Bot Club 116:22–30
Bush JK, Van Auken OW (1991) Importance of time of germination and soil depth on growth of
Prosopis-glandulosa (leguminosae) seedlings in the presence of a C-4 grass. Am J Bot
78:1732–1739
Bush JK, Van Auken OW (1995) Woody plant-growth related to planting time and clipping of a
C-4 grass. Ecology 76:1603–1609
Cohn EJ, Van Auken OW, Bush JK (1989) Competitive interactions between Cynodon-dactylon
and Acacia-smallii seedlings at different nutrient levels. Am Midl Nat 121:265–272
Correll DS, Johnston MC (1979) Manual of the vascular plants of Texas. The University of Texas
at Dallas, Richardson, TX
Gould FW (1969) Texas plants: a checklist and ecological summary. Texas Agricultural Experiment
Station Bull, College Station, TX
Grace JB (1995) On the measurement of plant competition intensity. Ecology 76:305–308
Grace JB, Tilman D (1990) Perspectives on plant competition. Academic, New York
Grime JP (1979) Plant strategies and vegetation processes. Wiley, New York
Harper JL (1977) Population biology of plants. Academic, New York
Taylor FB, Hailey RB, Richmond DL (1966) Soil survey of Bexar County, Texas. USDA, Soil
Conservation Service, Washington
Twolan-Strutt L, Keddy PA (1996) Above- and belowground competitive intensity in two contrasting wetland plant communities. Ecology 77:256–270
Van Auken OW (1994) Changes in competition between a C 4 grass and a woody legume with differential herbivory. Southwestern Nat 39:114–121
Van Auken OW (2000) Shrub invasions of North American semiarid grasslands. Annu Rev Ecol
Syst 31:197–215
Van Auken OW (2009) Causes and consequences of woody plant encroachment into western North
American Grasslands. J Environ Manage 90:2931–2942
References