Tree-Grass Interactions in Savannas
Tóm tắt
Savannas occur where trees and grasses interact to create a biome that is neither grassland nor forest. Woody and gramineous plants interact by many mechanisms, some negative (competition) and some positive (facilitation). The strength and sign of the interaction varies in both time and space, allowing a rich array of possible outcomes but no universal predictive model. Simple models of coexistence of trees and grasses, based on separation in rooting depth, are theoretically and experimentally inadequate. Explanation of the widely observed increase in tree biomass following introduction of commercial ranching into savannas requires inclusion of interactions among browsers, grazers, and fires, and their effects on tree recruitment. Prediction of the consequences of manipulating tree biomass through clearing further requires an understanding of how trees modify light, water, and nutrient environments of grasses. Understanding the nature of coexistence between trees and grass, which under other circumstances are mutually exclusive or unequal partners, yields theoretical insights and has practical implications.
Từ khóa
Tài liệu tham khảo
Anderson RC, 1997, Savanna, Barren and Rock Outcrop Plant Communities of North America.
Archer S. 1994.Woody plant encroachment into southwestern grasslands and savannas: rates, patterns and proximate causes.InEcological Implications of Livestock Herbivory in the West, ed. M Vavra, W Laycock, R Pieper, pp. 13–68. Denver: Soc. Range Manage.
Archer S, 1995, Trop. Grassl., 29, 218
Archer S. 1996.Assessing and interpreting grass-woody plant dynamics.InThe Ecology and Management of Grazing Systems, ed. J Hodgson, A Illius, pp. 101–34. Wallingford, UK: CAB Int.
Bourliere F, ed. 1983.Tropical Savannas. Amsterdam: Elsevier. 730 pp.
Burgess TL. 1995.Desert grassland, mixed shrub savanna, shrub steppe, or semidesert scrub? The dilemma of coexisting growth forms.InThe Desert Grasslands, ed. MP McClaran, TR Van Devender, pp. 31–67. Tucson: Univ. Ariz. Press
Cole MM, 1986, The Savannas: Biogeography and Geobotany.
Escudero A, 1985, Oecol. Plant., 6, 73
Fulbright JE, 1987, Wildl. Soc. Bull., 15, 560
Gadgill M, Meher-Homji VM. 1985.Land use and productive potential of Indian savannas.InEcology and Management of the World's Savannas, ed. JC Tothill, JJ Mott, pp. 107–13. Canberra: Aust. Acad. Sci.
Gardener GJ, McIvor JG, Williams J. 1990.Dry tropical rangelands: solving one problem and creating another.InAustralian Ecosystems: 200 Years of Utilization, Degradation and Reconstruction, ed. DA Saunders, AJM Hopkins, RA How, pp. 279–86. Geraldton, West. Aust.: Ecol. Soc. Aust.
Gutierrez JR, 1979, Oecol. Plant., 14, 151
Harris DR, 1980, Human Ecology in Savanna Environments.
Hoffman MT, 1990, S Afr. J. Sci., 86, 462
Johnson RW, Tothill JC. 1985.Definition and broad geographic outline of savanna lands.InEcology and Management of the World's Savannas, ed. JC Tothill, JJ Mott, pp. 1–13. Canberra, ACT: Aust. Acad. Sci.
McClaran MP, 1989, Madroño, 36, 141
McPherson GR, 1991, Gt. Basin Nat., 51, 316
Merz RW, 1956, J. For., 54, 774
Noble JC, 1997, The delicate and noxious scrub: CSIRO research into native tree and shrub proliferation in the semi-arid woodlands of Eastern Australia.
Palaez DV, 1994, Oecologia, 81, 501
Pressland AJ, 1975, Aust. J. Bot., 23, 965
San José JJ, 1991, Acta Oecol., 12, 237
Scholes RJ, Hall DO. 1996.The carbon budget of tropical savannas, woodlands, and grasslands.InModelling Terrestrial Ecosystems, ed. A Breymeyer, D Hall, J Melillo, G Agren, pp. 69–100. Chichester: Wiley
Scifres CJ. 1980.Brush Management: Principles and Practices for Texas and the Southwest. College Station, TX: Texas A&M Univ. Press
Sinclair ARE. 1979.Dynamics of the Serengeti ecosystem.InSerengeti: Dynamics of an Ecosystem, ed. ARE Sinclair, M Norton-Griffiths, pp. 1–30. Chicago: Univ. Chicago Press
Stewart OC. 1955.Fire as the first great force employed by man.InMan's Role in Changing the Face of the Earth, ed. WL Thomas, pp. 115–33. Chicago, IL: Univ. Chicago Press
Strang RM, 1969, Com. For. Rev., 48, 26
Tothill JC, Mott JJ, eds. 1985.Ecology and Management of the World's Savannas. Canberra: Aust. Acad. Sci. 384pp.
Walker BH, 1987, Determinants of Tropical Savannas.
Walker BH. 1987.A general model of savanna structure and function.InDeterminants of Savannas, ed. BH Walker, pp. 1–12. Paris: IUBS
Walter H, 1971, Ecology of Tropical and Subtropical Vegetation.
Werner PA, 1991, Savanna Ecology and Management: Australian Perspectives and Intercontinental Comparisons.
Westoby M, 1979, Israel J. Bot., 28, 169
Young MD, 1993, The World's Savannas: Economic Driving Forces, Ecological Constraints and Policy Options for Sustainable Land Use.