ABSTRACT
Summary In the tropics, grasslands or grazing lands are found where the forest vegetation climax has been subjected to fire, grazing, felling, or other disturbances. Grazing lands in the tropics form various ecosystems under the major climatic types. Delineation of such ecosystems is possible through remnants of the climax vegetation of undisturbed or least-disturbed areas. Several subecosystems exist as serai stages under each ecosystem, the floristic composition of which is a reflection of the edaphic and soilmoisture-fertility conditions. Biological production in terms of energy for grazing animals varies among these ecosystems and subecosystems. Reconstruction of the adaptable competitive flora with woody browse components reveals significant upward trends in harvestable biomass production (energy) for grazing animals. In the evolution of new competitive and adaptive ecosystems in grasslands, examples of Indian work are cited. Natural grassland ecosystems in India provided much less energy than the reconstructed adaptive, floristic combinations with a browse component. The latter systems yielded more than double the energy of the others. Additionally, the complementary and associative effects of the woody browse component in the reconstructed ecosystems influence the micro-environmental changes beneficial to the herbaceous component of the system. Several reconstructed adaptable competitive floristic ecosystems, even for microsites of a major ecological region, are possible and are suggested to yield higher biomass. For ecosystems — namely, Themeda-Arundinella, Phragmitis-Saccharum-Imperata, Dichanthium-Cenchrus-Lasiurus, and Sehima-Dichanthium — provided energy to the extent of 1,700, 3,400, 2,215, and 2,550 kcal/m2/yr (in the second case, of course, not all is consumable because of coarseness). The reconstructed adaptable and competitive ecosystem with woody browse provides energy as high as 3,697 kcal/m2/yr. When compared with desert grasslands, low mountain, and mixed prairies, these reconstructed adaptive competitive ecosystems provided far more energy. Tropical and subtropical grazing-land ecosystems could be usefully modified by either substitution or integration of several new adaptable ecosystems with browse as a component. Such studies can be extended to the waste areas of the tropics (over 944 million ha in Africa, Latin America, and the Indian subcontinent; several hundred million ha in Southeast Asia; and around 50% of the grazing areas of Australia). This paper emphasizes the utilization of a combined herbage-browse pastoral system in the evolution of competitive adaptive grazing-land ecosystems.
