Study Area

Nova Vida Ranch (Figure 9.1) covers an area of 22,000 ha, and is a mixture of native forest and well-managed pastures of various ages. The climate of the region is humid tropical, with a dry season from May to September. Annual rainfall is 2200 mm. Annual mean temperature is 25.6°C. Mean temperature for the warmest and coolest months varies by less than 5°C, and mean annual relative humidity is 89% (Bastos and Diniz, 1982). Soils are classified as Podzolicos Vermelho-Amarelo (Red-Yellow Podzolic) in the Brazilian classification scheme, and as Ultisols (kandiuldults) in the U.S. soil taxonomy (Moraes et al., 1995). This soil type covers about 35% of the Brazilian Amazon Basin (Bernoux et al., 1998a, 1998b; Cerri et al., 1999).

The native forest vegetation of the ranch is classified as "open humid tropical forest," with large numbers of palms, mainly Orbignya barbosiana, Oenocarpus spp., Jessenia bataua, Euterpe precatoria, and Maximiliana regia (Pires and

Jessenia Bataua Images
Figure 9.1 Location of Nova Vida Ranch, Rondonia State, Amazon region, Brazil.

Prance, 1986). Selective logging removed three or four economically valuable trees per hectare in the forest sites (Piccolo et al., 1996). The pasture sites were developed by a slash-and-burn technique used to clear the original forest, and then establish the grass species (Graga et al., 1999). This was done by cutting brush in March, followed by tree harvest in June and July. The remaining trees and bush were burned at the beginning of the next rainy season in September or early October, followed by seeding of pasture grasses. All pastures were created in a similar manner, and after grass establishment pasture areas have been well managed, that is, adequate grazing control (maximum of two animals per hectare) and frequent control of weed invasions. The pastures cleared in 1911, 1972, 1987, and 1989 are dominated by brachiarao (Brachiaria brizantha), and the pastures cleared in 1951, 1979, and 1983 are dominated by coloniao (Panicum maximum). Mechanized agricultural practices or chemical fertilizers were not used on any of the pastures (Steudler et al., 1996).

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