ABSTRACT
World population is now 4.3 billion. According to United Nations experts, this number will triple during the next century, greatly accelerating the demand for food and energy resources. Thus, it is highly necessary to search for crops adapted to a wide range of climatic zones and for genotypes that will produce maximum yields. Many tropical savannahs are now used predominantly as rangelands. This situation is being modified in some regions, such as the Venezuelan Llanos, where the farmers are developing the integrated systems of production that will permit optimal use of the spatial and temporal heterogeneity of the savannahs. The activity of cultivated communities in the Venezuelan Llanos was evaluated using the mass balance method and micrometeorological measurements. The procedures involved estimations of the carbon dioxide and water vapor exchange rates, and source and sink strength distributions within the communities.
