Management changes over time. By definition, agroforestry systems include
multiple components with different life cycles. In some systems, the tree
component may be fixed over time but the crop component may vary every
year. Crop and tree components may be used for several functions (wood,
fruit or leaf products, soil protection, fencing, staking, etc.) either simultaneously
or with change over time. System objectives and management may vary
with rainfall conditions. For example, shrubs generally cut for mulching crops
may be used for livestock feed in drought years. Unlike crops, trees can be
manipulated or managed as individuals. In addition such management influences
function, performance and long-term growth. Component and factor
interactions depend on complex and poorly understood factors such as
allelopathy, effects on pest populations, or resource-sharing. Tree-crop interfaces
for most species combinations are poorly understood ]Huxley et al.,
1989].