Classification of Agro-forestry System on Socio-economic Basis
Based on such socioeconomic criteria as scale of production and level of technology input and management, agroforestry systems have been grouped into three categories
a) Commercial, b) Intermediate and c) Subsistence Systems
Commercial Agro-Forestry Systems:
The term commercial is used whenever the sale of the production of the output (usually a single commodity) is the major aim of the system the scale of operations is often moderate to large and land ownership may be government, corporate or private. Commercial production of shade-tolerating plantation crops such as coffee, tea and cocoa under over storey shade trees; rotational timber/food crops systems in which a short phase of food-crop production is used as a silvicultural method to ensure establishment of the timber species (various forms of taungya); commercial grazing and ranching under large-scale timber and pulp plantations etc.
Intermediate Agro-Forestry Systems:
Intermediate Agro-Forestry systems are those between commercial and subsistence scales of production and management, production of perennial cash crops and subsistence crops undertaken on medium to small size farms wherein the cash crops cater for the cash needs and the food crops meet the family’s food needs.
Subsistence Agro-Forestry System:
Subsistence Agro-Forestry systems are those wherein the use of land is directed towards satisfying basic needs and is managed mostly by the owner/occupant and his family. Cash crops, including sale of surplus production of commodities, and all forms of traditional shifting cultivation are the most widespread examples
Ecological Classification of Agro-forestry Systems:
Based in the major agro ecological zones, agroforestry systems are grouped into the following categories:
1) Humid/sub humid lowlands,
2) Semi-arid/arid lands,
3) Highlands
Agroforestry Systems in Humid/Sub Humid Lowlands:
This is characterized by hot humid climate for all or most of the year and an evergreen or semi – evergreen vegetation. The lowland humid and sub humid tropics (commonly referred to as the humid tropics) are by far the most important ecological region in terms of the total human population it supports, extent of area and diversity of agro forestry and other land-use systems. Because of climatic conditions that favour rapid growth of a large number of plant species, various types of agroforestry plant associations can be found in areas with a high human population, e.g. various forms of home gardens, plantation crops with combination and multilayer tree gardens. In areas of low population density, trees on rangelands and pastures, other silvopastoral systems, improved fallow in shifting cultivation and multipurpose tree wood lots etc. are the major agro forestry systems.
Semi-Arid and Arid Lands:
This region is characterised by rainfalls confined to 9-12 hours per day in July-Sept 2 to 4.5 wet months, vapour pressure deficit ranging from 9 mb in Jan to 30 mb in April-May, solar radiation incidence (400-500 cal/cm2/day), high wind velocity (20 km/hour), high potential evapotranspiration (6 mm/day) and high mean Aridity index (70-74.8%).
Agroforestry Systems in Tropical Highlands:
This area is characterised by uneven topography, varying levels of rainfall, degraded and shallow lands at high altitude to deep rich soils in valleys and great climatic variations. The Himalayan region is an excellent example of this type of area. Land use problems in the highlands are similar to those in humid or dry lowlands, depending on climate, with the addition that sloping lands and step terrier make soil erosion a major concern.