Three Alternate Land Use In Dryland Ecosystems
Consistent with the policy of conservation and desirability of preserving the integrity of the ecosystem, the alternate land use systems could be classified into
i) agro forestry
ii) pastoralism and
iii) tourism which includes wild life.
Agro forestry systems of land use:
Agro forestry is a collective term for a land use system in which woody perennials (trees and / or shrubs) are eliberately mixed on the same land management unit as crop and / or animals either in some forms of spatial arrangement or in time sequence. An ideal agro forestry system should result in a sustainable increase in overall production using management practices compatible with social cultural and economic of the local population.
In agro forestry land use systems, there are three basic sets of elements of components that are managed by man viz. tree, the herb (agricultural crops including pasture species) and the animal. This leads to a simple classification of agro forestry systems as given below.
Agri silvi cultural – Crops and trees including shrubs / vines / tress.
Silvi pastorl – Pastures / animals and trees.
Agro silvopastoral – Crops / pastures / animals / trees
Agrihorticulture – Crops / fruits species
Silvi – horticulture – Trees / fruit species
Silvi Horti pastoral – Trees / fruit species / animal / pastures.
Agri Silvi system:
Agri silvi cultural system could be practiced in areas where wood lands can be created. The planting consists of both annual crops and perennial trees. This type of approach is most commonly observed in the cultivated areas. The perennial tree species are planted in a single row or multiple of rows in a strip at a interspaces distance of 15 – 40 m between two strips. The interspaces are utilized for growing annual / seasonal crops. The preference of choice for tree selection may lie in Acacia spp. Azadirachta indica, Dalbergia sissoo; Eucalyptus spp; Casuarinas spp; Albizzia spp; and Leucaena leucocephala, prosopis spp and caliandra spp. Growing of perennial tree species on bunds / strips may also act as wind breaks in areas where high wind velocity is a problem resulting in wind erosion and desiccation of soil moisture. Certain tree species offer the possibility of providing at least a portion of optimum crop nutrients by natural leaf drop or by lopping for purposes of green leaf manuring. This includes both fixed nitrogen as well as other nutrients recycled from the deeper soil depth. This is especially true with Acacia albida which when matures (after 3 years) is said to be deciduous in the Kharif season. As such it offers less competition for light and moisture at the time when crops need them most.
In India agriculture and forestry have co – existed for many years in close proximity. Agro – forestry systems of land use are not new to our rich heritage. Farmers from time immemorial have been growing useful tree species with agricultural crops which used to supply fodder, fuel and small timber for himself and his live stock. The best examples available are ; growing of Prosopis cineraria (Khajri) with agricultural crops in Rajasthan and in black soils of Northern Karnataka and the other parts of the country. The other practices then prevailing where growing of perennial tree species such as Acacia’s neem mango tamarind on farm boundaries.
Agro forestry offers a good scope for more efficient use of land; water, other natural and human resources. The main advantages of this system would be:
i) Progressive land improvement by providing vegetation cover and brief to bring about soil and water conservation and production of organic material for enrichment of soil.
ii) Recycling of plant nutrients is possible due to roots of perennial tree species penetrating deep into the soil and absorbing the plant nutrients and depositing on the soil surface through leaf litter.
iii) Perennial tree species are photosysnthetically active through out the year and hence produce large quantities of biomass.
iv) Legumes plants may provide for fixation of atmospheric nitrogen and thereby enrich the site conditions and
v) Provide employment opportunities to the people.
Structural basis of classification of agro forestry systems:
Structure of the system can be defined in terms its components (constituents) and the expected roles (functions) of each (manifested in terms of outputs). It is not only the nature of components that is important but also their arrangement.
Silvi – Horti / agro – Horti system:
The concept of silvi – Horti / agro – Horti or combination of agricultural crops, perennial tree and fruit species could profitably be adopted in both arable and non arable marginal and sub – marginal lands.
Semi wild but useful fruit species such as cashew, Ber, annonaceas fruit species, Chiranji, phalsa carrisa, mango, sapota, guava, tamarind and jack fruit trees are planted in regular strips or inter planted with silvi component. In areas receiving higher rainfall of 1000 m and above coconut can be planted as in being practiced in coastal Karnataka and Kerala. In the agro Horti – silvi system of land use the distance between the two horticultural plants within the strip may be quite apart to avoid competition. The inters trip space between the two horticultural plants can be used for planting fast growing economic silvi – cultural species such as leucaena casuarinas, Dalbergia teak and albizza. The tree plants are cut for wood after 4 – 6 years so that the competion could be minimized. The idea behind planting tree species as an intercrop with horticultural plants is to obtain biomass production before horticultural plants attain full growth, and later to obtain fodder or green manure material by frequent cutting and create thicker vegetation for better soil dwater conservation.
Many plant species of different heights and architecture, planted in an orderly manner form a multi stored and close cover vegetation with different biological cycles in agro – Horti / agro – Horti – silvi system. In coconut and areca nut plantations other perennial or semi perennial and / or annual crops like tapioca, elephant foot yam, dioscrea, turmeric, ginger, colocasia, sweet potato, groundnut, vegetables and pulses, pineapple, bana, papaya can possible by grown. High density multi species systems are capable of generating high biomass; high income and can meet various needs of the farmer.
Silvi pastoral system of land use:
The fodder requirement for the growing cattle population in the country by 2000 – AD is expected to be around 700 mit against the present supply of 540 m.t. The gap will be of the order of 250 m.t. and to meet this demand the country will require 10 m ha of additional area. To achieve this every demanding increase of fodder the area under soil erosion problems, marginal and sub marginal lands waste lands village grazing areas need to planted with suitable forage species or in combination with economic perennial tree species preferably tree species yielding fodder.
In such land use systems, ideal species of woody perennials should be fast growing, hardy, with wide ecological aptitude, tight crown with multilayer branching and leaf orientation and of multiple use to the rural population. The forage component need to be very hard, easily colonising, palatable, nutritious and with strong establishment through roots or self sown seeds. For arid and semiarid areas species like Acacia tortillas. Albizzia amara, Hardiwickia binata, ledcaena leucocephala with Cenchrus ciliaris, Cenchrus setigerus, Dichanthium annufatum chresopogon fulvus sehima nervosum etc find greater adaptability. Legume species such as stylosanthes spp., have been found very versatile. On difficult sites Desmodium, Alcidcarpus and sesbania would promise as primary colonisers. Tourism and wild life system of land use.
Tourism as a means of expoiting and developing the potential of arid and semiarid areas needs careful consideration. The wildlife fauna of the arid region is unique resource and need attention for their conservation. It would help to develop more and more desert parks which attract the tourism and provide employment opportunities.