Social forestry plantations are usually taken up in non-forest areas which are not suited for agriculture or where agriculture is not practiced e.g., denuded wastelands, erosion prone areas, road side strips, canal bank strips, bunds, etc.
Criteria for Selection of Suitable Trees for Social Forestry:
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i. Greater photo synthetic efficiency – mainly for production of more biomass
ii. Improved capability of fixing biological nitrogen
iii. Inbuilt system for genetic improvement
iv. More resistance towards biological and environment stresses
v. Better capability for nutrient and water uptake, reduced losses of nitrogen fertilizer from the process of nitrification and denitrification.
vi. Relatively fast growth
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vii. Multiple uses
(1) Severely Eroded Mountain Slopes:
i. Locality Factors:
Soil is poor, shallow and stony. Excessive erosion has washed away the topsoil. Very often, such areas are exposed to severe wind erosion. Excessive runoff results in low soil moisture content. Grazing incidence is very high, hence the seedlings need adequate protection.
ii. Preparation:
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Contour trenches along the contours are usually made on slopes up to 20 per cent. Patches or pits are adopted in very rocky areas.
iii. Choice of Species:
Different species are adopted under varying conditions viz., Pinus roxburghii, Acacia catechu (Moist sub-tropical); Acacia catechu, A. modesta, Prosopis juliflora, Robinia psedoacacia (Dry sub-tropical); Pinus wallichiana, Cedrus deodara (Temperate) and Eucalyptus, Prosopis spp. (Peninsular India).
(2) Ravines:
Extensive ravine lands occur in the Chambal and Yamuna river catchments, encompassing parts of U.P., M.P., Rajasthan and Haryana.
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i. Locality Factors:
Soil varies from sandy to stiff clayey with enough lime to lead to the formation of a kankar pan. This obstructs the rain water from infiltrating deeper into the soil. The average annual rainfall in the region is 700 mm with frequent drought years having precipitation of less than 200 mm. Soluble salts are concentrated just below the surface giving rise to chronic saline alkalinity.
ii. Preparation:
Bunds are constructed in the catchment areas for safe disposal of the excess water. Staggered trenches are dug at a spacing of 3.5 m x 4.5 m on the same contour line or lines which are 4.5 m apart. Continuous trenches are made in the valley areas with a safe passage for water provided at regular intervals.
iii. Choice of Species:
Acacia catechu, Melia azedarach, Prosopis juliflora, Dalbergia sissoo, Pongamia pinnata, Albizia spp. (sandy soil); Acacia arabica, A. leucophloea, Terminalia ajuna, Prosopis spicigera (Clayey soil).
(3) Grasslands:
i. Locality Factors:
Soil aeration, drainage and biological condition are largely poor. Dense roots may be formed by some grasses like Imperata and Ischaemum. These are difficult to eradicate. The fast growth rate of grasses makes it difficult for plantations to come up unassisted by frequent and heavy weeding. Grasses also increase the incidence of grazing, fire and frost.
ii. Preparation:
If possible, the entire area should be subjected to deep ploughing in strips.
iii. Choice of Species:
Acacia catechu, A. arabica, Ailanthus excelsa, Eucalyptus hybrid, Dalbergia sissoo, Bombax ceiba (U.P. terai); Cupressus torulosa, Populus ciliata, Robina pseudoacacia, Grevillea oppositifolia, Pinus roxburghii, P. wallichiana (Western Himalaya); Morus laevigata, Terminalia myriocarpa (N.E. India).
(4) Abandoned Fields:
i. Locality Factors:
Soil may usually be poorly fertile because of repeated raising of agriculture crops without manuring and top soil being washed away. Drainage, aeration and moisture content of the soil are also poor. The condition becomes further worse, if the abandoned field was previously used for storing water and puddling for rice cultivation.
Because of the fact that the land remained under cultivation for a long time, soil organisms beneficial for tree growth may have disappeared. Weeds may be heavy if the period of time between cultivation and tree raising is long.
ii. Preparation:
Soil digging may be carried out in strips. Care should be taken to ensure that the time lag between abandoning of cultivation and plantation is as short as possible. If conditions permit, ploughing of the entire area should be carried out by tractor.
iii. Choice of Species:
Mixed plantations are preferred to monoculture. Eucalyptus hybrid, Bombax ceiba, Dalbergia sissoo, Terminalia tomentosa, Acacia catechu, Prosopis juliflora (plains of North India).
(5) Dry Areas with Irrigation:
Dry areas with irrigation are available for social forestry plantation in parts of Punjab, Haryana, Western U.P., Rajasthan and Tamil Nadu.
i. Locality Factors:
Soil conditions vary from sandy to clayey with high alkalinity. Kankar pan may also occur. Maximum temperature in the region is 45°C and hot, dusty winds blow during the summer. The temperature falls down considerably during the winter months, when conditions of frost may occur.
ii. Preparation:
The area to be planted will have to be leveled and stumps removed so as to bring about effective irrigation. In Punjab and Haryana, ploughing is done by caterpillar tractors, following which the area is divided into large, irrigation blocks. Trenches about 30 x 30 x 30 cm are formed at a spacing of 3 m. Irrigation is usually done by flooding and care is taken to ensure that there is no over flooding.
iii. Choice of Species:
Tamarix spp., Acacia catechu (poor kankar soil), Prosopis juliflora, P. spicigera. Cassia spp., Eucalyptus (soils free of salts); Acacia catechu, A. arabica, Bombax ceiba, Morus alba, Syzygium cumini, Eucalyptus, Populus ciliata, Dalbergia sissoo (Mixed plantation).
(6) Dry Areas without Irrigation:
i. Locality Factors:
Dry areas are generally subject to serve wind and water erosion. Annual rainfall is below 900 mm, areas with minimum precipitation experience only a few occasional showers amounting to about 200 mm each year.
During summers, the temperature may soar up to 45°C, often accompanied by hot, dusty winds. Winter frosts are common in many areas. There is a great pressure of humans and animals on the land and this poses a severe threat to any plantation programme that may be taken up.
ii. Preparation:
Soil is dug as deep as possible. Contour trenches are formed in sloping areas. The dug up soil is heaped to form a ridge along the portion of the trench. Care is taken so as not to heap the soil on a hard surface, else on reaching hard ground, the roots will tend to curl sideways.
iii. Choice of Species:
Fast growing, drought and frost resistant species viz., Acacia arabica, A. leucophloea, Dalbergia sissoo, Albizia lebbeck, Zizyphus jujuba, Cassia siamea, Casuarina equisetifolia, Pongamia spp., A. catechu, A. Senegal, Eucalyptus, Ailanthus excelsa, Holoptelia integrifolia, Cassia fistula, Prosopis juliflora, Anacardium spp. should be selected for such difficult areas.
(7) Coastal Sandy Area:
i. Locality Factors:
Soil is in the form of pure sand which keeps on shifting under the pressure of wind. Moisture retentively is zero and any precipitation seeps into the ground almost immediately. Water table occurs to within a few meters from the surface and wells can easily be dug up for irrigation. Underground water is usually brackish.
Rainfall is fairly heavy and relative humidity high. Strong winds blow across these areas, often carrying salt with them. Further, there is considerable human and animal pressure on the land.
ii. Preparation:
Pits of 30 cm (diameter) x 30 cm (depth) with spacing varies from 1.5 m x 1.5 m to 3.5 m x 3.5 m, depending upon the local conditions and the species being raised. If the soil is less sandy, ploughing by tractor may also be done.
iii. Choice of Species:
Casuarina equisetifolia, Acacia auriculiformis, Eucalyptus hybrid, Pongamia pinnata.
(8) Inland River Sands:
i. Locality Factors:
Soil comprises of almost pure sand which is of unstable nature and deficient in mineral nutrients. One redeeming feature is that the ground water table is not very low and hence there is a possibility of irrigation by underground water. Very high temperatures are experienced during the summer months, when the mercury may rise up to about 45°C. Severe frost conditions occur during winters.
Average annual rainfall is moderate, with bulk of the precipitation being received during the monsoons. Atmospheric humidity is low. There is a heavy human and animal pressure on the land. High grazing incidence leaves the land barren.
Whatever vegetation exists is consumed either by man in the form of fuel or by animals as fodder. Riverine vegetation may occur along the fringes of the sandy wastes and these too are under heavy biotic pressure so much so that such forests have become highly depleted.
ii. Preparation:
Under certain conditions the sands are unstable and hence there is a need to stabilize it. This may be brought about by introducing certain grasses and shrubs (e.g. Saccharum, Aristidis etc) so as to stabilize any prospective planting site. Later on, trenches and pits are dug for planting.
iii. Choice of Species:
Species capable of growing under extremely harsh conditions viz., Acacia catechu, Albizia procera, Melia azedarach, Ailanthus excelsa, Ricinus communis, A. arabica, Azadirachta indica, Pongamia pinnata, Prosopis juliflora, Haplophragma spp. are selected.
(9) Arid (Desert) Areas:
Tropical desert comprises about 3.2 lakh sq. km area in the country. About three fifth of this area is in Rajasthan and the remaining in small pockets in Gujarat, Punjab, Haryana, Maharashtra, Andhra Pradesh and Karnataka.
i. Locality Factors:
Extremely dry climatic conditions prevail. During summers, the temperature may rise above 45°C. Very often, very strong, hot and dust laden winds blow across the countryside. On the other hand, during winters the temperature may fall to 3°C and conditions of severe frost occur.
There is usually a sudden diurnal variation of temperature. Precipitation is extremely low and erratic. Relative humidity remains very low for a major part of the year. Soil varies from pure sand to sandy. The land is subject to heavy human and animal pressure.
ii. Preparation:
Immediately after a particular area is available for planting, it is closed against entry by humans and animals. Mulching is usually done to stabilize the area.
iii. Choice of Species:
Prosopis juliflora, P. spicigera, Acacia arabica, A. Senegal, Ricinus communis, A. catechu, Zizyphus spp., Albizia lebbeck. However, before raising tree species, certain herbs and shrubs viz., Zizyphus nummularia, Cassia auriculata, Lasiurus hirsutus, Tamarix articulata, Calligonum polygonoides, Panicum antidotale, Saccharum munja may be introduced.
(10) Wind Breaks and Shelterbelts:
i. Wind Breaks:
Windbreak is a protective plantation in a certain area, against strong winds. It is usually comprised of a few rows of trees (or shrubs) spaced 0.5 to 2.5 m apart. Usually wind breaks are created around fields which are lashed by severe winds. In certain cases, 1 to 1.5 m high earthen ridges are formed and grasses like Saccharum spp are planted. Once these ridges have become stabilized, planting of trees is done and the spacing varies with the species.
ii. Shelterbelts:
Shelterbelt is a wide zone of trees, shrubs and grasses, planted in rows, usually at right angles to the direction of the prevailing winds.
The main objectives are:
i. To deflect the air currents
ii. To reduce the velocity of the prevailing winds
iii. To provide general protection to the leeward areas against the effects of wind erosion
iv. To protect the leeward areas from the desiccating effects of hot winds
The following are the main characteristics of shelterbelts:
i. Shape and Composition:
Shelterbelts have a typical triangular shape. This can usually be brought about by raising tall trees in the centre.
ii. Density and Width:
A certain degree of penetration by winds is planned, as by raising a solid wall, the protection decreases very fast on the leeward side. Shelter belts of up to 50 meters width are considered ideal under Indian conditions.
iii. Height and Spacing:
The ratio of height and width should roughly be 1:10. However, this figure may vary with local conditions.
iv. Orientation:
Orientation of the shelterbelt depends upon the direction and velocity of the prevailing winds. Shelterbelts may be raised in quadrangles if wind directions tend to change very often.
v. Length:
Length is an important consideration so far as shelter belts are concerned, because at the fringes of these zones eddies are formed and this results in an increase in the wind velocities. The minimum length of a shelterbelt should be about 25 times its height.
vi. Choice of Species:
a. Grasses:
Saccharum spontaneum, Panicum antidotale, S. munja, Cenchrus spp.
b. Shrubs:
Calotropis procera, Clerodendron phlomoides, Cassia auriculata, Dodonaea viscosa
c. Trees:
Acacia Arabica, Capparis aphylla, A. leucophloea, Dalbergia sissoo, Lannea coromandelica, Tamarix articulata, Eucalyptus spp., Parkinsonia aculeata, P. spicigera.
(11) Roadside Strips:
Large strips of land lies barren along the roads. Emperor Ashoka was the first Indian King who raised trees along roadsides. In modern India, Chaturvedi drew the attention of the government towards this aspect in 1938. Since then, millions of trees have been raised along national and state highways and other roads all over India.
i. Locality Factors:
Soil conditions usually vary from sandy to stiff clay. Borrow pits upset the natural drainage and may result in conditions of water logging. Climatic conditions vary from area to area through which the roads pass. Usually very high summer temperatures are experienced. Bulk of the precipitation is received during the monsoons.
Pressure of human population is very severe. Lopping for fodder and fuel wood is a common feature. Owners of cattle, goats, cows, sheep, buffaloes, camels, etc. let loose their animals to graze upon these areas.
ii. Preparation:
Pits of 60 cm x 60 cm x 45 cm are dug during the winter months when the soil is easy to dig. Ridges may have to be formed in area of water logging. Pits are dug in 6 to 10 rows on both sides of the road. In certain water logged areas of northern India, small mounds of earth are formed in which Eucalyptus is planted. The pits are so dug that they are exactly opposite to each other on either side of the road.
iii. Choice of Species:
Species to be raised should be hardy, evergreen or winter deciduous, wind firm and fast growing at least in the early stages. Some suitable species are Acacia Arabica, Azadirachta indica, Albizia procera, Ficus bengalensis, Mangifera indica, Cassia fistula, Populus spp., Bauhinia variegata, Eucalyptus spp, Ficus glomerata, Tamarix articulata, Cassia javanica, Delonix regia, Jacaranda ovalifolia.
(12) Railway Line Strips:
i. Locality Factors:
Soil conditions vary from sandy to stiff clayey. There are also vast stretches of user land, which have formed due to alkalinity. Biotic pressure on the neighbouring forests is severe. Lopping for fodder and fuel wood is very common.
ii. Preparation:
Trenches are dug up in areas where sowing is to be carried out whereas, pits are dug in areas to be planted. Care is taken to ensure that the first row is at a minimum distance of 6 m from the centre of the track or at the toe of the embankment (whichever is more).
No preparation needs to be done on inner portions of curves or near level crossing as raising plantations in such areas will cause a traffic hazard and hamper visibility. Similarly, trees are not to be raised within a distance of about 200 m on either side of railway signals.
iii. Choice of Species:
Hardy species viz., Acacia catechu, Azadirachta indica, Eucalyptus spp., Cassia fistula, Ficus bengalensis, Jacaranda ovalifolia, Madhuca indica, Prosopis juliflora, A. arabica, Albizia procera, Delonix regia. Cassia javanica, Ficus infectoria, Populus spp., Mangifera indica, Terminalia arjuna are usually selected.
(13) Canal Banks:
i. Locality Factors:
Soil conditions vary from area to area. Usually, these may vary from sandy to clayey. In certain localities, usar soil may have formed due to seepage from the canal. Seepage may also result in conditions of water logging in the canal bank strips. As the canals usually run through agricultural areas where there are practically no forests, biotic pressure on canal bank plantations is very severe.
ii. Preparation:
a. Haryana Technique:
The first row is raised along the outer edge of the canal road, with plants about 6 m apart.
b. Uttar Pradesh Technique:
The strip on the left bank is planted whereas that on the right bank is sown. Pits for planting are of 60 x 60 x 60 cm size.
c. Rajasthan Technique:
Planting is to be done on either banks and spacing adopted is 3 x 4 m.
iii. Choice of Species:
Hardy species viz., Acacia arabica, Delonix regia, Ficus bengalensis, Jacaranda ovalifolia, Robinia pseudoacacia, Swietenia macrophylla, Cassia javanica, Eucalyptus spp., Populus spp., Dalbergia sissoo, Parkinsonia aculeata, Vateria indica are selected.
(14) Saline and Alkaline (Kankar) Soils:
About 7 million hectares of land in the country are affected by varying degree of salinity and alkalinity, and it is estimated that the area is increasing at an alarming rate of 10,000 hectares per year. In a country, where the percentage of forest area is less than the desired level and where there are practically less forests in the predominantly agricultural zone, afforestation of saline and alkaline soils can go and long way to meet the requirement of grasses, fuel and small timber of the villagers.
i. Locality Factors:
The value of pH is usually very high and usually there occurs a kankar pan in the soil. The tract is subjected to severe human and animal pressure in the form of overlapping, grazing, browsing, etc.
ii. Preparation:
Soil preparation is done by digging pits so as to break the kankar pan. Pits are usually 30 to 60 cm wide and up to 2 m deep. In areas where the soil is highly alkaline, pits need to be filled with non-alkaline soil brought in from elsewhere. Mounds have to be made in water logged areas. Soil ameliorants such as gypsum, farm yard manure, etc. may also be added.
iii. Choice of Species:
Azadirachta indica, Eucalyptus hybrid, Terminalia arjuna, Acacia catechu, Albizia procera, Pongamia pinnata, Prosopis juliflora, Acacia arabica.
(15) Lateritic Soils:
i. Locality Factors:
Soil is shallow, highly ferruginous and lacking in essential nutrients.
ii. Preparation:
Soil preparation is done by tractor ploughing followed by ridging. Manual labour may also be used to dig trenches and form a ridge-ditch pattern.
iii. Choice of Species:
Acacia arabica, Alstonia scholaris, Anacardium occidentale, Eucalyptus spp., Casuarina equisetifolia, Dendrocalamus strictus.