Meeta Sharma
2016 International Journal of Advanced Research  
The arid regions of India cover an area of 317,090 km 2 and lies a 24 0 -29 0 latitude and 70 0 -76 0 longitude. The region is spread over seven states, viz., Rajasthan, Gujarat, Punjab, Harayana, Maharashtra, Karanataka and Andhra Pradesh, the north-western part of the country constituting almost 90% of the total arid zone area. Thus Rajasthan state alone accounts for 60% of the arid zone of India. The mean annual rainfall varies from 100 mm in the northwest to 450 mm in the eastern part of
more » ... asthan. Over 9% of the total Annual rainfall occurs between June and September. The mean maximum temperature during the summer is 40 0 C. The mean winter season temperature varies from 14 0 C to 16 0 C. The potential evapotranspiration during summer is 7 to 9 mm/day, during the monsoon 5.3 to 6.4 mm/day and in winter ranges from 1.8 to 2.9 mm/day. Thus, the evapotranspiration far exceeds precipitation throughout most of the year. High wind velocity is characteristics during summer and monsoon season throughout the north-western arid zone. The wind speeds are minimum during the post monsoon period. In arid semi-arid areas, moisture availability is a major limiting factor for successful establishment and early growth of trees. On sloping land the survival and establishment of the seedlings is particularly difficult because the little water available from rainfall tend to run off down the slope. Planting in sunken pits and triangular (V-shaped) and semi-circular bunds might improve the survival and growth rates of seedlings over normal planting pits under these conditions, due to increase water availability, reduced wind speed of reduced evapotranspiration. Forests and trees like many other plants, suffer from attack by insect pests and diseases which cause a lot of damage, resulting in poor tree growth, poor timber quality, and in some cases, complete destruction and reduction of forest cover. Thus, trees and forests need to be protected from these agents of destruction. With the ever increasing human and livestock population, the amount of forest per capita is declining particularly in the less industrialized or developing areas of the world. It is estimated that the land under forest in developing countries is about 2100 million hectares, or more than half of the forested land on earth. Considerable effort is needed therefore to increase the productivity of the existing forests and to afforest suitable areas. Diseases and insect pests constitute the major biological determinants of forest productivity in the natural forests and particularly in plantations, thus offsetting the effort in increasing wood production to meet the growing needs of an increasing population. Indian arid zone covers 31.7 million ha hot desert and 0.78 million ha cold desert, which is about 12 percent of the country"s total geographical area. The mean annual rainfall in the region varies from 100 mm in the north-western sector of Jaisalmer to 550 mm in eastern districts of Rajasthan, Gujarat and Haryana. The rainfall is highly erratic having 65 percent coefficient of variability. Drought and famines are quiet frequent rendering crop production a risky enterprise. Other climatic features, adversely affecting the plant growth are: (i) wide variation in temperature (minimum 0 o C in winter and maximum reaching 50 o C in summer), (ii) strong winds (with average velocity 20-30 Km/hrs and reaching as high as 130 Km per hour occasionally), (iii) high potential evapotranspiration (7-13mm/day in summer) and (iv) soil sandy, infertile, underlain with hard pan, at places having duny and rocky topography. Forestry scenario of the region is very grim, with only 2.61% forest area. Sustained forestry production of forest resources in arid and semi-arid areas of India is of vital importance for the life support systems of the country. Arid and semi-arid tracts of India cover around 1.26 million Km 2 ., which accounts for 38% of the country area. Khejri (Prosopis cineraria) trees in the farmers fields is a common feature of arid and semi-arid landscapes. In fact, an adequate tree covers forms the basis of sustained agricultural, horticultural and forestry production in the inhospitable environmental conditions of the arid and semi-arid areas through conservation of land resources. Continuing over-exploitation of natural vegetation by ever increasing human and livestock populations has resulted in extensive deforestation with consequent negative impacts on production forestry. Int. J. Adv. Res. 4(8), 2099-2116 2101 experiments on the biology and efficacy of parasites and predators of important insect pests of these tree species. State of the art (major pests /diseases weeds):= Acacia tortilis:- Acacia tortilis A. tortilis close-up view Acacia tortilis, is native of Sudan, Ethiopia, Yemen, Somalia, part of Kenya, Tanzania, Arabia and Southern Israel. It is usually a medium size tree of 4 to 12 m height, sometimes a shrub or bush 1.5-18 m high, occasionally of 21 m. Bark on trunk usually rough and fissured, grey to black brown. Crown usually flat and spreading (parasol type) but sometimes (especially in sub sp. raddiana) rounded. Young branchlets densely to sparsely pubescent or glabrous to subglabrous. Spines paired; some short and hooked, up to about 5 mm long, others long straight, slender, whitish, 1.2-8(-10) cm long, never enlarged or inflated. Petiole usually with a gland. Pinnae 2-10, occasionally to 14 pairs on a short rachis up to 2 (-4) cm long, usually glandular between the top 1-3 and lowest 1-2 pairs of pinnae. Leaflets 6-20 pairs per pinna, glabrous to densely pubescent, 0.5-2.5(-6) mm long, 0.2-1(-1.5) mm wide. Flowers white or yellowish-white, scented, in round fluffy heads 0.5-1.1 cm in diameter, on axillary peduncles 0.4-2.5 cm long. Pods variable indehiscent or slowly dehiscent, contorted or spirally twisted, very rarely and abnormally (Kenya) pods straight or nearly so, glabrous, pubescent or tomentellous, rarely with spreading hairs. Seeds oblique or parallel to long axis of pods.
doi:10.21474/ijar01/1427 fatcat:46blssgfxfewrarrusrx3l24gq