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Shelterbelts and windbreaks
- 1. Structure and functions of shelterbelts and windbreaks BY CH. BHARGAVI ID- 20200475 MSC 1ST YEAR
- 2. CONTENTS Abstract Introduction Shelterbelts Purpose Characteristics Choice of species Windbreaks purpose Characteristics Species Conclusion Reference
- 3. Abstract As a result of scarce vegetation cover that can alter the movement of wind, dryland areas are predominantly windy. Harsh winds can remove moisture from plants, soils and the micro climate. Wind can also be an agent of soils erosion and land degradation. Agricultural production systems, local ecology, living conditions, etc. can often be improved by planting trees as windbreaks and shelterbelts. Research findings indicated that windbreaks as part of their ecological role, have contributed to the increase crop yields.
- 4. This approach has also a tremendous positive impact on the wellbeing of wildlife as it will help in giving food, cover and space to wild animals. Apart from this, windbreaks can also be a viable source of edible fruits, honey, firewood, fodder and timber. Hence, the conservation of remaining vegetation in the environment and the establishment of windbreaks and shelterbelts will help to increase agricultural productivity and biodiversity benefits for the agrarian communities. Since this and other ecological functions have a paramount importance, the role of trees as windbreaks and shelterbelts needs to be further considered and properly understood
- 5. INTRODUCTION Based on the nature of components agroforestry systems are classified into four types: 1. Agri silviculture 2. Silvi pastoral 3. Agro silvipastoral 4. Others We are now going to study Shelterbelts and windbreaks under agri silvicurtural system where the basic components are agricultural crops and trees.
- 6. shelterbelts These are belts/blocks consisting of several rows of trees established at right angles to the prevailing wind.
- 7. The purposes are: to deflect air currents, to reduce the velocity of prevailing winds, to provide general protection to the leeward areas against the effects of wind erosion, to protect the leeward areas from the desiccating effects of hot wind, to provide food, fodder, timber etc Carbon sequestration Increases biodiversity.
- 9. CHARACTERISTICS Shape and composition: Triangular shape. This can usually be brought about by raising tall trees in the center.
- 10. Density and width : Partially penetrable shelterbelts are best. Shelter- belts up to 50 m width are considered ideal under Indian conditions. Height : it effects the distance to which protection will be afforded. Higher the height greater is the zone of protection. The ratio of height and width should be roughly 1:10. Orientation: Orientation of shelter-belts depends on the direction and velocity of the prevailing winds. Length: The minimum length of a shelter-belt should be about 25 times its height
- 11. Characteristics of tree species used for shelterbelts: Fast growing Wind firm Drought resistant Unpalatable to animals It should not be leafless when protection is needed It should be economically a multipurpose species.
- 12. Choice of species Grasses: Saccharum spontaneum, S. munja, Panicum antidotale, Cencrus sp. Shrubs: Calotropis procera, Clerodendron phlomoides, Cassia auriculata, Dodonaia viscosa Trees: Acacia arabica, A. leucopholea, Dalbergia sissoo, Lannea coromandelica, Eucalyptus spp., Tamarix, articulata, Parkinsonia aculeata, Prosopis juliflora, Prosopis Spicigera ,Casuarina equisetifolia.
- 13. windbreak Wind-breaks are strips of trees and/or shrubs planted to protect fields, homes, canals or other areas from wind and blowing soil or sand.
- 14. PURPOSE to protect livestock from cold winds to protect crops and pastures from hot, drying winds to reduce/prevent soil erosion to provide habitat for wildlife Carbon sequestration to reduce evaporation from farmlands to improve the microclimate for growing crops and to shelter people and livestock, for fencing and boundary demarcation
- 15. CHARACTERISTICS Permeability: Permeable wind breaks: It allows some wind to pass through it forming a cushion of slow moving air on both upwind and downwind sides which deflects the main volume of wind upwards and prevents it from descending for some distance. These windbreaks cause less reduction in wind velocity(25 and 75 percent) but gives protection for longer distance. Species: permeability can be obtaining by carefully selecting trees and shrub species.
- 16. Dense wind breaks: It is used when high level of protection is needed for small areas. Dense wind break causes greater reduction in wind speed but protects for short distance. Species: Eucalyptus and casuarina forms dense wind breaks.
- 17. Orientation: Wind-breaks planted north-south are a good compromises as they provide protection from winds coming from the western quarter. They also give better shading of adjacent crops and pastures than wind-breaks planted east-west. Height: On level ground a windbreak will reduce the speed of wind for about 25 times the tree height on down windside. Maximum reduction of wind speed is in the area 5 to 15 times the tree height away from the wind break. Example: Wind break of 20m tall will give protection from 100m on upwind side to 500m on downwind side.
- 19. Length: Wind breaks are most effective when they stretch without major gaps for distances exceeding 12 times the mature height of the trees. Number of rows: Eucalyptus are generally unsuitable as single-row wind-breaks because of their habit of losing their lower limbs. The main disadvantage of a single row is that if one tree is lost, gap is created, which reduces the efficiency of the entire wind break. Wind breaks of three to five rows are more effective for most farm situations and are less affected by gaps caused by mission
- 20. Tree spacing: Spacing varies based on protective and productive purposes of wind break. For timber yielding trees the height of wind break and intervals can be increased. For protecting valuable crops, wind break should be tall and far. In dry areas plants are widely spaced for reducing competition. Recommended spacing is 2x3m. Gaps: In multi row wind breaks this can be eliminated by angling the gap at about 45 degrees to the prevailing wind direction. Alternatively, a few plant, trees or shrubs can be used on either side of the gate or track to broaden the gap and reduce the funneling effect. Plant 5- 6 trees at an angle to main belt as wing.
- 21. Planting lower shrubs each side of gap Forming an angled winbreak
- 22. Angling sides of the windbreak Planting short windbreak in front of gap
- 23. Species Trees with narrow, vertical growth are ideal for windbreaks. Eucalyptus, Cassia, Prosopis, Leucaena, Casuarina, Acacia, Grevillea, Syzygium, Dalbergia etc.
- 24. CONCLUSION: Well established and managed windbreaks and shelterbelts provide manifold benefits to the efficiency of ecological and ecosystem services. However the establishment of windbreaks and shelterbelts in many instances is not getting much attention for the mere fact that the growth and development period of trees usually takes time for immediate benefits. But once established it will have a sustained and long lasting positive impact on the environment.
- 25. REFERENCE Textbook of agroforestry by B.S. Chundawat and S.K. Gautam(1993), CBS publishers & distributors PVT LTD. www.unl.edu/nac/windbreak.htm Argall, J. and G. Chiasson. 1996. Windbreak Technology for Wild Blueberry Fields. Factsheet A.4.0. New Brunswick Department of Agriculture and Rural Development. [Online]. www.gnb.ca/0171/10/0171100001-e.asp (Page consulted on September 15, 2010). Molla Mekonnen Alemu United Nations Development Programme International Journal of Ecosystem Ecological Benefits of Trees as Windbreaks and Shelterbelts p-ISSN: 2165- 8889 e-ISSN: 2165-8919 2016; 6(1): 10-13