 | Special Public Works Programmes - SPWP - Planting Trees - An Illustrated Technical Guide and Training Manual (ILO - UNDP, 1993, 190 p.) |
 |  | (introduction...) |
| | Preface |
| | Introduction |
|  | 1. Planning a plantation |
| | (introduction...) |
| | 1.1 What regeneration method to use? |
| | 1.2 What species to establish? |
| | 1.3 Whether to plant a single tree species or a mixture of several? |
| | 1.4 What type of planting stock to use? |
| | 1.5 What planting pattern to use and how many seedlings to plant? |
| | 1.6 When to plant? |
| | 1.7 How to protect the seedlings? |
| | 1.8 The plantation plan |
| | 2. Preparing the planting site |
| | (introduction...) |
| | 2.1 Clearing vegetation |
| | 2.2 Ground preparation |
| | 2.3 Marking where to dig the holes |
| | 2.4 Digging holes |
| | 2.5 Soil and water conservation measures |
| | 3. Handling seedlings |
| | (introduction...) |
| | 3.1 Packing and transport of seedlings |
| | 3.2 Storing seedlings |
| | 3.3 Quality of seedlings and grading |
| | 3.4 Stripping and trimming |
| | 3.5 Transporting seedlings from the road to the planting site |
| | 4. Planting techniques |
| | (introduction...) |
| | 4.1 Digging the holes |
| | 4.2 On-site distribution of the seedlings |
| | 4.3 Planting |
| | 4.4 Use of fertilizers |
| | 5. Adapting planting techniques to different site conditions |
| | (introduction...) |
| | 5.1 Favourable sites |
| | 5.2 Sites with high grass |
| | 5.3 Waterlogged sites |
| | 5.4 Dry sites |
| | 5.5 Eroding slopes and rocky sites |
| | 5.6 Steep slopes |
| | 5.7 Sand dunes |
| | 5.8 High altitudes with snow |
| | 6. Maintaining plantations |
| | (introduction...) |
| | 6.1 Weed control |
| | 6.2 Protection from grazing |
| | 6.3 Fire prevention |
| | 6.4 Protection from insects, diseases and rodents |
| | 6.5 Fertilizers |
| | 6.6 Replacement planting |
| | 7. Planting trees outside woodlots and forests |
| | (introduction...) |
| | 7.1 Trees in crop and grazing land |
| | 7.2 Alley cropping |
| | 7.3 Intercropping in rotation |
| | 7.4 Intercropping for tree planting |
| | 7.5 Shelterbelts |
| | 7.6 Road-sides and river-sides |
| | 7.7 Homesteads and public places |
| | 8. Organizing the work |
| | (introduction...) |
| | 8.1 Planning |
| | 8.2 Workforce |
| | 8.3 Labour requirements over the year |
| | 8.4 Worknorms |
| | 8.5 Coordinating the work |
| | 8.6 Tools and equipment |
| | 8.7 Supervision and control |
| | 8.8 Records to keep |
| | 9. Working conditions |
| | (introduction...) |
| | 9.1 Hours of work and rest |
| | 9.2 Nutrition and amenities |
| | 9.3 Wage systems |
| | 9.4 Training, job content and labour-management relations |
| | 9.5 Safety |
| | Appendices - Technical sheets |
| | Appendix 1 - Surveying and mapping of large planting sites |
| | Appendix 2 - Laying out and preparing soil and water conservation structures |
| | Appendix 3 - Survival count |
| | Some useful guides/handbooks |
| | Titles in the series of training elements and technical guides for SPWP workers |
7.5 Shelterbelts
Shelterbelts or windbreaks are strips of trees and other vegetation that reduce the force of the wind. They are very important in areas with frequent high winds and windblown sand. Often they consist of several rows of shrubs and trees of different heights.
Shelterbelts are most effective if they do not block the wind completely, like a wall, but force it to slow down. If the wind cannot pass through the shelterbelt at all, it will try to pass underneath it or over the obstacle. If it flows over the shelterbelt, it produces turbulence which is harmful for the crops behind the belt. If it goes underneath, the belt acts like a funnel and the wind becomes very strong. Therefore choose large trees for the centre row. On each side of this row plant one or two rows of smaller species. Outside these rows shrubs or other vegetation can be planted to make sure that the wind cannot pass underneath the belt. Plant the trees with close spacing, e.g. 1-2 m apart.
The trees need to be able to stand up to the wind and to have flexible branches and medium dense crowns. The crowns should be long and narrow rather than spreading (the Casuarina species, for example, forms ideal windbreaks). The species should preferably be able to provide by-products. A well chosen mix will not only provide shelter from the wind but will also yield fruits, firewood, etc. If Shelterbelts are planted across grass and cropland where animals are grazing, it will be advantageous to plant thorny shrubs along the edges so that the shelterbelts can provide protection from livestock, like a live fence.
The shelterbelts should be planted perpendicular (at a right angle) to the direction in which the wind usually blows. The length of the zone protected is about 10 times the height of the shelterbelts. If large areas are to be protected, parallel shelterbelts should be planted. The spacing between the shelterbelts should then be 10-20 times the height of the tree.
Shelterbelts
front view
side view one row of shrubs three
rows of trees
Schematic representation
good shelter belt = moderately dense
shelterbelt too dense - causes
turbulence
|
|