Site Selection, Survey and Treatment Plan - Afforestation, Reforestation and Forest Restoration in Arid and Semi-arid Tropics - page 69

Mulch lines can be aligned in a parallel, checkerboard, masonry, or diamond
pattern. Orientation is set with respect to the prevalent direction of wind. Maximum
length of the lines should be aligned across the direction of wind which is also the
direction of sand movement. Sometimes, complex patterns of sand movements can
be seen, where sand moves in all directions randomly. In such cases the checkerboard
pattern is preferred.
The stronger the movement of sand, the more should be the density of mulching.
Density of mulching is reckoned in terms of the length of mulch line per hectare of
area, or by the average spacing between two consecutive mulch lines. In the parallel
pattern a spacing of 5 m is standard, though it can be reduced to 4 m or even to
3 m where sand movements are stronger. In fact, in a given area the spacing can be
graded in such a manner that the most active part of the dune is given the smallest
spacing, and the relatively stable portion is mulched with larger interline spacing. In
this manner, it is possible to strike a balance between cost and effectiveness.
A mulch line should have a standard section, even though it is more difficult to
specify such a section. The average height of a mulch line should be 45 cm above
the ground and at least 15 cm buried in the ground. The average thickness of the line
should be 30 cm. It is important that the mulch line is compact and dense so that it
acts as an effective wind barrier.
Sowing seeds of shrubs and grasses along the mulch lines is highly desirable.
Mulch also acts as a reservoir of moisture. It provides shelter to the seeds, so that
seeds will not get blown away. In fact, even if no sowing is done, seeds from the
natural seedbank of the soil will get arrested along the mulch line. Though these
seeds may not be of the desirable species or of perennial soil binders, yet they do
perform the useful function of strengthening the mulch line. The best species to sow
are the naturally occurring indigenous species of shrubs and grasses. Pelleted sowing
is the standard practice, though naked seeds sown in larger quantities and carefully
embedded in soil will also be useful.
Planting in sand dunes should be carried out just after the first rains of the season.
No pits will be required to be dug as the soil is not compact. No saucers need to be
made, as no flow of water will occur on sand. No hoeing is required to be carried out,
since the sand is always in a naturally hoed condition. Thus, in fact, sands are easier
to plant in, compared to other soils. The unit cost of afforestation in sand dunes is
usually less than that in hills and uplands.
Species selection needs special attention while planning a plantation in sand dunes.
Fast growing and drought resistant species with a long and complex root system will
perform better. Indigenous species will generally prove to be successful, but species
like Acacia tortilis , Acacia nubica , and Prosopis juliflora are long tested and should
be preferred in a high risk area.

3.8.4.2 Afforesting Saline and Alkaline Soils

Saline soils pose the twin problems of waterlogging and excess salts, both inimical
to plant growth. A strategy for afforesting such soils should consider choice of