Successful Biological Methods for Combating Desertification at Degraded Areas of China - Combating Desertification in Asia, Africa and the Middle East - page 57

4.1.3 Suitable Physiographical Sites for Plant Species

The different site conditions of various parts of mobile barchan dunes impact the
growth of the sand binder species. Wind erosion and burial by sand are the two key
factors to limit the survival and growth of plants. The sand layers at the windward
slope (eroded part) are more solid and unfit to the development of root systems.
The sand layers at the leeward slope (sand burying part) are loose and fit to the
growth of the roots. Different species have their own respective properties, such
as Salix flavida , Calligonum arborenscens, Atriphaxis bracteata ,and Artemisia
sphaerocephala are adaptable to loose sand and to burying. Other plants like
Caragana korshinskii , Hedysarum scoparium and Artemisia ordosica are fit for
inter-plantation on the windward (solid) part (Yang et al. 2005 ). These scientists
suggested the following important points for planting species which are suitable at
different physiographical sites.
According to the principle of “appropriate varieties for suitable sites”, each of
the different species of sand fixing plants should be planted at the most suitable part
of the dunes as follows:

• Windward slope: this is the wind eroded part, even if straw grid sand barriers (see

Fig. 2.21 in Chap. 2 ) are built, there is still wind erosion. Its sand layer is more
solid so suitable plants include, Hedysarum scoparium , Caragana korshinskii ,
Caragana microphylla and Artemisia ordosica .

• Top of the sand dune: this is the crisscross part of sand burying and wind

erosion, the sand layer is looser and suits plants like Artemisia sphaerocephala ,
Calligonum spp. and Atriphaxis bracteata .

• Leeward slope: this is a sand piling part. Though its sand layer is looser, the

sand layer is dry and deep and transplanting can be arranged only after rain. The
species of Salix flavida , Calligonum spp. and Atriphaxis bracteata are appropri-
ate plants. Species like Artemisia ordosica and Artemisia sphaerocephala can be
directly seeded during rainy seasons.

• Foot of leeward slope: this is the sand burying part, where those sand resistant

plants such as Salix flavida , Calligonum spp. are suitable.

Proper management is also needed for survival of the sand-fixing plants. A
poor planting arrangement may cause an unfavorable impact to the growth and
survivorship of the plants. In locations where sand burying is less of a problem it
is unnecessary to adopt the mixing arrangement, where the area of windward slope
covers over 80 % of the total sand dune, and arrangements of mixed plantation
are more suitable than that of mono-species. At Shapotou Station in Ningxia,
experiments show that the most acceptable and practical arrangement is the mixture
of shrubs with semi-shrubs, namely, the mixed density of Caragana korshinskii or
C. microphylla with Artemisia ordosica or the mixture of Hedysarum scoparium
with Artemisia ordosica . The concentrated layer of the root systems of Artemisia
ordosica are distributed at the depth of 20 cm, that of Hedysarum scoparium is
mainly at a depth from 20 to 80 cm and that of Caragana korshinskii is at 40-90 cm