Introducing the study area
This study was conducted in the rangelands of Chenarnaz, Yazd province,
Iran (30° 03′ 51″ N - 30° 05′ 89″ N; 53° 00′ 16″ E - 54° 01′ 23″ E)
(Fig. 1). The average altitude is 2200 m asl. The average annual
temperature is 17.5°C and the average rainfall is 250 mm, which has a
semiarid climate based on Domarten index.
Sheep and goats are the dominant grazers in the region (ca. four heads
of sheep and/or goats per ha) during the year. Heavy grazing has led to
locally exposed soil. In addition, the previous examination of erosion
status in the study area showed that environmental and human factors had
a role in the occurrence of soil erosion and vegetation degradation.
Human activities such as intensive harvesting of medicinal plants and
the use of pharmaceutical products have reduced the density of plant
species and created empty gaps in the AGV in some places (Gravand et
al., 2016). Therefore, herbaceous revegetating bare soil and restoration
of degraded sites using of native plants is a priority. SSB has been
considered one of the major natural sources that facilitates the
recovery of degraded vegetation (Shang et al., 2016). We carried out
this study to quantify the potential of different species of shrubs to
increase the SSB associated with them and thus their potential use for
restoration. Therefore, it is important to identify firstly shrubs that
associated with larger and richer SSB and secondly, consider restoring
shrub species which have higher potential as SSB reservoir accompany
with higher palatability for grazing. Thereupon, three shrubs together
with surrounding herbaceous vegetation (hereafter called control) were
selected:
A) Amygdalus scoparia Spach (Rosaceae family) is a wild species
of almond that occupies large areas in many parts of central Iran and
its neighbouring countries. The extraction and use of the oil from theA. scoparia is of interest due to their fatty acids composition
that is comparable to those of olive oil (Sorkheh et al., 2016). The
plant is attractive for grazing animals due to its shade, fruits and
high palatability of leaves. It is a deciduous large shrub that grows to
a height of up to 6 m, having a single-elongate main stem. It produces
numerous long and green branches. Fruits are drupes and are 1 to 1.5 cm
long and 0.5 cm wide. They are ripened and dehiscent at the end of July
(Mozaffarian, 2012).
B) Daphne mezereum L. (Thymelaeaceae family) is a rounded-upright
deciduous shrub with an erect and bushy habit that typically grows to
1.5 m tall. All parts of this plant are poisonous to humans if ingested,
especially the fruits, sap and bark. Therefore, this shrub is
unpalatable for grazing animals. Nevertheless, fruits are attractive to
birds with no resulting ill effects (Mozaffarian, 2012). This species is
found globally in dry and semi-dry areas and, in the provinces located
in the central Iran.
C) Ebenus stellata Boiss. (Fabaceae family) is a thorny shrub
with a height of 30-120 cm, having short and oblong-leafy branches and
ternate leaves that are alternate and covered with dense silk flakes.
This species grows in large part of Iran including Kerman, Yazd,
Esfahan, Fars and Hormozgan provinces and some dry and semi-dry regions
of world (its native range is Oman and Iran to India). The canopy
structure is open with compact thorny branches that it is difficult to
graze livestock (Mozaffarian, 2012) (Fig. 2).