climate change on UAE - Stockholm Environment Institute-US Center

Plant species particularly halophytes found in
the sabkha could only be found in the margins
are restricted mainly to the margins. Other
species could grow only after heavy rainfall
which dilute the concentration of salts. e.g
Zygophyllum qatarense.
4.3. Sand Sheets and Dunes
The majority of land in UAE is covered by sand
sheets and dunes particularly the southern
areas. Two types of sands are identified a)
white coastal sands originated from marine
sediments. b) The yellowish to grey siliceous
sands found mainly in large tracts of the inland
and are produced from the weathering of quartz.
Coastal white sands are derived from recent
marine sediments and are rich in carbonate.
Generally sand sheets absorb rain water and act
as reservoirs for water in the short to medium
term. The most dominant plant species in the
sand of UAE is the Cyperus conglomeratus.
Other associated perennials include Dipterygium
glaucum and Limeum arabicum. Cyperus
being unplatable, was able to survive the
heavey grazing better than other species, such
as Centropodia forskaolii, Panicum turgidum
and Pennisetum divisum. Observations in one
of the protected ares (Al Wathba) have shown
that good germination of Cyperus occurs after
incidents of heavy rainfall in the late spring,
when temperatures are already quite high
again. It also indicated the occurrence of many
premature death of seedlings under insufficient
rainfall during the sensitive early stages of its
growth. South of Abu Dhabi City, some stands
of shrubby tree (Haloxylon persicum) (‘ghada’),
are found, mainly in the form of poorly established
plant community.
4.4. Piedmont Alluvial and
Interdunal Plains
The alluvial plains are found along the western
edge of the Hajar Mountain range. They consist
of pebbles and coarse rock detritus at the foot
of mountains and sand and finer gravel further
west, plus interstitial alluvium. Small trees,
dwarf shrubs and succulents are the dominant
plants in the alluvial plain. The north-eastern
part of the UAE is dominated by Acacia
tortilis (‘samr’)-the classic species of rocky
and gravelly plains. In the Madam Plain of East
Coast a vegetation type similar to open Acacia
woodland is observed. The acacia is found in
association with shrubs such as Lycium shawii
and Gaillonia aucheri (= Jaubertia a.), as well
as the succulent cactus-like Euphorbia larica
and semi-succulent Ochradenus arabicus.
Other species found in the alluvial plains
are the Prosopis cineraria and Acacia
ehrenbergiana along with A. tortilis/ Scattered
in a few localities in the east of Abu Dhabi
A. ehrenbergiana is found in sandy to silty
interdunal plains. The toxic species of Rhazya
stricta (‘harma’) which is generally regarded
as a gravel plain species is usually found in the
east of the country. Its toxicity derived animals
to shrink from grazing it, giving it the chance
to increase and dominate – to the extent that
its presence is usually regarded as a sign of
land degradation that dominate after the
disappearance of other species such as Acacia
tortilis and Haloxylon salicornicum. Both
Haloxylon salicornicum and Aerva javanica
are often associated with Rhazya.
The other species that also indicate land
degradation from heavy human disturbance is
Calotropis procera (ushar), an extremely fastgrowing
tree that can begin producing flowers at
an early age and found in the alluvial plains and
low dunes. Species like Haloxylon salicornicum
is only slightly tolerant of salt and could be
replaced by other species like Zygophyllum
qatarense as soil salinity increases. Other
regular associates on interdunal plains include
the perennials Fagonia ovalifolia, a small
woody plant, Heliotropium digynum, found
mainly on sandy interdune corridors, and H.
acciferum, a plant that tolerates more saline,
gravelly substrates.
The interdunal plain which is already speciespoor,
is dependent on winter rainfall and in
years of low precipitation its seedlings may
not be able to germinate. Another factor that
limits the growth of annual plant is the high soil
salinity. Inland sabkha is frequently developed
in the interdunes, and vegetation may be
completely lacking there.
4.5. Mountains and Wadis
The Hajar range is the major mountain system
of south-eastern Arabia, about 20-50 kilometers
wide dissected by numerous wadis, and reaches
elevations of more than 1000 m. The mountain
extends some 700 km from the Musandam
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Climate Change Impacts, Vulnerability & Adaptation