Vegetation of Thumamah Nature Park: a managed arid land site in Saudi Arabia
A., El-Sheikh, M. . 2013
Thumamah Nature Park is located at about
100 km north of Arriyadh (Saudi Arabia), having an area
of 170 km2. The Park was established since 30 years ago.
The aim of this study is to analyze the vegetation structure
in relation to the environmental factors in different habitat
types. The phenological activities around the year of the 20
dominant species were monitored. 119 species were identified,
of which 51 (43 %) annuals and 68 (57 %) perennials
after 30 years of exclusive human impact. The
Saharo-Arabian component species were the highest
among the monoregional species (64 %) in most life forms,
while the Sahelien-Somali Masai attained the highest
among the biregionals (46 %). The TWINSPAN, DCA and
CCA analyses separated seven vegetation groups. The first
two groups were dominated by psammophytic species,
which occupy the lower sandy plain as shown in group I
with Rhanterium epapposum–Rhazya stricta and group II
with Pennisetum divisum–Haloxylon salicornicum. The
escarpment habitat was characterized by three groups, viz.,
group III with Acacia gerrardii–Panicum turgidum, group
IV with Panicum turgidum and group V with Acacia ehrenbergiana–
Lasiurus scindicus. Vegetation in the upland
plateau was represented by the remaining two groups;
group VI with Helianthemum lippii and group VII with
Helianthemum kahiricum. The environmental variables
that affect the species distribution and diversity in the park
include the altitude, soil texture, pH, EC, Ca, Mg and Mn.
The increased plant species richness, turnover, evenness
and cover were mostly due to the increase of the herbaceous
species. Plant populations showed interspecific
variations in their relative timing of phenological phases
with reproductive activity period ranged between 3 and
6 months with unimodal flowering peak. Three floweringfruiting
activities were recorded during late winter–spring,
summer and late autumn–early winter. In an attempt to
explain the vegetation dynamics after 30 years conservation,
the progressive succession varied among the different
habitat types, including the lower sandy sites, the escarpment
and the upland rocky habitats, which reflect the
relationship between altitude, edaphic factors and the type
of vegetation units in each habitat type after exclusion of
the human impact.
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