عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Coastal zones are dynamic parts of the Earth. They and arid lands are the most favorable areas for wind processes (Mahmoodi, 2002). The coast is a zone where land, sea and air (the lithosphere, hydrosphere and atmosphere) meet and interact (Bird, 2008). It is a region of very high physical energy and biological diversity (Murthy et al., 2002). They are the basis of important ecosystems, supporting valuable communities of plants and animals (Kidd, 2001, 1). Coastal species are more widely distributed; they predominate in habitats with sand movement and the herbaceous component prevails (Castillo and Moreno-Casasola, 1996).
Sphaerocoma auchri Boiss belongs to Caryophyllaceae family and paronychioidae subfamily. According to Asadpour & Soltanipour research (2017), this species distributed in coast of Sudan, Egypt, west of Pakistan, south east of Arabia and south and south east of Iran including Hormozgan province (Gheshm, Bandar Abbas, Charak, Larak, Kish, Bandare Lengeh, Jask and Minab) and Sistan-O-Baluchestan province (Chabahar and Konarak). This plant is one of important spicies on coastal sand dunes of Hormozgan province that play a magnificent role in soil conservation.
The study areas contain 7 sites throughout east to west of coast belt in hormozgan province. They are located at 25o 36’-26o 58’N, 54o 22’-58o 59’E, in south of Iran at the north of Oman Sea and Persian Gulf. In general the region under research could be assumed a dry land with very low rain and its remarkable nature is windy, sand storm, torrent shower, thunder-storm, higher humidity and hazy down(Akbarian et al., 2006).
In order to investigating on Sphaerocoma aucheri vegetative condition, 7 sites have been selected. Different vegetative parameters as canopy cover, long and small diameters, density and height of each individual plant were studied. In order to do soil characteristics measuring (for 16 physical and chemical soil factors), in each of the identified sites, 9 profiles are established and 3 samples (0-25, 25-50 and 50-75 cm depths) were taken from each one.
Results and discussion
According to the comparison between soil parameters of Sphaeroma aucheri habitats and adjacent areas, apart from temperature, soil texture, Ec, ph, total Ca+Mg, Caso4, Na content, SAR, potassium soluble content are most important factors on stablishing of Sphaeroma aucheri habitats; saturated moisture percentage and potassium content are in second importance.
The saturated moisture percentage, Ec, pH and lime content ranges as 25.67-34.79, 0.43-5.93, 7.61-8.75, 26.43-60.69, 0-28 respectively. Sand and SAR contents ranges from 52 to 94 and 0.5 to 29.52 respectively. The soil pH is alkaline and lime is found in all soil profiles. The electric conductivity is below 4 in all of the areas and below 2.5 in most areas. This plant spreads in non-salty and ordinary soils. Maximum elevations in all of the sites do not reach 100 meters.
Results showed plant density has negative relation to saturated moisture percentage and positively relation to lime content. Also there are a negative relation between silt and K contents of first depth of profiles, clay of second and third depth with plant density and a positive relation between sand content of first and second depth with density. Canopy cover of this plant has negative relation with saturated moisture and clay content of all depths and positive relation with sand of first depth. There is a negative relation between mean diameter of the plants and height saturated moisture percent. These results indicate the effect of soil particle (texture) on vegetative parameters.
Generally it would be concluded, there is the relation between soil particles (soil texture) with the vegetative parameters of the studied species. Sandy texture leads to drainage and clay texture, causes soil moisture. (Bybourdi 1993; Foth, 2011; Sadeghi, 2016). Particle size windows (PSWs) are interpreted as reflecting different modes of sediment transport and deposition (Clarke et al., 2014). Sand dunes occur in two distinct habitats: along the coasts of seas and rivers, on the one hand, and on the barren waterless floors of deserts, on the other (Bagnold, 1954). Based on the sedimentology of sand mass grains and in relation to sediment sources, coastal plain sand masses can be divided into interior sand masses, resulting from the erosion of the coastal plain surface, and coastal sand masses, that originate from the tidal zone (Akbarian; 1393). In coastal sand masses, sand is removed from tidal foreshores and deposited onto backshores by sea breezes (Akbarian, 2014; Shayan et al., 2014 and Shayan et al., 2016). These with interior sand masses which are mainly located on the upper reaches of the plain are different from genesis aspect. (Akbarian, 2014).
Based on results Sphaerocoma aucheri grows on coastal sand dunes, which have lost their clay and silt during the sea processes and are mainly composed of sand and high levels of lime (Oyster lime shells' particles). It does not inhabit on the internal sand masses which are formed as a result of the coastal plain surface erosion, which have high silt and clay percentages. Hence, it can be used as an indicator for differentiating coastal masses from internal sands (desert dunes).