عنوان مقاله [English]
Plant species that make up nebkas are important elements that stabilize quicksands and have the ability to survive under wind sedimentshe aim of this study was to statistically analyze the geomorphological characteristics and sediments of Nebka sediments in order to stabilize quicksands in the Sirik region of Hormozgan province. In the present study, 3 regions, in each region, 5 representative regions and in each representative region, 10 transects of 1000 meters with a distance of 500 meters from each other and perpendicular to each other were placed in each linear transect. In each nebka, nebka height, nebka length and base of nebka, canopy diameter, nebka volume, nebka base diameter and nebka sand stabilization area were measured. Also, to determine the amount of geomorphological changes of the sampled nebkas during the 30-year period, Landsat satellite images of OLI sensor from 1990 and 2020 were used. Then, using ENVI 5.3 software, the area's wells and other existing uses were determined. The results showed that there was a significant difference between the variables in the three regions at the level of 95%. With the increase of plant height in Sirik from 1.7 to 2.2 meters, the volume of sediment dune increases from 15 to 72 cubic meters and in Mishi region with increasing plant height from 1.65 to 3.5 meters, the volume of sediment from 15 to 45 Cubic meters has increased. Also, the study of changes in the area of nebkas in the region during the last 30 years using satellite image processing showed that the area of nebkas in the region has decreased from about 67 hectares in 1369 to about 59 hectares in 1399. Due to the importance of nebkas, efforts should be made to protect them and these destroyed areas should be rehabilitated with salvadora persica seedlings.
Plants in arid and semi-arid regions, by reducing wind speed and stabilizing quicksands, form the Nebka geosystem, which plays an important role in desertification and environmental protection. One of the world's ecological crises is the phenomenon of desertification. Controlling this crisis requires a proper understanding of its causes and processes. Desertification is the reduction of environmental potential and the destruction of natural resources and ecosystems (ecosystems) whose regional and trans-regional effects affect aspects of human life. The ecological crisis in arid and semi-arid desert areas on the one hand and the uncontrolled exploitation of humans on the other hand, has caused the expansion of deserts and has created a major problem at the national level. One of the solutions to prevent the spread of deserts is the stabilization of quicksands by Nebka fields (Arab Ameri and Halabian, 1396).
Nebka or sand dunes, hemezari spread in areas where sand is trapped by vegetation and usually form in semi-arid, hot and dry, hot and humid areas (Amini et al., 2011, quoted by Thomas and Tousar). Drought resistance and plant network roots can contribute to the growth and stability of nebkas in any region (Nishimura and Tanaka, 2001). An important point in the development process of Nebka is the vegetation conditions and the morphology of Nebka is mainly controlled by the vegetative pattern of plant species (Pour Khosravi and Vali, 2010). The formation of nebkas as one of the cumulative forms of sediment in desert areas is due to the entrapment of wind sediments in their transport path, which are mainly stabilized at the foot of plant shrubs. Nebka plays a very important role in stabilizing the ecosystems of arid and arid regions. For example, its most important role is in the maintenance of vegetation. The formation of Nebka by the plant causes physico-chemical changes in soil such as: increase in organic matter, change in acidity and increase soil nutrients (Zamani et al., 2013).
Material and methos
In the present study, one-dimensional and longitudinal sampling was performed in 3 areas separately. In each area with 5 representative areas, 10 transects of 1000 meters with a distance of 500 meters from each other and placed vertically. In each linear transect. Then, to start the sampling, points were selected by GPS as an indicator at equal distances from the start of the nebka landscape in 5 areas under study. Two Landsat satellite images from 1990 and 2020 were used to determine the morphometric changes of the sampled nebka over a 30-year period. In the other hand, the shape of Nebka is a function of plant species, height and surface cover of the host plant. The height of Nebka varies from a few decimetres to a few meters and its length varies from one meter to several meters. As the amount of sediment increases, the plant continues to grow to prevent burial, and this growth is to the extent that the plant's roots are in contact with groundwater; But where the groundwater drops or the roots of the plant do not reach the moisture, this connection of cutting and destruction of Nebka begins, which eventually leads to the death of Nebka (Neghaban et al., 2013).
ith the trapping of sand by plants and its development, nebkas are formed, which occur primarily in arid and semi-arid environments. Nebkae are found around saline species, plains, wells, along shores, and in areas where the plant is present (Anna Tangberg, 1995). Dry and ultra-dry conditions prevailing in a large part of Iran with less than 710 mm of rainfall per year, has caused about 40 million hectares of the country to cover desert areas, sand dunes and areas with little vegetation (Refahi, 2004). Nebks are very important in stabilizing mobile sands in desert and semi-desert areas and make human settlements and facilities somewhat safe from the onslaught of wind sands (Negharsh and Latifi, 2008). The formation of nebka by the plant causes physico-chemical changes in the soil such as: increase in organic matter, change in pH and increase in soil nutrients (Zamani et al., 2013).