By Somayeh Zahabnazouri, IUCN CEM Young Professional.
The Fahraj plain lies in the southeast of Kerman Province on the southern margin of the Lut Desert, which is locally known as Lut-e Zangi Ahmad. Citriculture and palm gardening are the main livelihoods of the residents in this region. This area is characterised by the presence of Nebkhas. According to the IUCN Evaluation Report, 2016, Nebkhas can reach 12 m or more in height. Previous investigations indicated that the highest Nebkhas located at the western margin of the Lut basin on the Takab plain were no more than 12 meters in height; our field investigations revealed that on the Fahraj plain, there are Nebkhas greater than 20 meters in height. This would suggest that some of these Nebkhas are among the highest that have been reported in the world. Some were connected by rows of Tamarix and formed very long ridges more than 200 meters in length. It seems that their form may be due to human activity. These giant Nebkhas are the unique bio-geo-morphological landscape typically found in the arid region.
Role of the water table
Variability in the groundwater table’s depth directly impacts the vegetation in the study area. Vegetation establishment occurred during periods of the higher water table. During periods when the water table lowered, the vegetation died. The dunes became active again or were buried by active aeolian sands because vegetation growth could not keep up with the sedimentation rate.
Role of Plant species
The researchers believe that the formation of such phytogenic mounds (Nebkhas) creates patches that can strongly influence the spatial distribution of plant and soil resources. In land restoration of arid and semiarid environments, it is important to study the potential role of such biological patchiness that may provide sites for the coexistence of species with different life and growth forms.
Tamarix aphylla, a shrub in the Tamaricaceae family, plays a major role in reducing dust and sand storms in the region by trapping aeolian sediments and accumulating them in the form of Nebkhas. Compared to T. aphylla, Prosopis cineraria, a multipurpose plant that provides various products to people on the Fahraj Plain and supports local communities, have in some cases negatively impacted the arid lands of Fahraj. According to field observations in the Fahraj area, no Nebkhas seem to occur around P. cineraria. On the Fahraj plain, we have found that soils in the arid region Prosopis jungles are cemented, having a low water penetration capacity. Therefore, they seem to enhance flood events. Also, the surface sediments are active in Prosopis jungles, which suggests that this species does not play a significant role in sand stabilisation in the Fahraj region.
In addition, Prosopis seems to exclude other plant species, decreasing the diversity of plant species associated with it. It also has other adverse effects, affecting crop yields, as well as animal and human health. Despite its negative effects on the Fahraj Plain, Prosopis has potential uses as fuel, charcoal, fodder, food, bio-char, bio-control, windbreaks, shade, construction and furniture materials, and soil stabilisation. Therefore, we could say that this species does not seem to function in slowing aeolian sediment transport and does not aid in decreasing sand storms.
Need for conservation action
In southeastern Iran, there is an increase in the rate of people facing dust storms and desertification in the last decades. In Fahraj Tamarix jungle reduces the consequence of desertification by trapping dust and sands around shrubs and shaping Nebkha, but these Nebkhas are under devastation and extinction. Groundwater drops and drilling deep wells instead of the traditional water system in Qanats, Prosopis domination in some areas, using the soil in Nebkhas as a fertiliser and lack of awareness in people about the importance of Nebkhas are some of the main factors that we need to work on to save them.
Ms Somayeh Zahabnazouri is currently a PhD Graduate in Physical Geography at University of Tehran.