Document Type : Research Paper
Authors
1 Associate Prof., Forests and Rangelands Research Department, Khuzestan Agricultural and Natural Resources Research and Education Center, Agricultural Research Education and Extension Organization (AREEO), Ahvaz, Iran
2 Assistant Prof., Forests and Rangelands Research Department, Khuzestan Agricultural and Natural Resources Research and Education Center, Agricultural Research Education and Extension Organization (AREEO), Ahvaz, Iran
3 Expert, Khuzestan Natural Resources and Watershed Management Department
4 Assistant Prof., Soil Conservation and Watershed Management Research Department, Khuzestan Agricultural and Natural Resources Research and Education Center, Agricultural Research Education and Extension Organization (AREEO), Ahvaz, Iran
Abstract
Introduction
Iran is located in the arid and semi-arid belt of the world and is very far from moisture sources. Arid and desert areas, due to a lack of moisture, high temperatures, strong winds, soil erosion, and land degradation caused by human activity, have created tough conditions for plant growth and development, such that only a relatively limited number of plant species can survive. Native plants of such areas are considered highly valuable species due to their ability to adapt to harsh environmental conditions and play a crucial role in the region's climate, soil formation, and hydrology; therefore, their identification is of great importance. With the aim of monitoring and recording spatial data statistics of meteorological, hydrometric, erosion and sedimentation, vegetation cover, soil and groundwater climatic parameters, the Shush representative basin station was established in 2007 by the General Directorate of Natural Resources and Watershed Management of Khuzestan Province. In addition to the Moorlands, shallow depressions and old gullies are observed in this basin, some of which have been stabilized due to enclosure and reduction of livestock pressure. These stabilized depressions themselves act as natural micro-reservoirs and have provided suitable conditions for the establishment of permanent species by increasing infiltration, reducing surface runoff, and trapping plant seeds. In this study, the floristic composition, richness, and species diversity were compared in plots located in stabilized micro-watersheds (treatment) and hills (control). The results of the study showed that the indices of percent cover, number of species, and diversity in the treatment were significantly higher than in the control. These findings indicate that stabilized gullies can act as small foci of gene pool and nurse habitats and, if properly managed, can help improve the stability of vegetation cover in arid regions and consequently soil conservation. Therefore, integrated management, including targeted enclosure, control of active gullies, and patchy protection of natural micro-watersheds, can be a low-cost and eco-friendly model for restoring degraded rangelands in southwestern Iran.
Materials and methods
In this study, vegetation cover analysis was conducted in the Shoosh representative basin area using biodiversity indices. During the appropriate growing season (early February to late March), during field visits, a list of plant species in the area was taken, and typification was performed based on the presence of Shrub and perennial species. In each type, the size of the data plot was determined using the minimum area method and using snail plots and species surface curves. The location of all plots was recorded with a GPS device. 20 plots (a total of 40 plots) were constructed separately in the shallow depressions and stabilized gullies (treatment) and the slopes of the hillocks (control). In each plot, the percentage of living cover of each species was noted with the name, the percentage of litter and debris, and the percentage of bare ground. Species diversity indices were calculated, and the vegetation cover of the plots was compared using an independent t-test. Species number, vegetation cover percentage, and species diversity indices (Simpson, Shannon, and Hill diversity indices) were calculated using PAST 2.17 software. Python version 3.13 programming environment was also used to analyze species diversity, compare different indices, and create some graphs. All data were transferred to an Excel file for subsequent statistical analysis using SPSS 27 software.
Results and discussion
In the enclosed and protected area of the Shush representative area, 70 plant species belonging to 29 families were identified. The Fabaceae, Astraceae, Poaceae, and Brassicaceae families are the largest families in the region in terms of number of species, with 11, 8, 8, and 6 species, respectively. Of the 70 identified species, 45 plant species, such as Astragalus ensifer, Astragalus fasiculifolius, and Astragalus obtusifolius, have soil conservation value and are among the perennial plants of the region. In the Shush representative area, there is a significant difference at the one percent level between the average number of species, percentage of cover, dominance, Simpson, and Shannon indices in the treatment plots compared to the control plots. However, although there is a difference between the value of the uniformity index of the treatment and control sections, it is not significant. These results indicate that stabilized depressions, by increasing water infiltration and reducing surface runoff, have provided conditions for the establishment of permanent species. From a soil conservation perspective, increasing living cover and the presence of permanent species in these micro-catchments reduce the bare ground surface and, as a result, reduce the erosion. Therefore, if properly managed, these depressions can help improve soil conservation and vegetation stability as nurse habitats and gene pools; however, a distinction should be made between active erosional gullies and stabilized gullies with a positive role.
Conclusions
Natural watershed management phenomena with self-organization play a very important role in the restoration of degraded rangelands. These measures help improve soil structure and increase water infiltration by reducing surface water runoff and controlling soil erosion, and provide suitable conditions for seed germination and the establishment of plant species. This research in the representative area of Shoosh as a model example can be generalized to other arid regions. The presence of shallow depressions and stabilized gullies with various depths in the region, like a mother, is actually a nurse for plant species and allows them to develop in that region. However, the rate of restoration of arid regions is slow, and these areas have a very fragile system, and more time and opportunity are needed to achieve ideal conditions. In other words, despite the emergence of suitable vegetation due to the micro-natural watersheds, they are still very sensitive and vulnerable areas, and the diversity of vegetation depends on the rainy season due to the predominance of short-lived species. Therefore, an important point that should be considered is management, planning, and the use of existing conditions. In addition to preventing destruction in the area, purposeful fencing and grazing management (appropriate grazing time, prevention of excessive grazing, timely removal of livestock from the area, resting the pasture for reconstruction and restoration) should be considered in the area. Unfortunately, in many desert and arid areas, tree planting is used for restoration, an activity that is very costly and requires subsequent care. While the best method is to take inspiration from the natural process in desert and arid areas. The results of this study showed that the stabilized depressions in the Shoosh representative area, by playing the role of natural micro-reservoirs, provided conditions for the establishment of permanent species and were effective in reducing bare land and improving soil protection. These results indicate that utilizing the capacity of these micro-reservoirs, along with targeted enclosure and grazing management, can be a low-cost and eco-friendly approach to restoring degraded rangelands in arid regions.
Keywords
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