Kopetdaghi Sainfoin (Hedysarum kopetdaghi Boriss.) as a Rangeland Plant Response to some Environmental Gradients in Nature Habitats of Khorasan Razavi Province

Introduction[1]A significant area of the country's rangelands has been destroyed, or their population has been severely reduced due to various factors such as uncontrolled exploitation, climate change, and other factors. Irregular and out-of-season grazing in different regions and the mismatch of the number of livestock with forage production capacity in the country's rangelands has reduced the population of edible plants in a region and reduced livestock's power supply in the country. Hedysarum kopetdaghi plant is an important species that grows in the rangeland ecosystems of North Khorasan, Khorasan Razavi, and Golestan provinces. It is one of the high-quality perennial herbaceous species that is mainly seen as a companion species in combination with summer pasture types in the country's northeast. The forage of this plant is of good quality and is grazed in all vegetative and reproductive stages. Considering the importance of forage, determining ecological factors affecting vegetation changes and examining the response of this species to changes in ecological factors in different ecological conditions, and determining the different stages of growth of this species in Khorasan Razavi province was studied by generalized Additive Model (GAM). Materials and MethodsKopetdaghi sainfoin (H. kopetdaghi) responses to some environmental gradients were studied ‎in its natural habitat in the northern heights of Binalood )Kalate Ahan( and the heights of Hezar Masjed (Marichgan), respectively. Vegetation sampling was done by the systematic-random method. The plant growth calendar (phenology) was recorded in different stages of vegetation, flowering, maturation, and seed fall, plant drying, and the phenological diagram of the plant were drawn in accordance with the Embrothermic curve. At the data preparation stage, initially the nominal and sequential variables such as soil texture and the relative data in the column related to each factor were identified. Generalized Additive Model (GAM) was used to investigate the response of this species to soil and topographic factors. The percentage of canopy cover of O. chorassanica was used to explore the relationship between species and the environment, and the ecological range was calculated as a function of the Gaussian response. Results and DiscussionThe results indicated that H. kopetdaghi is more distributed on sandy loam to silty loam soils. It has the highest yield in moderate amounts of sand (about 50%) and silt (about 35%). The results also showed that the relationship between the density of H. kopetdaghi and altitude (m. ASL) increases but then decreases with increasing altitude more than 1700 meters. It seems that altitude is a limiting factor (e.g. decreasing temperature and increasing light intensity) that affects species distribution. The response pattern of H. kopetdaghi along the gradient of litter and lime percentage of the soil followed the monotonic increase model, but along the gradient of the soil stones and pebbles, percentage followed the monotonic decrease model. The results also showed that the range of H. kopetdaghi canopy cover was 0.5%-1.82%, the density was 0.05-0.21 plants m-2, and dry biomass was 2.14-6.64 g.m-2, and the mean of ‎dry forage yield was 38.5 g.plant-1. ConclusionOverall, this study indicated ‎that H. kopetdaghi showed a significant response to changes in factors such as soil texture, saturation moisture content, lime percentage, organic carbon content, acidity, soil slope percentage, and litter percentage of soil surface. Among these factors, soil texture, lime content, and soil saturation moisture content are the most important factors affecting the presence and performance of this species, which can provide valuable information for the use of this species in degraded rangeland operations in areas with similar ecological characteristics. According to the above results, the cultivation of H. kopetdaghi is recommended as a palatable forage in low-yielding drylands with precipitation more than 200 mm. It is necessary to continue research on planting this species as well as its role in forage production and sustainable production in rain-fed grains.