Evaluation of the reaction of Salsola arbusculiformis Drob in the Shoghan plain of North Khorasan to environmental factors using a generalized additive model

One of the fields in vegetation ecology is understanding the relationships between plant species and environmental factors and analyzing species reactions along the slope of environmental factors. Considering the importance of Salsola arbusculiformis Drob in soil conservation and forage production, the reaction of this species to environmental factors was investigated using the Generalized Additive Model in Shoghan region of North Khorasan province. For this purpose, a systematic random-method was used to measure plant parameters and environmental factors. Canonical Correspondence Analysis was used to examine the relationship between vegetation and environmental factors. The results showed that environmental factors such as percentage of sand, sulfate ions and soil bicarbonate, annual rainfall and altitude, respectively, expressed 5.8, 11.4, 5.7, 9.1 and 7% of the existing variance and have an important role in vegetation changes in the studied habitat. The study of the reaction of this species to environmental factors showed that out of 25 environmental variables studied, 14 variables had a significant effect on plant yield (p <0.01). The response pattern of the studied species along the slope of factors such as acidity, percentage of sand and clay, altitude and finally the percentage of slope was unimodal. The optimal growth limit for each of the above factors was 8.4, 66%, 28%, 1452 meters and 5%, respectively. The response of this species to the amount of sulfate and percentage of soil lime followed a decreasing model, so that with increasing the values of these factors, its yield decreased. The response pattern of the desired species was in two modes, along the slope of factors such as chlorine, sodium, organic carbon, nitrogen, soil salinity and average annual temperature. This model indicates a competitive constraint startsrecalong the peripheral slope. The results also showed that this species has the highest yield in the northern slopes. Studying the reaction of the desired species along the slope of topographic and soil factors provided valuable information for determining the ecological needs of this species, which can be considered in rangeland improvement operations in similar areas.