The present study investigates the ecological requirements of Astragalus curvirostris Boiss., with emphasis on determining the ecological factors that affect the distribution of plant species, and the species’ response to changes in ecological factors using a Generalized Additive Model (GAM) in the Iranian Province of Zanjan from 2017 to 2019. Randomized-systematic sampling was used to collect vegetation data. Data analysis was performed using SPSS17 and CANOC4.5 software. The results showed that the growth and development of A. curvirostris change according to environmental factors linked to the composition of the soil and the variety of the other species present. This model is indicative of a competitive limitation along the environmental gradient. By understanding all environmental parameters, the necessary steps could be taken towards planning proper management programs, including rangeland grazing management and determining the proper moment for seed collection, which will result in the conservation, improvement, and restoration of rangelands.

The uncontrolled exploitation of soil and plants by people has generated important ecological imbalances all over the world. This manuscript focuses its attention on the ecosystem of Ferula gummosa (FG). FG belongs to the Apiaceae family and has a vast distribution from central Asia to South Africa, as well as northwest Iran, including the Zanjan Province. This plant has diverse applications across industrial, forage and medicinal fields. To investigate the effective factors on the FG distribution, four main natural habitats were selected based on field visits and a literature review. Then, environmental factors, such as climate features, topography conditions, and soil characteristics, were collected and analysed. According to the results, the slope is mainly north-northeast with a slope of 55 to 70 degrees, and an elevation range above 2200 m is suitable for the growth of FG in the Zanjan Province. The main companion plants were Silene bupleuroides L. and Thymus kotschyanus. The results show that in the habitats where FG grew, the soil was mostly shallow, sometimes semi-deep and consisting mainly of loam, loamy sand, loamy clay and mostly clay loam with very low salinity (less than 0.7 dS/m), and was in the neutral range of soil acidity (6.9 to 7.33). Soil organic carbon was relatively high, but the amount of nutrients, such as phosphorus and potassium, was less than optimal in these soils. Next, using a Geographic Information System (GIS), maps of homogeneous areas for possible FG establishment across the province were created. In conclusion, the main factors affecting the FG distribution in the Zanjan Province were land use conversion, harvesting fodder and grazing livestock, improper exploitation of rangelands, pests and diseases of Ferula gummosa in the region. The ecological data collected on FG may be useful to understand how human action can affect the existence and extinction of many plant species.