Allowable use of 5 key species of alpine rangelands in Lorestan

Range species have varying sensitivities to livestock grazing, which can be exacerbated by climatic conditions. Preserving high-quality pasture and edible species and maintaining plant composition and productivity in the pasture ecosystem requires appropriate levels of pasture exploitation. Thus, knowledge of the allowable use of rangeland species is essential for the management of these ecosystems. This study aimed to determine the allowable use of key species in Zagheh alpine rangelands.

The study selected 40 average stands of the species Astragalus curvirostris, Bromus tomentellus, Festuca ovina, Onobrychis melanotricha, and Picris strigosa to determine allowable use. The stands were subjected to different levels of harvest treatment over five years (2011-2016), with stands 1-10 left unharvested and used as a control. Stands 11-20, 21-30, and 31-40 were subjected to 25%, 50%, and 75% harvest treatments, respectively. An additional ten plants were selected as annual witnesses and weighed using an electric scale with an accuracy of 0.01 grams. The data collected included vigor, mortality, plant height, and production, which were analyzed using MSTAT-C software.

The study found that O. melanotricha increased in production with a 25% harvest treatment, but harvesting at 50% and 75% caused stands to die. Harvests of 25%, 50%, and 75% increased the production of B. tomentellus compared to the control. F. ovina showed greater resistance to harvesting than other species, with the highest production in the control and 75% harvest treatments. A. curvirostris should not be grazed more than 50%, while P. strigosa is not very sensitive to grazing in the flowering stages and after but is sensitive to grazing in the first season.

The allowable use of species can be expressed as follows: F. ovina can tolerate up to 75% harvest, while O. melanotricha can tolerate 25%, A. curvirostris 25-50%, B. tomentellus 50%, and P. strigosa 25-50%. However, the grazing season must be carefully observed to ensure successful management of rangelands.