بررسی اثر میزان رطوبت، رس خاک و شوری بر جوانه‌زنی و رشد گونۀ اسپرسی همدانی hedysarum criniferum boiss تحت شرایط گلخانه و رویشگاه

در اکوسیستم‌های مرتعی، بررسی و شناسایی عوامل تاثیرگذار بر جوانه‌زنی و رشد گونه‌های باارزش به‌منظور مدیریت، اصلاح و احیای مراتع ضروری است. ازاین‌رو در مطالعۀ حاضر تاثیر فاکتورهای دورۀ آبیاری، شوری آب و درصد رس بر جوانه‌زنی بذر و ارتفاع نشا‌های گونۀ اسپرسی همدانی hedysarum criniferum به‌عنوان یکی از گونه‌های بومی و خوش‌خوراک مراتع ایران بررسی شد. ازاین‌رو آزمایشی بر پایۀ فاکتوریل و در قالب طرح کاملاً تصادفی با سه فاکتور دورۀ آبیاری در سه سطح 7، 10 و 14 روزه، شوری آب در سه سطح کمتر از 1 (0.4)، 2 و 4 دسی‌زیمنس بر متر و تغییرات رس خاک در سه سطح 0، 10 و 20% و سه تکرار در گلخانۀ دانشگاه صنعتی اصفهان در سال 1398 انجام شد. منحنی عکس‌العمل این گونه نیز نسبت به شرایط بارش، شوری آب و میزان رس خاک در 8 رویشگاه این گونه در 5 استان کشور با استفاده از روش مدل خطی تعمیم‌یافته (glm) بررسی شد. نتایج نشان داد که از بین سه تیمار فوق تنها تیمار دورۀ آبیاری بر طول نشا‌های جوانه‌زده و درصد جوانه‌زنی گونۀ اسپرسی همدانی تاثیر معنی‌داری داشتند (5% = α)، به‌طوری که بیشترین درصد جوانه‌زنی و ارتفاع نشا‌های جوانه‌زده در دورۀ آبیاری 7 روزه مشاهده شد. در طول این دورۀ آبیاری به‌طور متوسط ارتفاع نشا‌ها 4.93 سانتی‌متر و جوانه‌زنی بذر %77.77 برآورد شد. عکس‌ العمل گونۀ‌ نسبت به این عوامل در شرایط رویشگاه نشان داد که ارتفاع و تراکم گونه‌ها نسبت به افزایش میزان بارندگی و ec به‌ترتیب افزایشی و کاهشی بود، درحالی‌که عکس‌العمل این گونه نسبت به افزایش رس خاک روند کاهشی و بعد از آن افزایشی بود. این مطالعه نشان داد که در شرایطی که بارندگی کافی نیست، آبیاری بر رشد بذور و زنده‌مانی گونۀ اسپرسی همدانی تاثیر بسزایی دارد و بذرپاشی یا کپه‌کاری این گونه زمانی قابل توصیه است که پس از آن احتمال بارندگی بالا باشد.

investigating the effect of moisture, salinity, and the soil’s clay content on the germination and growth of hedysarum criniferum boiss under natural habitat and greenhouse conditions

introduction: in addition to pasture grazing, animals are fed on such sources as manual forage, farm straw, etc. therefore, due to various socioeconomic reasons, overgrazing and forage shortage exert adverse effects on rangelands, leading to their degradation. on the other hand, excessive exploitation of rangelands and changes in their use has led to the expansion of invasive species, altering the rangelands’ species composition and influencing the relevant ecosystem’s functions and services, which, consequently, ends in the destruction of ecosystems worldwide. in this regard, in cases where the invaluable and important species are overgrazed, the improvement of the rangelands containing perennial, highyielding, and palatable species is recommended to restore the rangeland’s production capacity, reduce the competitiveness of invasive species, and increase the vegetation both quantitatively and qualitatively. thus, it could be argued that identifying the factors involved in the germination and growth of invaluable species in rangeland ecosystems is required for the management, improvement, and restoration of rangelands.materials and methods: this study sought to investigate the effect of irrigation interval, water salinity, and the soil’s clay content on the seed germination and the height of germinated seedling of hedyasrum criniferum which is an endangered, palatable species indigenous to iran’s rangelands, under greenhouse and natural habitat conditions. to this end, a factorial experiment was performed in terms of irrigation interval at three levels of 7, 10, and 14 days, water salinity at three levels of <1 (0.4), 2, and 4 ds m1, and added clay contents at three levels of 0, 10, and 20% under greenhouse conditions with three replications, using a random sampling method. moreover, the glm method was applied to examine the factors affecting the herbal parameters of the hedyasrum criniferum species.results: the study’s results revealed that out of the three treatments mentioned above, only the irrigation interval had a significant effect on the h. criniferum species’ germinated seedling height and its germination percentage (α = 5%), with the greatest amount of germination (77.77%) and the highest germinated seedling’s height (4.93 cm) being observed in the sevenday irrigation interval based on the comparison of means. according to the species’ response curves, while the species’ height showed an ascending trend in proportionate to the precipitation rate, it had a reverse trend in proportionate to salinity. as for the clay content, it was found that the species’ height decreased up to 25% with an increase in the clay content. however, the trend was increasing for over 25% clay content.on the other hand, the analysis of the species’ response curve in terms of the amount of germination density indicated that while the number of germinated seeds increased with an increase in the precipitation rate, it decreased with an increase in salinity. moreover, the number of germinated seeds responded to clay content the same as it reacted to the species’ height, getting decreased with up to a 25% increase in the clay content.discussion and conclusion: as found in this study, irrigation interval is a more important factor than the other two treatments. the tolerance level of germination and seedling growth was found to be at a 14day irrigation interval, 4 ds m1 salinity level, and 20% added clay content. therefore, it could be argued that lowering the irrigation intervals may help the root growth. furthermore, maintaining the moisture at 400 cm away from the soil profile can facilitate root growth and thereby increase photosynthesis. however, increasing the irrigation intervals may disrupt photosynthesis by creating a shortage in the soil’s moisture and decreasing the production of photosynthate materials to be transformed into the plant’s growing parts, checking the growth of the plant’s height.