نوع مقاله : علمی - پژوهشی
نویسندگان
1 دانشجوی دکتری، گروه جنگلداری و اقتصاد جنگل، دانشکده منابع طبیعی، دانشگاه تهران، کرج، ایران
2 دانشیار، گروه جنگلداری و اقتصاد جنگل، دانشکده منابع طبیعی، دانشگاه تهران، کرج، ایران
3 گروه علوم دامی، دانشکده کشاورزی، دانشگاه تهران، کرج، ایران
4 گروه علوم طبیعی، دانشکده علوم، دانشگاه تامپسون ریورز، کملوپس، کانادا
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Background and Objective: Persian juniper (Juniperus excelsa M. Bieb.) is a long-lived tree species that is highly tolerant of harsh environmental conditions and typically grows in mountainous regions. Owing to its ecological, medicinal, and industrial values, this species plays a critical role in mountain ecosystems. However, declining precipitation and ongoing climate change have increasingly threatened its survival. Therefore, improving management and nutritional practices to enhance the drought tolerance of juniper seedlings has become essential. The application of soil amendments such as biochar and vermicompost is considered an effective approach to mitigating the adverse effects of drought stress in plants. By improving the physical, chemical, and biological properties of soil, biochar and vermicompost can alleviate drought stress and promote plant growth. Although the individual effects of these amendments have been investigated in various plant species, their combined effects on drought-tolerant species such as juniper in arid regions have received limited attention. Accordingly, the present study aimed to evaluate the individual and combined effects of biochar and vermicompost on growth, biochemical traits, and leaf nutrient concentrations of juniper seedlings under different irrigation regimes.
Material and Methods: This study was conducted on two-year-old juniper seedlings as a factorial experiment arranged in a completely randomized design under greenhouse conditions at the Faculty of Natural Resources, University of Tehran (Karaj, Iran). Seedlings were subjected to three irrigation levels: 100% field capacity (full irrigation or control), 75% field capacity (mild drought stress), and 50% field capacity (severe drought stress). Soil amendment treatments included biochar (5% of pot volume), vermicompost (15% of pot volume), a combined application of biochar (2.5%) and vermicompost (7.5%), and a control without soil amendment. The measured traits included plant biomass, chlorophyll content, proline concentration, antioxidant enzyme activities, and leaf macronutrient concentrations.
Results: The results indicated that, in the absence of biochar and vermicompost, drought stress at 50% field capacity led to a significant reduction in growth and nutritional indices of juniper seedlings. Compared with the 100% field capacity treatment, shoot biomass decreased by 26%, root biomass by 20%, total chlorophyll by 18%, essential oil yield by 24%, and leaf nitrogen, phosphorus, and potassium concentrations by 29%, 25%, and 28%, respectively. In contrast, this level of drought stress increased proline content by 24% and enhanced the activities of the antioxidant enzymes catalase and superoxide dismutase by 97% and 105%, respectively. Moreover, the combined application of vermicompost and biochar produced more pronounced improvements in the measured traits than the individual application of either amendment. Under the 50% field capacity treatment, the combined amendment increased shoot biomass by 15%, root biomass by 14%, total chlorophyll by 13%, proline content by 12%, essential oil percentage by 11%, essential oil yield by 25%, and leaf nitrogen, phosphorus, and potassium concentrations by 24%, 21%, and 22%, respectively, compared with the non-amended control.
Conclusion: Although drought stress at 50% field capacity markedly reduced juniper growth and limited nutrient uptake in leaves, the results demonstrate that the combined use of vermicompost and biochar under drought conditions—particularly at 75% field capacity—can substantially mitigate the negative effects of water deficit. This combination significantly improves plant growth indices, enhances the uptake of essential nutrients in leaves, and increases essential oil production in juniper seedlings. As a result of these positive effects, water-use efficiency under stress conditions is improved, indicating that this approach is not only environmentally sustainable but also an effective and cost-efficient strategy for drought stress management. Overall, the findings suggest that the combined application of vermicompost and biochar represents a practical and reliable solution for maintaining seedling health and improving the performance of juniper in arid and semi-arid regions, and it is recommended as part of forest restoration and afforestation programs under conditions of limited water availability.
کلیدواژهها [English]
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