Key Takeaways & Executive Findings
- •• • Drought resistance ranking: Lolium perenne > Melilotus officinalis > Setaria viridis > Elymus dahuricus > Medicago sativa > Astragalus adsurgens > Artemisia oxycephala, based on membership function analysis integrating germination rate, vigor index, and drought resistance index. • • Under severe drought (soil moisture 5.11%, 40% field capacity), Lolium perenne and Melilotus officinalis showed significantly higher germination rates (P<0.05), indicating superior tolerance for arid restoration. • • The lower soil moisture threshold for seed germination is 5.11% (40% of field capacity); however, optimal irrigation range is 5.11%–10.22% (40%–80% field capacity) to balance water use efficiency and seedling vigor. • • Nonlinear threshold effects were observed: germination parameters declined nonlinearly with decreasing moisture, highlighting the need for precise water management in mine dump restoration.
Abstract
This study evaluated the drought resistance of seven dominant plant species from the Inner Mongolia desert steppe during seed germination to identify suitable species for ecological restoration of arid mining dumps. Seeds were subjected to soil moisture gradients ranging from 2.56% to 12.77% to simulate drought stress. Germination percentage, growth parameters, germination index, simplified vigor index, and drought resistance index were measured. A multi-dimensional evaluation system was constructed using the membership function method. Results showed that with increasing water stress, germination parameters generally declined nonlinearly. Under severe drought (soil moisture 5.11%), Lolium perenne and Melilotus officinalis exhibited significantly higher germination rates than other species (P<0.05). Comprehensive evaluation ranked drought resistance as: Lolium perenne > Melilotus officinalis > Setaria viridis > Elymus dahuricus > Medicago sativa > Astragalus adsurgens > Artemisia oxycephala. These findings indicate that Lolium perenne, Melilotus officinalis, and Setaria viridis possess strong drought resistance and can serve as pioneer species for vegetation reconstruction in mining areas. Furthermore, a soil moisture content of 5.11% (40% of field capacity) was identified as the lower threshold for seed germination, providing a quantitative basis for water management in arid mining ecological restoration.
1. Introduction
Ecological restoration of arid mining areas faces a critical bottleneck: the extremely low water-holding capacity of spoil substrates, coupled with nutrient deficiency and salinization, severely inhibits seed germination and seedling establishment. Conventional approaches relying on introduced species often fail due to poor adaptability and high mortality under drought stress, leading to secondary degradation of restored vegetation. The study site, Manglai Coal Mine in Inner Mongolia, receives only 163.18 mm annual precipitation against an evaporation of 2564.3 mm, exacerbating water scarcity. Thus, selecting native species with inherent drought tolerance is imperative for sustainable restoration.
This research addresses the gap by systematically evaluating the germination responses of seven native desert steppe species under controlled soil moisture gradients (2.56%–12.77%). Unlike single-metric assessments, the study employs a multi-dimensional membership function analysis integrating germination rate, vigor index, and drought resistance index to rank species. This approach provides a robust framework for identifying pioneer species and determining the critical soil moisture threshold for germination, offering quantitative guidance for water management in arid mine restoration projects.
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ZHANG Tingting, LI Xin, FEI Xihao, QU Laiye, YU Yan (2026). Drought Resistance Evaluation of Dominant Species in Inner Mongolia Desert Steppe During Seed Germination. Chinese Journal of Environmental Engineering. https://doi.org/10.12030/j.cjee.202505103
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Frequently Asked Questions
What is the physiological basis for the nonlinear decline in germination parameters under increasing drought stress?
The nonlinear decline is attributed to the threshold response of seed imbibition and metabolic activation to water availability. Below a critical soil moisture level (5.11%), enzymatic activities and cellular expansion are severely impaired, leading to abrupt reductions in germination. The data show that at 5.11% moisture, germination rates for the most tolerant species (Lolium perenne) remained significantly higher (P<0.05) than others, indicating differential adaptive mechanisms such as osmotic regulation and seed coat permeability.
How does the recommended irrigation range (5.11%–10.22% soil moisture) translate into practical water management for mine dump restoration?
The range corresponds to 40%–80% of field capacity. Maintaining soil moisture within this range ensures sufficient water for germination while minimizing water waste. At 10.22% (80% field capacity), some species exhibited higher vigor indices, suggesting that upper-range irrigation may enhance seedling establishment. However, economic and ecological considerations favor the lower bound (5.11%) as a minimum threshold to avoid unnecessary irrigation costs in arid regions.
What are the limitations of using the membership function method for drought resistance ranking?
The membership function method integrates multiple indices but assumes equal weighting, which may not reflect the relative importance of each trait under field conditions. Additionally, the ranking is based on germination-stage responses only; post-germination survival and long-term field performance may differ. Future studies should incorporate multi-stage evaluations and field trials to validate the rankings.
Can the identified drought-resistant species (Lolium perenne, Melilotus officinalis, Setaria viridis) be effectively established in nutrient-poor, saline-alkaline mine spoils?
While these species showed superior germination under drought, the study did not assess their performance under combined stresses of salinity and nutrient deficiency. The spoil soil had pH 8.19 and low organic matter (9.78 g/kg), which may pose additional challenges. Further research is needed to evaluate their establishment success in actual spoil conditions, potentially with soil amendments.
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