关键词: 土壤抗冲性, 尾矿库, 物种多样性, 根系

Abstract: Vegetation on the dam body after the closure of the tailings pond blocks pollutant diffusion and consolidates soil and water. Exploring the correlation between vegetation restoration and soil anti-scourability is conducive to ensuring the geological safety of dam body, and would provide a reference for the ecological restoration in the mining area. The space-for-time substitution method and typical plot method were used in this study. We carried out community survey, anti-scourability test, and root morphology analysis over five representative vegetations with different restoration years (2, 8, 14, 20 and 26 years) in the Majiatian tailings pond in Panzhihua City, with the natural vegetation of the surrounding mountains without tailings disturbance as the control (CK). The results showed that: (1) The restored vegetations were dominated by herbaceous plants. The number of perennial plant species increased with the increase in the restoration duration. Dodonaea viscosa and Leptochloa chinensis were the dominant shrub and herbaceous species adapted to the tailings pond in the long term, respectively. (2) The Shannon diversity index (H), species richness index (D) and Simpson dominance index (H′) of the herb layer of the restored communities exhibited a trend of decreasing-increasing-decreasing-increasing with the restoration duration. The magnitude of the fluctuation was rapid and then slow. The D was the lowest in the restored community at the end of the 8th year of restoration (P<0.05), with D of the restored communities for shrubs and herbs were significantly lower than that of the CK community (P<0.05). (3) The soil anti-scourability coefficient (AS) showed a trend of decreasing and then increasing with the restoration duration. The AS of the community restored for 26 years was significantly higher than that of the other restored communities (P<0.05), but still significantly lower than that of the CK. (4) The number of root tips, number of branches, root length density, root surface area density, root volume density of fine roots (root diameter less than 1 mm) showed a highly significant positive correlation with the D value of the herbs (P<0.01). The herbaceous diversity index was positively correlated with the AS, indicating that herbaceous diversity promoted the morphological development of root systems and further enhanced the soil anti-scourability. With the increases of vegetation restoration duration, the fluctuation of plant species diversity slowed down and the soil anti-scourability increased. The diversity of herbaceous species and the development of fine root morphology have an important influence on the improvement of soil anti-scourability in tailings ponds.

Key words: soil anti-scourability, tailings pond, species diversity, root system