不同造林树种对铁尾矿基质理化性质和土壤动物的影响

为了探讨不同造林树种对铁尾矿基质改良及土壤动物的影响,在唐山迁安马兰庄铁尾矿区选择尾矿坡面直接造林成功的沙地柏、紫穗槐、毛白杨3种树种,测定林内尾矿理化性质和土壤动物,并与裸尾矿进行对比分析。结果表明:(1)紫穗槐林对铁尾矿土壤容重、总孔隙度、非毛管孔隙度和饱和持水量的改善效果最好,沙地柏林对改善毛管孔隙度、田间持水量和毛管持水量的效果最好。(2)3个树种造林均使尾矿砂p H值明显降低。紫穗槐林对尾矿砂有机质、全氮、碱解氮、速效磷、速效钾含量的积累效果最好,沙地柏林和紫穗槐林均有利于尾矿砂中全钾含量的积累。(3)紫穗槐林下土壤动物数量和多样性最高,沙地柏林次之。铁尾矿土壤动物与环境因素灰色关联度分析表明,全氮、有机质、碱解氮、土壤容重与土壤动物多样性关系密切,植被覆盖率和植被高度对土壤动物多样性影响最小。(4)主成分分析结果表明:紫穗槐林对铁尾矿基质理化性质和土壤动物综合改良效果最好,其次是沙地柏林,杨树林的改良效果不明显。但进行值被恢复后,各样地的立地条件均优于裸尾矿。

Effects of different forestation species on the substrate physicochemical properties and soil fauna in iron tailings

A large amount of tailings were formed in the process of metal mining, thereby bringing about serious ecological environment problems in the local area. Iron tailings are a kind of tailings, which directly are formed by crushing the iron ore. And their physichemical properties are obviously different to the conventional cultivation soil. From the point of chemical properties, the iron tailings have not been driven by biological factors to accumulate organic matter and other nutrients so that their fertility is low. From the point of physical properties, the loose structure and rough texture of the iron tailings lead to poor water retention. These poor physichemical properties which are unfavourable to plant growth bring great difficulty in the ecological restoration for abandoned mine. We can know that biological factors play a crucial role in the formation of soil according to this ecological theory between soil and organisms. Thus we should select the plants which have strong adaptability to iron tailings to construct artificial vegetation. The formation of artificial vegetation will be very effective on improving soil fertility as well as soil properties of iron tailings so that other organisms can enter and settle in the ecological conditions. Amorpha fruticosa is a good afforestatin species not only for soil erosion but also for desertification of land as one series of mesquite. Sabina vulgaris is the creeping evergreen conifruticeta, which is commonly used to conserve soil and water, control desertification and green urban landscape in semi-arid area of northen China. Populus tomentosa is a fast-growing broadleaf trees and a representative of native species in north China. Based on the advantages of the above three species, we made an investigation on physichemical properties and fauna of bare tailings soil in different type of vegetation to explore the influence of different afforestation species on properties and fauna. The results showed as follows: (1) Amorpha fruticosa has the best restoration effect on soil bulk density, moisture, saturation moisture capacity, total porosity and no capillary porosity, but Sabina vulgaris has a significant impact on capillary porosity, field capacity and capillary moisture capacity. (2) All of the forestion species could decrease the pH value of iron tailings obviously. Amorpha fruticosa is the most effective way to improve soil organic matter, total nitrogen, available nitrogen, available phosphorus and potassium. Sabina vulgaris and Amorpha fruticosa are both conducive to increase soil potassium. (3) The number and deversity of soil fauna under Amorpha fruticosa system was significantly greater than Sabina vulgaris. This research revealed by Grey relevant analysis (GRA) that soil fauna diversity was closely related to the total nitrogen, organic matter, alkali-hydro nitrogen and soil bulk density. However, the soil fauna appeared to be almost unaffected by the vegetation coverage and height. The result of a principal component analysis (PCA) indicated that the Amorpha fruticosa had the best comprehensive improvement of the physicochemical properties and soil fauna, followed by Sabina vulgaris and the improvement effect of Populus tomentosa was not obvious. In conclusion, Amorpha fruticosa is fine species of direct afforestation in iron tailings soil as the mesquite. In the respect of soil physichemical properties, Amorpha fruticosa has the more significant effect on soil improvement than Sabina vulgaris, but Sabina vulgaris is even better than Amorpha fruticosa in the respect of water conservation and deep soil improvement. To adapt to the long-term arid environment, Sabina vulgaris as evergreen coniferous shrub formed rich underground root system. This is especially important to the ecological slope protection and winter green landscape improvement which should be developed vigorously in future. Populus tomentosa is a local native tree species with the characteristics of fast-growing poplar, which indicates the weakest effect on soil improvement. But there also are obvious water conservation, ecological protection, soil improvement and other ecological benefits compared with the bare tailings.