| Surrounded with large emission of coal wastes,high cost of reclamation and low soil biological infertility after regular reclaimation,the main purpose of this thesis is to study the effects of different soil replacement depth on plant growth and soil properties in order to improve the current theory of soil and revegetation ecological reconstruction in reclaimed coal waste dumpsites,which can further provide the demonstration effects to a similar area in future.The field experiment was conducted on coal waste dumpsites at Tunlan mine,Gujiao,Shanxi province.It was set up as a 6 split plot design with two factors as follows:depth of soil replacement(40cm,80cm and 120cm)as the main plot and cultivation model(plant soybean area and natural restoration area,also named as planted areas and abandoned areas in later)as the sub-plot.Soil,plant and microorganism were chosen as research objects of this study.The optimum soil replacement depth was screened out,based on the cost and ecological effects of the different soil replacement depth on soil physical property,chemical property and biological property,as well as the plant growth and biomass.The experiment results of this thesis were as follows.(1)Whether planted or abandoned areas,there are certain degrees of effects of soil replacement depth on soil bulk density,the ratio of soil solid,liquid and gas-phase,soil water content and temperature.Soil bulk density in treatments 80cm and120 cm was lowered than that of treatment 40cm.There is a significant effect of soil replacement depth on the ratio of soil solid,liquid and gas-phase(p<0.05).It showed that the proportions of soil and liquid were decreased,while the proportion of gas phase was increased with the increase of soil replacement depth.Compared with treatment 40cm,the contents of soil sand were decreased in both treatment 120cm and 80 cm.Soil temperature at depth of 25cm was the highest in soil of the treatment 80cm.Soil water contents in both treatment of 120cm and 80 cm were obviously higher than that of treatment 40cm.Under the same soil replacement depth,soil temperature at depth of 25cm of planted areas was higher than that of abandoned areas.Soil water contents in planted areas from July to September were higher than that of abandoned areas.However,soil bulk density in abandoned areas was higher than that of planted areas.(2)Whether planted or abandoned areas,there are certain degrees of effects of soil replacement depth on the contents of soil organic matter,total nitrogen,total phosphorus and total potassium.Under the same soil replacement depth at planted areas,contents of soil organic matter,total nitrogen,total phosphorus,total potassium at depth of 0-20cm were higher than that of bottom layer at depth of 20-40cm,but no significant differences were found among different soil replacement depth treatments;Contents of soil available nitrogen,phosphorus at depth of 0-20cm were also higher than that of bottom layer at depth of 20-40cm.Furthermore,contents of soil available nitrogen,phosphorus at depth of 0-20cm in treatment ZZ-80 were significantly higher than that of treatment ZZ-40(p<0.01);Soil available potassium was not changed regularly with the increase of soil replacement depth.As for abandoned areas,there are certain degrees of effects of soil replacement depth on soil organic matter,total nitrogen,phosphorus and potassium,available nitrogen,phosphorus and potassium.Under the same soil replacement depth,soil total and available nutrient contents in planted areas were higher than that of abandoned areas.Soil organic matter fractions were showed the same trend,and the content is higher in planted areas than that of abandoned areas whether it is highly active,active or labile organic matter.In addition,the content of each organic matter fraction in the topsoil is higher than that of bottom layer.Soil pH in planted areas is also higher than that of abandoned areas.(3)There is not obvious effect of soil replacement depth on the number of soil microorganism,soil enzyme activities and soil respiration.However,the functional diversity of soil microbial community was changed with the increase of soil replacement depth.Although there is not obvious effect of soil replacement depth on the number of soil bacteria,actinomycetes,fungi numbers in planted areas,the total soil microorganism number in the thick soil replacement depth treatment(80cm and 120cm)was higher than that of treatment 40cm in abandoned and planted areas.Furthermore,it is the highest in the soil of treatment 80cm.Both soil microbial community metabolic activity and the ability to use carbon were the highest in the treatment 80cm whether it is planted or abandoned areas.The functional diversity of microbial communities was improved in the soil of the thick soil replacement depth treatments(especially treatment 80cm).Under the same soil replacement depth,Shannon diversity index(H)and carbon richness index(S)value were higher in planted areas than that of abandoned areas.There is an obvious effect of soil replacement depth on the soil catalase.The activity of soil catalase in treatment 120cm was higher than that of treatment 40cm whether in planted areas or abandoned areas.In addition,there are not clear effects of soil replacement depth on the activities of soil urease,soil alkaline phosphatase,soil invertase and soil respiration.(4)There are significant effects of soil replacement depth on the biomass,yield and natural colonized plant species.Soybean aboveground and underground biomass and soybean yield in thick soil replacement depth treatments(ZZ-80 and ZZ-120)were higher than that of treatment ZZ-40,and it was highest in the treatment ZZ-80.In abandoned areas,aboveground and underground biomass in naturally colonized plant communities was increased with the increase of soil replacement depth.Species of naturally colonized plant were also increased with the increase of soil replacement depth,and the richest species were found in the treatment LH-80.Artemisia capillaries,Setaria viridis and Cleistogenes squarrosa are species with high importance value in naturally colonized plant communities,which were found to settle on coal waste dumpsites of Gujiao mining area in Shanxi Province.The interspecific associations among 7 species were tested by using Spearman rank and Pearson correlation coefficients in this study.The results showed that the correlation associations of species-pairs among 7 species were not significant.This indicated that naturally colonized plant communities on coal waste dumpsite of Gujiao mining area had simple and weak community structures,and were in the early stage of succession.(5)Soil replacement depth at 80cm with soybean cultivation were the most economical and suitable model of soil replacement in coal waste dumpsites at Tunlan mine,Gujiao,Shanxi province.In summary,considering the cost and effects of different replacement depth on soil physical,chemical and biological properties,especially the highest biomass(ZZ-80)and richest species(LH-80),we conclude that soil replacement depth at 80cm with soybean cultivation are the optimum soil replacement model on coal waste dumpsites of Gujiao mining area in Shanxi Province,which can provide the demonstration effects to the similar area. |
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