| The ecological environment of Shendong Coalfield is congenitally fragile,sensitive to the impact of coal mining.Deep study on damage degree and recoverability of the subsidence areas at Shendong Coalfield is the foundation for restoration and reconstruction of degraded ecosystem.Bulianta Coalfield(non-subsidence area,subsidence for 1,3,8 and 11 years),located in Mu Us Sandland,and Daliuta Coalfield(non-subsidence area,subsidence for 1,2,6 and 13 years),located in Loess hilly area were taken as the study areas.The response characteristics and rules of soil physiochemical properties and vegetation to mining subsidence under different landform types of different subsidence goaf ages were analyzed,research of soil amelioration,soil reconstruction,regulation and control of water and fertilizer,and afforestation recovery were targeted carried out,using the research methods of field investigation,simulation experiment and pot experiment,combined with the mathematical statistics methods of principal component analysis and fuzzy evaluation.The main objectives were providing theoretical guide and technical support for land reclamation of difficulty sites in mining areas.the conclusions are as follows:1.Soil mechanical composition of 0-100cm was not significantly impacted by subsidence.Subsidence mainly affected physical clay of 0-20 cm,clay content reduced with subsidence age,desertification trend of surface was increased.2.1n Aeolian sand area,soil bulk densities at earlier subsidence stage(1 and 3-year subsidence)were significantly smaller than non-subsidence area,and total porosity performed conversely,which performed significantly obvious at crack area and shallow soil(0-60cm),and the differences disappeared with the increase of subsidence age.In loess hilly area,soil bulk density and total porosity were not sensitive to mining subsidence.3.In the Aeolian sand area,the average infiltration rate and initial infiltration rate of 1-year and 3 subsidence areas were significantly larger than non-subsidence area.Because of differences of precipitation and initial soil water content,soil infiltration depths of 1-year and 3 subsidence areas showed different variation characteristics compared with non-subsidence area.In loess hilly area,average infiltration rates,initial infiltration rates and infiltration depths had no differences between subsidence area and non-subsidence area.4.In the Aeolian sand area,the monthly average soil water content of 1-year and 3 subsidence areas were significantly lower than non-subsidence area,which performed significantly obvious at crack area and shallow soil(0-60cm),and the differences disappeared with the increase of subsidence age.Soil water contents of subsidence area and non-subsidence area in loess hilly area had no difference.Whether it was in Aeolian sand area or loess hilly area,influence range of subsidence fissures on soil water content mainly in a 1.0 m range on both sides of the fissures,and the water contents significantly reduced.5.No matter in Aeolian sand area or loess hilly area,soil organic matter content,total N,total P,total K and available K between subsidence area and among different subsidence ages overall showed no significant differences.In Aeolian sand area,available N and available P of 1 and 3-year subsidence areas were significantly lower than non-subsidence area,which performed significantly obvious at crack area and shallow soil(0-20cm).In loess hilly area,available N and available P decreased with subsidence ages,but available N of 13-year subsidence area was significantly lower than non-subsidence area,and available P of 6 and 13-year were significantly lower than non-subsidence area,which performed significantly obvious at crack area and shallow soil(0-20cm).6.By comparison soil physiochemical properties among different year subsidence area veries very mach.Generally in Aeolian sand area 1-year subsidence area were close to 3-year subsidence area,but different from non-subsidence area significantly,while 8 year area is similar to 11 year area.In loess hilly area it is indicated that both 1-year and 2-year subsidence areas were close to non-subsidence area,but 6-year and 13-year subsidence areas presented a degradation trend.7.Shrubs,semi-shrubs were dominant in Aeolian sand area,perennial and annual,biennial herbs synergized.Perennial herb played an overwhelmingly role in loess hilly area,plants of other life forms in the communities played lower roles;the status and role of arbors in the community were smaller,and their position and role would disappear when under longer subsidence years.Complexities of plant family and genera compositions were different in different study areas.In the Aeolian sand area,it only exist one family and several genera,and the vegetation composition gradually tended to complicate with increasing subsidence age;in the loess hilly area,the vegetation had a phenomenon of several genera belonging to one family and several species belonging to one genus,and the vegetation composition was more complicated than Aeolian sand area.Stabilities of plant communities were different in different study area,the family of dominant plant species and vegetation evolution obviously changed with subsidence ages in Aeolian sand area;subsidence would not obviously affect the vegetation,the plants diversity and stability were relatively higher in loess hilly area.8.The best application range of PAM(one soil amendment)should be mixed application with a content of 400-600 mg/kg.When the aquasorb concentration was 0.2%,Pinus sylvestris showed the best adaptation to complexed soil(sand + sheep manure +aquasorb).The best combination of multi-factors-water-saving technical measure for Amygdalus pedunculata should be plastic film mulching + aquasorb(80g/plant)+proportions of fertilizers(local soil:mixed organic fertilizer=4:1),for Xanthoceras sorbifolia should be plastic film mulching + proportions of fertilizers(local soil:mixed organic fertilizer =2:3),and for Cerasus humilis should be plastic film mulching +proportions of fertilizers(local soil:mixed organic fertilizer = 2:3).9.The adaptabilities of different tree species to different landforms were quite different Pinus sylvestris var.mongolica,Elaeagnus angustifolia and Salix cheilophila were suitable in Aeolian sand area;Caragana korshinskii Kom,A.pedunculata and Pinus tabuliformis were suitable afforestation species for mining subsidence area of loess hilly area. |
