The Ecological Efficiency Analysis And Evaluation Of Revegetation In Iron Tailings In Tangshan

In this paper, taking various vegetation restoration patterns in iron tailings inTangshan as the research object, the effects of different vegetation restoration patterns onthe plant community characteristics and physichemical properties of iron tailings werestudied through fieldwork and lab observations. By combing the grey correlation andcorrelation coeficient to screen indexes and establish index system, the ecologicalefficiency of revegetation in iron tailings in Tangshan was evaluated by the method ofgeneral comprehensive evaluation and fuzzy comprehensive evaluation. Aims to providethe basis for vegetation restoration in iron tailings.The main results were as follows:(1)The plantation community structure was simple in every vegetation restorationpattern. On the vertical structure, the tin tile was divided into the tree layer, the shurb layerand the herb layer. The populus tomentosa forest was divided into the tree layer and theherb layer, the rest of the vegetation restoration patterns were divided into the shurb layerand the herb layer. The shurb layer of the amorpha forest, stripping rock stretched amorphaforest and tin tile grew more lush, and the coverage was80%、70%、65%, repectively. Theherb layer of the stripping rock stretched amorpha forest and bringing mixed forest grewmore lush and the coverage was58.29%、56.38%, repectively.(2) In terms of the species diversity index, the different vegetation restoration patternswere ranked in descending order as follows: populus tomentosa forest>stripping rockstretched amorpha forest>bringing mixed forest>amorpha forest>tin tile>sabina forest.Although the stripping rock stretched amorpha forest had the highest number ofherbaceous species composition, the diversity index was less than populus tomentos forestbecause of its species distribution.(3) There was a greater difference btween the total biomass in different vegettionrestoration patterns. The populus tomentos forest had the largest total biomass whichreached31.71t/hm2, followed by the amorpha forest which reached20.78t/hm2，and theywere far greater than other patterns.(4) Different vegetation restoration patterns could effectively improve the siolstructure and the capacity of water conservation of iron tailings, but the role was not thesame. In terms of improving the siol structure, amorpha forest, populus tomentos forest and bringing mixed forest had obvious effect on the improvement of the surface soil structure,but sabina forest, stripping rock streched amorpha forest and tin tile had obivious effect onthe improvement of the deep soil stucture. Amorpha forest had the best effect on theimprovement of the bulk, total capillary and total moisyure. The bulk had been reduced by12.10%, and the total capillary and total moisyure had increased by31.13%and56.61%,repectively. Sabina played the most significant role in promoting the capillary porosity,filed moisyur and capillary moisyur, which had increased by21.02%,47.46%and39.73%respectively. The stripping rock streched amorpha forest had the obvious effect on theimprovement of the no capilary porosity, which had increased by160.42%. In terms of thewater-holding capacity of the litter, amorpha forest was more better than stripping rockstreched amorpha forest.(5) In terms of the indexes of nutrient content of iron tailings, the pH value of thetailing sand was higher. The organic matter, nitrogen and potassium were in a state of acuteshortages. The total phosphorus content was higher, but the available phosphorus contentwas low which must be approved by years of weathering and biological activation processto ensure the availability of phosphorus. After the vegetation restoration, the nutrientcontent of tailing sand had different degree of improvement. Compared with the baretailings, the soil pH value had been decreased obviously, and increased with the increase ofsoil depth. In addition to the total phosphorus content, the nutrient content in eachvegetation restoration pattern had been decreased with the increase of soil depth. Theorganic matter, total nitrogen, alkali solution nitrogen, total potassium and availablepotassium content in stripping rock stretched amorpha forest, amorpha forest, tin tile,bringing mixed forest and sabina forest had increased in comparison with bare tailings. Theorganic matter in stripping rock stretched amorpha forest was6.24times that of the baretailings. Amorpha forest and stripping rock stretched amorpha forest could effectivelyimprove the total nitrogen and alkali solution nitrogen content. The total nitrogen wasrespectively3.75times and3.85times that of bare tailings, and the alkal solution nitrogenwas respectively7.35times and7.87times that of bare tailings. The stripping rockstretched amorpha forest had the most obvious effect on the accumulation of potassium.The total potassium content was6.66times that of bare tailings, and the avaible potassiumcontent was1.75times that of bare tailings. In terms of phosphorus, tin tile, amorpha forestand bringing mixed forest had certain effect on the accumulation of available phosphoruscontent, but the effect on the accumulation of total phosphorus in each vegetationrestoration pattern was not obvious.(6) By adopting the method of grey correlation and correlation coeficient, twentythree indexes were screened out which refleced the chatacteristics of the plant community,soil physichemical properties in iron tailings.Utimately, the bulk, total porosity, capillaryporosity, no capillary porosity, pH value, organic matter, alkali solution nitrogen, avalable phosphorus and available potassium,a total of nine facters were determined as theecological efficiency evaluation indexes of iron tailings. The evaluation results of generalcomprehensive evaluation and fuzzy comprehensive evaluation were consistent, whichillustrated that the two kinds of evaluation method was effective.a.The result of general comprehensive evaluation was: amorpha forest>tin tile>stripping rock stretched amorpha forest>sabina forest>bringing mixed forest>populustomentosa forest>bare tailings.b.The result of fuzzycomprehensive evaluation was: the amorpha forest was “good”,tin tile, stripping rock stretched amorpha forest and sabina forest was “general”, bringingmixed forest and populus tomentosa forest was “worse”, bare tailings was”poor”.