Analysis On Soil Structure Improvement And Efficacy Of The Soil And Water Conservation In Tangshan Iron Tailings Revegetation

In this paper, Tangshan Iron tailings were taken as the object of study. The physicalstructure of soil in different revegetation patterns were surveyed and mensurated in thisstudy. The improvement of different revegetation patterns effect on the soil structurewas studied importantly. We builted runoff simulation field on the representativepatterns of revegetation, and observed the parameters on the water loss and soil erosionafter each rainfall and then analysed the effect of soil and water conservation byrevegetation. The results were as follows:It had been improved noticeably between soil replaced and others. Sand grainssized around100um had the most quantity, sand grains sized under100um higher thantailings obviously, sand grains whose size between100um to1000um lower thantailings obviously. The sand grains size of other revegetation patterns were similar withtailings, and it had no significant difference between different solum, sand grains whichsized around250um took the most quantity, grains which sized less than30um took thefew quantity, grains which sized less than5um took the least quantity. Excepted theTorch tree pattern which had soil replaced had more than50%gravel, the content ofgravel in other pattern had less then20%. the organic in soil raised obviously afterrevegetation. Compared with controlled bare tailing, the organic in soil of Torch treepattern, Mixed pattern, River locust pattern, Sea-buckthorn pattern and Sabina vulgarispattern had respectively increased by164%,160%,77%,77%and57%, but still lowerthan the normal value. The increasing of the organic in soil by vegetation restorationmeasures had an increasing effect on the quantity of large macro aggregate, but not tooobvious. In contrast, the mechanical composition and the physical extrusion had greaterinfluence on the quantity of large macro aggregate in soil.The unit weight of the Torch tree pattern was equal to the tailings, and others werelower than tailings after revegetation. Compared with tailings, Sea-buckthorn pattern,Sabina vulgaris pattern, Mixed pattern and River locust pattern had reduced by1%,7%,10%and12%. Compared with tailings, total porosity of soil, capillary porosity and noncapillary porosity of fields after revegetation had all increased visibly. The total porosityof River locust pattern, Sabina vulgaris pattern, Torch tree pattern, Mixed pattern andSea-buckthorn pattern had respectively increased by31%,28%,27%,23%and1%. Thecapillary porosity of Torch tree pattern, Sabina vulgaris pattern, River locust pattern,Sea-buckthorn pattern and Mixed pattern had respectively increased by26%,21%,13%, 11%and1%；The non capillary porosity of Mixed pattern, River locust pattern, Sabinavulgaris pattern and Torch tree pattern had respectively increased by136%,125%,73%and47%, and only Sea-buckthorn pattern had reduced by42%. Compare with tailings,the field capacity, capillary moisture capacity and saturation moisture content of soilhad all increased after revegetation. The field capacity of Sabina vulgaris pattern, Torchtree pattern, Sea-buckthorn pattern, River locust pattern and Mixed pattern hadrespectively increased by47%,46%,20%,16%and12%; The capillary moisturecapacity of Sabina vulgaris pattern, Torch tree pattern, River locust pattern,Sea-buckthorn pattern and Mixed pattern had respectively increased by40%,35%,21%,21%and16%; The saturation moisture content of River locust pattern, Sabina vulgarispattern, Mixed pattern, Torch tree pattern and Sea-buckthorn pattern had respectivelyincreased by57%,38%,38%,27%and2%. River locust, Torch tree and Sea-buckthornhad an obvious effect on improving the physical properties and organic of soil in surfacesoil, and the River locust had the best effect. Pinus tabulaeformis and Sabina vulgarishad a large effect on improving the physical properties of soil in deep soil. Mixed Pinustabulaeformis and River locust pattern could improve the physical properties of soilcomprehensively.The initial infiltration rate of soil had increased after revegetation. It ranked asfollows: Sea-buckthorn pattern（18.71mm/min）＞Torch tree pattern（12.73mm/min）＞Shrubs and herb（s11.45mm/min）＞tailing（s9.66mm/min）; The steady infiltration rate ranksas follows: Sea-buckthorn pattern（13.24mm/min）＞tailings（8.49mm/min）＞Torch treepattern（7.88mm/min）＞Shrubs and herbs（7.62mm/min）. Phenomena of serious water lossand soil erosion will be occured after the rainfall in the tailings without revegetation, itcontained large numbers of soil, and caused serious soil erosion. Compared with tailings,the soil part from soil and water loss and the amount of soil erosion of the Torch treepattern had reduced by3%and2%. But the frequency of soil and water loss hadincreased and the volume of runoff had increased over4times. Runoff times of Shrubsand herbs pattern matches with Torch tree pattern. It can also reduce the soil part fromsoil, the amount of soil erosion and the water loss, but waker than the Torch tree pattern,Equal to the155%,135%and132%of the Torch tree pattern. Compared with tailings,the volume of runoff, the amount of soil erosion and the soil part from soil and waterloss of the Sea-buckthorn pattern had reduced by50%,40%and30%, and thefrequency of soil and water loss had also reduced. Although the Sea-buckthorn patterngot better result than Torch tree pattern on reducing the volume of runoff and frequencyof soil and water loss, the effect on the soil part from soil and water loss and the amountof soil erosion still worse than the latter.