Evaluation On Effects Of Different Tree Species On Soil Improvement In The Coastal Saline Land Of Yellow River Delta

In order to study the soil improvement effects of different tree species in the coastal saline land of the Yellow River Delta,We adopted the method of soil sampling combined with laboratory measurement to analyze the rule of the water-salt movement,the soil physical,chemical and biological properties,the correlation of four different plantations with the control of the unplanted land.And using the principal component analysis to evaluate the soil quality of four different plantations synthetically,so as to provide the scientific basis for the selection of green trees and sustainable development in the coastal saline land of the Yellow River delta.The results proved that the four salt-tolerant species had certain improvement effect on the coastal saline land in Yellow River delta.The main research contents and results were as follows:1.Using the salt-tolerant species to afforest the coastal saline land would affect the water-salt movement,and the water-salt movement appeared certain seasonal and levels in plantation soils.The distribution of soil salt contents had obvious surface assembly,the maximum value appeared to the surface layer of control,and the salt-tolerant species had a significant effect on reducing the soil salt content of surface layer.2.The soil structure and physical properties of the coastal saline land have improved in some degree after planting salt-tolerant species.Compared to the control,the average soil bulk density of 0-60 cm soil layer in different tree species were decreased by 2.25%-7.08%,while the total porosity were increased by 3.16%-10.63%.The capillary porosity,non-capillary porosity and field capacity of different tree species were increased at the same time.3.The pH value in surface layer of different tree species were significantly decreased,the average pH value of 0-60 cm soil layer were reduced by 2.53% compared to the control.The average organic matter content were increased by 96.76%-276.39%,the content of ammonium N,nitrate N,available P,available K were increased by 76.47%,757.74%,32.76%,30.13% respectively.The effect of every tree species on cation exchange performance and exchangeable sodium percentage was different,the exchangeable sodium percentage of different plots decreased in the order: Tamarix chinensis(27.38%)> Pyrus betulifolia(23.34%)> CK(19.45%)> Fraxinus chinensis(15.97%)> Salix psammophila(13.34%).4.The research of soil enzyme activity and microbial quantity of different tree species shows that the soil enzyme activity were reduced gradually with the increase of soil depth.Compared to the control,the average activity of phosphatase,catalase,urease,sucrose in 0-60 cm soil layer of different tree species were increased by 47.09%,11.52%,41.07%,76.00% respectively,and the amount of fungi,bacterial,actinomycetes were increased by 6.33-42.96,3.57-55.53,0.67-3.56 times respectively.The soil enzyme activity and microbial properties were improved obviously after afforestation.5.Using principal component analysis to evaluate the 22 soil quality indicators,the comprehensive scores were as follows: Salix psammophila(1.521)> Fraxinus chinensis(1.234)>Pyrus betulifolia(0.073)> Tamarix chinensis(-0.631)> CK(-2.197).It turned out that Salix psammophila performance the best improvement in saline land,followed by Fraxinus chinensis,then by Pyrus betulifolia,and Tamarix chinensis was the lowest.