| Soil salinization has become a serious environmental problem in the world.Compared with physical and chemical methods,biological methods have proved to be the most effective,sustainable and environment-friendly methods.Halophytes are the native plant species that can finish their life cycles in saline environment equal to or higher than 200 mmol·L-1Na Cl.Halophytes are widely distributed in the world,Halophytes are widely distributed and varied in natural environment,and they are valuable resources for saline-alkali land improvement.There is a large area of saline-alkali land in China.The Yellow River Delta is a typical coastal saline soil.Most of the 8 million mu of marginal land in the Yellow River Delta is saline-alkali land with high soil salinity and low nutrient content,which is not suitable for the growth of common crops.The ecosystem of newborn wetland is fragile,and the secondary salinization of soil is seriously threatened by sea tide,storm surge and other disasters.In recent years,the degree of land reclamation is increasing,which has led to the further degradation of the soil,the planted forest and the fragile environment in Yellow River Delta.Environmental problems have seriously restricted urban greening,ecological construction and economic development in the Yellow River Delta.It is of great significance to fully develop and utilize the rare land resources such as saline soil in the eastern region and to develop new ecological economic industry,which will contribute to the ecological construction,urban greening and the development and utilization of saline-alkali land in the coastal area of the Yellow River Delta.In order to improve the ecological civilization,economic and cultural level and to enhance the comprehensive competitiveness of the Yellow River Delta,we must greatly develop forestry and establish a stable ecosystem.In the past decades,we have collected a large number of salt-tolerant tree varieties from all over the country and carried out studies on the evaluation of their salt tolerances.Finally,we have screened out two tree species that can survive in the severe saline-alkali land:Tamarix chinensis and Elaeagnus angustifolia L.Now,it is the limiting factor to establish planting techniches and the planting mode of halophyes such as Tamarix chinensis and Elaeagnus angustifolia L.in saline-alkali land.In this study,Tamarix chinensis and Elaeagnus angustifolia L.were to construct the cultivation technique and supporting management mode,which provides the practical techniques for improving the survival rate,preservation rate and forest coverage rate of trees in high salinity land in the Yellow River Delta.The main results are as follows:In this study,Tamarix chinensis Lour and Elaeagnus angustifolia L.adapting to high salinity were uesed to investigate the tending techniques planting mode in saline land.The effects of different fertilizer applications on the properties of saline soil and growth parameters Tamarix chinensis Lour and Elaeagnus angustifolia were in detail studied by the experiments.The results showed that the organic fertilizer application significantly promoted the plant height and biomass accumulation of Tamarix chinensis,and markedly improved the physicochemival parameters of saline soil such as salt content,organic matter content,soil bulk density and p H.The most suitable fertilizer(N+P5O2+K2O?4%,organic matter?30%)amount is 3600 kg·hm-2fertilizer.Compared with control,the net growth of plant height and biomass of Tamarix austromongofica was 34 cm and about 500 g in a year,respectively.In addition,the p H value of the soil decreased by 0.17,the bulk density of the soil decreased by 5%,the hydrolyzed nitrogen and available phosphorus increased to more than twice of the original value,and the available potassium in the soil increased by about 30%.The net growth of plant height of Tamarix chinensis Lour in one year was increased by 40 cm,and the net growth of above-ground biomass was increased by1500 g.The hydrolytic N content in the soil increased to more than twice of the CK,the available P content increased to more than 50%,the available K increased by about 10%,the soil p H decreased by 0.31 on average,and the soil bulk density decreased by 4.6%.In order to take a look insight into the effect of different ages of the seedlings on the survival rate in saline soils,different ages of Tamarix chinensis seedlings were transplanted in the saline soils,and the Tamarix chinensis with a plant height of 60?160 cm and a stem diameter of 2?8 cm had a survival rate of over 80%,significantly higher than other seedlings,which was suitable for transplanting in saline land.The effects of organic fertilizer(N+P5O2+K2O?4%,organic matter?30%)on the growth parameters of Elaeagnus angustifolia L.and the physicochemical propertyies of saline soil were studied by means of organic fertilizer application experiment.The results showed that organic fertilizer significantly promoted the elongation of plant height and the accumulation of biomass.When 2100kg·hm-2fertilizer was applied,the net growth of plant height in one year was 30 cm,and the net average growth of biomass was 1200 g per plant,which was the optimal fertilizer application.The application of organic fertilizer increased the nutrient content in the saline soil,the content of hydrolytic nitrogen increased to more than 2 times,the content of available phosphorus increased to 5 times,the content of available potassium increased to more than 50%,and the salt content and p H of the soil were reduced.Compared with control,the p H value of the soil under fertilization decreased by 0.61 on average.The apllication of chemical fertilizers to Elaeagnus angustifolia L growing in saline soil was explored.When the fertilizer application amount was 187.5 kg urea plus 187.5 kg calcium superphosphate per hectar,the net growth rate of plant height in one year was17.3 cm and the net growth rate of biomass was 1001.6 g,which was the most suitable.In this paper,the adaptability of one-year-old Elaeagnus angustifolia seedlings in salt-alkali land was explored,the survival rate of the salt-alkali land was50%in the soil in the saline soil with a salt content of 2.3%,the survival rate of the salt-alkali land was about 70%when the soil salt content was less than 1.5%.These results indicate that the salinity threshhold of Elaeagnus angustifolia is 2.3%and Elaeagnus angustifolia can be planted in the salt-alkali land with less than 1.5%of salt content.The effect of different plant spacing on plant growth morphology was explored by means of thinning seedlings experiment.The larger plant spacing,the trunk more curved.Therefore,density of the planting(plant spacing?5cm)is the suitable planting density for Elaeagnus angustifolia seedling propagation.Several hundred Tamarix gallica Bunge seedlings were obtained and the experimental process of tissue culture was further optimized.The root culture and increment culture of Tamarix gallica Bunge could be completed by MS medium with simple operation.In summary,the tending techniques and planting mode of Tamarix chinensis and Elaeagnus angustifolia L.in high salinity land have been constructed,which provides technical support for the large-scale forest planting in saline land and provides a guarantee for the urban greening of Tamarix chinensis and Elaeagnus angustifolia L.in the coastal cities such as Tianjin and Dongying. |
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