Effects Of Fertile Island On The Rates Of Soil Nitrogen Mineralization And Nitrification Under Tamarix Plant

Soil salinization is a serious environmental problem worldwide,which not only causes huge economic losses,but also threats the survival and development of local residents and the ecological safety in the whole area.Therefore,it is crucial for us to understand the mechanism of desalinization effects by plants especially for halophytes in desert saline environment.Biological improvement has been widely considered better to improve soil salinization than physical and chemical methods.In this study,we collected soil samples from outer and inner layer of tamarisk canopy at both severe and mild salinization area of Shule river basin,northwestern region of Hexi corridor.The physical and chemical properties,enzyme activity,rates of nitrogen mineralization and nitrification of soil samples were measured.The main objectives were to illuminate:(1)The fertile island of tamarisk in the desert saline environment and its influence on the spatial distribution of nutrition and ion in soil.(2)The effect of fertile island on the activity of soil urease,protease,nitrate reductase and the relationships between soil enzyme activity and soil nutrients content.(3)The influence of fertile island on the rates of soil nitrogen mineralization and nitrification.The main results were as follows:(1)Fertile island of tamarisk significantly increased soil organic matter(SOM),total nitrogen(TN)and Soluble potassium(K+),and significantly decrease the contents of salt cations e.g.sodium(Na+),magnesium(Mg2+)and calcium(Ca2+).The fertile island effects of tamarisk in severe salinization habitat is more significant than that in mild salinization habitat.(2)The activity of soil urease(Ure)and protease(Pro)are positively correlated with the SOM,and TN;Soil EC was not correlated with the activity of Ure and Pro but significantly correlated with Nit;These results suggected that the soil enzymes activities are significantly affected by the degree of salinization and content of SOM and TN.(3)Soil EC was significantly negatively correlated with the rate of soil nitrification(Nn).Nn is almost completely inhibited when EC>20 dS m-1.SOM was significantly positively correlated with the rate of soil mineralization(Nm);Soil EC has no significant effect on Nm.(4)Plant species richness was significantly reduced by salinization.