Growing responses of four exotic alder seedling under different nitrogen concentrations.

The experiment on four exotic alder including Alnus glutinosa,A.rubra,A.nitida and A.incana growing under four different concentrations of nitrogen was conducted in a greenhouse in order to research the alder's responses under different nitrogen concentrations and stresses.The results showed that the growing parameters of alder on the survival percent of transplanting,plant height,ground diameter,biomass,root-top ratio,relative content of chlorophyll(SPAD) and rooting parameters(length,superficial area,volume and tips of root) were significant among different materials and different nitrogen concentrations,the different level of nitrogen significantly affected the growth of alder.Specifically,the survival percent of transplanting went down with the going up of nitrogen concentration,and the plant height,ground diameter,relative content of chlorophyll and rooting parameters went up when nitrogen varied from 0 to 1/2 normal nitrogen,yet went down at one or two times of normal nitrogen(E.G.Bollard formula).The relative content of chlorophyll went up with the concentration of nitrogen increasing from 0 to 2 normal nitrogen,and its trend during one year period showed rising firstly and then descending.The relationship between the value of SPAD and biomass did not appear positive correlation.The appropriate concentration for growing on alder was 1/2 normal nitrogen.The order of performance of growth among the four alder was Alnus glutinosa,A.rubra,A.nitida and A.incana.So,A.glutinosa and A.rubra potentially could be used as plantation trees of ecological protection and short-rotation lumber in the beach and low hills of middle and lower reaches of Yangtze River.