The Research On The Interspecies Effect Of Fraxinus Mandshurica And Larix Gmelinii Forest Plantation

Fraxinus mandshurica and Larix gmelinii are main afforestation species in northeastern China, they have higher ecological and economic value. Silviculture practice shows that the productivity and gowth of Fraxinus mandshurica and Larix gmelinii mixed plantation is much higher than pure plantation, showing a successful type of mixture.The reason is the interaction and feedback between plants and soil environment play an indispensable role in it..The plants make the inorganic elements return to the soil gradually by the litter decomposition, providing nutrients for the soil organisms simultaneously, keeping soil fertility,being an important material base of the detritus food chain in ecological systems.The litter decomposition is a long process,in which the physiochemical environment of soil will change as the chemical composition of the litter change.In the process of plant growth, root exudates can regulate plant nutrition and produce allelochemicals which affect the growth of neighboring plants, produce the poison effect that influence their growth and change the structure of the soil by the interaction with soil microorganisms. soil microorganisms is an important indicator of the index of soil fertility, beneficial microbes can increase the utilization rate of nutrients, promote the ability of plants to absorb nutrients, loose improve soil and enhance the resistance to disease, while harmful microbes can affect the health of plants growth.By the indoor experiment, our study analysised the influence of four kinds of larch root exudates on the seedling height, ground diameter, biomass, root activity, mycorrhizal infection rate and soil microbial community structure of Fraxinus mandshurica. Then we detected the relationship between the soil physicochemical properties, root exudates and the type and quantity of soil microorganisms in the field stand ages of Fraxinus mandshurica plantation, Larix gmelinii plantation and the mixed plantation. Our results suggested that:adding the 2,4-2 hydroxy benzoic acid+ferulic acid,7-hydroxyl coumarin+ferulic acid, Ferulic acid+ abietic acid, improved the growth of fraxinus seeding significantly,while adding the 2,4-2 hydroxy benzoic acid+abietic acid,7-hydroxyl coumarin+abietic acid and 7-hydroxyl coumarin+ferulic acid+abietic acid constrained the growth of fraxinus seeding significantly.Different Phenolic Acids in soil environment may exist a coordination relationship and the result of the coordination had beneficial or harmful effects on plants.Adding the 2,4-2 hydroxy benzoic acid+ferulic acid improved the root activity of fraxinus seeding,suggesting 7-hydroxyl coumarin had a inhibitory effects on root activity in the combination of 2,4-2 hydroxy benzoic acid+7-hydroxyl coumarin+ferulic acid.2,4-2 hydroxy benzoic could decrease the mycorrhizal infection rate of fraxinus seeding significantly,may be 2,4-2 hydroxy benzoic had a poison effect on mycorrhizal fungi.The field investigation found that:soil total carbon, total nitrogen content decreased gradually with the increase of soil depth, performing a trend of upper soil depth higher than lower, and the highest content of C in the hardwood forest.The number of fungi reduced with the increase of soil depth.10-20 cm soil depth N had a significant positive correlation with G+Bacteria and soil animals.Bacteria biomass was the highest among microbes in various types of plantation.We preliminary obtained the interrelationship between root exudates and soil microorganisms in Fraxinus mandshurica plantation, Larix gmelinii plantation and the mixed plantation. It lay the foundation for investigating the mechanism for improving the productivity of Fraxinus mandshurica-Larix gmelinii mixed forest,at the same time, it can make people understand the relationship between allelochemicals and soil microorganisms.