Effects Of Juglans Mandshurica And Pinus Koraiensis Mixture On Soil Characteristics And Fine Root Traits

Manchurian walnut(Juglans mandshurica)and Korean pine(Pinus koraiensis)are important afforestation tree species in northeast China.The pure artificial coniferous plantations are not advocated due to a single composition,simple structure,and poor ability to maintain soil fertility.In order to preferably exert the multi-functional benefits of the forest and improve the resistance.Establishment of mixed forests is the common trend of artificial afforestation.The mixed plantation of Manchurian walnut and Korean pine is one of the main mixed cultures in northeast China.However,previous studies have ignored the effects of mixed planting on soil extracellular enzymes,microorganisms,and fine root characteristics.Therefore,pure Manchurian walnut plantation,pure Korean pine plantation,mixed plantation of Manchurian walnut and Korean pine were selected as the research stands,three 20 m × 30 m standard plots were set for each stand to take soil and roots samples,and investigate the productivity and vegetation diversity,and then bring back the soil and roots.Soil nutrient content,extracellular enzyme activity,microbial diversity and structure,fine root function was determined based on the productivity and vegetation diversity investigation.The aim was to explore the effect of mixed culture on soil factors and root traits;to construct the correlation of various soil factors and analyze the relationship between fine root traits and mycorrhizal infection.The main results of this study are as follows:(1)Compared with pure Manchurian walnut plantation,the mixed culture of Manchurian walnut and Korean pine significantly increased soil moisture content,soil water holding capacity,soil porosity,the contents of soil total phosphorus,available phosphorus,and microbial biomass nitrogen,while reduced the contents of ammonium nitrogen,nitrate nitrogen,microbial biomass phosphorus.Compared with pure Korean pine plantation,mixed planting significantly increased the contents of soil total phosphorus,total potassiumand,available phosphorus;and the effects of different soil layers were different,and the changes were not consistent.There is a certain correlation between soil physical index and soil chemical index.(2)In general,the extracellular enzyme activity gradually decreased with the soil-layers depth increased.The activities of L-leucine amnopeptidase(LAP)and Peroxidase(POD)in the mixed culture of Manchurian walnut and Korean pine were significantly higher than those of pure Korean pine plantation.Compared with the pure Manchurian walnut plantation,the ?-glucosidase(AG)and Acid phosphatase(AP)activities of the coniferous and broad-leaved mixed plantation were lower;different types of enzymes had different relationships with soil physical and chemical properties.(3)The mixture of Manchurian walnut and Korean pine increased the abundance and diversity of the soil bacterial community and changed the structure of the soil bacterial community.Soil bulk density.and ?-glucosidase(AG)and ?-1,4-N-acetylglucosaminidase(NAG)had the greatest influence on soil bacteria.Mixed culture significantly increased the abundance of fungal communities and the diversity of Manchurian walnut fungal communities.Soil total potassium and ?-glucosidase(AG)had the greatest impact on soil fungi.(4)Mixed culture increased the fine root diameter and reduced the root tissue density of Korean pine,reduced the specific root length of Manchurian walnut,and had no significant effect on the root tissue.Mixed planting increased the diameter of the column,mycorrhizal infection rate and the infection index of Manchurian walnut,but reduced the thickness of the cortex,while reduced the cortex thickness,the mycorrhizal infection rate and the infection index,and increased the diameter of the column of the Korean pine.The morphology and anatomy of fine roots were closely related to mycorrhizal infection.In short,the establishment of mixed culture of Manchurian walnut and Korean pine improved soil nutrient and water content,accelerated the circulation of soil nutrients and increased the activity of extracellular enzymes,increased soil microbial diversity and change the composition of soil microbial communities.The diameter of the fine roots is increased,and mixed culture increased the tissue density,the diameter of the column and the infection rate of mycorrhiza of Manchurian walnut.