Effects of Nitrogen and Phosphorus Combined Fertilization on Fine Roots and Soil Microorganisms of Machilus Pauhoi
Abstract
Machilus pauhoi is a precious tree species and timber forest in the subtropical forest system of China, and the increase in soil nitrogen input will have a profound impact on soil microorganisms. However, it is still unclear about the relative growth rate, fine root traits, and the optimal nitrogen to phosphorus ratio of soil microorganisms of Machilus pauhoi. The essay taking the 3-year-old artificial wood-shaven Machilus pauhoi forest as the research object, five fertilization treatments with different nitrogen and phosphorus ratios were set up (Including control group). Based on the investigation and analysis of Machilus pauhoi's growth in different seasons, fine root characteristics, soil physical and chemical properties and soil microorganisms in 0-20cm soil layer, the influence mechanism of nitrogen and phosphorus combined fertilization on Machilus pauhoi's relative growth rate, fine root characteristics, soil physical and chemical properties and microorganisms was preliminarily revealed, and the synergistic influence mechanism of fine root, soil and microorganisms on Machilus pauhoi's growth was discussed. In September, the content d of soil (TN), soluble organic nitrogen (DON), soil organic matter (SOM) and TP reached the maximum level, and the comprehensive effects of combined fertilization of nitrogen and phosphorus on them should be kept at the best N: P ratio, with the range of 10~12. Bacteria, fungi, actinomycetes, microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) all reached the maximum in September. Different combined fertilization of nitrogen and phosphorus is beneficial to the growth of the three major flora and the retention of soil carbon and nitrogen nutrients by microorganisms, so it is necessary to keep the overall N: P ratio between 10 and 12. SRL and RTD of 0-1mm fine roots are the main fine root factors that affect the relative growth rate (RGR) of whole plant biomass of Machilus pauhoi. MBN is the main microbial factor affecting RGR; Soil TN, DON and SOM are the main soil factors affecting RGR. Through stepwise regression analysis of fine roots, soil and microbial factors, it is found that MBN, DON and soil TP are the main environmental factors that can most affect RGR.