The Effect Of Biochar On Soil Microbial Diversity And Community Structure

Microorganisms are important participants in soil biological chemistry process, it plays an important role in the formation of soil fertility. Many reports have suggested that biochar maintain the initial carbon skeleton and macro pore structure in the process of production, biochar is recommended as an additive to influence soil physico-chemical properties, improvement of soil fertility, providing a refuge for soil microorganism to increases the soil microbial activity, microbial abundance, community composition and microbial functional diversity. In order to study different soil types, different dosage of biochar and fertilizer, we design the simulated culture experiment, field experiment and pot experiment by denaturing gradient gel electrophoresis (DGGE), Miseq high-throughput sequencing and Biolog to evaluate the effect of soil bacterial abundance, diversity, community structure and even carbon (C) utilization capacities with biochar addition.The simulated culture experiment used biochar derived from rice husk, red soil (Guangdong province Huizhou city), saline alkali soil (Liaoning province Panjin city), brown soil (Liaoning province Shenyang city) were conducted with biochar application rates:0t ha-1, 10t ha-1,20t ha-1 and 40t ha-1. The addition of biochar can increase the soil microbial carbon content and saline alkali soil microbial nitrogen content, while red soil and brown soil microbial nitrogen content decreased. The red soil pH increased with the biochar application rates increased, while the saline alkali soil and brown soil decreased. It deduced that the biochar improvement effect was decided with acid-base property between biochar and soil, and then effect the microbial community structure. The addition of biochar increased soil physico-chemical properties(soil moisture content, pH, soil microbial biomass carbon content, soil microbial biomass nitrogen content, carbon:nitrogen). Alpha diversity analysis revealed the effect of biochar on soil microbial richness and diversity. The principal component analysis indicated the significant difference in community structure of saline alkali soil with biochar addition, while indifference in brown soil. The difference in community structure of red soil with biochar addition was lager than saline alkali soil and brown soil. Redundancy analysis (RDA) revealed that the relationship environment factors (pH, soil moisture content and microbial biomass nitrogen content), dominant microorganisms and different treatments. The effect of pH on microorganisms was higher than MBN and soil moisture content. Soil moisture content and MBN were positive correlation, MBN and pH were negative correlation, soil moisture content and pH were no significant correlation. The addition of biochar increased different soil’s membrane transport and amino acid metabolism, and meanwhile decreased gene replication and repair function. The microbial community abundance and structure’s variation can induce the soil microbial functional change. The addition of biochar increased Nitrospira abundance, it participate in the oxidation of nitrite and nitrogen cycle. Some Bacilli belong to Firmicutes had ability to use carbon source, promoting plant growth rhizospheric microorganism and prevent the plant disease.The field experiment used biochar derived from cornstalk, including 8 treatments (1) CK1-CK2:control. (2) BC-CK2:returning straw carbonization with no fertilizer. (3) CK1-N: single nitrogen fertilization. (4) BC-N:returning straw carbonization with single nitrogen fertilization. (5) CK1-PK:potassium and phosphate fertilizer. (6) BC-PK:returning straw carbonization with potassium and phosphate fertilizer. (7) CK1-NPK:N, P, K fertilizer. (8) BC-NPK:returning straw carbonization with N, P, K fertilizer. The experiment conducted in 2014 and 2015, the amount of the straw returning to field was 2.55 t ha-1. The addition of biochar increased soil physico-chemical properties, increased soil microbial carbon. The effect of biochar on soil microbial nitrogen stem from the regulation of biochar to soil nitrogen, especially when biochar application rates at 20 t ha-1 and 40t ha-1, the C/N increased more. Biochar adjust soil nitrogen cycle mainly through change nitrogen maintain and transform, and then direct and indirect effect microbial diversity. Alpha diversity analysis revealed that the index of ACE and chaol were highest in BC-N, and lowest in CK1-CK2. The addition of biochar increased some functional microbial abundance, such as Bradyrhizobium had azotification, Anaeromyxobacter had bioremediation of heavy metal pollutants in the environment, Burkholderia as rhizosphere microorganisms had biodegradation, control and promote plant growth.A pot experiment was conducted with biochar application rates:Control (0 t ha-1), BC1 (20 t ha-1) and BC2 (40 t ha-1). The addition of biochar stimulated the growth of actinomyces and bacteria, especially the ammonifying bacteria and azotobacteria, but had no significant effect on fungi proliferation. The phylogenetic distribution of the operational taxonomic units could be divided into the following groups with the biochar addition:Firmicutes, Acidobacteria, Gemmatimonadetes, Actinobacteria, Cyanobacteria and α-,β-, γ- and δ-proteobacteria (average similarity> 95%). Cyanobacteria and α-proteobacteria can fix nitrogen in the atmosphere through symbiotic relationship with plants. Biochar application had a higher capacity for using L-asparagine, Tween 80, D-mannitol, L-serine, y-hydroxybutyric acid, N-acetyl-D-glucosamine, Glycogen, Itaconic acid, Glycyl-L-glutamic acid, a-ketobutyricacid and Putrescine, whereas had received decreased capacities in using the other 20 carbon sources in Biolog Eco-plates. Redundancy analysis (RDA) revealed that the soil physico-chemical properties, indices of bacterial diversity, and C metabolic traits were positively correlated with the appearance of novel sequences under BC2 treatment. Our study indicated that the addition of biochar can increase culturable microbial abundance and shift bacterial genetic structure without enhancing their capacities in utilizing C sources in Biolog Eco-plates, which could be associated with the pore structure and nutrients from biochar. Future work should be conducted to evaluate the long-term effect of biochar on functionality of soil microbial communities. It illustrated that addition of biochar play a positive effect on environment factors and microbial community.In brief, addition of biochar can change the soil physico-chemical properties(soil moisture content, pH, MBC, MBN, available N, P, K; TOC, TN, C/N, etc), and then indirect effect soil microbial community. It had significant effect on microbial community with different biochar application rate, while the difference were inconformity during short time sampling time. The experimental result indicated that biochar can increase soil microbial abundance and diversity, change of soil bacterial population distribution, improvement of the metabolic characteristics on soil microbial carbon source, and the induced the change of soil function.