| Cerasus sachalinensis Kom. is native to the northeastern region of China. It is widely used as a rootstock of sweet cherry in cool regions such as Dalian and Qinhuangdao. However, the roots of C. sachalinensis Kom. are very sensitive to soil environment. When grafted cherry plants reaching fruiting stage, undeserved soil management will easily causing the worsen of rhizosphere micro-ecological, which leading to the reduction of tree vigor result from rapidly decreases of root function. It will lead to dead tree when serious and brings great loss of production. Whereas, soil of most cherry orchard in China are with low organic carbon content, low cushion performance, and poor basic fertility. The effectiveness of soil carbon is a dominant factor controlling microbial flora and function. Aiming at the above problems, we study the mechanism of microorganisms in carbon turnover in the rhizosphere of Cerasus sachalinensis Kom.. Combining with the detection of sensitivity index-root respiration, the responding of C. sachalinensis Kom. root respiratory metablism to soil carbon level and microbial environment were determined. We interpreted the role of microorganisms playing in carbon turnover and energy cycling in the rhizosphere and the microorganisms are not only the componets of soil carbon, but also promoters of carbon decomposition and transformation. Therefore, this study provide the basis for the discussion of directional regulating soil carbon level in cherry rooting zone and establishment the soil management measures to promote plant growth and development. The research results were as follows:1. The results of soil sterilization, PGPR inoculation ans biological agent inoculation experiments showed that soil sterilization significantly decreased the content of soil MBC, whereas inoculation of PGPR and biological agent had different effects on the content of MBC. The root basis biochemical pathways of respiration metabolism and related key enzymes activity changed, which eventually led to changes of Cerasus sachalinensis Kom. biomass. Comparing with PGPR inoculation, effects of soil sterilization was more significantly, which significantly increased the growth index of Cerasus sachalinensis Kom. such as plant height, leaf number and leaf area. Results of laboratory incubation experiment showed that soil sterilization, PGPR inoculation and root exudates could change bacterial community structure and the effects changed with time. In September, soil MBC content, organic cabon content and bacterial community richness improved significantly.2. The results of adding different structure of exogenous carbon sources glucose, starch and cellucose to the rooting zone of cherry showed that both of unstable carbon such as MBC and stable carbon such as soil organic carbon changed significanly. Microbials prefer to use easily available carbon, and use the recalcitrant carbon after decomposition of it. Exogenous cellulose addition increased the cellulase activity of cherry rooting zone soil in short time, and amylase activity increased in starch treatment. Adding exogenous carbon obviously changed the soil microbial community composition and improved soil microbial activity, but changed with time. Metabolic activities of soil microbial communities were the most strongest at 15 d after being treated. Soil enzyme activities and microbial community function tended to restore the original level with the extension of time. Glucose addition significantly increased the cherry root total respiratory rate and root vitality. Starch addition siginificantly increased the cherry root vitality, but changed root total respiratory rate slightly. Whereas cellulose addition siginifacantly increased the root total respiratory rate and decreased the root vitality.3. The results of adding different amount of glucose to rooting zone of Cerasus sachalinensis Kom. showed that soil MBC content and soil respiratory rate increased with the increased of added glucose amount during 3-7 d after being treated, and then decreased to the original level. Soil organic carbon dicreased at the 7 d in the treatment which added glucose-C equivalent to the MBC, and decreased at the 15 d in the treatment which added glucose-C equivalent to the 5 times of MBC. Changing of MBC content, soil respiration and soil organic carnon could prove the happen of primming effect. Results of high throughput sequencing analysis of soil in different treatments showed the distribution of bacteria in the soil are affected by amount of glucose added, and the effects are reflected in the different classification level of the bacteria. Bacteria changed at the species level when the added glucose-C equivalent to the 10% of MBC. Bacteria changed at the genuses and species level when the added glucose-C equivalent to the MBC content, and changed at the phylums, genuses and species level when the added glucose-C equivalent to the 5 times of MBC. Corresponding changes in microbial community structure and soil carbon pool can conclud that the main reason of primming effects occured after adding easy available carbon source glucose are the changed of soil microbial community composition. The main bacteria changed include phylums such as Proteobacteria, genuses such as A4, Flavisolibacter, Aquicella, Candidatus Solibacter, Gemmata, Planctomyces, Rhodoplanes, DA101, Kaistobacter and species such as Bacillus, Candidatus Solibacter, A4, Hyphomicrobium, Aquicella, Sphingobium, Rhizobium, Paenibacillus, Thermomonas, Kaistobacter, Agrobacterium, Pseudoxanthomonas, Lysobacter, Candidatus Koribacter. Results of the soil samples treated by glucose-C equivalent to MBC content using DNA-SIP showed that 5,6,7 and 8 fractions were heavy fractions in the 3 d.5,6,7,8 and 9 fractions were heavy fractions in the 7 d,6,7, 8,9 and 10 fractions were heavy fractions in the 15 d and 8,9 and 10 fractions were heavy fractions in the 30 d. Using high-throughput sequencing method to detect the mixture of heavy fraction, which comprised with the mixing DN A heavy fractions in different treatments and different time respectivily. Results showed that relative abundance of the Proteobacteria and Pseudomonas were the largest, which were the main bacteria phylum and genus in 3-15 d.4. Results of the experiment of adding exogenous available carbon source glucose, and less easily to use carbon source straw stalks and nitrogen showed that adding exogenous carbon source and nitrogen source could improve the soil respiration rate and content of MBC at 3-7 d after being treated. Nitrogen addition made the C/N ratio closer to the C/N ratio suitable for microbial growth, which alleviated the rapidly rising of the microbial activity, and could maintain the high soil organic carbon content for a longer time. Root total respiratory rate of Cerasus sachalinensis Kom. appeared two peaks at 7 d and 60 d after being treated, which were higher in the two treatments than that in control. Root respiratory rate of based biochemical pathways were affected by key enzymes activities, which closely relative to soil carbon metabolism. Root respiratory rate of AOX changed slightly during the whole experiment period. |
PDF Full Text Request