The Effect Of Different Halophytes On The Soil Microbial Diversity

Yellow River Delta, one of the three largest river estuary deltas in China, has high potentials of land development and utilization, but the widely distributed saline soils here in the coastal area at Bohai-Sea severely restrict the development of agriculture. The quite high salt content of the saline soils mainly chlorates, ranging from 0.4% to 3% in the surface layer, worsens the soil structure and lowers the soil fertility. Considering the soil properties and other conditions in Yellow River Delta, we used the traditional plate culture method and modern molecular biology techniques to study the effect of different halophytes on the soil microbial diversity, the long-term cultivation of halophytes'effects on soil microbial community, and the seasonal dynamics changes of soil microorganism. Based on these, we can study the changes of microbial diversity of Yellow River Delta saline-alkali soil in the ecosystem improvement and treatment stage, and study the forest quality improvement and ecology recovery technology. The main contents and results of this study are presented as followings:1. We established a simple, rapid, cost-effective method for the extraction of microbial DNA from different samples, including the saline-alkali soil.We chose the saline-alkali soil samples from the Yellow River Delta as the research objects, used 21 kinds of extraction methods and four kinds of purification methods to extract and purify the soil DNA, and established a simple, rapid, cost-effective method for the extraction of microbial DNA——microwave method. It could be effectively used in different samples(fertile soil, active sludge, riverbed sullage, sand, alkaline land soil, album canis and leaves of Arabidopsis salsuginea), and the PCR amplification results showed that the extracted DNA can be directly operated in molecular biology, which demonstrated the method has broad applicability.2. We ascertained the effect of different halophytes on the soil microbial diversity.After the cultivation of halophytes, the number of soil microbial in the five kinds of halophytes rhizosphere showed that the total number of microorganisms in the soil were significantly increased, but the degree of change was t not the same, the sequence of the influence on the increase of the soil microbial number were: Tamarix chinensis Lour.>Limonium bicolor(Bge.) Kuntz>Iris ensata Thunb>Lonicera japonica>Atriplex centralasiatica Iljin>CK, and the salt-tolerant micro-organisms'number and proportion has declined. The results indicated that the total number of physiological microorganism showed the following rule: Ammonifying>Aerobe azotobacter>Aerobe cellulolytic>Bacillus>Thiobacillus>Desulphurizing bacteria>Nitrosomonas>Nitrifiers>Dennitrifying bacteria. The amount of ammonfying and aerobe azotobacter took absolute dominance, the number of different plots followed as:Tamarix chinensis Lour.>Limonium bicolor(Bge.) Kuntz>Lonicera japonica>Iris ensata Thunb>Atriplex centralasiatica Iljin>CK. Various physiological microorganism groups of soil would not only help maintain soil fertility but also enhance the lives of other rhizosphere microbial activity. In this experiment, Tamarix chinensis Lour. had the greatest influence on soil microorganisms and could significantly increase their number of the soil, and the amounts of ammonification bacteria, aerobe azotobacter, aerobe cellulolytic and Nitrosomonas were the majority.The results of RFLP and RAPD analysis indicated that after the cultivation of halophytes, the type and quantity of soil microbes were changed, RFLP analysis showed that the six plots'16S rDNA amplification products were digested by HinfI and Csp6I giving birth to the similar bands, even though they had different brightness. The RAPD fingerprints showed substantial differences among the different soil samples, and according to apparent changes in the number and size of amplified DNA fragments, the Shannon-weaver index of different plots was Tamarix chinensis Lour.>Lonicera japonica>CK>Limonium bicolor(Bge.) Kuntz>Atriplex centralasiatica Iljin>Iris ensata Thunb, and the Pielou index were CK>Lonicera japonica>Atriplex centralasiatica Iljin>Limonium bicolor(Bge.) Kuntz>Iris ensata Thunb>Tamarix chinensis Lour..3.Ascertained the effect of long-term cultivation of halophytes on the microbial diversity.Using the traditional means to determine the rhizosphere microbial changes in the types and quantities of different halophytes growing for long years, the result of the study indicated that the number of micro-organisms significantly increased after halophytes planted, and the Tamarix chinensis Lour. showed greater influence, which could significantly increase the number of micro-organisms, and at the same time the salt-tolerant bacteria'proportion was decreased significantly. After two-year cultivation, the number of microorganisms reached to the maximum, and the ratio of bacteria and fungi (B/F) significantly descended with the continuous cultivation. The total number of micro-organisms and nitrogen-transform bacteria were reduced, meanwhile, the number of fungi increased. The Suaeda heteroptera Kitagawa. had the similar effect, and it could increase the number of micro-organisms.4. We primarily ascertained the seasonal dynamics of soil microorganism quantities.There were significant changes of soil microorganism quantities in different seasons, and the microorganisms of different months showed a certain variation in the same halophytes'rhizosphere: the bacteria in every plot had an absolute advantage both in the number and proportion, and the number of micro-organisms were more in July, and less in September. In the same period, the number of soil microorganisms in the halophytes rhizosphere was: Tamarix chinensis Lour. >Suaeda heteroptera Kitagawa.>Limonium bicolor(Bge.) Kuntz. The dynamic changes of physiological microorganism groups had their own laws, but the number of each group still followed the rules: Ammonifying>Aerobe azotobacter > Aerobe cellulolytic > Bacillus > Thiobacillus > Desulphurizing bacteria>Nitrosomonas>Nitrifiers>Dennitrifying bacteria, no matter when it was in April, July or September.