Some Ecological Studies On Soil Microorganisms And Heterotrophic Nitrogen-fixing Bacteria On Caloglossa Body In Mangroves Of Jiulongjiang Estuary, Fujian Of China

Mangrove forests are woody plant communities in the intertidal regimes of tropical and subtropical coasts. Microorganisms are compositions and main decomposers of ecosystem, which promote material cycle and energy flow in ecosystem. In this thesis, it was detailed studied with some classical microbiological and ecological experimental means' and biological statistical methods that vertical distribution and seasonal changes of microbial counts and microflora of bacteria, actinomycetes and fungi in three soil layers from 0 to 60 cm in mangroves of Jiulongjiang Estuary, Fujian of China; It was also investigated that relation between soil environmental factors and counts of soil microorganisms, seasonal changes and microflora of heterotrophic nitrogen-fixing bacteria on Caloglossa body in mangroves, relation between seasonal dynamics of heterotrophic nitrogen-fixing bacteria and nutrient elements of Caloglossa sample, and antimicrobial activity of soil microorganisms in mangroves. In addition, dilution plate method was improved when it was applied in mangrove area.1. Effect of salinity on microbial counts of mangrove soil was first systematical investigated by dilution plate method, and the results indicated that the effect of salinity of media and dilution water on microbial counts of mangrove soil was significant. The seawater was not suitable for the preparing media because the increase of salinity of media would decrease the microbial counts of mangrove soil. The salinity of media should be at low concentrations, which should be within 5%o, 10%o and 5-15%o for actinomycetes, fungi and bacteria respectively. The effect of seawater was better than that of freshwater for bacterial isolation when both were respectively served as sterile dilution water. However, as was contrary to actinomycetes and fungi. It was concluded that most bacteria, actinomycetes and fungi of soil in mangrove area were terrestrial origin according to their effect of salinity of media and dilution water on isolation counts.2. Vertical distribution and seasonal changes of main chemical factors in three soil layers from 0 to 60 cm were first systematical investigated in two subtropical mangrove forests. The results showed as following:(1) The pattern of vertical distribution of organic matter in mangrove soil reflected the roots distribution. Surface roots were abundant in Avicennia marina forest, so organic matter of soil in top layer (0-20cm) was the most there. However, the organic matter of soil in Kandelia candel forest was the most in middle layer (20-40cm)because roots were abundant in middle layer while there were fewer roots on surface soil. Content of organic matter in bottom layer (40-60cm) was generally lower in two mangrove forests. Vertical distribution of total nitrogen and organic matter was not completely identical, which was related with decomposition of soil organic matter. Content of soil organic matter in two mangrove forests was generally the highest in winter and the lowest in summer, and that in spring and autumn were between winter and summer, but as was contrary to total nitrogen. Seasonal patter of organic matter and total nitrogen reflected seasonal changes of the activity of heterotrophic soil microorganisms. The concentration of total phosphorus in mangrove soil decreased with increase of soil depth, but the variation on vertical distribution was little. The concentration of total phosphorus in mangrove soil was somewhat higher in spring, which was probably related with input of phosphorus from outer environment. Vertical distribution and seasonal changes of C/N value and N/P value depended on change of total nitrogen to a great extent. Vertical distribution and seasonal changes of total potassium, calcium and magnesium presented some indefinite characteristics with certain random, which can not be looked as widespread still in mangrove area because of the lack of available data at present. Vertical identity between salinity and total sodium in mangrove soil owed to their same main source-seawate...