| Paclitaxel, which is extracted from Taxus, it has a special therapeutic effectiveness in treating many types of cancer and is vividly called the "final defense line of the terminal cancer". In the meantime, the contents of Paclitaxel are extremely low in natural Taxus, predatory cutting down natural Taxus could pose extremely threat to its survival in the field. Taxus media is a natural hybrid which produced by crossing T. cuspidate and T. baccata. T. media gains the advantage over by higher content Paclitaxel, growing fast, good adaptive ability and strong resistance, which becomes a good breed to instead of natural Taxus. To study the seasonal dynamics of microbial community structure, MBC, soil nutrient and enzyme activities of rhizosphere is helpful to future understand the inter-relation between the rhizosphere microbial community structure and T. media, which can provide some reference for scientific cultivation and utilization of T. media.This research uses dilution-plate method, MPN method to measure the seasonal variation of composition of microorganism in rhizosphere soil of different age of T. media. Using fumigation extraction-capacity analysis measure the dynamic change of microorganism biomass C. Using potassium capacity method, micro-Kjeldahl method, fluorescence spectroscopy, Alkali-hydro diffusion method,0.5mol/LNaHCO3 method, NH40AC molten flame photometric method, pH meter respectively determine soil organic matter, total N, total K, available N, available P, available K and pH. Using 3,5-dinitrosalicylic acid method, titration with potassium permanganate method, phenol sodium-sodium hypochlorite Colorimetric method, Disodium phenyl phosphate assay, 3.5-dinitrosalicylic acid method respectively measure invertase, catalase, urease, alkaline phosphate, cellulose. Using root tissue extract by extraction-filtration method to research the effecting to the microbial number with root tissue extract.Results show that, with the increase of growing years,1, The number of rhizosphere microorganisms and Shannon-wiener index totally increased and showed summer>spring>autumn. 2. Rhizosphere and non-rhizosphere soil MBC increased and showed summer>spring>autumn, rhizosphere MBC significantly higher than non-rhizosphere.3. Rhizosphere soil orangic matter, total N, available N, total K, available K, available P showed an increasing trend and pH were reduced as the growing years. Rhizosphere soil invertase, urease, alkaline phosphate, cellulose totally increased and catalase induced, each index of soil nutrient and enzyme activities equally showed summer> autumn>spring.4. Taxus media's root tissue extract of different tree age treated the soil, the soil bacterial and actinomycosis showed forward increase and decrease afterward trend but fungus reduced. After treated by 17a and 19a root tissue extract, soil microbial diversity was significantly higher than other soils.The results above represent that:1. With longer growing years, T. media's root size and root surface area were lager which resulted in higher root exudates and supplied the more fertile nutrient substance, which gave a boost to the increase of the number of microorganisms and MBC.2. T. media's root exudates can improve the physical and chemical characteristics of soil, the longer the growing years, the greater the effect.3. The enzyme activities of invertase, urease, alkaline phosphate, cellulose reflected the stronger mineralization to organic C, N, P of longer growing T. media's root to a certain degree, which was benefical to the growth and development of T. media.4. Usually, the higher species diversity, the more stable of ecosystem.17a and 19a T. media's root could persistent increase the soil microbial diversity.Therefore, We suggest that interplant the seedling(la) which has lower survival rate in 17a plot and 19a plot to improve the survival rate. |
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