Ecological Distribution Of Soil Microbial Physiological Groups Of Alpine Grassland In The Eastern Qilian Mountains And Identification Of The Dominant Fungi

As a main part of the agricultural ecosystem of grassland, soil microorganisms play vital roles in many processes, such as energy flowing and subtance conversion & cycling as well as soil developing and maturation. It is a sensitive index of any variation in environmental conditions as well. Constitutions and quantities of population are two key parameters for evaluating the soil quality. Therefore, it is very significative to study quantity of soil microbial population, diversity of population, ecological distribution characteristics and physiological fuction groups enhancing productivity of grassland ecosystem for sustainable development.Seven different representative vegetation types of alpine grassland in Eastern Qilian Mountains, which were Rhododendron fruticosa shrub land, Salix cupularis fruticosa shrub land, Dasiphoru fruticosa shrub land, Polygonum grassland, Grass steppe, Swamp grassland and Kobresia grassland were selected to be experimental samples. Traditional research methods were adopted to study quantitive seasonal dynamics and ecological distributional characteristics of soil main microbial physiological groups. The role of all physiological populations in grassland was analysed preliminarily. Dominant fungi-fusarium were identified and classfied by adopting combination bio-method and common identification method, and three representative species of those dominant fungi were selected to measure their biological features. The results were as follows:1 The ecological distributional charactristis and function of soil microbial physiological groups (1)Seasonal dynamics 1) The amount of ammonfying bacteria in shurb sampling sites showed the increasing trend. The quantity was the least in May and most in Nov.. All the grassland sampling sites increased first and decreased later with the peak value in September. 2) The amount of Bacillus in shurbs was up to the peak value in November, showing great significant difference with other sampling sites (P <0.01), while that in grasslands was higher in July and Nov. than in May and Sep.. 3) In shurb sites, the amount of aerobe azotobacter was higher in July and Nov. than in May and Sep., which showed great significantly difference with other shrub sites (P <0.01). In grasslands, the peak value was in July 4)In shurbs, the peak value of aerobe cellulolytie was in Nov. while the quantity was relatively low in May, July and Sep., showing great significant difference compared with other shrub sites (P <0.01). In grassland, the peak value was in July while the quantity was lower in Sep. and lowest in May. 5)The amount of oligotrophic cellulolytic was up to the peak value in Sep. in shrub land while that was in July in grassland. 6) The quantity of oligotrophic azotobacter was up to the peak value in Sep. in shrub land while that was in July in grassland. 7) In shrub land, the amount of denitrifying bacteria was the highest in July, then declined gradually in May, Sep. and Nov. In grassland, the peak value appeared in Sep. while minimum was in May. 8) The peak value of the total number of physiological groups was differ in different months. In shrub land, the peak value of Rhododendron fruticosa shrub land appeared in July while that of Salix cupularis fruticosa shrub land and Dasiphoru fruticosa shrub land was in Nov.. In grassland, the tendency of physiological groups changed in the same way. The peak value appeared in Sep..(2) Dynamics of soil depth The results showed that the quantities of ammonfying, bacillus, dennitrifying bacteria (except Swamp meadow), aerobe arotobacter, oligotrophic azotobacter (except Swamp meadow), aerobe cellulolytic and oligotrophic cellulolytic in 0-10cm soil layer were much more than that in 10-20cm soil layer.(3) Dynamics of vegetation groups The results indicated that the total number of microbial physiological groups showed the following rule: Kobresia meadow﹥Swamp meadow﹥Grass steppe﹥Polygonum meadow﹥Salix cupularis fruticosa shrub land﹥Rhododendron fruticosa shrub land﹥Dasiphoru fruticosa shrub land. The number of microbial physiological groups in meadow soil were more than that in shrub land soil.The total quantity of each microbial physiological group member in alpine shrub land and meadow soil The results showed that ammonifying﹥dennitrifying bacteria﹥aerobe azotobacter﹥oligotrophic azotobacter﹥bacillus﹥aerobe cellulolytic﹥oligotrophic cellulolytic. The amount of ammonfying took absolute dominance while that of cellulolytic was the lowest. Aerobe azotobacter played an important role in fixing nitrogen while aerobe bacteria was vital in fibrin-dissolving. Nitrogen fixation caused by azotobacter was one of the important origins of nitrogen resources in alpine grassland.2 The dominant soil fungiFusarium is the absolutely dominant fungi in the alpine grassland soil. On the foundation of routine identification, rDNA ITS sequence analysis and multiply comparation were applied to identified those twelve predominant fungi, and the phylogenetic tree was estabished. Thus, we primarily ascertained that 8 belonged to F.tricinctum, 3 belonged to F.oxysporum and 1 belonged to F.equiseti .The analysis results showed that there were different discrepancy in cultural morphology and gene sequence in various Fusarium, which indicatd that Fusarium in autochthonic soil was rich in diversity.3 The biology characteristics of three FusariumThe results showed that there were significant differences on the biological characteristics of three Fusarium. The suitable growth temperature for F. tricinctum and F.equiseti was 5～35℃and the optimum was 20℃, while that for F.oxysporum was 15～35℃and the optimum was 25℃. All of them could grow at pH 4～8.5 and pH 7 was the optimum .The optimum carbon sources of F.tricinctum and F.equiseti was starch, while the optimum nitrogen sources of those was ammonium chloride.The optimum carbon source of F.oxysporum was glucose and the optimum nitrogen source was peptone.