| Soil has far-reaching contribution on the function of terrestrial ecosystems,and it is the aggregation sites and the most suitable living environment for natural microbial. Desert grassland is an ecotone between grassland and desert in Inner Mongolia vegetation. It is a fragile ecological environment, which is the interaction between various components of landscape. In a word, it is a great significant to study.The traditional methods and molecular biology methods (DGGE) are used firstly to study and research seasonal dynamic changes of soil microorganism in desert grassland of Inner Mongolia. The main contents of this study include: the seasonal dynamic changes of soil microbial amount,biomass, soil enzyme,soil respiration and soil nutrients in desert grassland of Inner Mongolia; The functional groups of soil microorganisms, the advantages of micro-organisms and the specific microbial species are analyzed by DGGE in different seasons of Inner Mongolia desert grassland. In this paper, the main conclusions as follow:⑴It is very different between the various types of soil microorganisms in desert grassland of Inner Mongolia. The relationships among the amount of them is Bacteria (aerobic)>actinomycetes>Bacillus bacteria> Self-nitrogen -fixing bacteria> fungi. The total number of soil microorganisms, as well as microbial biomass C, has obvious seasonal dynamic changes. The total number of microorganisms in summer and autumn is larger than that in spring and winter. The soil microbial biomass is larger in spring and summer.⑵The soil enzyme activity and soil respiration are impacted by the soil degradation and seasonal dynamic changes. The seasonal dynamic changes of invertase and catalase is similar in two plots, but polyphenoloxidase,urease and soil respiration are not similar. Invertase is the higher in spring and wenter than that in autumn and summer; catalase is the highest in winter and is lowest in spring. In the mild degradation plot DM, polyphenoloxidase,urease,soil respiration are higher in autumn and spring; In the severe degradation plot SH, polyphenoloxidase,urease and soil respiration are big in summer. In the mild degradation plot DM, soil enzyme activity is bigger than that in the severe degradation plot SH; soil respiration hasn't obvious distinction in two plots.⑶Soil nutrient and soil moisture have obvious seasonal dynamic changes, but PH hasn't. The total carbon and total nitrogen are the biggest in summer and are smallest in spring; total phosphorus and total potassium are small in winter; the soil moisture is big in spring. In the mild degradation plot DM, total carbon,total nitrogen,total phosphorus and soil moisture are higher than that in the severe degradation plot SH. But total potassium and PH haven't obvious difference in two plots. ⑷The method of molecular biology are applied firstly in soil microorganism of Inner Mongolia grassland ecosystems. The gap is filled, which was studied by any scholars at home or abroad. It is convenient and rapid to extract DNA of the desert grassland soil by the soil DNA extraction kit. The DNA can be used for the following analysis of the molecular biology. According DGGE strap brightness and the strap number of digital results, we can know that: the diversity of microbial is large in spring and autumn; the diversity of microbial is low in summer and winter. The bacterial diversity index of the mild degradation plot DM is higher than that of the severe degradation of plot SH.⑸Two samples of the site DM and the site SH have different dynamic changes of bacterial community structure; Bacterial community structure of two samples are conspicuous distinction. Bacterial community structure in the desert grassland of Inner Mongolia is formed by three major clusters: Broteobacteria,Bacteroidetes and Acidobacteria. Of the sixteen clones obtained from DGGE patterns, uncultured bacterium are about 70% in all bacterium. It can reflect the superiority of the modern molecular biology techniques (DGGE) in the soil microbial research.
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