Study On The Dynamic Of Soil Microorganism In Alpine Grassland Under Disturbance In Tianzhu

The number and distribution of soil microorganisms (fungi, actinomycetes and bacteria) and microorganism physiological groups of alpine grassland under different disturbance in Tianzhu were investigated and analyzed by using plate colony count and MPN methods, the results were as follows:1. Distribution and number pattern of microorganism1) The number of soil microorganisms (fungi, actinomycetes, bacteria) greatly varies with soil depth. The number within 0-20cm is much higher than that within 20 to 40 cm (around 2 to 7 times). This means that the number of soil microorganism have the obvious vertical distribution pattern along with soil depth. The number of soil microorganism is higher in the surface layer, and radically decrease with the depth of soil layer.2) The number of soil microorganisms (fungi, actinomycetes, bacteria) shows a seasonal pattern and the general trend is as follows (although a little difference among different disturbing condition): Within 0-20 cm, significant seasonal changes were observed. The number of soil microorganism is high in July. It rises to the highest in August and drops down to the lowest in September. Within 20-40 cm, it shows the same trend, but the variational range is very small.3) Total number of microorganism is much different among different disturbed habitant and it ranges from 8.47 X 106 cell/g dry soil to 16.22X106 cell/g dry soil. The order is annual artificial grassland > fenced grassland > perennial artificial grassland >soil pile (in zokor damaged grassland) >un-fenced grassland. Among the three groups of microorganism, the number of bacteria is the highest (82.29% to 86.09%), then followed by actinomycetes (13.91% -17.71%) and fungi (0.017%~ 0.023%). Bacteria and actinomycete accounts for 99.9% of the total.4) The distribution pattern of each group under different disturbance varies. The order is as follows: fenced grassland> annual artificial grassland >perennial artificial grassland > soil pile > un-fenced grassland for fungi; Annual artificial grassland > perennial artificial grassland > fenced grassland > soil pile > un-fenced grassland for actinomycete; Annual artificial grassland > fenced grassland > perennial artificial grassland > soil pile > un-fenced grassland for bacteria.2. Number dynamics of three physiological groups1) The number of three physiological groups (nitrobacter, anaero-nitrogen fixing bacteria, aero-nitrogen fixing bacteria, denitrobacter, anaero-celluloses decomposing bacteria, cellulose decomposing bacteria) greatly vary with soil depth. The number in 0-20cm is much more than that in 20-40 cm (around 2 to 10 times).2) The number of three physiological groups under different disturbance shows different pattern and the tend is as follows: fenced grassland > perennial artificial grassland > annual artificial grassland > soil pile > un-fenced grassland for nitriobacter; Fenced grassland > annual artificial grassland > soil pile > perennial artificial grassland > un-fenced grassland for aero-nitrogen fixing bacteria; Soil pile > un-fenced grassland > perennial artificial grassland > annual artificial grassland > fenced grassland for anaero-nitrogen fixing bacteria; Annual artificial grassland > perennial artificial grassland > fenced grassland > soil pile > un-fenced grassland for denitrobacter; Fenced grassland > perennial artificial grassland > annual artificial grassland > un-fenced grassland > soil pile for aero-cellulose decomposing bacteria; Fenced grassland > perennial artificial grassland > annual artificial grassland > un-fenced rangeland > soil pile for anaero-cellulose decomposing bacteria.3) The number dynamics of three physiological groups under different disturbance shows different patterns along with time and the tend is as follows: Within 0-20cm, soil microorganisms change greatly. Within 20-40 cm, it shows the same trend as that in 0-20cm, but variation range is not obvious. This result indicates that the soil microorganisms show seasonable variation pattern in 0-20 cm and almost no seasonable variation in 20 to 40 cm.3. T...