| Plant Growth Promoting Rhizobacteria (PGPR) refers to a kind of microorganism which can free live in soil or colonize in rhizosphere, surface and interior of root, stem and leaf. It can directly or indirectly promote or regulate plant growth. PGPR can promote the growth of plants directly or indirectly by transforming the invalid N, P and K in soil to valid form plants or secreting plant hormone. The PGPR of current study mainly refers to Nitrogen-fixing bacteria, Phosphate solubilizing bacteria and potassium bacteria. The topic of this research is mainly by investigation and researching the eucalyptus plantations inoculated PGPR, including the by measure of eucalyptus plantation increment, soil nutrients content, soil microbial quantity, soil enzymes activity and the investigation of plant diversity under the eucalyptus plantation; It aims at discussing the relationship between PGPR and soil nutrients, and plant diversity, and offering theoretical basis of the sustainable development of eucalyptus. The main results of this study are as follows:1. inoculating PGPR can improve the increment of eucalyptus obviously. Soil microbial quantity of eucalyptus plantation:bacteria>fungi> actinomycetes, Nitrogen-fixing bacteria>Phosphate solubilizing bacteria> Potassium bacteria. Inoculating the PGPR can obviously inprove the soil microbial quantity; the activity of protease, catalase, urease and catalase in soil; the content of organic matter, total nitrogen, total phosphorus, available nitrogen and rapidly available nitrogen in soil; the plant diversity under forest. But it obviously reduces the content of total potassium and rapid available potassium in soil.2. There are39species of ligneous plants and17species of herbaceous plant under eucalyptus plantation in investigative area. The structure under the eucalyptus plantation is simple, and the species is less. Euphorbiaceae, Morace and Rosaceae are mainly dominanted in shrubs. Compositae, Gramineae and Pteridaceae are mainly dominantedin herbaceous plants under the forest.3. Species richness index and diversity index can be improved by inoculating the PGPR. But species evenness index cannot be influenced obviously. Eucalyptus plantation which inoculated N6bacteria strain has the maximum plant diversity index. Diversity index, richness index and evenness index of its shrub layer and herbaceous layer are all highest.4.Through the soil to promote correlation born bacteria, enzyme activity and soil nutrient between nitrogen-fixing bacteria and urease activity was significantly associated solutions of inorganic phosphorus bacteria and protease, urease, acid phosphatase activity was significantly associated solution of potassium bacteria peroxide significantly related catalase; soil organic matter content and nitrogen-fixing bacteria, solution of inorganic phosphorus bacteria, protease, urease, acid phosphatase was significantly positively correlated with catalase correlation is not significant; total phosphorus and solutions of inorganic phosphorus bacteria phosphatase was significant positive correlation; total potassium content and solution of potassium bacteria, catalase was significantly negatively correlated with protease showed a significant negative correlation; nitrogen content and solution of inorganic phosphorus bacteria phosphatase showed a significant positive correlation; available phosphorus content phosphatase activity was significantly correlated with the solution of inorganic phosphorus bacteria, urease was a significant positive correlation; potassium and potassium solution bacteria, catalase was a significant negative correlation.5. Through the correlation analysis of plant diversity index and soil biological factors, it is show that:plant richness index and soil protease showed a significant positive correlation; diversity index was significantly positively correlated with ACP, phosphatase solubilizing bacteria and Nitrogen-fixing bacteria; no significant correlation between the evenness index of herbaceous layer and biological factors; evenness index of shrub layer and ACP activity showed a significant positive correlation.6. Plant diversity index was highly significantly positivly correlated with soil content available nutrients and rapid available phosphorus;no significant correlation between evenness index of herbaceous layer and soil nutrients; evenness index of shrub layer was highly significantly positively correlated with rapid available phosphorus and significantly correlated with available nitrogen. All this showed that plant distribution under eucalyptus plantation is correlated with the content available nitrogen and rapid available phosphorus in soil.7. Adopt increment of eucalyptus plantation, soil microbial quantity, soil nutrient content and plant diversity index to make principal component analysis in order to get comprehensive assessment of the ecological efficiency of eucalyptus plantations. The ecological efficiency of each bacteria strain is showed as:N6>Nc>N1>P1>40K>14K>9K>CK, according to the scores. Fungus overall ecological effects of eucalyptus plantations is the best, followed by solubilizing bacteria, solution of potassium bacteria are the worst. |
