The Effects Of Dispersion Of Stellera Chamaejasme L. Population On Soil Nutrient Availability Of Grassland

The dispersion of Stellera chamaejasme L. population in Horqin grassland does fearful harm to the pasture. In order to investigate its intrinsic relationship with the grassland degradation, we conducted a survey in the Horqin grassland, which has a large numer of S. chamaejasme L.population, to discuss the effect of dispersion of S. chamaejasme L. population on soil nutrient availability. We also discussed the intrinsic mechanisms among dispersion of S. chamaejasme L. population, the soil enzyme activities and microbial diversity. The research shows the following results.1) the dispersion of S. chamaejasme L. population significantly increases the content of organic matter, total nitrogen and total phosphorus in soil. Meanwhile, soil available nutrients (ammonium, nitrate, available phosphorus and potassium) also shows an upward trend. These state that dispersion of S. chamaejasme L. population can accelerate the transformation of soil nutrients. At the same time, it increases the salinity of the soil, which causes the deterioration of grassland.2) The dispersion of S. chamaejasme L. population can significantly improve the activity of urease, phosphomonoesterase and significantly reduce the activity of polyphenoloxidase in soil, while it has no significant effect on the activity of protease, dehydrogenase and nitrate reductase in soil. This indicates that urease, phosphomonoesterase, polyphenoloxidase are more sensitive to the environmental changes, and play an important role in the changes in degraded grassland soil nutrients.3) The dispersion of S. chamaejasme L. population has little effect on genetic diversity of soil dominant bacteria, but leads to the change of soil functional microbial groups, for instance the composition and structure of ammonia-oxidizing bacteria and ammonia-oxidizing archaea are changed.4) The grow of S. chamaejasme L. can improve the effectiveness of soil N. The mainly mechanism is that it changes the soil environment and the community structure of ammonia-oxidizing bacteria (AOB), which improves soil hydrolase activity, then accelerating the soil ammonia oxidation process. Meanwhile, changes in soil environment are also conducive to exerting enzymatic activity and improving nitrogen availability,S. chamaejasme L. secures a favorable position in the competition with other herbs and gradually become the dominant species in the community by changing their growth environment. This is also one of the main reason causing grassland deteriorating.