Effects Of Stimulating Nitrogen Deposition And Increasing Precipitation On Nitrogen Mineralization In A Stipa Baicalensis Meadow Steppe

Nitrogen deposition and precipitation pattern change has a profound impact on terrestrial ecosystems. Precipitation and nitrogen content is frequently the primary limiting resource of productivity in grassland ecosystem It is an important factor affecting ecosystem function in grassland ecosystem whether nitrogen flow is balance or not. Based on a Stipa baicalensis meadow steppe of Inner Mongolia as the research object, we use PVC tube closed-top in situ incubation method.To explore the change of Nitrogen mineralization in grassland under increased nitrogen deposition and precipitation, We designed the experiment with the nitrogen addition and increased precipitation in a Stipa baicalensis grassland of eastern Inner Mongolia and we set up different gradient of nitrogen and precipitation. Increased nitrogen by the ammonium nitrate and urea, respectively 70% and 30% of the total amount of nitrogen. Including three levels: high N application is divided into 12 g N m-2 a-1,medium(6 g N m-2 a-1), low(0g N m-2 a-1, the natural fertility); Precipitation enhancement through the sump tank intercepting rainfall irrigation method to increase are high(2/7) of natural precipitation, rainfall in 1/7(increase natural precipitation), low(natural precipitation) three levels; Using increase nitrogen, increase water and increase nitrogen increase water interaction is used as a total of nine kinds of gradient process, each kind of processing four repeat, to acquisition of soil ammonium nitrogen and ammonium nitrate nitrogen content and mineralization rate and some soil physical and chemical properties. Main conclusions are as follows:(1) Overall, during the period of 6 to 8 months, increase of soil ammonium nitrogen content was obviously higher than the growth in nitrate content. From the point of ammonium nitrogen content, high nitrogen(N2) under the condition of the soil in August to ammonium nitrogen content significantly increased with the increase of moisture content, and high water(W2) under the condition of soil ammonium nitrogen content of August also appear as nitrogen levels increased and the marked increase in the trend. Increasing nitrogen and precipitation treatment in improving soil ammonium nitrogen content exists in the process of promoting the interaction effect of each other. The point of nitrate nitrogen content, nitrogen, precipitation enhancement processing is not interaction effect. Increasing the influence of nitrogen treatment for nitrate content is larger, the precipitation enhancement processing for soil nitrate content in almost no effect.(2) Increased nitrogen, precipitation, and the interaction effect on June 10th- July 10, July 10-10 August interval of soil ammonium net rate and net nitrification rate were not significant. However, precipitation treatment for June 10-10 August two months interval has significant effect on the rate of soil ammonium net effect. Similarly, increased nitrogen treatment for June 10 th August 10 intervals of soil net nitrification rate reached significant level. Increase nitrogen, precipitation enhancement processing of grassland ecological system of soil nitrogen mineralization process with the influence of the cumulative effect of on time.(3) Water is affected soil ammonium nitrogen and ammonium soil net rate of the main factors, and nitrogen levels on soil nitrate and soil net nitrification rate effect is remarkable. Due to soil nitrate content is much higher than ammonium nitrogen content, therefore, soil total nitrogen levels for the mineralization process and the concentration of inorganic nitrogen to a certain extent masks the effects of moisture factor.In conclusion, different gradient increasing nitrogen and precipitation in a Stipa baicalensis meadow steppe soil nitrogen mineralization process and are having a significant impact on soil nitrogen content. However, the effect of increased nitrogen and increased water treatment for soil ammonium nitrogen and nitrate is different. Increased nitrogen more influence soil nitrate content and net nitrification rate, thus affecting soil inorganic nitrogen content and nitrogen mineralization. Overall, the pattern of atmospheric nitrogen deposition and precipitation change under the background of grassland of inorganic nitrogen and the change of the net nitrogen mineralization rate could be a litter, plant and soil environment and the result of many factors such as soil microbial interactions.