Effects Of Nitrogen Addition On Ecosystem Stoichiomtry Characteristics In Degraded Grasslands

In order to understand the response of the ecological stoichiometry charact eristics of degraded grassland ecosystem to nitrogen addition. In this study, by mowing and grazing in Typical Steppe in Xilinguole use the different degrade d grassland as the research object. For mowing resulted in lightly degraded gr assland (LD plot) and caused by overgrazing is heavily degraded grassland (H D plot). This study designed 4 nitrogen adding gradient (0,10,17.5,28 g N/m2), conducted a two-year nitrogen addition experiment. Through the resea rch on the C, N, P element content and the stoichiometric ratio of the aboveg round part, root system and soil of grassland plants, analyze the effects of nitr ogen addition on the ecological stoichiometry of "plant root soil" system in dif ferent levels of degraded grasslands, To reveal the effect and mechanism of ni trogen addition on different types and different degrees of degraded grassland. To provide a scientific basis for the study of degraded grassland restoration an d management in Xilinguole League.The main conclusions are as follows:(1) Nitrogen addition has a certain effect on the aboveground and undergr ound biomass of lightly degraded plot and the underground biomass of Heavil y degraded plot.plant root shoot ratio and nitrogen gradient showed significant negative correlation in two plots.(2) The total N content and N/P were significantly increased in the two p lots of main plant population, and two plots of the plant population C/N decre ased with the increase of nitrogen; There was no significant effect on the cont ent of C, N and P in the soil of two plots, and the Lightly degraded plot’s N /P has a certain improvement; To a certain extent, the total C/P, N/P and C of the two plots were improved, and reduced the total P content in the surface layer of Heavily degraded plot’s.(3) There was a significant correlation between total N and P and the un derground part of Lightly degraded plot’s plant community, while total C and the underground part of the community has no significant correlation. There w as no significant correlation between the upper part and the underground part of the Heavily degraded plot, may be related to the complexity of the successi on stage of grassland degradation.(4) According to the threshold value of the plant limiting elements, the u pper part of the two plot’s plants could be judged to be limited by nitrogen; t he root systems of the two plots were limited by the P element, and were mo re obvious with the addition of nitrogen. Two plots of the soil lack of N and P two elements same time.(5) Generally speaking, N10 (30g NH4NO3) is the most suitable nitrogen addition in Lightly degraded plot, in this treatment, the performance of plant s oil is the best. This study did not find the appropriate amount of nitrogen add ition in Heavily degraded plot’s. Nitrogen addition is conductive to mowing ca used lightly degraded grassland restoration, and for the severely degraded grass land due to excessive grazing, compared with nitrogen addition, the enclosure is more favorable for its recovery.